gamma-Aminobutyric acid-dependent motility induced by avermectin B1a in the isolated intestine of the guinea pig.

In the isolated ileum of the guinea pig, neurally mediated rhythmic longitudinal mechanical activity was induced by avermectin, a macrolide anthelmintic that releases gamma-aminobutyric acid (GABA) and modulates the GABAA-receptor-ionophore complex. This avermectin-induced activity was dependent on GABA, being reduced or abolished by bicuculline, a GABAA-receptor antagonist, and by 3-mercaptopropionic acid which prevents neural GABA release. These results provide additional direct evidence that GABA is a functional neurotransmitter in the myenteric plexus of the guinea pig intestine, evidently involved in the regulation of intestinal motility.