Cocaine self-administration in rats influenced by environmental conditions: implications for the etiology of drug abuse.

The present study investigated the possibility of environmental factors as an explanation for between-subject differences in cocaine self-administration. Weaning rats (21 days) were housed in isolated or aggregated conditions for 6 weeks and were tested for intravenous cocaine self-administration (0.1-1.0 mg/kg/infusion). Rats housed in groups failed to reliably self-administer this drug whereas isolated rats readily acquired an operant to receive infusions of cocaine. These data suggest that environmental factors play a major role in determining individual differences in the propensity to self-administer cocaine and that, as such, they should be considered more seriously by those interested in the basis and treatment of drug abuse.