Nitric oxide synthase in autonomic innervation of the cat carotid body.

In the cat carotid body, nitric oxide synthase (NOS) immunoreactivity and NADPH diaphorase activity localize in nerve fibers mainly associated with blood vessels and occasionally lying close to glomus cells. The NOS-positive innervation originates in part from multipolar ganglion cells scattered in and around the carotid body and in the glossopharyngeal nerve. In the superior cervical ganglion, NOS and diaphorase staining localizes to many preganglionic axons and also to a small population of vasoactive intestinal peptide-positive, presumably cholinergic, ganglion cells. Positively stained ganglion cells are absent in the petrosal ganglion and very rare in the nodose ganglion, although both sensory ganglia display characteristic distributions of cells immunoreactive for calcitonin gene-related peptide, substance P and tyrosine hydroxylase. The NOS-positive innervation of the carotid body thus appears to be autonomic, originating mainly from a population of dispersed ganglion cells, and probably parasympathetic in nature. The superior cervical ganglion also may supply some pre- or postganglionic NOS-positive axons. Nitric oxide released from these nerves could affect glomus cell activity directly or indirectly by vasoregulation.