The effect of GABAergic agents on opiate analgesia

The present study shows that the intraventricular injection of muscimol (250 ng/ventricle), a potent GABA receptor agonist, strongly antagonized morphine and β-endorphin analgesia. Furthermore, isoguvacine, a compound structurally related to muscimol, and nipecotic acid and guvacine, inhibitors of GABA uptake, administered intraventricularly markedly attenuated the analgesic effect of morphine. These results further substantiate that the GABAergic system is involved in morphine analgesia. A possible mechanism of action is discussed.