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  • 1
    Electronic Resource
    Electronic Resource
    Light microscopical study of dendrites and perikarya of interneurones mediating la reciprocal inhibition of cat lumbar alpha-motoneurones (1990)
    Springer
    Anatomy and embryology 181 (1990), S. 381-388 
    Details
    ISSN: 1432-0568
    Keywords: Ia interneurones ; Dendrites ; Horseradish peroxidase ; Intracellular injection ; Light microscopy ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Interneurones which mediate disynaptic inhibition from la muscle spindle afferents of the quadriceps nerve to lumbar alpha-motoneurones were stained with intracellular injection of horseradish peroxidase. Seven best stained and most satisfactorily preserved cells were selected for analysis, and the light microscopic morphology of their cell bodies and dendrites were quantitatively investigated in parasagittal sections. The perikarya were located dorsal or dorso-medial to the motoneurones; they had mean diameters of 51 × 27 μm and a mean volume of 35820 μm3. The cells had 3 to 7 dendrites, which were arranged asymmetrically around the parent somata. The dendrites extended mainly in the dorso-ventral direction, in which the mean tip to tip distance for each cell was 1742 μm. The dendrites had few spines and they branched almost only in bifurcations. On the average, each process divided 3.5 times and in each cell they gave rise to 14.9 branching points as well as a total combined length of more than 7000 μm. Primary dendrites had a mean length of 193 μm which was generally shorter than the lengths of the branches of higher order. A more detailed analysis of two cells revealed the mean width of primary dendrites to be 5.6 μm while that of the 5th order processes was 1.5 μm. The mean tapering of individual dendritic branches per unit length was 17%, being somewhat more pronounced for the distally located segments, while at branching points the sum of daughter processes approximately equalled the diameter of the parent process. The surface area and volume of the dendrites constituted 90% and 83% of the total surface area and 46% and 37% of the total volume of the two cells, respectively, excluding the axons. The Ia interneurones differed considerably among themselves with respect to the quantitively investigated parameters. They resembled the inhibitory Renshaw cells of the cat with regard to the number of dendrites, the poverty of spines, and the relationships between cell body diameter and width of primary dendrites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186910
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  • 2
    Electronic Resource
    Electronic Resource
    Depression of transmission from group II muscle afferents by electrical stimulation of the cuneiform nucleus in the cat (1995)
    Springer
    Experimental brain research 105 (1995), S. 25-38 
    Details
    ISSN: 1432-1106
    Keywords: Cuneiform nucleus ; Synaptic transmission ; Spindle afferents ; Spinal cord ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of short trains of electrical stimuli applied within the cuneiform nucleus and the subcuneiform region were examined on transmission from group I and group II muscle afferents to first-order spinal neurons. Variations in the effectiveness of transmission from these afferents were assessed from changes in the sizes of the monosynaptic component of extracellular field potentials evoked following stimulation of muscle nerves. Field potentials evoked from group II muscle afferents in the dorsal horn of the midlumbar and sacral segments and in the intermediate zone of the midlumbar segments were reduced when the test stimuli applied to peripheral nerves were preceded by conditioning stimulation of the cuneiform nucleus or the subcuneiform region. The depression occurred at conditioning-testing intervals of 20–400 ms, being maximal at intervals of 32–72 ms for dorsal horn potentials and 40–100 ms for intermediate zone potentials. At the shortest intervals, both group II and group I field potentials in the intermediate zone were depressed. Conditioning stimulation of the cuneiform nucleus depressed group II field potentials nearly as effectively as conditioning stimulation of the coerulear or raphe nuclei. We propose that the nonselective depression of transmission from group I and II afferents at short intervals is due to the activation of reticulospinal pathways by cells or fibers stimulated within the cuneiform area. We also propose that the selective depression of transmission from group II afferents at long intervals is mediated at least partly by monoaminergic pathways, in view of the similarity of the effects of conditioning stimulation of the cuneiform nucleus and of the brainstem monoaminergic nuclei and by directly applied monoamines (Bras et al. 1990). In addition, it might be caused by primary afferent depolarization mediated by non-monoaminergic fibers (Riddell et al. 1992).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242179
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  • 3
    Electronic Resource
    Electronic Resource
    A long propriospinal system with direct effect on motoneurones and on interneurones in the cat lumbosacral cord (1974)
    Springer
    Experimental brain research 21 (1974), S. 169-194 
    Details
    ISSN: 1432-1106
    Keywords: Stimulation ; Spinal cord ; Propriospinal neurones ; Lumbosacral motoneurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Stimulation of the lateral funicle was performed at different segmenta levels in the cat in order to investigate the connecxions of long propriospinal neurones with ipsilateral lumbosacral motoneurones and interneurones projecting directly to them. In one series of experiments the propriospinal contribution was assessed from the difference between the effect of maximal stimulation in C 1 (activating supraspinal descending fibres) and in more caudal segments (activating supraspinal and propriospinal fibres). In another series on cats with chronic hemisection in C 3 pure propriospinal effects were evoked by stimulation of the thoracic spinal cord. In both series it was shown that volleys in long propriospinal neurones evoke monosynaptic EPSPs and disynaptic EPSP and/or IPSP in many flexor and extensor motoneurones; an extracellular monosynaptic focal synaptic potential was recorded in lamina VII of Rexed. The effects evoked by stimulation of the Th 11 segment after chronic C 3 hemisection were not found after chronic Th 10 hemisection. It is therefore tentatively suggested that they were due to stimulation of long descending propriospinal neurones originating in the lower cervical and upper thoracic segments, their axon trajectory being in the middle of the lateral funiculus and conduct at velocity 100 m/sec. Other effects evoked by stimulation of Th 11 after chronic Th 10 hemisection are ascribed to antidromic activation of axons of ascending neurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234388
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  • 4
    Electronic Resource
    Electronic Resource
    Projection of individual pyramidal tract neurons to lumbar motor nuclei of the monkey (1979)
    Springer
    Experimental brain research 34 (1979), S. 73-89 
    Details
    ISSN: 1432-1106
    Keywords: Motor cortex ; Monkey ; Corticospinal projections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The projection of individual pyramidal tract (PT) neurons from the hindlimb area in the precentral gyrus of the cerebral cortex to the lumbar spinal cord was studied in the monkey by systematically searching for sites within identified regions of the spinal gray from which the PT neurons could be antidromically activated by local stimulation. All investigated neurons belonged to the fast conducting fraction of PT neurons. The following results were obtained. 1. Each PT neuron could be activated from more than one region of the spinal gray matter, including identified spinal motor nuclei and areas dorsomedial to these nuclei, but not the intermediate nucleus or regions dorsal to it. “Passage areas” and “termination areas” were defined. 2. Half of the PT neurons with termination areas within motor nuclei had these areas in more than one nucleus. There were thus strong suggestions for synaptic contacts of some PT neurons with motoneurons of more than one muscle. 3. Four groups of three or four neurons were recorded simultaneously by the same cortical electrode. Comparisons of passage and termination areas within groups revealed both similarities and differences in projections of neighboring neurons. Every neuron was activated from some region(s) where others of the group were not. Common passage areas, or passage and termination areas, for two or three neurons of a group within at least one motor nucleus were found for all groups. Termination areas in the same motor nucleus have been found for the majority of the neurons of only one group. These common projection areas are compatible with, but do not prove, that a group of adjacent PT neurons has common target cells in the spinal cord.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238342
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  • 5
    Electronic Resource
    Electronic Resource
    The rubrospinal tract. IV. Effects on interneurones (1972)
    Springer
    Experimental brain research 15 (1972), S. 54-78 
    Details
    ISSN: 1432-1106
    Keywords: Red nucleus ; Rubrospinal tract ; Lumbosacral interneurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The effect of stimulation of the red nucleus on interneurones in the dorsal horn and intermediate region in the lower lumbar spinal cord has been investigated in cats. It has been ascertained that the effects are mediated by the rubrospinal tract. 2. Extracellular monosynaptic focal potentials evoked by single volleys in the rubrospinal tract were recorded in Rexed's layer VI and VII from a region partly overlapping with that in which focal potentials from group I muscle afferents are evoked, but extending more ventrally. 3. Monosynaptic excitatory action from the rubrospinal tract (recorded in 60 of 340 interneurones) was found in two main categories of interneurones: a) cells monosynaptically activated or disynaptically inhibited from group I muscle afferents and b) cells di- or polysynaptically activated from the flexor reflex afferents or exclusively from cutaneous afferents. The cells under a) are located more dorsally than those under b) but both within the region in which rubral focal monosynaptic potentials are recorded. There was no evidence suggesting that rubrospinal fibres have monosynaptic connexions with interneurones not influenced from primary afferents. 4. Many of the group I interneurones in the intermediate region are without monosynaptic connexions from the rubrospinal tract as are the dorsal horn cells monosynaptically activated from cutaneous afferents and dorsally located cells which do not receive monosynaptic connexions from primary afferents but are polysynaptically activated from the FRA. 5. Late (di- or polysynaptic) excitatory, inhibitory or mixed postsynaptic rubral effects are common and were found in interneurones with or without monosynaptic connexions from primary afferents but receiving similar effects from the FRA. The occurrence of spatial facilitation between peripheral nerves and the rubrospinal tract in evoking late PSPs suggests that the late rubral PSPs are evoked by activation of interneurones transmitting actions from primary afferents. 6. Some consequences of the conjoint control of interneurones from primary afferents and the rubrospinal tract are discussed. The monosynaptic effects from the rubrospinal tract are considered in relation to the rubral control of Ib reflex pathways and to the disynaptic rubromotoneuronal PSPs evoked by monosynaptic activation of last order interneurones of polysynaptic reflex pathways from primary afferents. The late rubral effects on interneurones are discussed in relation to interactive mechanisms between segmental interneuronal pathways. Rubrospinal and corticospinal effects are compared. This work was supported by the Swedish Medical Research Council (Project No. 14X-9407C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234958
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  • 6
    Electronic Resource
    Electronic Resource
    Effects from the sensorimotor cortex on the spinal cord in cats with transected pyramids (1967)
    Springer
    Experimental brain research 3 (1967), S. 117-134 
    Details
    ISSN: 1432-1106
    Keywords: Supraspinal effects ; Extrapyramidal pathways ; Spinal activity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Effects of stimulation of the sensorimotor cortex on activity of the lumbosacral cord were studied in pyramidotomized cats. The following actions initiated by corticofugal volleys were found: 1. postsynaptic effects on motoneurones, mainly excitatory in flexor motoneurones and inhibitory or excitatory in extensor motoneurones, 2. facilitation of spinal reflexes to motoneurones at an interneuronal level, 3. depolarization of presynaptic terminals of group Ib and cutaneous fibres. The latencies of the earliest cortical effects on motoneurones as indicated by modification of monosynaptic reflexes or PSPs were 9–12 msec. Experiments with lesions of different spinal tracts suggest that the effects on motoneurones are mediated mainly by pathways in the ventral part of the lateral funiculus (probably reticulospinal), the facilitation of reflex transmission by pathways in the dorsal part of the lateral funiculus (probably rubrospinal) and primary afferent depolarization by both the former and the latter pathways. The strongest cortical effects were evoked by stimulation of an area around the postcruciate dimple.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233257
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  • 7
    Electronic Resource
    Electronic Resource
    Integration in descending motor pathways controlling the forelimb in the cat (1981)
    Springer
    Experimental brain research 42 (1981), S. 269-281 
    Details
    ISSN: 1432-1106
    Keywords: Reticulospinal fibres ; Cortico-, rubro-, tectospinal tracts ; C3-C4 propriospinal neurones ; Forelimb motoneurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Effects of stimulation in the medullary reticular formation (RF) on C3-C4 propriospinal neurones (PNs) were investigated in two series of experiments: (1) indirectly by analyzing how propriospinal transmission to forelimb motoneurones is modified by reticular stimuli; (2) directly by intracellular recording from C3-C4 neurones, which were identified as propriospinal by their antidromic activation from the C6 segment. Propriospinally mediated disynaptic EPSPs evoked in motoneurones from the pyramid (Pyr) and the red nucleus (NR) were effectively facilitated by conditioning stimulation in the RF with a time course of facilitation indicating monosynaptic linkage to the PNs. Propriospinally mediated trisynaptic IPSPs were facilitated less regularly and sometimes instead depressed by conditioning stimulation in the RF. The depression is at least partly due to inhibition of the first order PNs. Recording from C3-C4 PNs revealed that many of them were excited or inhibited by single stimuli in the RF. The brief latency of the EPSPs evoked in these neurones shows monosynaptic linkage from fast reticulospinal fibres. Some IPSPs were similarly monosynaptically evoked from fast fibres and observations are presented suggesting that longer latency IPSPs are monosynaptically mediated by slower fibres. Facilitation of propriospinal transmission to motoneurones as well as the EPSPs and IPSPs in PNs were evoked from a region within or close to the nucleus reticularis gigantocellularis. Convergence of monosynaptic EPSPs from Pyr, NR, tectum, and RF was common in C3-C4 PNs. Linear summation of the EPSPs from RF with those evoked from cortico-, rubro-, or tectospinal tracts shows that the former are not due to stimulation of collaterals which the latter tracts may have in RF. Mediation of the EPSPs and IPSPs by descending, rather than by antidromically activated ascending fibres, was indicated by temporal facilitation produced by RF stimuli, subliminal for evoking monosynaptic PSPs in the PNs. Stimulation of the labyrinth did not evoke disynaptic PSPs in any of the PNs investigated. It is concluded that the C3-C4 PNs projecting to forelimb motoneurones can be excited not only from the cortico-, rubro-, and tectospinal tracts (Illert et al. 1977, 1978) but also by reticulospinal fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237494
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  • 8
    Electronic Resource
    Electronic Resource
    The heteronymous monosynaptic actions of triceps surae group Ia afferents on hip and knee extensor motoneurones in the cat (1986)
    Springer
    Experimental brain research 61 (1986), S. 443-446 
    Details
    ISSN: 1432-1106
    Keywords: Motoneurones ; Ia afferents ; Monosynaptic EPSPs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Monosynaptic connections from the group Ia afferents of triceps surae onto quadriceps, anterior biceps and semimembranosus motoneurones have been demonstrated in the cat. They appear to be equivalent to those found between triceps surae and thigh muscles in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239533
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  • 9
    Electronic Resource
    Electronic Resource
    Antispastic effects of l-dopa (1996)
    Springer
    Experimental brain research 111 (1996), S. 296-304 
    Details
    ISSN: 1432-1106
    Keywords: Spasticity ; Stretch reflex ; Spinal cord ; l-dopa ; Monoamines ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Antispastic effects of the noradrenaline and dopamine precursor l-3,4-dihydroxyphelanine (l-dopa) were investigated in 11 subjects in which exaggerated stretch reflexes developed after spinal cord injuries. The effects were evaluated from changes in the electromyographic (EMG) response of the quadriceps muscle during tendon jerks evoked by standardized taps over the patellar tendon, in clonus and in resistance to passive movements of the limb. After administration of l-dopa, EMG responses occurring 30–150 ms after the tendon tap decreased to about 50% of control, and clinical tests revealed a marked decrease in the resistance to muscle stretches and in the degree of clonus. The effects were maximal within about 1 h. The depressive actions of l-dopa are interpreted as being exerted primarily at the spinal level, since they were evoked in paraplegics and tetraplegics. The results support the previous hypothesis that group II muscle afferents contribute to the exaggerated stretch reflex in spastic patients because l-dopa depresses transmission from group II but not from group I muscle afferents. They also indicate the possibility of using l-dopa in the treatment of spastic patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227307
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  • 10
    Electronic Resource
    Electronic Resource
    The rubrospinal tract. III. Effects on primary afferent terminals (1972)
    Springer
    Experimental brain research 15 (1972), S. 39-53 
    Details
    ISSN: 1432-1106
    Keywords: Red nucleus ; Rubrospinal tract ; Primary afferent terminals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Effects evoked by stimulation of the red nucleus on primary afferent terminals in the lower lumbar segments of cats have been investigated by recording dorsal root potentials (DRPs) and by recording (intracellularly and by excitability measurements) the primary afferent depolarization (PAD) evoked in terminals of different afferent systems. Control experiments suggest that the effects are mediated by the rubrospinal tract. 2. Stimulation of the red nucleus evoked a large DRP and correspondingly there was a pronounced PAD in Ib and low threshold cutaneous afferents. A dual effect was found in Ia afferent terminals; sometimes a weak PAD was detected while in other cases there was dominating primary afferent hyperpolarization (PAH). 3. Rubrospinal volleys are found to facilitate transmission of DRPs evoked from Ia, Ib, cutaneous and high threshold muscle afferents, presumably by exerting an excitatory action on the interneurones mediating the effect from these afferents. Stimulation of the red nucleus may also inhibit transmission in the pathway mediating depolarization of Ia afferent terminals from Ia afferents, probably by activating a segmental pathway from the flexor reflex afferents from which the same effect is evoked. It is postulated that the PAH evoked in Ia afferents from the red nucleus is due to this inhibitory effect and caused by a removal of a tonic PAD in them. 4. The possible role in motor regulation of the rubral effects on primary afferent terminals is discussed in relation to the rubrospinal effects on reflex pathways to motoneurones. This work was supported by the Swedish Medical Research Council (Project No. 14X-94-07C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234957
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