CHRONIC NICOTINE TREATMENT DECREASES DOPAMINE D2 AGONIST BINDING IN THE RAT BASAL GANGLIA

To elucidate possible actions of nicotine on dopamine D2 receptor binding, the effect of chronic continuous (-)nicotine treatment (osmotic pumps s.c., 0.125 mg kg h-2, 14 days) was studied in the binding of [H-3]N-propylnorapomorphine ([H-3]NPA) and [I-125]sulpride in coronal cryostat sections in the rat. Quantitative autoradiography showed that nicotine decreased the binding of [H-3]NPA in the basal ganglia, preferentially in the nucleus accumbens and olfactory tubercle. In contrast, [I-125]sulpride binding was not affected. Nicotine decreased the K(D) value of [H-3]NPA by 27% and decreased the B(max) value by 17%, using filter-wiped sections. These results indicate that chronic continuous nicotine treatment affects the D2 receptor and that this effect may be involved in the development of nicotine dependence.