title: Postsynaptic inhibition of oculomotor neurons involved in vestibulo-ocular reflexes arising from semicircular canals of rabbits.
abstract: 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 are for the following reasons; its latency was compatible with that of the IPSP's 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 IPSP's 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.
mesh_terms: D000200:Action Potentials; D000818:Animals; D005071:Evoked Potentials; D009119:Muscle Contraction; D009801:Oculomotor Muscles / Q000502:physiology; D009802:Oculomotor Nerve / Q000502:physiology*; D011817:Rabbits; D012018:Reflex; D012665:Semicircular Canals / Q000294:innervation*; D014725:Vestibular Nerve / Q000502:physiology*