Synergistically interacting dopamine D1 and NMDA receptors mediate nonvesicular transporter-dependent GABA release from rat striatal medium spiny neurons

Anton N M Schoffelmeer, Louk J M J Vanderschuren, Taco J. De Vries, Francois Hogenboom, George Wardeh, Arie H. Mulder

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Abstract

Given the complex interactions between dopamine D1 and glutamate NMDA receptors in the striatum, we investigated the role of these receptors in transporter-mediated GABA release from cultured medium spiny neurons of rat striatum. Like NMDA receptor-mediated [3H]-GABA release, that induced by prolonged (20 min) dopamine D1 receptor activation was enhanced on omission of external calcium, was action potential-independent (tetrodotoxin- insensitive), and was diminished by the GABA transporter blocker nipecotic acid, indicating the involvement of transporter-mediated release. Interestingly, lowering the external sodium concentration only reduced the stimulatory effect of NMDA. Blockade of Na+/K+-ATPase by ouabain enhanced NMDA-induced but abolished dopamine-induced release. Moreover, dopamine appeared to potentiate the effect of NMDA on [3H]-GABA release. These effects of dopamine were mimicked by forskolin. μ-Opioid receptor-mediated inhibition of adenylyl cyclase by morphine reduced dopamine- and NMDA-induced release. These results confirm previous studies indicating that NMDA receptor activation causes a slow action potential-independent efflux of GABA by reversal of the sodium-dependent GABA transporter on sodium entry through the NMDA receptor channel. Moreover, our data indicate that activation of G- protein-coupled dopamine D1 receptors also induces a transporter-mediated increase in spontaneous GABA release, but through a different mechanism of action, i.e., through cAMP-dependent inhibition of Na+/K+ATPase, inducing accumulation of intracellular sodium, reversal of the GABA carrier, and potentiation of NMDA-induced release. These receptor interactions may play a crucial role in the behavioral activating effects of psychostimulant drugs.

Original languageEnglish
Pages (from-to)3496-3503
Number of pages8
JournalJournal of Neuroscience
Volume20
Issue number9
Publication statusPublished - 1 May 2000

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