ABSTRACT
The distribution of NADPH-diaphorase positive neurons in normal and spontaneously hypertensive rats was examined using enzyme histochemical techniques. The alimentary tract (AT) was used as a model for the site of the identification of this nitric oxide synthase marker, because of the high neural density in this system. In a bid to show the possible sites of nitric oxide (NO) in the enteric nervous system of the rat, different segments of the AT were examined for the presence of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d)-activity using conventional enzyme histochemical techniques. NADPH-d-positive neurons were observed in the myenteric and submucous plexuses of the different parts of the AT. Some isolated neurons innervating the smooth muscle of the gut also showed NADPH-d- activity. The NADPH-diaphorase-positive neurons have relatively long dendrites that lie parallely to the smooth muscles of the AT. It is concluded that NADPH-diaphorase is present in the neurons of the myenteric and submucous plexuses of the esophagus, stomach, duodenum, jejenum, ileum, colon and rectum of the normal rat. The number of these NADPH-d-positive neurons is about the same in both the myenteric and the submucous plexuses. The NADPH-d-reactivity indicate the presence of nitric oxide synthase, an enzyme involved in the synthesis of NO. The NO in the AT would probably function either as neurotransmitter or as a second messenger in the autonomic regulation of the alimentary tract functions. In addition to the distribution and possible functions of NADPH-d-positive nerves in the AT an update on the functions and pharmacological actions of NO in normal and SHR is given in the discussion.
Key words: Enteric nervous system. Nitric oxide, NADPH, Cardiovascular system, Neurotransmitter, Neurochemistry, rat, SHR.
