D-2 dopamine receptors inhibit release of aspartate and glutamate in rat retina.
Release of endogenous Asp, Glu and gamma-aminobutyric acid (GABA) has been investigated using synaptosomes prepared from rat retina. Exposure in superfusion to a depolarizing concentration of KCl (30 mM) evoked overflow of Asp and Glu, which were almost entirely Ca-dependent. However, 70% of the GABA release was Ca-independent. Dopamine (DA) almost completely inhibited the K(+)-evoked release of Asp and Glu in a concentration-dependent manner, but the release of GABA was only partly inhibited. The potencies of DA (IC50) to Asp and Glu release were 12 and 30 nM, respectively. A selective D-2 receptor antagonist, S-sulpiride, counteracted the DA-induced inhibition of Asp and Glu release, but a selective D-1 antagonist, SCH 23390, showed no effect. The data suggest that D-2 dopamine receptors located on the Asp and Glu neurons in rat retina may inhibit the release of these excitatory amino acids.
Kamisaki
Y
Y
Department of Clinical Pharmacology, Tottori University School of Medicine, Yonago, Japan.
Hamahashi
T
T
Mita
C
C
Itoh
T
T
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D004298:Dopamine / Q000494:pharmacology; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D008297:Male; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000502:physiology*; D017448:Receptors, Dopamine D2; D012160:Retina / Q000378:metabolism*; D013469:Sulpiride / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D005971:Glutamates; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D001224:Aspartic Acid; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D013469:Sulpiride; D011188:Potassium; D004298:Dopamine