Localization of NADPH-diaphorase in pelvic afferent and efferent pathways of the rat.

The NADPH diaphorase histochemical reaction was used in combination with retrograde axonal transport of Fluorogold (FG) from the major pelvic ganglion (MPG) to determine if NADPH diaphorase is contained within afferent and preganglionic efferent pathways to pelvic visceral organs. In L6 and S1 dorsal root ganglia, 68.5% and 62.2%, respectively, of FG-labeled afferent neurons were NADPH-diaphorase positive. In the sacral parasympathetic nucleus (SPN) of the L6 and S1 spinal cord segments, 49.4% and 51.7%, respectively of FG labeled preganglionic efferent neurons were NADPH-diaphorase positive. NADPH-diaphorase-positive neurons were also observed in laminae I and II of the dorsal horn, around the central canal and in the dorsal commissure. In addition, fiber-like NADPH diaphorase staining was present in superficial dorsal horn, Lissauer's tract and the lateral edge of the dorsal horn extending into the region of the SPN. If NADPH diaphorase activity in neurons does indicate a physiological function of nitric oxide, then nitric oxide may have a role as a neuromodulator or neurotransmitter within visceral afferent and preganglionic efferent pathways to the pelvic viscera in the rat.