Action of Cholinergic and Anticholinergic Drugs at the Crossed Olivocochlear Bundle-hair Cell Junction

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Abstract
Both cholinergic and anticholinergic drugs introduced into the scala tympani of guinea pigs were found to block the effects induced by electrical stimulation of the crossed olivocochlear bundle. Strychnine, d-tubocurare, and decamethonium were most potent in this activity. Eserine did not potentiate the effects of electrical stimulation of the crossed olivocochlear bundle but did potentiate the effects of acetylcholine and in high concentrations blocked the crossed olivocochlear bundle. Acetylcholine (247 μM) in combination with eserine (20 μM) mimicked the effects of the crossed olivocochlear bundle by producing an augmentation of the cochlear microphonics and an inhibition of the action potential. The acetylcholine (247 μM)-eserine (20μM) combination also produced a reversible blockade of the crossed olivocochlear bundle and the mimicking effects of subsequent perfusions with the drug combination. The mimicking effect of the acetylcholine (247 μM)-eserine (20 μM) combination was blocked by d-tubocurare. These results further extend the evidence which has accumulated towards proving that acetylcholine is the transmitter substance of the crossed olivocochlear bundle.