Isolation rearing alters the effects of buspirone in the forced swimming test

Abstract

Social isolation in the early stages of life has been reported to change a variety of behaviors of the adult animal and the responsitivtty to psychotropic drugs. In the present experiments, we compared isolation and socially reared rats in three complementary paradigms for assessing responding to the forced swimming test. Both isolation and socially reared rats were exposed to the swimming test: 1) without drug pretreatment; 2) following acute systemic administration of a 5-HT1A partial agonist, buspirone (0.1, 0 5 and 1 mg/kg i.p.) or saline; 3) following chronic injected with buspirone (0 5 mg/kg i.p.) or saline. Male Wistar rats were raised from weaning either alone (isolation rearing) or in groups of six rats/cage (social rearing) Four weeks later, these rats were tested for their sensitivity to buspirone using the forced swimming test (Porsolt et al., 1978, Eur J Pharmacol 47, 379-391). The results demonstrate that the isolation reared rats showed significantly less immobility time and more struggling than the socially reared rats. Buspirone 1.0 5 nig/kg i.p.) caused a marked decrease in immobility time and increase in struggling compared to the saline treated group. These effects were significantly greater in the isolation reared rats than the socially reared rats. In chronic experiments, in which all rats were repeatedly injected for 7, 14 and 21 days, the buspirone treated rats (both isolation and socially reared rats) still showed significantly less immobility time and more struggling than the saline treated groups These responses were greater in isolation compared to socially reared rats. The results suggest that rearing in isolation may produce some of its behavioral effects through central serotonergic mechanisms, and that 5-HT1A receptor may be involved in behavioral despair.