GABA A and GABA B antagonists prevent the opioid inhibition of endogenous acetylcholine release evoked by glutamate from rat neostriatal slices

Abstract

We have examined the role of the GABAergic system in the opioid inhibition of endogenous acetylcholine (ACh) release from rat neostriatal slices by blocking either γ-aminobutyric acid-A (GABA A) or GABA B receptors. GABAergic antagonists (bicuculline or phaclofen) completely blocked μ- (morphine or DAGO) and δ-opioid (DPDPE) inhibition of glutamate-evoked endogenous ACh release in a concentration-dependent manner. However, GABA antagonists were ineffective in blocking the opioid inhibition of potassium-evoked endogenous ACh release. These findings point to the important role of the GABAergic system in the regulation of μ- and δ-opioid inhibition of cholinergic neurons stimulated by glutamate.