Classification of the enteric nerve cells of the porcine small intestine into two subpopulations using enzyme histochemical techniques

Abstract

Using acetylcholinesterase (AChE), nicotinamide adenine dinucleotide diaphorase (NADHd), and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) enzyme histochemical techniques, the ganglionated plexuses of the porcine enteric nervous system were investigated in small intestine whole-mount preparations. Both AchE and NADHd techniques revealed a majority of the neurons in the ganglia of all three major plexuses. The AchE technique also demonstrated clearly the axodendritic networks of the plexus myentericus. Intraganglionic blank areas revealed the localization of negative cell groups. A very high correlation was found between the activity of both enzymes in one neuron, although this correlation was certainly not linear. Many neurons exhibited a stronger signal for one enzyme. A very small part of the positive nerve cells showed intense staining for both AchE and NADHd. The NADPHd technique demonstrated that the NADPHd-positive neurons fill the negative intraganglionic spaces in the ganglia. Double staining with the two other enzymes showed virtually no colocalization of NADPHd with either NADHd or AchE in the porcine jejunal enteric ganglia. Little negative intraganglionic spaces were seldom found, leaving room for perhaps still more negative enteric neurons. Based upon these results we suggest that the enteric neurons of the porcine small intestine can be subdivided into AchE-NADHd and NADPHd subpopulations. Since the latter colocalizes with the neuronal NO synthase enzyme, we further suggest a subdivision of the enteric nerve cells into AchE-NADHd and NOS-NADHd neurons.