NITRIC-OXIDE SYNTHASE, CHOLINE-ACETYLTRANSFERASE, CATECHOLAMINE ENZYMES AND NEUROPEPTIDES AND THEIR COLOCALIZATION IN THE ANTERIOR PELVIC GANGLION, THE INFERIOR MESENTERIC GANGLION AND THE HYPOGASTRIC NERVE OFTHE MALE GUINEA-PIG

By the indirect immunofluorescence method, the distribution of nitric oxide synthase (NOS)-like immunoreactivity (LI) and its possible coloc alization with neuropeptide immunoreactivities, with two enzymes for t he catecholamine synthesis pathway, tyrosine hydroxylase (TH) and dopa mine beta-hydroxylase (DBH), as well as the enzyme for the acetylcholi ne synthesis pathway, choline acetyltransferase (ChAT) were studied in the anterior pelvic ganglion (APG), the inferior mesenteric ganglion (IMG) and the hypogastric nerve in the male guinea pig. The analyses w ere performed on tissues from intact animals, as well as after compres sion/ligation or cut of the hypogastric nerve. In some cases the colon ic nerves were also cut. Analysis of the APG showed two main neuronal cell populations, one group containing NOS localized in the caudal par t of the APG and one TK-positive group lacking NOS in its cranial part . The majority of the NOS-positive neurons contained ChAT-LI. Some NOS -positive cells did not contain detectable ChAT, but all ChAT-positive cells contained NOS. NOS neurons often contained peptides, including vasoactive intestinal peptide (VIP), neuropeptide tyrosine (NPY), soma tostatin (SOM) and/or calcitonin gene-related peptide (CGRP). Some NOS cells expressed DBH, but never TH. The second cell group, characteriz ed by absence of NOS, contained TH, mostly DBH and NPY and occasionall y SOM and CGRP. Some TH-positive neurons lacked DBH. In the IMG, the N OS-LI was principally in nerve fibers, which were of two types, one co nsisting of strongly immunoreactive, coarse, varicose fibers with a pa tchy distribution, the other one forming fine, varicose, weakly immuno reactive fibers with a more general distribution. In the coarse networ ks, NOS-LI coexisted with VIP-and DYN-LI and the fibers surrounded mai nly the SOM-containing noradrenergic principal ganglion cells. A netwo rk of ChAT-positive, often NOS-containing nerve fibers, surrounded the principal neurons. Occasional neuronal cell bodies in the IMG contain ed both NOS-and ChAT-LI. Accumulation of NOS was observed, both caudal and cranial, to a crush of the hypogastric nerve. VIP accumulated mai nly on the caudal side and often coexisted with NOS. NPY accumulated o n both sides of the crush, but mainly on the cranial side, and ENK was exclusively on the cranial side. Neither peptide coexisted with NOS. Both substance P (SP) and CGRP showed the strongest accumulation on th e cranial side, possibly partly colocalized with NOS. It is concluded that the APG in the male guinea-pig consists of two major complementar y neuron populations, the cholinergic neurons always containing NOS an d the noradrenergic neurons containing TH and DBH. Some NOS neurons la cked ChAT and could represent truly non-adrenergic, non-cholinergic ne urons. In addition, there may be a small dopaminergic neuron populatio n, that is containing TH but lacking DBH. The cholinergic NOS neurons contain varying combinations of peptides. The noradrenergic population often contained NPY and occasionally SOM and CGRP. It is suggested th at NO may interact with a number of other messenger molecules to play a role both within the APG and IMG and also in the projection areas of the APG. (C) 1997 Elsevier Science B.V.