Isolation changes the incentive value of sucrose and social behaviour in juvenile and adult rats

The present study was undertaken to assess the motivational aspects of soci al behaviour in juvenile and adult rats using the conditioned place prefere nce (CPP) test and anticipatory behaviour for social contact. In addition, the consequences of social isolation during different periods of age on the motivational properties of sucrose-drinking and adult social behaviour wer e studied. Social play and adult social contact could be used as incentives for place preference conditioning and for inducing conditioned hyperactivi ty (anticipation) in rats. Both social activities have motivational propert ies for individually housed rats, whereas group-housing dramatically reduce d the motivational aspects of adult social contact. In contrast, sucrose-dr inking appears to have motivational aspects independent of the housing cond ition. Adult social behaviour could not induce a CPP in juvenile isolated r ats, suggesting that juvenile isolation during 4-5 weeks reduced the motiva tional aspects of adult social contact. It seems likely that no CPP was est ablished as a result of the reduced level of social behaviour during the co nditioning sessions. Additionally, juvenile isolation during 4-5 weeks appe ared to also decrease the motivational properties of sucrose-drinking in ma turity, because the intensity of anticipation in response to sucrose was si gnificantly suppressed. Thus, the data suggest that juvenile isolation duri ng 4-5 weeks decreases the motivational properties of both social contact a nd sucrose-drinking in later life. (C) 1999 Elsevier Science B.V. All right s reserved.