Neurotransmitter candidates in the vomeronasal organ of the rat.

Conclusion: The rich supply of nerve fibres containing neurotransmitters, particularly those containing SP and CGRP, is suggested to be a prerequisite for the recognition of chemical irritants as part of a chemical sense. Objective: The present study was designed to examine the distribution of different neurotransmitter candidates in the vomeronasal organ (VNO) of rats. Materials and methods: The distribution of neurotransmitter candidates was studied in the vomeronasal organ of the rat using immunocytochemistry. Results: The neuronal marker protein gene product 9.5 revealed a very rich supply of nerve fibres within and beneath the sensory epithelium, around blood vessels and glands. A moderate supply of nerve fibres containing tyrosine hydroxylase and neuropeptide Y was mostly seen close to blood vessels. Numerous nerve fibres containing nitric oxide synthase and vasoactive intestinal peptide were seen around blood vessels and in the subepithelial layer, with occasional fibres within the epithelium. Only few fibres located in the subepithelial layer contained pituitary adenylate cyclase activating peptide. Nerve fibres containing substance P and in particular calcitonin gene-related peptide were abundant in and beneath the epithelium and scattered in the submucosal layers around blood vessels.