Self-administered nicotine activates the mesolimbic dopamine system through the ventral tegmental area

Abstract

Microinfusions of the nicotinic antagonist dihydro-beta-erythroidine (DH beta E) were used to examine the role of the mesolimbic dopamine system in nicotine reinforcement in rats. Infusions of DH beta E into the ventral tegmental area (VTA) prior to the start of i.v. nicotine self-administration sessions resulted in a significant decrease in the number of nicotine infusions voluntarily obtained. In contrast, the same doses of DH beta E infused into the nucleus accumbens were without effect on nicotine self-administration. The reductions caused by DH beta E were specific to nicotine reinforcement; neither operant responding maintained by food, cocaine self-administration, or spontaneous locomotor activity were altered by local applications of DH beta E within the VTA. The reduction in nicotine self-administration following treatment in the VTA was also specific to the nicotinic antagonist, and was not duplicated by infusions of the muscarinic antagonist atropine. Partial lesions of the pedunculopontine tegmental nucleus, the likely origin of cholinergic fibers to the VTA, were without effect on nicotine self-administration, suggesting that the effects of DH beta E were not due to disruption of a tonically active cholinergic input to the VTA from this source. These data show that nicotine acts within the VTA region to initiate processes which are critical to the reinforcing properties of the drug.