CHOLINERGIC, NITRIC OXIDERGIC INNERVATION IN CEREBRAL-ARTERIES OF THECAT

Using immunoperoxidase labeling (IPL) and immunofluorescence labeling (IFL) methods, and each followed by NADPH diaphorase (NADPHd) histoche mical staining in the same specimen, colocalization of choline acetylt ransferase (ChAT) and NADPHd, indicative of nitric oxide synthase (NOS ), in cerebral pial arteries and the sphenopalatine ganglia (SPG) of t he cat was examined. In addition, retrograde axonal tracing using true blue was performed to determine if cerebral perivascular nerves conta ining ChAT and NADPHd originate in the SPG. Consistent results were ob tained from IPL and IFL methods, indicating that the middle cerebral a rtery (MCA) and the circle of Willis received dense ChAT-immunoreactiv e (I) and NADPHd bundles and fine fibers. Almost all ChAT-I fibers and NADPHd fibers were found to be coincident in the arteries examined. A few fine fibers exhibited only NADPHd staining. In the SPG, approxima tely half of the ganglionic cells were both ChAT-I and NADPHd positive , while the remaining cells were positively only for NADPHd staining. One week after application of true blue on the middle cerebral arterie s (MCA), the fluorescent true blue was found in the ganglionic cells o f the SPG. Some of the true blue-positive cells contained both ChAT-im munoreactivity and NADPHd staining. These results provide morphologica l evidence indicating that all ChAT-I fibers in the MCA and the circle of Willis contain NOS, and that these fibers originate in the SPG, al though not all NOS-I ganglionic cells in the SPC send fibers to pial v essels. These results also support the hypothesis that acetylcholine ( ACh) and nitric oxide (NO) are synthesized and co-released in the same neurons in cerebral perivascular nerves. Based on the reported findin gs that NO mediates a major component of neurogenic vasodilation, and that ACh acts as a modulator, the present results demonstrate the pres ence of a cholinergic, nitric oxidergic innervation in cerebral arteri es of the cat. (C) 1997 Elsevier Science B.V.