Neuroendocrine and behavioral effects of vasopressin in resting and mild stress conditions.

Neuroendocrine and behavioral effects of subcutaneously administered AVP (6 micrograms/kg b.wt.) were determined in resting conditions and after the mild stress of transportation to and placement in a novel environment. In resting conditions, systemic administration of AVP caused a rapid increase in blood glucose level and a long-lasting increase in CORT secretion. A decrease in circulating plasma NE level was observed. AVP did not affect adrenal medullary E secretion. The stress-induced sympathetic activation, as reflected in plasma NE level, was inhibited 60 min after AVP administration. Stress-induced increases in blood glucose, CORT, and E secretion were not influenced by AVP. In resting condition, AVP caused a 60-min lasting increase in grooming behavior with a concomitant decrease in time spent resting. Sixty minutes after administration, the behavioral activation after the stress of transportation and placement in a novel environment was more rapidly terminated in AVP-treated rats than in vehicle-treated control rats. The state- and time-dependent modulation of spontaneous behavior suggests that AVP has arousing properties shortly after administration when marked pressor and endocrine effects are apparent. In a later phase, AVP may facilitate dearousal mechanisms following stress-induced behavioral activation.