Agonist affinity for D2S and serine mutant receptors
| Agonist | Affinity | ||||
|---|---|---|---|---|---|
| D2S | S193A | S194A | S197A | ||
| Dopamine | K H | 0.005 (0.002–0.01) | 2b (1–3) | 4b (2–7) | 0.02 (0.01–0.04) |
| K L | 2 (1–3) | 500b (331–769) | 40b (26–49) | 3 (2–4) | |
| K L/K H | 400 | 250 | 10 | 150 | |
| NPA (nm) | K H | 0.003 (0.001–0.008) | 0.7b (0.3–2) | 3b (2–5) | 0.03 (0.01–0.8) |
| K L | 3 (2–4) | 90b (70–125) | 300b (180–480) | 7 (5–9) | |
| K L/K H | 1000 | 128 | 100 | 233 | |
| DHX | K H | 0.02 (0.01–0.04) | N.D. | N.D. | 0.03 (0.02–0.04) |
| K L | 1 (0.7–2) | 7b (6–9) | 5b (5–6) | 1.4 (1.0–2.0) | |
| K L/K H | 50 | N.D. | N.D. | 47 | |
| Quinpirole | K H | 0.008 (0.0006–0.01) | 0.1 (0.05–0.4) | 0.03 (0.005–0.2) | 0.05 (0.03–0.1) |
| K L | 2 (1–3) | 5 (3–10) | 203-a (8–30) | 2 (1–3) | |
| K L/K H | 250 | 50 | 666 | 40 | |
| 7-OH-DPAT | K H | 0.001 (0.0007–0.002) | 0.01 (0.006–0.03) | 0.01 (0.004–0.03) | 0.002 (0.001–0.006) |
| K L | 0.3 (0.2–0.5) | 3 (1–5) | 0.8 (0.3–2) | 0.5 (0.3–0.8) | |
| K L/K H | 300 | 300 | 80 | 250 | |
The apparent high (K H) and low (K L) affinity values in μm, except as indicated for NPA, of the receptors for agonists were determined by inhibition of the binding of [3H]spiperone to membranes prepared from C6 cells stably expressing wild-type or serine mutant D2S receptors and are expressed as the geometric mean (followed by the limits defined by the standard error) from at least three independent experiments. Affinity values for [3H]spiperone determined from saturation analyses were used to calculateK H and K L values from experimentally determined IC50 values.
N.D., not detectable.
↵3-a p < 0.05, b p < 0.01 compared with D2S (Dunnett’s post hoc repeated-measures analysis of variance).