Changed accumbal responsiveness to alcohol in rats pre-treated with nicotine or the cannabinoid receptor agonist WIN 55,212-2

Alcohol, nicotine, and cannabinoid acutely increase the activity of the mesolimbic dopamine (DA) pathway. Although polysubstance consumption is a common pattern of abuse in humans, little is known about dopamine release following pre-exposure to these drugs. The purpose of this study was to test whether alcohol-induced dopamine release into the nucleus accumbens (NAc) shell is modified by different pre-treatments: water (i.g.), alcohol (1 g/kg, i.g.), nicotine (0.4 mg/kg, s.c.), and WIN 55,212-2 (1 mg/kg, s.c.). Male Wistar rats were treated (i.g.) for 14 days with either water or alcohol. In the following 5 days rats were injected (s.c.) with vehicle, nicotine, or WIN 55,212-2. Finally, a cannula was surgically implanted into the NAc shell and alcohol-induced extracellular dopamine release was monitored in freely moving rats. Alcohol (1 g/kg; i.g.) only increased the release of dopamine when animals were previously treated with water. This DA increase was markedly inhibited by (subchronic) treatment (5 days) with nicotine or WIN 55-212-2 as well as by previous (chronic) exposure to alcohol (14 days). These data demonstrate that pre-treatment with nicotine and the cannabinoid agonist WIN 55,212-2 is able to change the sensitivity of the NAc shell in response to a moderate dose of alcohol. Therefore, cannabinoid and nicotine exposure may have important implications on the rewarding effects of alcohol, because these drugs lead to long-lasting changes in accumbal dopamine transmission.