DISTRIBUTION OF CHOLINE ACETYLASE AND CHOLINESTERASE AND THE ACTION OF CHOLINERGIC DRUGS ON THE CAT VESTIBULAR SYSTEM
1972 年 30 巻 suppl-3 号 p. 77-89
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1972 年 30 巻 suppl-3 号 p. 77-89
A neurochemical and neuropharmacologic study was undertaken in the cat to obtain further evidence of the role of acetylcholine in vestibular function. It was shown that the vestibular nerve contains about half or less the enzymatic activity of choline acetylase, acetylcholinesterase, cholinesterase, and total cholinesterase than nucleus vestibularis lateralis.
Field potentials as well as discharge of single neurons of nucleus vestibularis lateralis (NVL) were studied in locally anesthetized, decamethonium immobilized ventilated cats before, during, and after vestibular nerve and reticular formation stimulation. Various cholinergic agonists and antagonists and the adrenergic agonists l-DOPA and d-ampheta-mine, were then given i.v. to determine their effects. Three major evoked potentials to vestibular nerve stimulation were recorded in NVL. These potentials were labelled N1 N2 and N3 on the basis of polarity and latency. Although the N2 and N3 waves were not much affected, the N2 wave was dramatically enhanced by physostigmine and reduced by scopolamine.
About half of 'NVL neurons excited by vestibular nerve stimulation responded to muscarinic cholinergic drugs. NVL responses to RF stimulation were primarily nicotinic and were blocked by the nicotinic antagonist, mecamylamine, but not trimethadinium. Some neurons excited by RF stimulation were enhanced by l-DOPA or d-amphetamine. The data indicate that cholinergic mechanisms are strongly involved in vestibular function. Adrenergic mechanisms are also involved, but to a much lesser extent.
