Nicotine-induced convulsions in cats and central nicotinic receptors

The effects were investigated of intracerebroventricular (ICV) injections in the cat of ganglionic blocking agents, antimuscarinic drugs, alpha and beta adrenergic blocking substances, dopamine antagonists, an antihistamine, reserpine and a 5-hydroxytryptamine antagonist as well as the inhibitors of catecholamines, 5-hydroxytryptamine and acetylcholine synthesis upon convulsions produced by nicotine, which was similarly injected. Mecamylamine and hexamethonium but not atropine, scopolamine, yohimbine, phenoxybenzamine, tolazoline, propranolol, practolol, chlorpromazine, haloperidol, antazoline and methysergide abolished the convulsions evoked by nicotine. Furthermore, reserpine, but not 6-hydroxydopamine, as well as 5,6-dihydroxytryptamine and hemicholinium blocked the convulsions caused by nicotine. It appears, therefore, that the convulsions produced by nicotine are mediated through central nicotinic receptors. However, the depressed catecholaminergic, 5-hydroxytryptaminergic and histaminergic mechanisms induced by reserpine can also suppress the convulsions evoked by nicotine.