Nitric oxide synthase immunoreactive neurons in the rat kidney.

The presence of neurons with nitric oxide synthase (NOS) immunoreactivity was investigated in the rat kidney. Whole kidneys were examined by means of serial sections. The indirect immunocytochemical technique using polyclonal antibody raised against rat brain type Ia NOS and the histochemical technique for nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase are used in this study. NOS-immunoreactive (NOS-IR) neurons varied in size and were observed: (1) associated with nerve bundles at the hilus of the kidney, (2) in the proximity of the lower or middle portion of the interlobar arteries, and (3) on the wall of the renal pelvis. We are presenting anatomic evidence for the presence of neurons in the rat kidney. Their location is consistent with the existence of a parasympathetic innervation of the rat kidney.