QUANTITATIVE STUDY OF THE NADPH-DIAPHORASE-POSITIVE MYENTERIC NEURONSOF THE RAT ILEUM

The subpopulation of myenteric neurons able to synthesize nitric oxide was studied quantitatively in the adult rat, using the NADPH-diaphora se histochemical method on whole-mount preparations of distended dista l ileum. The spatial density of NADPH-diaphorase-positive myenteric ne urons was 2388 +/- 193/cm(2) (S.D.; five rats), comprising about 27% o f the nerve cell bodies per ganglion. Most neurons were intensely stai ned and displayed predominantly a Dogiel type I morphology; about 8% o f the labelled nerve cells were ovoid neurons, exhibiting a pale cytop lasmic reaction product. The mean somatic size of all NADPH-diaphorase -positive myenteric neurons was 446 +/- 40 mu m(2), with a mean nuclea r size of 96 +/- 18 mu m(2) (mean values +/- S.D.; five rats). Such va lues fell exactly within the range of neuronal sizes of the total myen teric population, marked by means of NADH-diaphorase histochemistry. T herefore, the morphometric analysis did not identify any peculiar cell size feature, characterizing this specific nerve cell subpopulation. Thus, the present study provides quantitative data on the size, densit y and proportion of those myenteric neurons that may synthesize nitric oxide in the distal ileum of the rat.