SEGREGATION OF VIPERGIC-NITRIC OXIDERGIC AND CHOLINERGIC-NITRIC OXIDERGIC INNERVATION IN PORCINE MIDDLE CEREBRAL-ARTERIES

The distribution of nitric oxide synthase (NOS)-, choline acetyltransf erase (ChAT)-, and vasoactive intestinal polypeptide (VIP)-immunoreact ivities, and nicotinamide adenine dinucleotide phosphate diaphorase (N ADPHd)-reactivities in the sphenopalatine ganglia (SPG), and perivascu lar nerves in middle cerebral arteries of the pig was investigated by double-staining techniques using combined immunofluorescence and histo chemistry methods. In the SPG, almost all ganglionic cells were NOS-im munoreactive (I) and NADPHd-positive, and both NOS immunoreactivities and NADPHd reactivities were completely co-localized. ChAT-I ganglioni c cells accounted for 75%, while VIP-I ganglionic cells represented 42 % of all ganglionic cells. Almost all VIP immunoreactivities were co-l ocalized with ChAT immunoreactivities, and all ganglionic cells that w ere VIP-I and/or ChAT-I were NOS-I and NADPHd-reactive. None of the ga nglionic cells in the SPG were immunoreactive to calcitonin gene-relat ed peptide (CGRP). CGRP immunoreactivities, however, were found to sur round some ganglionic cells. In middle cerebral arteries, all adventit ial NOS-I bundles and fine fibers were coincident with NADPHd fibers. Almost all adventitial ChAT-I bundles and thin fibers, and VIP-I mesh- like fibers stained positively for NADPHd, while the mesh-like NADPHd fine fibers were not ChAT-I. Simultaneous labeling using antibodies ag ainst VIP and ChAT further indicated that VIP-I fibers were closer tha n ChAT-I fibers to the smooth muscle. In rare occasions, perivascular fibers were found to be stained for both ChAT and VIP, showing that mo st ChAT-I and VIP-I fibers were not coincident. These results suggest that ChAT and VIP are rarely co-localized in perivascular nerves in mi ddle cerebral arteries, and point out that the neurotransmitter and th e modulator that are co-localized within the same nerve cell body may distribute totally independently and differently at the terminal level . The present results also indicate that in cerebral perivascular nerv es, the combination of nitric oxide (NO) and acetylcholine (ACh), as w ell as the combination of NO and VIP, are localized in the same nerve with different axons containing either NO plus ACh, or NO plus VIP. Th ese findings support the hypothesis that ACh and VIP may act as modula tors in regulating presynaptic release of NO, and therefore, cerebral neurogenic vasodilation, from their respective perivascular cholinergi c-nitric oxidergic and VIPegic-nitric oxidergic nerves. (C) 1998 Elsev ier Science B.V. All rights reserved.