Postnatal exposure to cocaine in rats housed in an enriched environment: effects on social interactions

Abstract

This study was undertaken to evaluate the effects of environmental enrichment (EE) in rats exposed to cocaine during the first month of postnatal life by examining several categories of social behaviour (play fighting, social investigation, comfort behaviours and invitation to play). Wistar rats were divided in four groups: pups exposed to cocaine hydrochloride (15 mg/kg body weight/day), sc, in two daily doses, from postnatal day (PND) 1 to 28 and reared in EE; exposed to cocaine as previously described and reared in standard environment (SE); saline-exposed and reared in EE; pups saline-exposed and reared in SE. On PND 21, 24 and 28, social interactions were examined for 10 min. Results show that cocaine animals reared in SE decreased the frequency of play solicitation. Control animals reared in EE exhibited decreased play fighting and social investigation behaviours compared to SE-reared rats. Animals postnatally exposed to cocaine when reared in EE displayed more comfort and invitation to play behaviours and decreased social investigation compared with SE-reared animals. The results suggest that in rats postnatally exposed to cocaine, EE rearing elicited differences in both processing of environmental stimuli and a response to social challenges. Human & Experimental Toxicology (2007) 26, 303-309