Gaba induced excitatory responses in the guinea-pig small intestine are antagonized by bicuculline, picrotoxinin and chloride ion blockers.

Contractions of the guinea-pig ileum elicited by GABA were reversibly antagonised by various concentrations of picrotoxinin and bicuculline. This antagonism was specific for GABA-induced responses, responses to ACh, BK, and HA being unaffected. The chloride ion channel blockers, furosemide, 2 x 10-4 mol/l, and piretanide, 5.5 x 10-5 mol/l, substantially reduced GABA-induced contractions of the ileum but not those elicited by ACh or electrical stimulation of the cholinergic nerves. The action of GABA in stimulating the intrinsic cholinergic nerves appears to be Cl- dependent.