THE DISTRIBUTION OF NITRIC-OXIDE SYNTHASE-IMMUNOREACTIVITY, ADENOSINEDEAMINASE-IMMUNOREACTIVITY AND NEUROPEPTIDE-Y-IMMUNOREACTIVITY THROUGH THE ENTIRE RAT NUCLEUS-TRACTUS-SOLITARIUS - EFFECT OF UNILATERAL NODOSE GANGLIONECTOMY

The present study has employed immunocytochemistry on free-floating se ctions of adult rat medulla oblongata to characterise the distribution of nitric oxide synthase- (NOS), adenosine deaminase- (ADA) and neuro peptide Y- (NPY) immunoreactivity (IR) throughout the entire rostro-ca udal axis of the nucleus tractus solitarius (NTS). In addition, unilat eral nodose ganglionectomy was performed in a group of rats to determi ne whether any observed immunoreactivity was associated with central v agal afferent terminals. NOS-IR was found throughout the entire NTS, i n cells, and both varicose and non-varicose fibres. Furthermore, unila teral nodose ganglionectomy resulted in a clear reduction in NOS-IR (v isualised with diaminobenzidine) in a highly restricted portion of the ipsilateral medial NTS. Similarly, ADA- and NPY-containing cells, fib res and terminals were also found throughout the adult rat NTS. Howeve r: following unilateral nodose ganglionectomy, there was no apparent r eduction in either ADA-IR or NPY-IR on the denervated side of the NTS. These data indicate a role for nitric oxide, purines and neuropeptide Y as neuromodulators within the rat NTS, although only nitric oxide a ppears to be primarily associated with vagal afferent input. Adenosine deaminase and neuropeptide Y-containing neurons appear to be predomin antly postsynaptic to vagal input, although their possible association with vagal afferents cannot be completely excluded. (C) 1998 Elsevier Science B.V. All rights reserved.