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 Gαq/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; retoxipride, pipamperone and L 741626 being silentat 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 (Erev: 68%-92% vs. 1 μM tropapride) with a t1/2 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-magntude 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.
- CHO-K1 cells
- Ca response
- Dopamine antagonist
- Recombinant human dopamine D receptor
ASJC Scopus subject areas