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

Cell Tissue Res. 1996 Apr;284(1):29-37. doi: 10.1007/s004410050564.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Guinea Pigs
  • Intestine, Small / chemistry*
  • Intestine, Small / enzymology
  • Intestine, Small / innervation
  • Motor Neurons / chemistry*
  • Motor Neurons / enzymology*
  • Motor Neurons / immunology
  • Myenteric Plexus / cytology
  • Myenteric Plexus / immunology
  • Nerve Fibers / chemistry
  • Nerve Fibers / enzymology
  • Nerve Fibers / immunology
  • Nitric Oxide Synthase / analysis
  • Nitric Oxide Synthase / immunology*
  • Tachykinins / analysis
  • Tachykinins / immunology
  • Vasoactive Intestinal Peptide / analysis
  • Vasoactive Intestinal Peptide / immunology
  • gamma-Aminobutyric Acid / analysis
  • gamma-Aminobutyric Acid / immunology*
  • gamma-Aminobutyric Acid / physiology


  • Tachykinins
  • Vasoactive Intestinal Peptide
  • gamma-Aminobutyric Acid
  • Nitric Oxide Synthase