Effects of vasoactive intestinal peptide on canine prostatic contraction and secretion

Vasoactive intestinal peptide (VIP)-like immunoreactivity was found in intrinsic autonomic ganglion cells and nerve fibers located at the surface and within the canine prostate. In anesthetized dogs, porcine VIP (100-3,000 ng/kg iv) decreased arterial pressure and increased heart rate but did not result in the release of fluid from the prostate, indicating that VIP neither contracted glandular smooth muscle to expel fluid nor provoked secretion. Intravenous infusions of VIP at 10, 50, 100, and/or 200 ng X kg-1 X min-1 produced dose-related decreases in arterial pressure, increases in heart rate, and potentiation of the secretory response to the intravenous administration of pilocarpine and to electrical stimulation of the hypogastric nerves at 2 but not at 20 Hz. VIP at 1 microgram/ml neither contracted isolated strips of prostate nor modified their contraction by norepinephrine. It is unlikely that VIP mediates hypogastric nerve-induced prostatic contraction or secretion in the dog, but VIP may serve as a neuromodulator of nerve-induced secretion.