Effects of nicotine withdrawal on central dopaminergic systems

The behavioral and neurochemical manifestations in rats 24 h following the cessation of 14-day nicotine administration were investigated. Animals were implanted subcutaneously with osmotic minipumps which continuously released either saline or nicotine (1.5 mg/kg/day or 3.0 mg/kg/day) for 14 days. After the animals were withdrawn from nicotine for 24 h, we observed a significant decrease of locomotor activities and a reduction of dopamine contents in the striatum and nucleus accumbens. Nicotine withdrawal did not affect the body weight, food, or water consumption, and no deficit in the acquisition of a conditioned avoidance task was found in these animals. In addition, nicotine withdrawal did not alter the density or the binding affinity (K-d) of ligands to D-1 and D-2 receptors in the striatum. Although nicotine withdrawal did not alter the density or binding affinity of ligands to D-1 receptors in the nucleus accumbens, the maximum number of D-2 receptor sites were reduced by nicotine treatment. These results offer possible neurochemical mechanisms for changes of locomotor activity which occurred in rats during nicotine abstinence.