THE INFLUENCE OF NICOTINE PRETREATMENT ON MESOACCUMBENS DOPAMINE OVERFLOW AND LOCOMOTOR RESPONSES TO D-AMPHETAMINE

Pretreatment with psychostimulant drugs causes sensitisation of their effects on locomotor activity and dopamine (DA) overflow in the nucleu s accumbens (NAcc) and there is evidence for similarities in the mecha nisms involved. This study used in vivo microdialysis in conscious fre ely moving rats to investigate the extent to which pretreatment with n icotine causes sensitisation to D-amphetamine. Pretreatment with nicot ine (0.4 mg/kg SC daily for 5 days) caused sensitisation of the locomo tor responses to D-amphetamine (0.1-0.5 mg/kg SC) but not cocaine (15 mg/kg IF). Nicotine pretreatment did not influence the increase in DA overflow into dialysis probes, located in the core of the NAcc, evoked by systemic injections of D-amphetamine or cocaine (15 mg/kg IP) but decreased the overflow evoked by the administration of D-amphetamine ( 1 x 10(-6) M) through the dialysis probe. The results provide further evidence for a dissociation between the expression of sensitised locom otor responses to psychostimulant drugs and sensitisation of their sti mulatory effects on DA overflow in the core of the NAcc. The results s uggest that the sensitisation of the effects of nicotine on DA overflo w in this subdivision of the NAcc may be pharmacologically specific to nicotinic drugs.