Immunohistochemical detection of vasoactive intestinal polypeptide (VIP) and the VIP receptor in the rat inner ear

Vasoactive intestinal polypeptide (VIP) is a 28 amino acid peptide that was originally isolated from porcine duodenum. The presence of VIP has been de monstrated in the central nervous system and peripheral tissues. However; t here have been feu, reports on VIP as a neurotransmitter, especially in the inner ear. To investigate the function of VIP in The rat inner ear, we exa mined the expression of VIP and the VIP receptor by immunohistochemistry. U sing the anti-VIP and VIP receptor antibodies, scattered fibres Fn the coch lear nerve trunk demonstrating VIP-like immunoreactivity were found, and th e spiral ganglion cells demonstrated ring-shaped VIP-like immunoreactivity. Immunoreactivity for the VIP receptor was predominantly found in the spira l ganglion cells. Our results suggest that VIP may play an important role a s a possible neurotransmitter not only in the local control of cochlear blo od flow, but also in the auditory system.