GABA and nitric oxide synthase immunoreactivities are colocalized in a subset of inhibitory motor neurons of the guinea-pig small intestine.
Simultaneous immunofluorescence labelling was used to determine the patterns of colocalization of immunoreactivity for gamma-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 layers, about 75% were NOS-IR. Conversely, 20% of NOS-IR nerve cells were GABA-IR. About 6% of GABA-IR nerve fibres innervating the circular muscle, but none innervating the longitudinal muscle, were TK-IR. Most GABA-IR fibres supplying the circular muscle, but none of those supplying the longitudinal muscle, were VIP-IR. From this study, and previous studies of projections of enteric neurons, it is concluded that most GABA-IR neurons in the guinea-pig small intestine are inhibitory motor neurons that also contain NOS-IR. A small proportion represents anally directed excitatory motor neurons that innervate the circular muscle and are also immunoreactive for TK.
Williamson
S
S
Department of Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria 3052, Australia.
Pompolo
S
S
Furness
J B
JB
D000818:Animals; D006168:Guinea Pigs; D007421:Intestine, Small / Q000737:chemistry* / Q000201:enzymology / Q000294:innervation; D009046:Motor Neurons / Q000737:chemistry* / Q000201:enzymology* / Q000276:immunology; D009197:Myenteric Plexus / Q000166:cytology / Q000276:immunology; D009412:Nerve Fibers / Q000737:chemistry / Q000201:enzymology / Q000276:immunology; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000276:immunology*; D015320:Tachykinins / Q000032:analysis / Q000276:immunology; D014660:Vasoactive Intestinal Peptide / Q000032:analysis / Q000276:immunology; D005680:gamma-Aminobutyric Acid / Q000032:analysis / Q000276:immunology* / Q000502:physiology
D015320:Tachykinins; D014660:Vasoactive Intestinal Peptide; D005680:gamma-Aminobutyric Acid; D019001:Nitric Oxide Synthase