Accumbal FosB/DeltaFosB immunoreactivity and conditioned place preference in alcohol-preferring AA rats and alcohol-avoiding ANA rats treated repeatedly with cocaine.

Transcription factor DeltaFosB has been implicated in the psychomotor responses and rewarding effects of drugs of abuse. In the present study, we compared the effects of cocaine on the expression of DeltaFosB-like proteins by immunohistochemistry in striatal brain areas of alcohol-preferring (AA) and alcohol-avoiding (ANA) rats. Cocaine was administered using a previously verified treatment paradigm that sensitized the locomotor response to cocaine in AA but not in ANA rats. We also studied the rewarding effects of cocaine with a conditioned place preference (CPP) paradigm in both lines of rats. Cocaine treatment increased the FosB/DeltaFosB immunoreactivity (IR) in the nucleus accumbens of AA rats but not in ANA rats. In addition, after repeated saline injections the accumbal FosB/DeltaFosB IR was significantly greater in saline-injected AA rats than in ANA rats. In the caudate-putamen cocaine significantly increased FosB/DeltaFosB IR, but no differences were found between the rats of two lines. In the CPP experiment, AA rats treated with cocaine 2.5 mg/kg preferred the cocaine-associated compartment, in contrast to ANA rats, which did not show such a preference. In conclusion, our findings show that AA rats are more sensitive to cocaine than ANA rats, and suggest that one possible mediator for this increased sensitivity could be the increased expression of fosB-derived proteins in the nucleus accumbens of AA rats.