Dynamic dopamine-antagonist interactions at recombinant human dopamine D(2short) receptor: dopamine-bound versus antagonist-bound receptor states.
Antipsychotic drugs comprise a wide range of structurally diverse compounds and are considered to be antagonists at dopamine D2 receptors. High-resolution kinetic analyses of their antagonist properties was performed by monitoring dynamic dopamine (DA)-antagonist interactions at the recombinant human dopamine D(2short) receptor. Time-dependent Ca2+ responses were measured following activation of a chimeric G(alphaq/o) protein in Chinese hamster ovary-K1 cells. DA (10 microM) induced a rapid, high-magnitude Ca2+ response (T(max) = 13.2 +/- 0.7 s) followed by a low-magnitude phase, which continued throughout the recorded time period (15 min). Of a large series of putative DA antagonists, (+)-UH 232 and bromerguride demonstrated positive, DA-like intrinsic activity at the presumably unoccupied, DA-free receptor; the other antagonists being silent. Antagonists differed in terms of their abilities to prevent the high-magnitude Ca2+ phase in the antagonist-bound receptor state, and to reverse the low-magnitude Ca2+ phase in the DA-bound state. The benzamide derivatives tropapride and nemonapride fully antagonized both the high- and low-magnitude Ca2+ response. Haloperidol, risperidone, and S 14066 also antagonized both responses but with a maximal effect of only 62 to 79%. Although preventing the high-magnitude response (85-95%), the further putative antagonists (+)-butaclamol (6%), bromerguride (27%), and domperidone (41%) reversed the low-magnitude response only weakly and partially. These Ca2+ data indicate that putative DA antagonists act differently, in particular, at the DA-bound D(2short) receptor.
Pauwels
P J
PJ
Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 17 Avenue Jean Moulin, 81106 Castres Cedex, France. peter.pauwels@pierre-fabre.com
Finana
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Tardif
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Wurch
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Colpaert
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D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D004298:Dopamine / Q000378:metabolism / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; D011994:Recombinant Proteins; D002118:Calcium; D004298:Dopamine