Action of Some Cholinomimetics and Cholinolytics on the Effect of the Crossed Olivocochlear Bundle (COCB)

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Abstract
The methods used to record the cochlear potentials, stimulate the Crossed Olivocochlear Bundle (COCB), and perfuse the scala tympani in guinea pigs were those described by Konishi [J. Acoust. Soc. Amer. 47, 1055–1062 (1970)]. Drugs were dissolved in a solution containing: NaCl, 139 mM; KCl, 5.6 mM; CaCl2, 2.2 mM; NaHCO3, 21 mM; 95% O2-5% CO2; with pH of 7.2–7.4. The perfusion solution increased the endocochlear potential (EP) and the. change in the scala-media potential evoked by COCB stimulation (DCS). The following doses of agents were found to reduce the DCS by approximately 50% at 5 min of perfusion through the scala tympani: carbamylcholine chloride, 50 μM; acteylcholine chloride, 550 μM; eserine sulfate, 400 μM; acetylcholine chloride, 250 μM plus eserine sulfate, 10 μM; choline iodide, 550 μM; nicotine tartrate, 1 mM; d-tubocurarine chloride, 5 μM; styrchnine sulfate, 5 μM; atropine methyl bromide, 25 μM; and atropine sulfate, 100 μM. Arecoline hydrobromide (1 mM) and eserine sulfate (10 μM) alone were inactive. The data are consistent with hypotheses that the COCB is cholinergic. [Supported by a Public Health Service grant and an NIH fellowship from NDS.]

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