Chronic Early Nicotine Exposure And The Effects On Cannabinoid Agonist-Induced Conditioned Place Preference

RM 218

Adolescent exposure to nicotine alters the response to a number of addictive drugs in adult rodents suggesting that early nicotine exposure may alter the reward centers in the brain. It is unknown whether the relationship between nicotine and marijuana is mediated by changes to neural reward centers. Therefore, the purpose of this study was to investigate whether chronic nicotine exposure starting in adolescence would act as a modifier of the rewarding properties of a cannabinoid drug in adulthood. To this end, male rats were chronically exposed to nicotine (0, 0.16, 0.32, or 0.64 mg/kg, subcutaneously) once daily from postnatal day (PD) 31 through PD 72 and were assessed for cannabinoidinduced conditioned place preference (CPP) using the cannabinoid agonist CP-55,940. On PD 60, a 14-day biased CPP procedure began which consisted of one preconditioning day, 10 conditioning days, one test day, and two rest days. Rats were primed with CP-55,940 (0, 10, 20, or 30 µg/kg, intraperitoneally) on the preconditioning day, with the same dose also used on conditioning days. Rats exposed to saline beginning in adolescence showed a preference for the high dose of CP-55,940 (30 µg/kg). This preference was eliminated by treatment with nicotine. However, exposure to nicotine (0.32 mg/kg) caused a preference for the low dose (10 ?g/kg) of CP-55,940. This suggests that nicotine use in adolescence produces dosespecific aversions to the cannabinoid agonist. Simultaneously, moderate doses of nicotine beginning in adolescence act in modifying the rewarding value of low doses of marijuana in adulthood.