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D 2 Dopamine Receptors in Calf Globus Pallidus: Agonist High‐ and Low‐Affinity Sites Not Regulated by Guanine Nucleotide
Author(s) -
Keyser Jacques,
Backer JeanPaul,
Convents André,
Ebinger Guy,
Vauquelin Georges
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb04091.x
Subject(s) - globus pallidus , gtp' , agonist , dopamine , spiperone , radioligand , dopamine receptor , medicine , chemistry , endocrinology , receptor , biology , basal ganglia , biochemistry , central nervous system , enzyme
By use of the radioligand [ 3 H]spiroperidol, D 2 3,4‐dihydroxyphenylethylamine (dopamine) receptor binding characteristics were studied in calf globus pallidus and compared with those of neostriatum. Antagonist competition curves were monophasic and revealed similar affinities for neostriatum and globus pallidus, suggesting a uniform receptor population with one affinity state for antagonists. In both regions, competition curves with the agonist dopamine were biphasic, distinguishing a high‐ and low‐agonist‐affinity state. In neostriatum and globus pallidus, respectively, 45% and 19% of [ 3 H]spiroperidol binding was displaced with high affinity and the remainder with low affinity. In neostriatum, the addition of 0.4 m M GTP resulted in a partial conversion from high‐ to low‐affinity state with a remaining highaffinity component of 15%. In globus pallidus, dopamine binding was not altered by GTP. The capability of GTP to modulate agonist binding to D 2 receptors appears to be dependent on their neuroanatomical localization.