Radioimmunologic localization of vasoactive intestinal polypeptide in hypothalamic and extrahypothalamic sites in the rat brain.

Using a specific radioimmunoassay (RIA), we have quantitated the hypothalamic and extrahypothalamic distribution of vasoactive intestinal polypeptide (VIP) in the rat brain. Highest concentrations of VIP were found in cerebral cortex, suprachiasmatic nucleus, and medial amygdaloid nucleus. Lower concentrations were found in the anterior hypothalamic area, medial preoptic area, peri- and paraventricular nuclei, and hippocampus. Significant levels of VIP were also found in the anterior pituitary. Very little VIP was detected in median eminence and cerebellar cortex. This distribution of VIP in areas of the rat brain known to be important to neuroendocrine function suggests a role for VIP in the control of anterior pituitary events.