D2 RECEPTOR-MEDIATED INHIBITION OF GABA RELEASE BY ENDOGENOUS DOPAMINE IN THE RAT GLOBUS-PALLIDUS

Attempting to better understand the role of the dopaminergic innervati on in the rat globus pallidus, we examined here whether or not endogen ous dopamine modulates the release of [H-3]GABA in superfused pallidal slices. The superfusion medium contained elevated (15 mM) potassium. The release of endogenous dopamine was induced by the dopamine release r drug, methamphetamine. Methamphetamine (100 mu M) inhibited by 46% t he release of [H-3]GABA. Methamphetamine inhibition was completely blo cked by reserpinization of the rats. It was also completely blocked by the D2 dopamine receptor antagonist sulpiride (10 mu M). Sulpiride al one caused a 105% increase in GABA release. The increase was not obser ved in slices from reserpinized rats. Quinpirole (10 mu M), a D2 dopam ine receptor agonist, inhibited (43%) [H-3]GABA release. The results s uggest that endogenous dopamine exerts an inhibitory effect on GABA re lease in the rat globus pallidus. The effect is mediated by D2 recepto rs presumably located on striatopallidal axon terminals. (C) 1997 Else vier Science Ireland Ltd.