VASOACTIVE-INTESTINAL-PEPTIDE STIMULATES ACTH AND CORTICOSTERONE RELEASE AFTER INJECTION INTO THE PVN

Vasoactive intestinal peptide (VIP), a neuropeptide originally isolated from the intestine, is widely distributed in the central and peripheral nervous systems and exhibits a broad range of biological actions. In the present study the effects of VIP on plasma ACTH and corticosterone (CORT) secretion were investigated in fasted, freely-moving male rats. Male rats, chronically implanted with a hypothalamic paraventricular nucleus (PVN) cannula, were injected with VIP doses (0.15-3.0 nmol/rat) of VIP or saline (control). Blood samples were collected (0.6 ml) from an intravenous catheter immediately preceding and at 15, 30, 60, 90 and 120 min following peptide administration. PVN administration of VIP increased the plasma ACTH and CORT levels in a dose-dependent manner and the maximal effect was obtained at 15 min after administration. At the highest dose tested, VIP increased ACTH and CORT to 167% and 342% of time-matched controls, respectively. These results demonstrate that the PVN is a sensitive site for VIP-induced elevation of plasma ACTH and CORT and imply that the VIP binding sites and immunoreactive terminals previously identified in this region may be involved in the central regulation of the pituitary-adrenal axis.