Characterization of the effect of nicotine on vasopressin and atrial natriuretic factor in the rabbit.

The effects of nicotine on the secretion of arginine vasopressin (AVP) and of the atrial natriuretic factor (ANF) were examined in conscious rabbits. Nicotine was shown to produce significant increases in plasma AVP from 1.7 +/- 0.4 to 75.3 +/- 35.1 pg/ml (P less than .05) and in plasma ANF levels from 39 +/- 11 to 121 +/- 52 pg/ml (P less than .05) within 5 min of an i.v. dose of 0.5 mg/kg. These nicotine-induced stimulations could not be inhibited by muscarinic (atropine), dopaminergic [(+/-)-sulpiride], alpha (phenoxy-benzamine) or beta adrenergic (propranolol) blockers or by a rapid infusion of fluids. Trimetaphan was ineffective in blocking the stimulation of AVP secretion but completely abolished the nicotine-induced secretion of ANF. The more lipophilic ganglionic blocker, mecamylamine, blocked the stimulation of the secretion of both peptides. The effect of nicotine on AVP production was confirmed in vitro using the rat hypothalamo-neurohypophysial system preparation where nicotine increased AVP secretion in a dose-dependent manner. This in vitro stimulation was blocked by the ganglionic blocker hexamethonium. The increase in ANF plasma concentrations was probably due to a primary response to nicotine, for although exogenous AVP (1 microgram i.v.) increased ANF levels by a factor of 3 (P less than .05), the AVP antagonist [-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid)-2- (O-methyl)tyrosine]arginine vasopressin did not prevent the nicotine-induced increase in ANF. Thus, nicotine or its effects appear to stimulate the secretion of ANF and not AVP. It was concluded that nicotine stimulates the secretion of AVP by activating central nicotinic projections to the hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)