Postsynaptic inhibition of oculomotor neurons involved in vestibulo-ocular reflexes arising from semicircular canals of rabbits

✍ Scribed by M. Ito; N. Nisimaru; M. Yamamoto

• Publisher: Springer-Verlag
• Year: 1976
• Tongue: English
• Weight: 655 KB
• Volume: 24
• Category: Article
• ISSN: 0014-4819
• DOI: 10.1007/bf00235015

✦ Synopsis

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.