Nitric oxide synthase and NADPH-diaphorase in neurons of the rat, dog and guinea pig nodose ganglia.

Localization of nitric oxide synthase (NOS) in the nodose ganglia of the dog, rat and guinea pig was investigated. A double-staining technique of NOS immunohistochemistry and NADPH-diaphorase (NADPHd) histochemistry was used; then the ratio of NADPHd-positive and NOS-positive cells to the total cells was calculated. The distribution of positive cells within the canine nodose ganglion was also investigated. NADPHd-positive neurons were detected in all the ganglia. Three intensities of reactivity to NADPHd histochemistry (strong, weak or negative) were detected in the neurons of all three species. There were more cells that stained strongly for NADPHd in the rat, but fewer in the dog and guinea pig, indicating that a species difference may exist. NADPHd-positive neurons were less abundant in the rostral third of the canine nodose ganglion than in the middle or caudal thirds. NADPHd reactivity was completely co-localized to the cells that demonstrated neuronal NOS immunoreactivity in the canine nodose ganglion. Thus, NADPHd histochemical reactivity may be a reliable marker of NOS in the nodose ganglion.