Extrahypothalamic distribution of vasoactive intestinal polypeptide (VIP)-like immunoreactivity in the chicken brain, Gallus domesticus

The distribution of VIP-immunoreactive neurons and fibers was detected in the extrahypothalamic areas of chicken brain by immunohistochemistry and light microscopy VIP-ir perikarya were found in the hippocampus and in the area parahippocampalis; in the area ventralis of Tsai, in the n. interpeduncularis, in the substantia nigra, in the substantia grisea centralis, in the locus coeruleus, in the n. subcoeruleus ventralis and in the n. pontis lateralis. VIP-ir fibers were seen in the lobus parolfactorius and throughout the brainstem mainly arranged in lateral and midsagittal position. This finding was discussed in relation to other studies performed on chicken and/or other avian brain. The distributional pattern of VIP-ergic system in the chicken brain suggests a possible involvement of VIP or VIP-like peptide in several neuroregulatory mechanisms.