Vasoactive intestinal polypeptide (VIP)-like immunoreactivity in the suprachiasmatic nucleus of the perinatal rat

Vasoactive intestinal polypeptide (VIP)-like immunoreactivity was examined in the suprachiasmatic nucleus (SCN) of the perinatal rat using the unlabeled antibody enzyme method of Sternberger. Our results showed that VIP-like immunoreactivity was present in cells and fibers of the SCN prior to birth. Immunoreactive neurons at this time appeared morphologically immature, and their distribution differed somewhat from that seen in the adult SCN.