NEURONAL NOS GENE-EXPRESSION IN GASTROINTESTINAL MYENTERIC NEURONS AND SMOOTH-MUSCLE CELLS

Nitric oxide synthase (NOS) has been characterized in different tissue s, and its localization has been suggested in different neuronal tissu es, including the myenteric neurons and other nonneuronal cells. The p resent study examined the distribution of the neuronal NOS (nNOS) mRNA in different tissues of the opossum gastrointestinal tract, internal anal sphincter (IAS) smooth muscle cells, and myenteric neurons using slot-blot and Northern blot hybridization techniques with a specific r at brain nNOS cDNA probe. Significant levels of nNOS gene expression w ere found in both smooth muscle cells and myenteric neurons of the opo ssum IAS. This finding was confirmed by reverse transcriptase-polymera se chain reaction analysis of the RNA obtained from cultured opossum I AS smooth muscle cells and myenteric neurons and also from human intes tinal smooth muscle and neuroblastoma cell lines. Pyloric sphincter ha d the highest level of nNOS gene expression compared with other gastro intestinal tissues. There was no significant difference in the nNOS ge ne expression between other sphincteric and nonsphincteric tissues exa mined. The present study shows the presence of nNOS gene expression in both neurons and smooth muscle cells. The higher levels of nNOS gene expression in the pyloric sphincter compared with other tissues may ha ve pathophysiological significance in some disease conditions.