Cocaine and morphine self-administration: effects of differential rearing

Two groups of Wistar rats were reared in either enriched or impoverished conditions for 100 days postweaning. These two groups were further divided and tested for cocaine or morphine preference in a two-bottle choice (water alternative) for 16 days. Enriched and impoverished rearing has previously been found to alter emotionality, conditionability, and body weight of adult rats. Validating previous reports of differential rearing effects on body weight, the enriched animals in the present study weighed less than their litter mates reared in impoverished conditions. Animals reared in the enriched environment consumed significantly more cocaine than animals reared in an impoverished one. No significant differences were observed for morphine self-selection as a result of differential rearing.