Distribution, chemical coding and origin of nitric oxide synthase-containing nerve fibres in the guinea pig nasal mucosa

The distribution, chemical coding and origin of nitric oxide synthase (NOS) -containing nerve fibres in the respiratory mucosa of the nasal septum of t he guinea pig were examined using nicotinamide adenine dinucleotide phospha te diaphorase (NADPH-d) histochemistry and immunohistochemistry. A rich sup ply of NADPH-d-positive nerve fibres was observed around blood vessels and in nasal glands where nerve fibres frequently penetrated into the epithelia of acini and intralobular ducts. NADPH-d reactivity was also found in the nerve fibres located under or within the respiratory epithelium. Combined i mmunofluorescence and histochemical staining of the same preparation demons trated virtually complete overlapping of NOS immunoreactivity and NADPH-d r eactivity in nerve fibres, indicating that NADPH-d can be used as a marker for NOS-containing neurons. Double-labelling using antibodies to vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), and calcitonin gene-re lated peptide (CGRP) revealed that NADPH-d-positive nerve fibres frequently contained VIP or NPY, but not CGRP. Pterygopalatine ganglionectomy signifi cantly reduced the number of NADPH-d-positive nerve fibres innervating the respiratory epithelium as well as blood vessels and nasal glands. Neither s uperior cervical ganglionectomy nor sensory denervation by capsaicin treatm ent affected the distribution of NADPH-d-positive fibres. These results ind icate that NOS-containing nerve fibres innervating the respiratory epitheli um as well as blood vessels and nasal glands in the guinea pig originate ma inly from the pterygopalatine ganglion, and suggest that NO may play a sign ificant role as a neurotransmitter and/or neuromodulator in the control of the respiratory epithelium as well as vasculature and nasal glands. (C) 200 0 Elsevier Science B.V. All rights reserved.