Mono- and divalent cations modulate the affinities of brain D1 and D2 receptors for dopamine by a mechanism independent of receptor coupling to guanyl nucleotide binding proteins

Naunyn-Schmiedeberg's Archives of Pharmacology
S Urwyler

Abstract

In order to clarify the question of whether the modulatory effects of cations on dopamine receptor affinities are brought about by shifts in the equilibrium of receptor - G protein - coupling, it was investigated whether mono- and divalent cations were still able to modulate rat striatal D1 and D2 receptor affinities after selective inactivation of the G-proteins linked to the two receptors. The Gs-protein coupled to the D1 receptor was eliminated by mild thermal inactivation, and the Gi- (or Go-) protein associated with the D2 receptor by alkylation with a low concentration of N-ethyl-maleimide. Incubation of striatal membranes at 60 degrees C completely abolished the specific binding of 3H-GTP. Both treatments resulted in an increase of the IC50-values for dopamine as a displacer of 3H-SCH 23390 from D1- and of 3H-spiperone from D2 receptors. Concomitantly, the formerly shallow D1 displacement curves became steeper, with their Hill coefficients increasing. This effect was less evident at D2 receptors. Guanosine triphosphate (GTP), which increased the IC50's of dopamine for both receptors approximately two-fold in control membranes, was without effect in pretreated samples, indicating an effective inactivation of the G-protein...Continue Reading

References

Jan 11, 1979·Nature·J W Kebabian, D B Calne
Jan 1, 1986·Naunyn-Schmiedeberg's Archives of Pharmacology·D Grigoriadis, P Seeman
Jun 1, 1986·Naunyn-Schmiedeberg's Archives of Pharmacology·M Minuth, K H Jakobs
Jan 1, 1985·Biochemical Pharmacology·P SeemanO Buchman
Jan 1, 1984·Progress in Neurobiology·U J Zimmerman, W W Schlaepfer
Jul 1, 1982·Proceedings of the National Academy of Sciences of the United States of America·M H MakmanP N Klein

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