Discriminative stimulus effects of intravenous nicotine in squirrel monkeys.

Three squirrel monkeys were trained to emit one response after IV administration of nicotine (0.1 or 0.18 mg/kg depending on the subject) and a different response after IV administration of saline. Subjects emitted nicotine-appropriate responses with substitutions of higher doses, but only emitted saline-appropriate responses after substitutions of lower doses. Discrimination performance was then maintained at 0.1 mg/kg of nicotine in all subjects. Neither morphine nor cocaine substituted for the effects of nicotine in any subjects across a range of doses up to those that suppressed responding. Ethyl-beta-carboline-3-carboxylate, an inverse agonist at the benzodiazepine receptor, substituted or partially substituted for nicotine in both subjects in which it was studied.