Abstract.
Real-time analysis of dopamine:antagonist interactions at the recombinant D2short receptor was performed by measuring time-dependent Ca2+ responses following activation of a chimeric Gα q/o protein in CHO-K1 cells. Terguride (57%), (+)-UH 232 (20%) and buspirone (16%) demonstrated dopamine-like intrinsic activity at the presumably unoccupied, dopamine-free receptor; remoxipride, pipamperone and L 741626 being silent at 1 µM. Each of the putative antagonists (1 µM) displayed a transient reversal capacity of the low-magnitude Ca2+ phase in the dopamine-bound receptor state (E rev: 68%–92% vs. 1 µM tropapride) with a t 1/2 between 8.8 s and 13.9 s upon antagonist addition; this capacity was either almost fully [remoxipride, pipamperone and (+)-UH 232] or partially [buspirone (31%), terguride (45%) and L 741626 (70%)] lost upon further incubation. The biphasic reversal Ca2+ profile of these dopamine antagonists is different from previously characterised dopamine antagonists which display either full reversal of the low-magnitude Ca2+ response with a fast or slow onset of action, or partial reversal stably present over the entire incubation period. The dynamic Ca2+ data strongly suggest that the dopamine D2short receptor can be blocked via multiple molecular mechanisms.
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Pauwels, P.J., Koek, W. Atypical kinetics for a series of putative dopamine antagonists to reverse the low-magnitude Ca2+ phase in the dopamine-bound D2short receptor state. Naunyn-Schmied Arch Pharmacol 365, 82–85 (2002). https://doi.org/10.1007/s00210-001-0487-9
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DOI: https://doi.org/10.1007/s00210-001-0487-9