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  • Rabbit  (9)
  • Vestibular  (7)
  • Deiters neurones  (6)
  • Inhibition  (4)
  • Deiters  (3)
  • 11
    ISSN: 1432-1106
    Keywords: Semicircular canal ; Vestibular-ocular inhibition ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anesthetized albino rabbits, electric stimulation of vestibular nerve branches innervating semicircular canals produced not only reflex contraction in certain extraocular muscles, but also a transient relaxation in others. From relaxing muscles was recorded a slow muscle potential that reflected depression of spontaneous spike discharges in muscle fibers. When recorded monophasically, spontaneous spikes of muscle fibers were superposed to form a direct current potential, and depression of the spikes resulted in a transient reduction of this direct current potential, i.e., the slow muscle potential. The slow muscle potential was correlated to the postsynaptic inhibition induced in oculomotor neurons through the vestibulo-ocular reflex arc for the following reasons; its latency was compatible with that of the IPSPs recorded from oculomotor neurons; it was removed by severing axons of the inhibitory second-order vestibular neurons; it was blocked by intravenous injection of picrotoxin as were the IPSPs in oculomotor neurons. By recording slow muscle potentials, a specific canal-muscle relationship for the vestibulo-ocular reflex inhibition of oculomotor neurons was shown to be complementary to that obtained for the vestibulo-ocular reflex excitation.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 24 (1976), S. 257-271 
    ISSN: 1432-1106
    Keywords: Semicircular canal ; Vestibulo-ocular reflex ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anesthetized albino rabbits, ampullary branches of the vestibular nerve were stimulated electrically. Prominent and stable reflex contraction was induced in extra-ocular muscles by applying single current pulses of relatively long duration, 3–5 msec. Survey with a glass microelectrode revealed that, during application of relatively wide pulses to a canal, primary vestibular fibers discharged impulses repetitively at a rate as high as 300–1400/sec and that after being transmitted across second-order vestibular neurons these impulses built up summated EPSPs in oculomotor neurons, large enough to trigger off motoneuronal discharges. From each semicircular canal, prominent reflex contraction was evoked selectively in two muscles; from the anterior canal in the ipsilateral superior rectus and contralateral inferior oblique; from the horizontal canal in the ipsilateral medial rectus and contralateral lateral rectus; and from the posterior canal in the ipsilateral superior oblique and contralateral inferior rectus. Acute lesion experiments indicated that signals for this excitation reached IIIrd and IVth nuclei via three different pathways; from the anterior canal through the ipsilateral brachium conjunctivum, from the horizontal canal through the ipsilateral fasciculus longitudinalis medialis and from the posterior canal through the contralateral fasciculus longitudinalis medialis.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 4 (1968), S. 310-320 
    ISSN: 1432-1106
    Keywords: Deiters neurones ; Cerebellum ; Inhibitory zone ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary By recording intracellularly from Deiters neurones of cats, there was a survey of those cerebellar areas that, when stimulated, produced inhibitory postsynaptic potentials (IPSPs) monosynaptically in Deiters neurones. The monosynaptic inhibitory area expanded longitudinally mainly along the ipsilateral vermal cortex of the anterior lobe. The ipsilateral cortex of the posterior lobe was also effective in inhibiting Deiters neurones though less prominently than the anterior lobe. The inhibitory fibers could be stimulated in the white matter of the cerebellum, predominantly in the ipsilateral side at rostral regions of nuclei fastigii and interpositus. It was further shown that the monosynaptic inhibition from the anterior and posterior lobes occurs chiefly in the dorsal portion of Deiters nucleus. Since in both the cerebellum and Deiters nucleus the spatial pattern of distribution of the inhibitory fibers conforms to that of the corticovestibular fibers as histologically defined, the experimental findings are in accord with the hypothesis that the cerebellar Purkinje cells are inhibitory in nature.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 26 (1976), S. 89-103 
    ISSN: 1432-1106
    Keywords: Vestibular ; Oculomotor ; Canal ; Inhibition ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anesthetized albino rabbits, electric pulse stimulation was applied to ampullary branches of the vestibular nerve. Reflex discharges evoked from a canal in an extraocular muscle were depressed very effectively by conditioning stimulation at a certain other canal. The present systematic survey revealed that this reflex depression occurred specifically in 3 combinations of conditioning and testing canals; 1. anterior and posterior canals of the same side; 2. anterior and posterior canals of the opposite sides; and 3. horizontal canals of the two sides. Occurrence of postsynaptic inhibition in oculomotor neurons, on the other hand, was indicated by appearance of slow muscle potentials in extraocular muscles. It was confirmed that this motoneuronal inhibition did not contribute to the reflex depression in the above combination (1). Even in combinations (2) and (3), the accompanying motoneuronal inhibition was eliminated by adjusting intensities of canal stimuli or by severing its pathway in the medulla, or it was discriminated from the reflex depression by their different latencies and time courses. Hence, it was concluded that the reflex depression was attributable, at least largely, to non-motoneuronal inhibition, presumably postsynaptic inhibition at relay neurons for vestibulo-ocular reflexes. Slow muscle potentials evoked from a canal were also used as testing responses, but their depression could not be detected after conditioning at other canals.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 10 (1970), S. 64-80 
    ISSN: 1432-1106
    Keywords: Intracerebellar nuclei ; Purkinje cells ; Inhibition ; Excitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized cats, synaptic events in cerebellar nuclei neurones were investigated with intracellular microelectrode techniques. These cells were identified by their antidromic activation along their axons and/or by their location in histological sections. In the cells of lateral nucleus IPSPs were induced monosynaptically during stimulation of the overlying hemispheral cortex of the cerebellum. In the cells of nuclei interpositus and fastigii, similar IPSPs were produced from the paravermal and vermal cortices, respectively. The postulate that the Purkinje cells exert an inhibitory action upon their target neurones thus applies not only to Deiters neurones, as previously proposed, but also to cells in the cerebellar nuclei. Stimulation of the cerebellar afferents at the inferior olive, the pontine nucleus and the lateral reticular nucleus produced EPSPs in cerebellar nuclei cells with relatively brief latencies, probably through axon collaterals of these afferents. The EPSPs were followed by IPSPs and slow depolarizations of disinhibitory nature, which, as studied previously in Deiters neurones, might be caused respectively by activation and subsequent depression of Purkinje cells through the cerebellar intracortical mechanisms.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 13 (1971), S. 306-326 
    ISSN: 1432-1106
    Keywords: Vestibular ; IIIrd nucleus ; PSPs ; Picrotoxin ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Microelectrodes were inserted into IIIrd cranial nucleus of anaesthetized rabbit. IIIrd nucleus was identified by observing the field potentials evoked antidromically by stimulation of IIIrd cranial nerve. After stimulation of VIIIth nerve extracellular field potentials, spike potentials in secondary vestibular fibers, and postsynaptic potentials in IIIrd nucleus neurones were recorded. VIIIth nerve impulses either excite or inhibit IIIrd nucleus neurones postsynaptically with disynaptic latencies around 1.7 msec. By local stimulation of the medulla, it was found that the secondary vestibular impulses inhibiting IIIrd nucleus neurones are mediated by the superior nucleus. The excitatory impulses are relayed by the rostral half of the medial nucleus as well as a certain structure(s) relevant to the brachium conjunctivum. Preliminary pharmacological investigations on the inhibition of IIIrd nucleus neurones are reported.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 2 (1966), S. 330-349 
    ISSN: 1432-1106
    Keywords: Deiters neurones ; IPSP ; Monosynaptic ; Purkinje cells ; Inhibitory neurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary During stimulation of the anterior lobe of the cerebellum, postsynaptic potentials were recorded intracellularly from ipsilateral Deiters neurones of the cat. In the majority of examined cells, the inhibitory postsynapic potentials were induced with short latency; 1.06 msec on the average from lobule III or IV. The latency was longer (1.23 msec) when the lobule V was stimulated, while it was shorter (0.86 msec) from the juxtafastigial region. It follows that the IPSP was produced via a monosynaptic pathway at a conduction velocity of 15 to 20 m/sec. Recording of the extracellular field potentials and focal stimulation within and around Deiters' nucleus further indicated that the inhibitory impulses propagated out of the cerebellum along a remarkable bundle of fibres which terminated within Deiters' nucleus. These results are all explicable by assuming that the cerebellar Purkinje cells are inhibitory in nature and so produce IPSPs monosynaptically in Deiters neurones via the long corticofugal fibres. Monosynaptic EPSPs were also detected in some Deiters neurones. They are considered to be mediated by the other pathways formed of axon collaterals of the cerebellar afferents.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 8 (1969), S. 190-200 
    ISSN: 1432-1106
    Keywords: Vestibular ; EPSP ; IPSP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neurones in the descending, medial and superior vestibular nuclei of the cats were explored with intracellular microelectrodes. Cerebellar- and spinal-projecting neurones were identified by their antidromic invasion from the region of fastigial nuclei and from the second cervical segment, respectively, and the others by their location. The central actions of the primary vestibular impulses upon these non-Deiters vestibular nuclei neurones were investigated by using electric stimulation of the ipsilateral vestibular nerve. Many of these cells received excitatory postsynaptic potentials (EPSPs) monosynaptically, similar to those evoked in the ventral Deiters neurones, as described elsewhere, except that the unitary EPSPs are often larger. Some cells received only polysynaptic EPSPs or IPSPs and a few cells were not influenced at all.
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  • 19
    ISSN: 1432-1106
    Keywords: Axon reflex ; Deiters neurones ; Cerebellar afferents ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary When recording intracellularly from cat's Deiters neurones, stimulation of the anterior lobe of the cerebellar cortex produced excitatory postsynaptic potentials (EPSPs) monosynaptically, in addition to the inhibitory ones (IPSPs) that were identified previously as being produced via Purkinje cell axons. The EPSPs were induced bilaterally from a wide area of the anterior and posterior lobes of the cerebellum, in contrast to the IPSPs that were evoked only ipsilaterally, mainly from the vermal cortex. The latency of the EPSPs was slightly, but significantly, shorter than that of the IPSPs. The presynaptic impulses responsible for these EPSPs were represented by the discrete field potentials and also by unit spikes of individual fibres. The pathway for these EPSPs and presynaptic impulses was pursued by testing their interference, in the manner of impulse collision and refractoriness, with those induced from various spots within or outside the cerebellum. It is found that the excitatory fibres for Deiters neurones extend transversely, and probably longitudinally too, over the culmen and pass out of the cerebellum through cerebellar peduncles. The major portion of them appears to originate from the medulla and a minority from the spinal cord. It is postulated that cerebellar afferents from these structures have synapses with Deiters neurones via their collateral branches, through which a kind of axon reflex occurs to Deiters neurones during stimulation of the cerebellar cortex.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 14 (1972), S. 511-526 
    ISSN: 1432-1106
    Keywords: Vestibular ; IIIrd nucleus ; Flocculus ; Inhibition ; Picrotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In anaesthetized rabbits, the vestibulo-ocular reflex was evoked by electric stimulation of VIIIth nerve and was observed by recording postsynaptic potentials and relevant field potentials in Illrd nucleus. The electric stimulation of flocculus produced a prominent inhibition of the vestibulo-ocular reflex in both the inhibitory component relayed by the superior vestibular nucleus and the excitatory component mediated by the brachium conjunctivum. The excitatory component mediated by the medial vestibular nucleus appeared to be free of the flocculus inhibition. The flocculus inhibition was blocked very effectively by systemic injection of picrotoxin. That the flocculus inhibitory action is due to monosynaptic postsynaptic inhibition of secondary vestibular neurones was demonstrated by direct stimulation of, and also by recording from, the superior nucleus. Recording from the superior nucleus was also performed in anaesthetized cats. All of these above results indicate that Purkinje cells in flocculus projecting to vestibular and cerebellar nuclei cells have inhibitory synaptic action. Flocculus stimulation produced also an excitatory effect upon vestibular nuclei neurones. However, this effect could be attributed to intracerebellar activation of the primary vestibular fibers which pass into the flocculus.
    Type of Medium: Electronic Resource
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