LOCALIZATION OF GABA(A) RECEPTOR IMMUNOREACTIVITY IN NO SYNTHASE POSITIVE MYENTERIC NEURONS

GABA(A) receptors were localized within laminar preparations of the ra t distal colon myenteric plexus using a monoclonal antibody (mAb 62-3G 1) to the affinity purified GABA(A) receptor/benzodiazepine receptor/C l- channel complex. The immunofluorescence procedure showed that appro ximately half of the myenteric ganglion cells displayed extensive GABA (A) receptor labelling of their soma. This population was further char acterised by treating some GABA(A)-receptor-labelled laminar preparati ons for the histochemical demonstration of nitric oxide (NO) synthase- related NADPH-dependent diaphorase activity. A subpopulation of the GA BA(A)-receptor-immunoreactive cells (35%) were also found to display i ntense NO-synthase-related activity. These findings extend our underst anding of the GABA(A)-receptor-related innervation of the rat gut wall herein referred to as 'A-GABAergic' and provides an anatomical basis for the pharmacologically-identified GABA-nitrergic pathway in the mam malian gut.