ABSTRACT
Porcine intestinal tissue proved to be an excellent source for the isolation of these structurally related peptides. The localization of vasoactive intestinal peptide (VIP) in brain structures known to be important in the control of anterior pituitary function suggested, to several groups, possible neuroendocrine actions of the peptide. VIP is present as well in the urogenital tract, endocrine tissues and all exocrine glands that have been studied. The presence of VIP receptors in the anterior pituitary was deduced from the evidence that the peptide could not only stimulate the secretion of prolactin, but also stimulate pituitary adenylate cyclase activity. The effect was dose-related and relatively long-lasting, remaining significant for the 90 min sampling period after cessation of VIP exposure. The anatomical distribution of VIP mirrors in its extent the wide variety of activities of the peptide within the gut.
