Behavioral effects of intraventricularly administered (-)-nicotine on fixed ratio schedules of food presentation in rats.

The behavioral effects of intraventricularly (IVT) administered (-)-nicotine on food-maintained behavior were studied. Rats responded by pressing a lever under various fixed ratio (FR) schedules. Infusion of 5 microgram of (-)-nicotine suppressed responding under an FR 16 schedule for 11-13 min. The effect was inversely related to the ratio size (16, 32, 64 responses per food delivery), but it was directly related to the infused (-)-nicotine dose (0.312, 0.624, 1.25, 2.5, 5.0, 10.0 microgram) when ratio size was held constant. Responses rates following the (-)-nicotine-induced suppression were similar to those obtained prior to infusion. The behavioral effects of (-)-nicotine were blocked, in a dose-related manner, by the centrally acting nicotinic-cholinergic antagonist, mecamylamine (0.05-3.0 mg/kg) but not by ther peripherally acting antagonist, hexamethonium (0.5-3.0 mg/kg), suggesting that the behavioral effects of IVT infusions of (-)-nicotine are mediated by central nicotine-cholinergic receptors.