Stimulation of specific Aeromonas antibody secretion in rat intestine by γ-aminobutyric acid

This study was undertaken to assess a possible role for γ-aminobutyric acid (GABA) in the regulation of intestinal secretion of IgA and IgG antibodies. Rats were immunized with culture supernatant of Aeromonas hydrophila isolate SSU. This culture supernatant contains a number of toxins that may be considered virulence factors. After 24 days of immunization, rats were anesthetized and a 10-cm intestinal segment was intubated and ligated at both ends in situ. The intestinal loop was perfused with phosphate-buffered saline (PBS). The effluents were collected for measurement of IgA and IgG by the ELISA. When compared with the effect of intravenous administration of normal saline in the control group, intravenous injection of GABA (30 mg/kg) resulted in a significant increase of IgA and IgG secretion in the experimental group. These stimulatory effects of GABA on secretion of IgA and IgG were abolished by bicuculline, a GABA-receptor antagonist, and by atropine, indicating that the GABA-stimulated secretion of IgA and IgG was mediated via the GABA receptors and cholinergic muscarinic receptors. These results suggest that GABA may participate in the nervous regulation of intestinal secretion of IgA and IgG antibodies in the rat.