Abstract
Electrical stimulation of the crossed olivo-cochlear bundle (OCB) of the anesthetized cat produces an inhibition of sound-evoked VIII nerve action potentials. The OCB has been shown to contain acctylcholinesterase ( Churchill et al., 1956) and synaptic vesicles ( Engstroem, 1958). It was therefore suggested that the OCB exerted its inhibitory effect by neurohumoral means and that the neurohumor might be acetylcholine (ACh). Hemicholinium number 3 (HC-3) was employed in the present study as a means for testing the hypothesis that ACh is involved in OCB-induced inhibition. Cats anesthetized with pentobarbital and with left middle ear muscle tendons severed were employed. Sound-evoked potentials were recorded from the left cochlear round window. The crossed OCB was stimulated electrically. All experimental drugs were injected via a cannula in the left axillary artery. Atropine (0.5–5 mg/kg), dihydro-β-erythroidine (2–10 mg/kg) and mecamylamine (2–5 mg/kg) infections did not antagonize OCB-induced inhibition. HC-3 (5 mg/kg) in the majority of cats reduced the OCB-induced inhibition. Choline injections and resting the preparation momentarily reversed the effect of HC-3. Under similar conditions, d-tubocurarine (2 mg/kg) produced no change in OCB-induccd inhibition.
Published Version
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