Conditioned increases in behavioral activity and accumbens dopamine levelsproduced by intravenous cocaine

In vivo microdialysis, behavioral activity assessments, and a conditioned p lace preference (CPP) test were used to investigate dopaminergic correlates of cocaine-conditioned behaviors. Over 12 days, rats were given either int ravenous cocaine (4.2 mg/kg) or saline (6 cocaine and 6 saline infusions) d aily in distinctively different environments. The following day, rats were tested in the cocaine- and saline-paired environments; 48 hr later, CPP was determined. The cocaine-associated environment elicited greater nucleus ac cumbens dopamine (NAcc DA) levels, hyperactivity, and place preference, tho ugh the emergence of DA increases was not in synchrony with peak behavioral activation. Although conditioned behavioral effects after repeated cocaine are well documented, direct evidence of increased NAcc DA in response to a cocaine-paired environment has not been previously reported. Discrepancies with previous work are attributed to a number of methodological difference s.