Regional differences in the number and type of myenteric neurons in the descending colon of rats.

The purpose of this study was to analyze the neuronal density of the myenteric plexus of the intermediate and antimesocolic regions of the descending colon of rats. Whole-mounts were stained with three different techniques of neuronal evidenciation. Through counts of the number of neurons in an area of 6.64 mm under light microscopy, we found 1,271 +/- 227.54 neurons with Giemsa in the intermediate region and 1,234 +/- 225.92 neurons in the antimesocolic region; with the NADH-diaphorase technique we found 530 +/- 92.97 neurons in the intermediate region and 539 +/- 146.72 neurons in the antimesocolic region; and through the NADPH-diaphorase histochemistry, we found 417 +/- 34.42 neurons in the intermediate region and 547 +/- 84.01 neurons in the antimesocolic region. We conclude that there is a variation in the density of NADPH-diaphorase positive neurons in the intestinal circumference; that the NADH-diaphorase positive neuronal subpopulation represented 42.7% of that stained with Giemsa; and that the NADPH-diaphorase positive neurons represented 37.8% of the whole myenteric population.