Relationship between dopamine D2 receptor-associated responses and operant ethanol self-administration in the rat: a factor analysis.

AIMS To characterize the relationship between dopamine D(2) receptor-associated responses and operant ethanol self-administration in Wistar rats. METHODS Thirty-two rats were first tested for apomorphine-induced sniffing and raclopride-induced catalepsy. Subsequently, the same subjects were initiated to lever press for ethanol in the sucrose-fading procedure. The subjects were allowed to respond for 8% v/v ethanol for 20 days. A factor analysis was used to characterize the relationship between D(2)-associated responses and parameters of sucrose and ethanol self-administration. RESULTS The analysis revealed three factors accounting for 88.3% of the total variability. The first factor comprised only parameters of ethanol-reinforced behaviour. Parameters of sucrose self-administration and cataleptic responses to raclopride loaded heavily on the second and third factors, respectively. None of the factors comprised apomorphine-induced stereotypy. CONCLUSIONS It appears that there is no relationship between apomorphine-induced sniffing, raclopride-induced catalepsy and operant responding for ethanol in Wistar rats. Our results, combined with previous reports, suggest that D(2) receptors are not primarily involved in the regulation of ethanol reinforcement.