Ligand affinity of dopamine D2 receptor in M2, A7, and CHO cells
| A7-D2 | M2-D2 | CHO-D2 | |
|---|---|---|---|
| Dopamine | 8,900 ± 2,630 | 10,100 ± 4,970 | 5,330 ± 2,020 |
| Dopamine + GTP2-150 | 25,175 | 26,455 | ND |
| 6,7-ADTN | 350 ± 70 | 330 ± 120 | ND |
| (−)-Sulpiride | 170 ± 40 | 160 ± 10 | ND |
| Haloperidol | 3.16 ± 0.29 | 2.41 ± 0.47 | 1.80 ± 0.60 |
K i values (nM) were calculated from [3H]spiperone (0.1–0.3 nM) competition binding of agonists and antagonists on D2 stably expressed M2 (ABP-280-deficient), A7 (genetically reconstituted ABP-280), and CHO cells. Curves were fitted as one-site competition binding. Data shown are the mean ± S.E. of three independent experiments, assayed in duplicate. D2 receptor expression levels were 2.48 pmol/mg of protein (M2) versus 2.55 pmol/mg of protein (A7). The stable CHO cell clone used contained receptor levels of 1.07 pmol/mg of protein. No significant change in either agonist or antagonist affinity for D2 receptors was observed in M2, A7, or CHO cells.
↵2-150 GTP concentration was 50 μM; K i was calculated as the average of two experiments.
ND, not determined.