Open field behavior of rats reared in different social conditions: the effects of stress and imipramine.

Behavioral changes in rats divided on the weaning day into two groups (crowded and isolated) were studied in the computerized open field. At the end of the experiment the effects of an acute stress (1 h long immobilization) on open field behavior, body weight and body temperature, were examined. In a separate experiment both groups of rats were chronically pretreated with tricyclic antidepressant imipramine (5.0 mg/kg, po), and subsequently exposed to the same stress procedure. Social deprivation significantly enhanced spontaneous locomotion and exploratory activity. Restraint stress significantly decreased exploration, body weight and temperature, in the isolated animals only. Chronic pretreatment of rats with imipramine significantly attenuated the effect of stress on motor and exploratory behavior, as well as stress-induced changes in body weight and temperature, in the group of isolated animals. The present data indicate sensitization to stress of behavioral and vegetative processes in socially deprived animals. The relationship between rearing conditions and behavioral and vegetative reactivity to the environmental challenges is confirmed.