Localization of nicotinamide adenine dinucleotide phosphate-diaphorase reactivity and nitric oxide synthase immunoreactivity in the lumbosacral dorsal root ganglia in guinea pigs

This study examined the distribution of reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) reactivity and nitric oxide synthase (NOS) immunoreactivity in the lumbosacral dorsal root ganglia (DRG) in male guinea pigs. A differential distribution of NADPH-d reactivity and NOS immunoreactivity was detected in neurons of DRG at different segmental levels. There were numerically more intensely stained NADPH-d and NOS reactive cells in the rostral (L1-L3) DRG compared with those at the caudal (L6-S4) levels. In the corresponding DRG, NADPH-d reactivity was not paralleled by NOS immunoreactivity. This was evidenced by the wide distribution of afferent neurons in the lumbosacral DRG stained for NADPH-d, yet only a small number of them exhibited NOS immunoreactivity. Double labelling study has shown that some of the NADPH-d positive neurons were NOS negative. Ultrastructurally, NADPH-d reaction product was associated with the membranes of various subcellular organelles, including the rough endoplasmic reticulum (rER), Golgi saccules, mitochondria and some segments of the nuclear envelop, whereas NOS immune-precipitate was patchily distributed throughout the cytoplasm. Present results suggest that nitric oxide (NO) may function as a neurotransmitter in the afferent pathways at lumbosacral segments. On the other hand, in view of their marked disparity in numbers and the lack of total one-to-one correspondence, it seems likely that the NOS positive neurons represent only a subpopulation of the NADPH-d positive cells in the lumbosacral DRG.