Presence of gamma-aminobutyric acid and glutamic acid decarboxylase in Auerbach's plexus of cat colon.

Regional distributions of endogenous gamma-aminobutyric acid (GABA) and ganglion cells in Auerbach's plexus were studied in the gastrointestinal tract of cats. GABA was determined by enzymatic and fluorometric assay. There was a positive correlation between the GABA content and the number of cells in this plexus. We analyzed the precise localization of GABA and glutamic acid-decarboxylase (GAD) in individual layers, mucosa, circular and longitudinal muscles and Auerbach's plexus, from freeze-dried sections of cat colon by the enzymatic cycling method. Both GABA contents and GAD activity in Auerbach's plexus were highest in all 4 layers. Thus, the possibility that GABA is synthesized and localized within Auerbach's plexus has to be considered.