Aspartate-releasing nerve terminals in rat striatum possess D-2 dopamine receptors mediating inhibition of release.
The release of endogenous aspartic acid has been investigated using synaptosomes from rat corpus striatum. Exposure in superfusion to a depolarizing concentration of KCl (15 mM) evoked an overflow of aspartate which was almost entirely calcium-dependent. When added to the superfusion medium, dopamine (DA) and the selective DA D-2 receptor agonists quinpirole (LY-171555) and pergolide inhibited the K+ -evoked aspartate release in a concentration-dependent manner. The natural agonist DA was very potent (IC50 = 1 nM). The selective D-1 receptor agonist SK&F 38393 had no effect on the release of aspartate. The selective D-2 receptor antagonist S-sulpiride, but not the R-enantiomer, antagonized the DA-induced inhibition of aspartate release. The DA effect was unaltered by SCH 23390, a selective dopamine D-1 receptor antagonist. The findings that 1) the release of endogenous aspartate evoked by depolarization was calcium-dependent and 2) the release of aspartate was potently modulated through D-2 receptors are compatible with the idea that aspartate is released as a transmitter from striatal axon terminals. The possibility that aspartate and glutamate are coreleased from these terminals is discussed.
Maura
G
G
Istituto di Farmacologia e Farmacognosia, Università degli Studi di Genova, Italy.
Carbone
R
R
Raiteri
M
M
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D003342:Corpus Striatum / Q000378:metabolism*; D004298:Dopamine / Q000494:pharmacology; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000502:physiology*; D017448:Receptors, Dopamine D2; D013469:Sulpiride / Q000494:pharmacology
D005971:Glutamates; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D001224:Aspartic Acid; D018698:Glutamic Acid; D013469:Sulpiride; D002118:Calcium; D004298:Dopamine