Pretreatment of either isoniazid, an aminoacid decarboxylase inhibitor, or GABA receptor antagonist picrotoxin prevented thedepressant effect of diazepam on the amplitude of phrenic discharge.

Results: GABA uptake inhibitor nipecotic acid-induced increase of MAP was blocked by GABAA receptor antagonist bicuculline, but not by GABAB antagonist CGP 35348;

It was found that the antagonist picrotoxin was unable to block the liver fluke to the excitatory effect of GABA, while it could partially block the roundworm to the inhibitory effect of GABA.