GABA and nitric oxide synthase immunoreactivities are colocalized in a subset of inhibitory motor neurons of the guinea-pig small intestine

Abstract

Simultaneous immunofluorescence labelling was used to determine the patterns of colocalization of immunoreactivity for γ-aminobutyric acid (GABA-IR) with immunoreactivity for nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP) and tachykinins (TK) in nerve cells and fibres of the guinea-pig small intestine. GABA-IR nerve cell bodies were located in the myenteric plexus and varicose fibres innervated the circular and longitudinal muscle, but did not form pericellular endings in the myenteric ganglia. GABA-IR nerve cells comprised 4-5% of all nerve cells in the myenteric ganglia. Of GABA-IR myenteric nerve cells, about 85% had NOS-IR and of GABA-IR nerve fibres in both muscle laye..