TABLE 1

D2 and A2A receptor density following prolonged ligand exposure in CAD cells expressing D2L-VN, A2A-CN, and A2A-CC

D2L-VN density was estimated in single point binding experiments using [3H]spiperone; A2A-CN and A2A-CC density was estimated in single point binding experiments using [3H]ZM 241-385. Data are means ± S.E.M. of at least four independent experiments assayed in triplicate. Receptor density in vehicle-treated cells was 2560 ± 260 (D2L, n = 10) and 5410 ± 520 (A2A, n = 5) fmol/mg protein. Untransfected cells did not exhibit detectable D2 and A2A binding levels in this single point assay.

Ligand Receptor Density
D2 A2A
% vehicle
Quinpirole (10 μM) 140 ± 5* 128 ± 4*
S-(−)-Sulpiride (10 μM) 172 ± 10* 124 ± 7*#
MECA (10 μM) 96 ± 7 122 ± 1*#
CGS15943 (10 μM) 85 ± 9 N.D.

  • N.D., not determined.

  • ↵* P < 0.05, one-sample t test.

  • ↵# P < 0.05, unpaired two-tailed t test compared with D2.