Bibliothek

Notizen: Summary Projections of the somesthetic ascending pathways to the superior colliculus (SC) of the cat have been demonstrated by means of the horseradish peroxidase (HRP) tracing technique. Following HRP injection in one SC, marked neurons were found in the contralateral dorsal horn and in the contralateral dorsal column nuclei, mainly the cuneate nucleus. Moreover, in the contralateral trigeminal complex, the sub-nucleus caudalis of the spinal nucleus of the Vth nerve, and the subnucleus oralis plus the main sensory trigeminal nucleus were labeled. Thus, the anterolateral system and the lemniscal system subserving face and forelimb sensation send afferent fibers to the contralateral SC.

Notizen: Summary In the cat caudate nucleus the same nine types of synapses are found as in putamen and fundus striati. The three parts of the striatum in the strict sense do not differ in the morphological differentiation of synapse types but only in their quantitative distribution. One-third of all synapses in the caudate nucleus are axo-spinous type IV synapses with a curved and divided asymmetric contact. This strongly suggests that the caudate nucleus interneuronal apparatus is dominated by centre-median input, in contrast to the putamen which is controlled by the cortico-striatal input to its internuncial cells and by its strong intrastriatal feedback mechanism. Extensive destruction of the convexity of the cortex and the medial cortex in one hemisphere results in dark degeneration of a large proportion of two of the nine types of caudate synapses: a) the axo-dendritic type VII synapses exciting the large aspiny caudate neurons and b) the axo-spinous type III synapses making contact with the small spiny neurons of the interneuronal cell apparatus.

Notizen: Summary Retrograde tracing experiments using horseradish peroxidase (HRP) have been utilized for demonstrating the origin of efferent projections of the ventral lateral geniculate nucleus (LGNv) in the cat. HRP-positive cells identifiable as origins of thalamic projections were found in LGNv after injections of HRP into the lateral central intralaminar nucleus. The labeled cells appeared concentrated in the medial part of the internal division of LGNv, consisting of medium-sized multipolar cells. Contralaterally, fewer labeled cells were present in the corresponding part of LGNv. In the case of injections of HRP into the midbrain (pretectum and superior colliculus), labeled cells in LGNv were distributed almost exclusively in its external division, composed of mainly small cells. Little overlap of the distribution of HRP-positive cells was seen in LGNv between the thalamic and midbrain injection cases.

Notizen: Summary It has previously been shown that unilateral ablation of the whole auditory cortex in the cat disrupts the precedence effect, and also interferes with the ability of the normal animal to discriminate in the Y-maze between a single sound on one side and a double sound consisting of a signal on both left and right sides. The present work has confirmed these effects and has shown that both can be obtained with lesions confined to AI and AII The ‘one-versus-two’ deficit has invariably been seen in all the animals studied, but a proportion of animals do not show the precedence effect deficit. It has been confirmed that the apparent success of some animals can be due to the training effect of the one-versus-two paradigm, as was proposed in the earlier paper; however it has also been shown that this cannot be the explanation in all cases. It has been demonstrated that cats are able to localize sounds behind them with some success; turning around in the start box to reverse right and left space is therefore a possible strategy for overcoming a unilateral deficit. However, even with the head ‘fixed’ in the forward-facing position, one animal was still able to run well above chance. The size of the lesion does not appear to be a correlate of the performance level.

Notizen: Summary Electron microscopical studies of the thalamic AV-AM nuclei substantiated the presence of two main types of neurons, i.e. principal (or relay) cells and Golgi type II interneurons. Characteristic synaptic islands are found in abundance in the AV-AM. Four different types of synaptic terminals have been identified in these islands: RL-boutons = large axonal terminals with round synaptic vesicles; RS-boutons = small axonal terminals with round synaptic vesicles; F1-boutons = small axonal profiles containing flattened synaptic vesicles, and F2-profiles interpreted as presynaptic dendrite appendages, bearing pleomorphic vesicles, both belonging to the Golgi type II interneurons. — The synaptic relations were studied in normal preparations and after lesions in the mamillary body, limbic cortex and hippocampus. The specific afferents (RL-boutons) — originating from the medial mamillary nucleus — are presynaptic to both relay cell dendrites and “presynaptic” dendrite profiles of Golgi type II interneurons, which in turn are presynaptic to the same relay dendrites (synaptic triads). RS-boutons originate mainly from limbic cortex and hippocampus.

Notizen: Summary A sudden and rapid angular displacement of the limb evokes, in human and monkey subjects, a segmented pattern of electromyographic activity in muscles which are stretched. While the first segment is acknowledged to represent a tendon jerk, it has been proposed that the second segment, occurring with a shorter latency than a reaction time, is mediated by a transcortical loop. The present experiments were conducted in cats to determine the properties of muscle responses to torque perturbations analogous to those used in the monkey, and to determine if the integrity of supraspinal pathways is required for the individual response segments to occur. Torque perturbations which flexed the forearm evoked a segmented response in the electromyogram of the cat triceps muscle. This response typically consisted of three early segments with latencies of 10, 30 and 60 msec which were similar to the M1, M2, and M3 segments described in the monkey. The M3 and occasionally M2 components were depressed when the cat followed rather than resisted the perturbation. A torque pulse of 10 msec duration was sufficient to elicit a near maximal M1 response while torque pulses in excess of 20 msec were required to evoke the M2 response. To determine if any of these components required mediation by the cerebral cortex, experiments were conducted in decerebrate and spinal cats. Similar torque perturbations produced segmented electromyographic responses in the triceps muscles which were indistinguishable in their timing from those observed in intact cats. The torque required to produce the segmented responses was comparable as well. All three segments were dependent upon the activation of receptors in the homonymous muscle and did not require cutaneous input. These observations show that receptor properties and/or spinal mechanisms involved in the stretch reflex are sufficient to produce a segmented response similar to that observed in intact animals.

Notizen: Summary The ascending and intrinsic projections of the superior olivary complex (SO) in the cat were investigated by injection of 3H-leucine and horseradish peroxidase (HRP) in SO and the inferior colliculus (IC), respectively. A topically arranged projection was demonstrated from the nucleus of the trapezoid body (NTB) to the ipsilateral lateral superior olivary nucleus (LSO) with a lesser connection in the opposite direction. The medial superior olivary nucleus (MSO) has a strictly ipsilateral projection, whilst LSO projects symmetrically through the lateral lemniscus (LL) of both sides, to end with topically arranged terminals in the ventrolateral part of the central nucleus of the inferior colliculus (CNIC). Terminal labelling found in the ventral and dorsal nuclei of LL (VNLL and DNLL) probably represents collaterals from bypassing fibres originating in MSO and LSO, respectively. These results were demonstrated by both techniques, whilst in addition the HRP method revealed an ipsilateral and a contralateral projection to IC from VNLL and DNLL, respectively.

Notizen: Summary Single unit recordings were carried out in the reticularis thalamic nucleus (RT) and the ventral lateral geniculate body (LGv) of chronically prepared alert cats under sinusoidal vestibular stimulation in the horizontal plane. Optokinetic stimulation was also used. Of the 57 recorded neurons, 12 present vestibular modulation in the dark, analogous to Duensing's and Schaefer's (1958) type I response in the vestibular nuclei. Responses of 26 cells are similar to response of type II vestibular neurons and 14 units have a type III response; the 5 remaining cells were activated by vestibular stimulation in the vertical sagittal plane. The majority of these cells does not present detectable direct visual responses, but 50% can be driven by Optokinetic stimulation. 74 % of types I, II and III neurons show saccadic responses to vestibular nystagmic saccades in the dark. About 60% present similar saccadic modulations during Optokinetic nystagmus and 55% keep this response for spontaneous saccades in the dark or in front of a striped background. The saccadic responses are constant for a given neuron in all cases of stimulation with latencies ranging from 30 msec prior to the beginning of the saccade to 120 msec after its onset. The histological localization of these units falls on one hand into the caudal part of the RT nucleus (type III neurons) above the dorsal lateral geniculate nucleus and on the other hand within the internal subdivision of the LGv and its rostral limit (all other types). The significance of this new, saccadic and vestibular focus in the feline thalamus is discussed in relation with the two previously known vestibular thalamic relays in terms of interrelations between the vestibular and the visual systems.

Notizen: Summary Different areas of the frontal cortex of the cat were injected with small amounts of horseradish peroxidase. The regions of labeled cells in the mediodorsal nucleus of the thalamus (MD) were related to the injected areas. Distinct relations between subdivisions of MD and of the prefrontal cortex were established: a rather large central sector of MD projects to the gyrus proreus and to the anterior parts of the gyri sigmoideus, rectus, and frontalis. A narrow lateral band of anterior MD neurons projects predominantly to an area on both sides of the sulcus praesylvius, whereas a postero-lateral band sends fibers to a region on the ventral anterior sylvian gyrus. The area between the presylvian sulcus and the sylvian gyrus is apparently free of MD afferents, but not of other thalamic afferents. A fourth sector of MD, situated dorsomedially, projects to the middle parts of the gyri rectus and frontalis. And a fifth sector, located ventrally to the dorsomedial MD sector, projects to the ventral part of the gyrus rectus. The established subfields of MD and of the prefrontal cortex are discussed with respect to previous anatomical research in the cat.

Notizen: Summary 1. In the cat visual cortex (VC), electrophoretic glutamate application at a depth corresponding to layer VI may have excitatory or inhibitory effects on relay cells of the lateral geniculate nucleus (LGN). Corticofugal excitation was seen, if the receptive field centers (RFCs) of the VC neurons recorded at the application site were within 2.3 ° of the RFCs of the LGN neurons under test. Inhibitory effects were seen if the RFCs of both cells were further apart up to 3.1 °. Glutamate application at more superficial cortical sites had no effect on LGN-neuron activity. 2. Cross-correlation analysis between spontaneous activities of simultaneously recorded VC and LGN neurons revealed excitatory cortico-geniculate connections in 18 pairs with RFCs separated by less than 1.7 °. In 15 pairs the peak latency of the excitation was 2–5 msec (3.4 msec in the average), 3 pairs showed long cortico-geniculate latencies (13–18 msec). The existence of a fast and slow cortico-geniculate system is suggested. 3. Inhibitory cortico-geniculate interaction was demonstrated with cross-correlation analysis in 8 pairs of which 4 had RFCs separated by more than 1.7 °. The onset latency of the inhibition was 2–7 msec except for 2 pairs with about 20 msec latency. 4. Most of the LGN neurons which were affected by cortical glutamate application or which showed an excitatory or inhibitory connection with a VC neuron were sustained cells, while the majority of VC neurons which were recorded in the effective glutamate application sites or which showed a significant interaction with LGN neurons in the cross-correlogram were binocularly driven and complex, with mostly large RFCs (mean diameter 3.5 °). They responded briskly to moving small spots as well as to moving slits. 5. It is concluded that the corticofugal excitatory effect is transmitted through monosynaptic links from VC neurons located in layer VI (complex cell) to LGN relay neurons (mostly sustained-cell) and this system is organized in a precise topographical manner. 6. In an Appendix neuron pairs which showed a positive correlation in the geniculo-cortical direction were described. The findings may support the view that complex as well as simple cells are driven monosynaptically from geniculo-cortical afferents of the sustained or transient type.

Notizen: Summary In the anesthetized cat, the posterior canal nerve (PCN) was stimulated by electric pulses and synaptic responses were recorded intracellularly in the three antagonistic pairs of extraocular motoneurons. Pure reciprocal effects were obtained in the motoneurons innervating the antagonistic pair of ipsilateral oblique muscles and the antagonistic pair of contralateral vertical rectus muscles. These responses consisted of low threshold disynaptic excitatory postsynaptic potentials (EPSPs) in either the contralateral superior oblique (c-SO) (trochlear) or contralateral inferior rectus (c-IR) motoneurons and of disynaptic inhibitory postsynaptic potentials (IPSPs) in either the ipsilateral inferior oblique (i-IO) or ipsilateral superior rectus (i-SR) motoneurons. In addition, disynaptic IPSPs were also found in (i-SO) motoneurons. Mixtures of low threshold (dior trisynaptic) EPSPs and IPSPs were found in all other extraocular motoneurons except for the contralateral lateral rectus (c-LR) motoneurons. These results may afford a basis for the characteristic eye movements induced by vertical canal nerve stimulation.

Notizen: Summary 1. The activity of cat semicircular canal and otolith afferents was studied during yaw and roll rotations, respectively, to examine their dynamic behavior. 2. A sinusoidal analysis of the canal afferent activities showed that their dynamic characteristics are similar to those of second order vestibular neurons, except for a two to three-fold lower absolute gain. This agrees with earlier studies using angular acceleration steps. 3. Both divisions of the eighth nerve were sampled so as to examine afferents from both the utriculus and sacculus. Within the range of inputs used (± 25 degrees lateral tilt), the presumed saccular afferents (inferior division) showed either a γ- or β-response. However, the gain of their response was generally much less than for the afferents of the superior division (mostly utricular). This behavior is to be expected on the basis of receptor orientations and the components of gravity acting upon the macular receptors. 4. In response to ramp changes in angular position, some otolith units showed a phasic-tonic response pattern, i.e., an overshoot followed by an adaptation to a new steady state level of activity. The majority of units showed predominantly tonic responses proportional to displacement. 5. During sinusoidal rotations the predominantly tonic units showed small phase leads of 0 to 15 degrees at 0.025 Hz which remained constant or decreased to 0 to −15 degrees at 1.0 Hz. The gains were flat or increased by up to 2 fold. The phasic-tonic units showed greater phase leads, 10 to 50 degrees, and gains which increased from 2 to 8 fold. 6. This behavior of otolith afferents suggests that they can provide information about both the magnitude and the rate of change of linear acceleration stimuli.

Notizen: Summary 1. The electrical activity of single trochlear motoneurons (TMns) and axons of second order vestibular neurons presumably terminating on these motoneurons were studied during natural stimulation of semicircular canals and otolith organs in cats anesthetized with Ketamine. 2. Null point analysis showed that TMns received an excitatory canal input from the contralateral posterior canal, and labyrinthine lesion experiments suggested that the functionally synergistic, ipsilateral anterior canal provides an inhibitory input. A small number of motoneurons showed orthogonal canal convergence. 3. In addition to the canal projections most TMns received an otolithic input. Firing rate was proportional to lateral head tilt and was of the β type. Most units also responded to pitch with an increase and decrease in firing rate on nose-up and nose-down positioning, respectively. Lesion experiments indicated that the otolith responses are the results of reciprocal innervation of TMns by contralateral (excitatory) and ipsilateral (inhibitory) otolith projections. 4. During sinusoidal rotation in yaw (canal only stimulation) the mean phase lag re acceleration of the response of TMns increased from 60 ° at 0.025 Hz to 126 ° at 1.0 Hz. In roll (canal plus otolith stimulation) the phase lag of TMn responses measured 180 ° and 130 ° at 0.025 and 1.0 Hz, respectively. Phase-lags measured in Vi and Vc axons were less by ca. 15 °. 5. The otolith contribution to TMn responses in roll was calculated by vectorial subtraction of the yaw from the roll responses: A phase lag of 10 (0.025 Hz) to 90 ° (0.5 Hz) re. displacement was noted and gain was constant over the same range. Similar lag dynamics were revealed in TMns when studied during ramp displacement of the head. 6. The possible functional role of central canal-otolith convergence and the differences between the responses of primary vestibular afferents and secondary vestibular neurons and TMns will be discussed.

Notizen: Summary It is known that kittens reared in ways that restrict movement while visual stimulation is received exhibit deficits in visually guided behavior. Presumably, the behavioral dysfunction is due to a lack of sensorimotor coordination during visual exposure. The current investigation was undertaken to study this effect both physiologically and behaviorally. Two groups of kittens were normally reared until they were nearly 4 weeks old. They were then placed in a darkroom and exposed daily for 1–2 hours while one eye was occluded. On alternate days, alternate eyes were covered. One group was restrained in a body cast while a given eye was exposed, but the kittens were free to move about while the other eye received visual experience. A second control group was alternately occluded, but freely mobile during all exposures. An additional cat was also unrestrained during daily rearing periods and neither eye was ever occluded. Behavioral tests showed clear deficits when the “passive” eye of the restrained-unrestrained group was used. Deficiencies were found in visually guided paw placing, pursuit eye movements, and jumping behavior to a platform. Responses of single cells were studied in area 17 of the visual cortex. Ocular dominance distributions showed marked reductions in binocularity for alternate occluder cats. The eye that had received exposure while animals were active in the restrained-unrestrained group also tended to predominate but the difference was not statistically significant.

Notizen: Summary In the previous study it was shown that cats were capable of making rapid and accurate adjustments in the force they applied to a lever in accord with information provided by a compensatory display. In the present study, isometric responses were examined in greater detail to determine 1. if a general control policy (or model) governing responses of different magnitudes could be inferred from the relations among output parameters and 2. if the earliest output measures were scaled to the preceding sensory events. The force adjustments elicited by the sudden motion of the display showed a linear relation between the peak force and the peak of its first derivative, dF/dt. Similarly, the peak d2F/dt2 was a linear function of dF/dt. By contrast, the times required to achieve the peak force and the peak dF/dt were largely independent of their magnitudes. These adjustments were produced by a burst of EMG activity in agonist muscles which coincided with the rising phase of dF/dt. The observations suggest that such motor outputs are determined by a pulse-step control policy. The amplitude of the pulse would control the rate of rise of dF/dt (and therefore also the peak force since the rising phase of dF/dt was of constant duration), and the step would control the level of the terminal steady state force. Both the peak force and the preceding peak dF/dt were highly correlated with the amplitude of the perturbation. Changes in display gain, which altered the required relation between input and output magnitudes, resulted in a gradual readjustment of the output parameters. It was concluded that the motor outputs were scaled from their inception to requirements dictated by the initial sensory information. The selection by the cat of the appropriate scaling function was contingent upon its previous experience with the device.

Notizen: Summary A versatile tracking task has been developed to assess the competence of feline subjects in using sensory information to initiate and guide limb movement. In the present study we investigated the response latency and the factors which affect it in order to define temporal constraints on the underlying processing of information. The paradigm makes use of an electromechanical display of the difference between the output of transducers in a manipulandum (controlled by the cat) and a target level (controlled by the experimenter). Because of inertia and friction, a step change in target level required 230 msec to fully shift the display. The animals were trained to match the position of the manipulandum (or the force they applied to it isometrically) to the target level for a food reward. Target perturbations elicited rapid position or force adjustments of appropriate direction and magnitude at short latency. Under isometric conditions, the latency of the response was an inverse function of the extent of display motion and of the peak rate of force change attained during the adjustment. Asymptotic values of the response time, measured from the perturbation to the first change in force applied to the lever, were typically between 50 and 70 msec. Since the motor responses were invariably initiated while the display was still moving, the animals must have used information contained in the derivatives of its motion. In the absence of visual cues, deflection of the vibrissae by the sudden motion of the display provided two of the four animals with sufficient information to initiate and guide their movements without changes in response latency. When vision was allowed, section of the vibrissae produced a persistent increase in response times of 15–20 msec. This difference in latency is compatible with the delays due to retinal transmission. The short time interval elapsing between stimulus and response strongly suggests that the topography and the metrics of the underlying transformations are adjusted by gating and/or biasing processes which precede the stimulus. It is concluded that sensory information can generate purposeful movements through pathways which include only a small number of central relays in series, independently of its modality.

Notizen: Summary The current source density (CSD) method in its one-dimensional approximation is used to analyze the field potentials in visual areas 18 and 17 of the cat, which were elicited by stimulating electrodes in the optic chiasm (OX), the optic radiation (OR) or in the respective cortical area itself. The CSD analysis reveals the basic pattern of excitatory postsynaptic activity. 1. In both visual areas the basic specific excitatory activity flows along three different intracortical pathways, all starting in layer IV: The first pathway relays activity from layer IV to supragranular pyramidal cells via strong, local connections to layer III and from there through long-distance connections to layer II. The second pathway conveys activity from layer IV to layer V, where it mainly contacts apical dendrites of layer VI pyramidal cells. This infragranular polysynaptic activity is not clearly resolvable into separate components, suggesting that it is conveyed by various groups of axons, among them long-distance horizontal connections. The third pathway has one synaptic relay within layer IV and then conveys activity to layer III. In addition, monosynaptic activity is revealed in layers VI and I. 2. In A 18 one coherent, fast-conducting group of afferents induces this basic activity pattern. In A 17 no such fast conducting input is resolvable; the supragranular activity is induced by a small group of afferents with intermediate conduction velocity, which terminate in the upper part of layer IV. The infragranular activity is induced by afferents with slower and widely scattered conduction velocities, which terminate in the lower part of layer IV. The layer VI input is very prominent in A 17 and also has a wide latency scatter. 3. The supragranular activity is more prominent in A 18 than in A 17 and the respective layers appear thicker, in accordance with anatomy. In A 17 the infragranular activity prevails and layers IV and VI appear very broad, again in accordance with anatomy. 4. Comparison of the CSDs with the original evoked potentials shows that the surface evoked potentials over A 18 reflect the three dipolar sink/source distributions of the coherent monosynaptic activity in layer IV and of the two prominent polysynaptic activities in layers III and II. The widely scattered activity in the lower part of layer IV in A 17 and all infragranular activities in both areas generate smaller, partly closed-field potentials; those are not discernible from the strong far-field potentials which originate from the supragranular activity and — especially in A 17 —from farther distant events.

Notizen: Summary The distribution of the interhemispheric projection from area 17 and 18 was studied using the anterograde degeneration technique. Besides the classical visual areas (17, 18, 19), area 21 and several visual areas in the middle suprasylvian sulcus also received visual callosal input. In the four terminal areas of the middle suprasylvian sulcus the projection was found to be focused on representations of the vertical meridian including the area centralis, as in the classical visual areas. An increase of the width of visual field represented in the zone of callosal terminations can be seen from area 17 through area 18 to area 19 and possibly this trend continues in the suprasylvian visual areas.

Notizen: Abstract The effects of the ergolene derivatives bromocriptine, dihydroergotoxine, methysergide, d-LSD, CF 25-397, and 29-712 on the metabolism of the biogenic amines in the brain of the rat were investigated. All six ergolene derivatives were found to increase the concentration of 4-hydroxy-3-methoxyphenylethylene glycol sulphate in the brain stem, i.e., to increase the turnover of noradrenaline (NA). Since in brain homogenates the agents inhibited the binding of 3H-dihydroergocryptine to α-adrenoceptors, but only weakly inhibited the binding of 3H-alprenolol to β-adrenoceptors, it is suggested that the increased turnover of NA may be a consequence of a blockade of α-adrenoceptors by ergolenes. All of the ergolenes increased the concentration of serotonin (5-HT) in the cortex, but only bromocriptine and 29-712 increased the concentration of 5-hydroxyindoleacetic acid (5-HIAA), the other compounds decreasing the concentration of this metabolite, i.e., inhibiting 5-HT turnover. Reserpine-induced PGO waves in the cat were inhibited by all six compounds, bromocriptine and 29-712 being the least active. Both of these findings suggest that the ergolenes possess serotonergic activity. The increase in the concentration of 5-HIAA after bromocriptine and 29-712 may be secondary to some action on other systems. The actions of the ergolenes on the metabolism of dopamine (DA) in the striatum are more complex. Bromocriptine, 29-712, and, to a much lesser extent, dihydroergotoxine reduced the concentration of 3,4-dihydroxyphenylacetic acid (DOPAC), i.e., they inhibited DA turnover. These findings are compatible with the proposed dopaminergic activity of the drugs. CF 25-397 caused a slight increase in the DOPAC concentration at high doses, and d-LSD and methysergide caused pronounced increases. At doses below 1 mg/kg i.p., d-LSD decreased the DOPAC concentration. This biphasic effect of d-LSD may be due to interaction with different types of DA receptors or may reflect some secondary action of the compound. The profiles of activity of the various ergolenes are discussed. Bromocriptine and 29-712, wich have similar profiles of activity, can be clearly differentiated from the other ergolenes. CF 25-397 seems to be a potent and, at low doses, specific serotonergic drug.

Notizen: Abstract The effect of the new 1,5-benzodiazepine clobazam on visual evoked potentials (VEP) and spontaneous EEG in the conscious rabbit and on spinal polysynaptic reflexes in the decerebrated cat was studied in comparison to the 1,4-benzodiazepine diazepam. Clobazam was half as potent as diazepam in depressing the amplitude of visual evoked potentials in the nonanaesthetized rabbit, whereas the depressing effect on spinal polysynaptic reflexes in the decerebrated cat was only 1/7–1/30 of the diazepam effect. The action of clobazam and diazepam on VEP also showed differences in time course, i.e., the peak effect of clobazam lasted from 1 to 6 h after application, whereas the effect of diazepam appeared after 10min and declined already after 1 h. Both compounds had similar effects on computer-analyzed spontaneous EEG in the rabbit (power spectrum analysis), with an increase of power in the beta-band (13–39 Hz) and a decrease in the alpha (8–13 Hz) and theta (4–8 Hz) bands.

Notizen: Summary Following stereotactically performed lesions in nucleus reticularis tegmenti pontis (N.r.t.) degenerating fibers are traced to the contralateral N.r.t., to the pontine nuclei, through brachium pontis to restricted areas of the cerebellar nuclei and to most parts of the cerebellar cortex where they terminate in the granular layer. Most degenerating fragments are found in the contralateral half of the cerebellum with the greatest density in the vermal lobules VI and VIIA and in the flocculus. Following injections of HRP in the various cerebellar lobules labeled cells are mainly present within limited groups in the N.r.t.. Injections in vermal lobules VI-VIII B give rise to labeled cells within circumscribed areas in the dorsal and ventral parts throughout the rostrocaudal extent of the N.r.t.. In cases with injections in lobule IX or the ventral paraflocculus labeled cells are found ventrally in the rostral half of the N.r.t., while following injections in the vermal lobules I-V labeled cells are mainly found in the ventral and caudal part of the N.r.t.. Following injections in the intermediate and lateral parts of the anterior lobe, Crus I and II, the paramedian lobule and the dorsal paraflocculus labeled cells occur within groups in medial and lateral parts throughout the rostrocaudal extent of the N.r.t.. Following injections in the flocculus labeled cells are found in a very distinct group in the dorsal and rostral part of the N.r.t., While an injection in the nodulus (lobule X) gave rise to a smaller group of labeled neurons in the dorsolateral corner in the caudal part of the N.r.t.. Labeled cells within processus tegmentosus lateralis (p.t.l.) are only found following injections in lobules VI-VIIIA, Crus I and II and the dorsal paraflocculus. From what is known about afferents to the N.r.t., it is concluded that no cerebellar lobule gets information from one only of these sources via the N.r.t.. Visual information can probably be mediated from the superior colliculus via the N.r.t. to the flocculus and to a minor extent to the vermal lobules VI-VIII B, and from the pretectum via the N.r.t. to both vermal and lateral parts of the cerebellum.

Notizen: Summary The light microscopical morphology and proteinase activities are studied during the first phases of implantation in the cat, i.e. at 12, 13 and 14 days post coitum (d.p.c.). Timed matings are used to obtain exact data on the time course of implantation events. Size and shape of the blastocysts and the topographical relationships between trophoblast, zona pellucida and endometrium are studied on cryostat sections. These observations indicate that the zona pellucida is being removed at 12 d p.c. by dissolution which starts at the abembryonic pole and lateral of the embryonic disc. Since the zona has, in spite of the considerable expansion of the blastocyst, a thickness of 8–10 μm at this stage, it must have undergone a process of swelling or material must have been added invisibly. Invasion of the trophoblast into the endometrium begins between 13 and 14 d p. c. and is fully under way at 14 d p. c. Widening of the glandular lumina in the neighborhood of the blastocysts at 12–13 d p.c. indicates an early preimplantation interaction between the blastocyst and the endometrium. Amino Acid Arylamidase (Aminopeptidase) activity is found, in histochemical tests, to be high in the trophoblast but low in the endometrium in all three investigated stages. Proteinase Activity is studied with a highly sensitive gelatin substrate film test. Moderate to medium activity is found in the trophoblast at 12–13 d p.c. Very high proteinase activity is present in the invasion zone at 14 d p.c. Experiments with a large number of specific proteinase inhibitors in vitro and preliminary investigation of pH dependence show that it is mainly due to a cathepsin-B-like endopeptidase. This enzyme can be traced to both the trophoblast and the uterine epithelium. The disintegrating zona pellucida shows, at 12 d p.c., only little gelatinolytic proteinase activity. A trypsin-like endopeptidase as described for the rabbit blastocyst could not be identified with certainty in the cat but there is some indication that it might be present at 12 d p.c. Considerable trypsin-like proteinase activity is found in scattered endometrial stroma cells at all stages. The possible physiological role of the described proteinases in implantation is discussed.

Notizen: Summary The blood, yolk sac, liver, spleen, and bone marrow from 65 timed embryos of 22 cats were examined using light microscopic means in six different age categories. Nucleated primitive erythroblasts derived from the yolk sac are mature by the 19th day and represent 98% of the circulating blood cells, some of them found circulating even at birth. Definitive yolk sac erythropoiesis comprises a span of up to 30 days. On the 36th day, hematopoietic contribution drops to 15%. Neutrophils and the first thrombocytes are present on the 17th day, eosinophils and lymphocytes by the 25th day. Hepatic hematopoiesis most likely begins with definitive erythropoiesis on abouth the 20th day; granulopoiesis occurs in the liver on the 25th day. Blood forming tissue in the liver amounts to 28% which drops to 4% at birth. Splenic hematopoiesis begins on about the 36th day but contributes little to the blood. Bone marrow activity begins at mid-term and supplies about 50% of the blood cells on the 45th day. Hematocrit values increase from 22% on the 36th day to 47% at birth, thus exceeding the normal value of adult cats. The red blood cell number increases from 0.8 million/mm3 on the 25th day to 3.8 million on the 45th day and 6.3 million at birth. The total leukocyte count (880 on the 45th day and 6.480 at birth) must be calculated from the differential count of nucleated cells. Primitive erythroblasts represent the most common nucleated cells on the 25th day; on the 36th and 45th day, definitive erythroblasts predominate, but are outnumbered by leukocytes at birth. On the 36th and 45th day, lymphocytes are the predominating cell type in the white blood picture. The contribution of the hematopoietic organs to the feline prenatal blood formation is shown graphically.

Notizen: Summary The Golgi architecture of the Fascia dentata and hippocampus is described in the cat. The main cell types are like those found in other species. The initial collaterals of granule cell axons were demonstrated and are commented on. The interneurons proved to be of several types and subtypes not observed in lower species. The intrinsic fibers and few of the afferents — both in the dentate fascia and in the hippocampus — are discussed.

Notizen: Summary Electronmicroscope studies have been performed on the greater splanchnic nerve and the nerve to the medial head of gastrocnemius muscle of control and acrylamide poisoned cats. Degeneration of unmyelinated as well as of myelinated fibres was observed in both nerves. In cats severely poisoned with acrylamide, some very large unmyelinated axons undergoing early degeneration were seen in the splanchnic nerve. In the nerve to medial head of gastrocnemius, there was a decrease in the proportion of large diameter unmyelinated axons.

Notizen: Summary An 18 month old cat had a 6 month history of abnormal high stepping gait, ataxia, muscle twitching and loss of sensory perception. The clinical course was interrupted by several episodes of temporary remission. The essential pathological features were those of a polyradiculoneuritis with segmental demyelination, focal mononuclear cell infiltration and hypertrophic onion-bulb formations. The condition is compared with chronic relapsing polyradiculoneuritis in the dog and in man.

Notizen: Summary A method based on an intracerebral coordinate system and contrast ventriculography was developed for Stereotaxic surgery in the cat. The intercommissural (CA-CP) line was used as the principal reference because its length showed little variability in animals within a wide weight range. The Stereotaxic coordinates of the substantia nigra (SN) in relation to the CA-CP line and the midline were evaluated in serial sections. Stereotaxic operations with the use of ventricular radiography were performed in different parts of the SN in 18 cats. Histological verification showed that the selected target regions within the SN were very accurately reached in all animals operated with this method. The precision of the Stereotaxic method based on the intracerebral coordinate system compared to the Horsley-Clarke method is discussed.

Notizen: Summary Light microscopic autoradiography and electron microscopy were used to trace the nigrothalamic projections and to study the sites of termination of this pathway in the cat. Injections of tritiated amino acids or electrolytic lesions were placed in the substantia nigra pars reticularis (SNr). An accumulation of radioactivity was found in the ventral medial nucleus and in the ventromedial part of the ventral anterior nucleus. At the ultrastructural level degenerating medium size synaptic boutons and medium size myelinated fibers were observed in these nuclei. The boutons contained clear pleomorphic vesicles and formed symmetrical type synaptic contacts with regular type dendrites and vesicle-containing dendrites. The present findings indicate that the ventral medial nucleus is the principal site of termination of nigrothalamic projections in the cat.

Notizen: Abstract Complete vascular isolation of the hindlimbs was performed in vagotomized cats under Sodium Pentobarbital anesthesia. The hindlimbs were perfused at constant flow with blood kept at a constant and physiological $$P_{0_2 }$$ , $$P_{{\text{C}}0_2 }$$ , and pH values by means of a specially designed pump-oxygenator system. The animals were hyperventilated with different CO2 mixtures (0%, 5%, 7% and 10% in O2) thereby changing blood gases and pH levels in the upper body but not in the hindlimb vascular bed. At body $$P_{{\text{aC}}0_2 }$$ (mm Hg) of 13.7 ±1.0 (means±SE), 30.6±1.05, 40,4±0,9 and 58.4 ±2.9 the hindlimb perfusion pressure (mm Hg) was, respectively 124±7.6, 138±7.4, 156±11.9 and 187 ±15.1. These changes in perfusion pressure were still present after complete peripheral chemoreceptor denervation but were abolished after section of the spinal cord at the T5 level. Since hindlimb perfusion pressure fell when body $$P_{{\text{aC}}0_2 }$$ was lowered below physiological levels it is concluded that part of the neurogenic vascular tone of the hindlimbs is maintained by a CO2 mediated stimulation of supraspinal structures.

Notizen: Abstract The cervical vagus nerve (VN) was electrically stimulated in Nembutal-anaesthetized cats. The responses recorded from the cerebellar surface were found in lob. V and VI in a bilateral sagittal strip perpendicular to the longitudinal axis of the folia. At a longer latency, potentials were also found in the paramedian lobule. Field potential analysis confirmed the existence of a sagittal strip in the deep parts of the lobules. The distribution of these potentials and their field potential profiles indicate that they are transmitted through the climbing fiber (CF) system. Experiments with local anaesthetics and deafferentation support our view that the potentials described in the vermis by Dell and Olson (1951) could be originated extracerebellarly. A strong parallelism was found between the amplitude of the cerebellar responses and the amplitude of the group B1 component of the vagal afferent potentials, having a conduction velocity between 4 and 20 m/s. The pathway by which the vagal afferents reach the inferior olive and the functional significance of these afferents are discussed.

Notizen: Summary The presence and distribution of myocardial α-adrenoceptors in different parts of the heart of various mammalian species was investigated. For this reason experiments were performed in isolated cardiac preparations of rats, guinea pigs and cats. In order to obtain more information about the nature of the cardiac α-adrenoceptors additional experiments were undertaken at different temperatures. These studies were aimed to show whether or not a conversion of β-to α-adrenoceptors or vice versa takes place. Moreover, we analyzed the influence of hypothyroidism on the sensitivity of α- and β-adrenoceptors of preparations from rats fed with propylthiouracil. Finally, we tried to find out whether stimulation of these α-adrenoceptors leads to the formation of the cyclic nucleotides cAMP and cGMP. The following results were obtained: 1. In right ventricular strips of rats, guinea pigs and cats phenylephrine stimulated α-adrenoceptors. After blockade of β-adrenoceptors the respective pD2-values of phenylephrine were 5.32, 5.99 and 5.33. The doseresponse curves obtained in the presence of α-adrenolytic drugs were shifted to the right without depression of the maximum. In the rat, in addition, the pA2-values for the α-adrenolytic drugs yohimbine (5.79) and phentolamine (7.85) were determined. They were at least 0.5 log units higher than those found in the rat for other α-adrenoceptors (Van Rossum, 1965) thus supporting the view that the population of cardiac α-adrenoceptors is different from that of other organs. In left ventricular strips of guinea pigs the pD2-value for the α-mimetic effect of phenylephrine was of the same order of magnitude as that obtained in the right ventricle. 2. In the papillary muscle of the right ventricle of guinea pigs and cats phenylephrine stimulated α-adrenoceptors. 3. In the left atrium of the rat, phenylephrine stimulated myocardial α-adrenoceptors (pD2: 5.58). Also in this preparation the pA2-values for yohimbine (6.36) and phentolamine (8.21) were different from those found for other α-adrenoceptors in the rat (Van Rossum, 1965). Likewise in strips from the left atrium of the cat myocardial α-adrenoceptors are present. 4. In spontaneously beating right atria of the rat a clear-cut positive chronotropic effect mediated by stimulation of α-adrenoceptors could not be demonstrated although in 6 out of 15 preparations a small positive chronotropic effect became evident. No positive chronotropic effect at all was obtained by stimulation of α-adrenoceptors in the cat right atrium. 5. In ventricular strips as well as in left atria from hypothyroid rats the pD2-value for the α-effect of phenylephrine was increased, in the atrium more than in the ventricle, while the pA2-values for yohimbine and phentolamine were not significantly different from the controls. Under these conditions a distinct positive chronotropic effect mediated by stimulation of α-receptors was found in the spontaneously beating rat atrium. 6. After stimulation of α-adrenoceptors in atria and ventricular strips of normal and propylthiouraciltreated rats, as well as in strips of guinea-pig ventricles or cat atria no elevation of cAMP and cGMP was observed. 7. The concept of a single adrenoceptor convertible from α- to β-type or vice versa was not supported by our experiments. These were carried out at different temperatures on left atria and on ventricular strips of rat hearts using the irreversible α-adrenoceptor blocking agent phenoxybenzamine. 8. The present experiments provide evidence for the existence of α-adrenoceptors in the myocardium of various mammalian species. Their stimulation produces positive inotropic effects without increases in heart rate.

Notizen: Summary Gene frequency surveys conducted in Alexandria and Cairo reveal genetic profiles which are extensions of those that characterize the cat populations of European cities. For nine selected comparisons with Alexandria, regression analysis indicates that a linear function best describes the relationship between Nei's and Cavalli-Sforza's genetic distance indices and geographic distance.

Notizen: Summary Following selective activation of four afferent paths that terminate exclusively on dendrites, only a small proportion of pyramidal cells in the hippocampal fields CA1 and CA3 discharged impulses. Following a single afferent volley, an EPSP was never observed even in cells synaptically excited. On tetanic stimulation (about 10/sec), a large EPSP developed, but this was not a prerequisite for an action potential. Studies of the extracellular field potentials corresponding to the EPSP and the population spike potential, indicated that the EPSP was generated across the dendritic membrane and that the spike was initiated in the neighbouring part of the dendritic tree, propagating from there along the thicker dendrites towards the soma. This conduction had an average velocity of 0.4m/sec, and, presumably, a relatively low safety factor. In certain cases, the intrasomatic electrode recorded small all-or-nothing spikes which presumably were generated in the dendritic tree. These small spikes (D-spikes) invaded the soma only if assisted by some additional depolarization, for example by frequency potentiation of excitatory synapses. The results indicate two functional types of pyramidal dendrites, the conducting and the synaptic type.

Notizen: Summary 1. Extracellular microelectrode recording has been employed to study the responses of three types of interneurones in the cat cerebellar cortex: basket cells, superficial stellate cells and Golgi cells. The large unitary spike potentials of single cells were sharply localized and presumably were generated by impulse discharges from the cell somata. The characteristics of their responses described below sharply distinguished them from Purkinje cells. 2. The parallel fibre volleys generated by surface stimulation of a folium evoked brief repetitive discharges that were graded in respect of frequency and number. Maximum responses had as many as 10 impulses at an initial frequency of 500/sec. 3. At brief test intervals there was facilitation of the response to a second parallel fibre volley; at about 50 msec it passed over to depression for over 500 msec. 4. Stimulation deep in the cerebellum in the region of the fastigial nucleus (juxta-fastigial, J.F.) evoked by synaptic action a single or double discharge, presumably by the mossy fibre-granule cell-parallel fibre path, but climbing fibre stimulation from the inferior olive also usually had a weak excitatory action evoking never more than one impulse. 5. J.F. stimulation also had an inhibitory action on the repetitive discharge evoked by a parallel fibre volley. Possibly this is due to the inhibitory action of impulses in Purkinje cell axon collaterals. 6. There was a slow (7–30/sec) and rather irregular background discharge from all interneurones. The inhibitory actions of parallel fibre and J.F. stimulation silenced this discharge for some hundreds of milliseconds, probably by Golgi cell inhibition of a background mossy fibre input into granule cells. 7. All these various features were displayed by cells at depths from 180 to 500 μ; hence it was concluded that superficial stellate, basket and Golgi cells have similar properties, discrimination being possible only by depth, the respective depth ranges being superficial to 250μ, 250μ to 400μ, and deeper than 400μ.

Notizen: Summary 1. When electrical stimuli were applied to the surface of a cerebellar folium by a local electrode (LOC), there was a propagated potential wave along the folium with a triphasic (positive-negative-positive) configuration. 2. Investigations by microelectrode recording established that this wave is produced by impulses propagating for at least 3 mm and at about 0.3 m/sec along a narrow superficial band or “beam” of parallel fibres. As expected from this interpretation, there was an absolutely refractory period of less than 1 msec and impulse annihilation by collision. 3. Complications occurred from the potential wave forms resulting from the excitation of mossy fibres by spreading of the applied LOC stimulus. These complications have been eliminated by chronically deafferenting the cerebellum. 4. When recording within the beam of excited parallel fibres there was a slow negative wave of about 20 msec duration, and deep and lateral thereto, there was a slow positive wave of approximately the same time course. 5. These potential fields were expressed in serial profile plots and in potential contour diagrams and shown to be explicable by the excitatory and inhibitory synaptic action on Purkinje cells: excitatory depolarizing synapses of parallel fibre impulses on the dendrites; and hyperpolarizing inhibitory synapses of stellate and basket cells respectively on the dendrites and somata. The active excitatory synapses would be strictly on the parallel fibre beam and the inhibitory concentrated deep and lateral thereto, which is in conformity with the axonal distributions of those basket and stellate cells that would be excited by the parallel fibre beam. 6. Complex problems were involved in interpretation of slow potentials produced by a second LOC stimulus at brief stimulus intervals and up to 50 msec: there was a potentiation of the slow negative wave, and often depression of the positive wave deep and lateral to the excited beam of parallel fibres. 7. Often the LOC stimulus evoked impulse discharge from the Purkinje cells, these discharges being inhibited by a preceding LOC stimulus.

Notizen: Summary Spontaneous post-synaptic potentials (PSP's) of neurones of the motor cortex are analysed (intracellular recording, Nembutal anesthesia, cats). Distinct EPSP's either appear grouped or more sporadically distributed. Spontaneous EPSP's only represent about 3–10% of all spontaneous PSP's. The mean amplitude of EPSP's is about 0.7 mV. The smallest EPSP's have an amplitude of 150–200 μV, smaller slow fluctuations of the membrane potential (MP) are seen occasionally. Amplitude histograms of spontaneous EPSP's are similar to those of evoked EPSP units following weak thalamic stimulation. — The rising time of spontaneous EPSP's varies between 2 and 15 msec. and is not correlated with the peak amplitude. The decay is almost exponential, the time constant is between 8 and 12msec., thus being slightly higher than the neurone time constant of cortical pyramidal cells (8.5±2.2 msec. Creutzfeldt et al., 1964b). No consistant differences in time course and amplitude of “EPSP units” after VL and CM thalamic stimulation and of spontaneous EPSP's was found. Cortical and thalamic components of post-tetanic depression of spontaneous and evoked PSP activity cannot be distinguished. Interval histograms are different whether all EPSP's during sporadic and grouped activity or whether only sporadically appearing EPSP's are counted. Non-grouped EPSP's show longer mean intervals (between 70 and 80 msec.). — During reversible deafferentation with K+-depolarization of afferent fibers and in the chronically isolated cortex no spontaneous EPSP's or IPSP's are found eventhough membrane fluctuations of cells in the latter preparation may sometimes be difficult to distinguish from real EPSP's. In the chronically isolated cortex, EPSP's and IPSP's can still be elicited by epicortical stimulation. — From these findings it is concluded that the observed spontaneous PSP's represent “unit” EPSP's and IPSP's due to afferent and collateral fiber activity and that no true miniature potentials due to spontaneous liberation of transmitter substance can be recorded. Thus, the “synaptic noise” of cortical neurones represents convergent activity on these cells and consequently cannot be considered as true “spontaneous noise”.