Article

Regulation of excitatory amino acid release by N-methyl-D-aspartate receptors in rat striatum: in vivo microdialysis studies.

Department of Cell and Molecular Biology, Catholic University of Chile, Santiago.
Brain Research (impact factor: 2.73). 08/1992; 585(1-2):105-15. DOI:10.1016/0006-8993(92)91195-K pp.105-15
Source: PubMed

ABSTRACT The microdialysis technique was utilized to study the effects of N-methyl-D-aspartate (NMDA) receptor ligands on the in vivo release of endogenous glutamate (Glu) and aspartate (Asp) from the rat striatum. Addition of NMDA (250 and 500 microM) to the dialysis perfusion solution resulted in a striking dose-dependent increase in extracellular concentrations of Glu and Asp in the striatum. The NMDA-induced effects were reduced in a dose-related way by prior perfusion with 75 microM dizocilpine (MK-801), a non-competitive NMDA receptor antagonist. MK-801, at 75 microM, produced no changes on basal levels of Glu and Asp. However, 100 microM MK-801 did increase Glu and Asp extracellular concentrations. Local infusion with 500 microM D-serine, an agonist at the glycine site associated to the NMDA receptor, significantly increased basal level of Glu, but not Asp. Such D-serine-induced effects were reduced by 7-Cl-kynurenic acid (200 microM), a selective blocker of the glycine site present in the NMDA receptor. It is proposed that activation of NMDA receptors by endogenous Glu and Asp enhances the subsequent release of these excitatory amino acids in the striatum. Part of these NMDA receptors might be located presynaptically on cortico-striatal nerve endings. In addition, postsynaptic NMDA receptors present in the striatum may also indirectly modulate the release of Glu and Asp, through trans-synaptic mechanism.

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Keywords

500 microM D-serine
 
7-Cl-kynurenic acid
 
75 microM dizocilpine
 
Asp extracellular concentrations
 
basal levels
 
cortico-striatal nerve endings
 
D-serine-induced effects
 
dialysis perfusion solution
 
dose-related way
 
excitatory amino acids
 
extracellular concentrations
 
glycine site present
 
N-methyl-D-aspartate
 
NMDA receptor
 
NMDA receptors
 
NMDA-induced effects
 
non-competitive NMDA receptor antagonist
 
postsynaptic NMDA receptors present
 
rat striatum
 
trans-synaptic mechanism