Consecutive diaphorase-acetylcholinesterase histochemistry in the myenteric plexus of frog stomach

An investigation was made on the frog stomach myenteric plexus with 2 different histochemical techniques. Neuronal perikarya were stained with nicotinamide-adenine-dinucleotide-diaphorase (NADHd), while the acetyl-cholinesterase (AChE) staining showed rather the axoarchitectonic arrangement of the frog myenteric plexus. In double-labelled "whole mounts", NADHd-positive cell bodies and AChE-positive nerve processes were revealed. Some of the nerve cells and neuronal processes did not exhibit AChE activity at all. Since glyoxylic acid-induced fluorescence (GIF) was not detected in the myenteric plexus, the presence of catecholamines can be excluded. As a consequence of these observations, we suggest the presence of a non-cholinergic, non-adrenergic intrinsic neuronal system in the frog stomach myenteric plexus, containing purines or peptides as transmitters.