Glutamatergic Control of Dopamine Release in the Rat Striatum: Evidence for Presynaptic N‐Methyl‐D‐Aspartate Receptors on Dopaminergic Nerve Terminals

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Abstract
The N-methyl-D-aspartate (NMDA) receptor-mediated regulation of the release of newly synthesized [3H]dopamine ([3H]DA) was studied in vitro, both on rat striatal slices using a new microsuperfusion device and on rat striatal synaptosomes. Under Mg2+-free medium conditions, the NMDA (5 × 10−5M)-evoked release of [3H]DA from slices was found to be partly insensitive to tetrodotoxin (TTX). This TTX-resistant stimulatory effect of NMDA was blocked by either Mg2+ (10−3M) or the noncompetitive antagonist MK-801 (10−6M). In addition, the TTX-resistant NMDA-evoked response could be potentiated by glycine (10−6M) in the presence of strychnine (10−6M). The coapplication of NMDA (5 × 10−5M) and glycine (10−6M) stimulated the release of [3H]DA from striatal synaptosomes. This effect was blocked by Mg2+ (10−3M) or MK-801 (10−5M). These results indicate that some of the NMDA receptors involved in the facilitation of DA release are located on DA nerve terminals. These presynaptic receptors exhibit pharmacological properties similar to those described in electro-physiological studies for postsynaptic NMDA receptors.