THE EFFECTS OF SELECTED CHOLINERGIC DRUGS AND STRYCHNINE ON COCHLEAR RESPONSES AND OLIVO-COCHLEAR INHIBITION

¹ Department of Pharmacology, Louisiana State University Medical Center, New Orleans, Louisiana

The pharmacology of olivo-cochlear (o-c) inhibition was investigated in cats anesthetized with Dial-urethane and paralyzed with gallarnine. Intravenous strychnine blocked the N₁ depression produced by i.a. acetylcholine as well as the effects produced by o-c bundle stimulation. Intraarterial hemicholinium (Schueler's HC-3) produced a partial block of o-c bundle stimulation effects. Intraarterial choline produced N₁ depression in control animals and animals which had received HC-3 and a complete block of o-c bundle stimulation effects in the HC-3 animals. Thus, the cochlear action of HC-3 appeared to be similar to its action at the neuromuscular junction. Intraarterial physostigrnine, atropine, gallamine and mecamylamine produced no significant changes in either control N₁ and microphonics or in the o-c bundle stimulation effects. it is concluded that a definitive evaluation of the pharmacology of olivo-cochlear inhibition cannot be made at this time.