Intrapallidal D-2 dopamine receptors control globus pallidus neuron activity in the rat

Because activation of D-2 dopamine receptors inhibits gamma -aminobutyric a cid (GABA) release from intrapallidal nerve terminals, we measured the effe cts of modifiers of dopamine D-2 receptors on the firing rate of single neu rons in the globus pallidus (GP) of the anesthetized rat. The predominant e ffect of intrapallidal administration of the selective D-2 agonist quinpiro le was an increase in the rate of spontaneous firing while the D-2 blocker sulpiride caused a decrease. The spontaneous firing of GP neurons is inhibi ted by stimulation of the GABAergic striatopallidal projection. We therefor e measured the effects of modifiers of D-2 receptors on striatal inhibition of GP neurons and found that intrapallidal quinpirole blocked the inhibito ry effects of striatal stimulation while sulpiride enhanced them. These exp eriments show that both the spontaneous rate of firing of pallidal neurons and its modification by striatopallidal inputs is controlled by intrapallid al dopamine D-2 receptors. In addition, taken together with other findings in the literature, our results suggest that activation of dopamine D-2 rece ptors within the globus pallidus leads to inhibition of GABA release from p resynaptic terminals. (C) 2001 Published by Elsevier Science Ireland Ltd.