Long-lasting effect of early handling on the peripheral benzodiazepine receptor.

The present study determined the impact of early handling (EH) in rats on behavioral response to environmental stress and on peripheral benzodiazepine receptor (PBR) binding characteristics (Bmax and Kd) in various organs. The behavioral consequences of EH in rats were expressed as increased exploratory activity in an open-field paradigm, when compared with nonhandled control rats. These findings are interpreted in terms of decreased emotionality. The biochemical consequences of EH, in both male and female rats, were expressed as the upregulation of PBR in the adrenal and kidney and the downregulation of gonadal (testis and ovary) PBR. It is possible that the long-lasting adrenal and renal changes in PBR expression in EH rats may enable better regulation of the hypothalamic-pituitary-adrenal axis, renin-angiotensin system, and autonomic nervous system responses to stress in adulthood. The significance of the EH-induced reduction in gonadal PBR for gonadal activity in adulthood is as yet unclear.