Apparent affinity of Asn-52 and Ser-121 mutant receptors for sodium-sensitive antagonists
| Drug | KI values | ||||
|---|---|---|---|---|---|
| D2 | N52Q | S121A | S121N | ||
| nM | |||||
| Epidepride | +sodium | 0.068 (0.059–0.079) | 0.039 (0.031–0.050) | 0.33 (0.23–0.48)3-a | 0.57 (0.45–0.72)3-a |
| − sodium | 1.85 (1.07–3.18) | 1.45 (1.18–1.79) | 1.34 (0.92–1.96) | 1.80 (1.37–2.36) | |
| Δsodium | 27 | 37 | 4 | 3 | |
| Tropapride | +sodium | 0.096 (0.060–0.153) | 0.15 (0.10–0.21) | 1.38 (0.99–1.93)3-a | 1.70 (1.21–2.39)3-a |
| − sodium | 4.65 (3.79–5.72) | 4.17 (2.97–5.85) | 4.31 (3.71–5.0) | 6.86 (5.12–9.20) | |
| Δsodium | 48 | 28 | 3 | 4 | |
| Piquindone | +sodium | 10.7 (8.3–13.8) | 5.5 (4.6–6.5) | 21.1 (13.7–32.5) | 46.7 (35.7–61.2)3-a |
| − sodium | 137 (103–183) | 71 (56–91) | 89 (68–117) | 181 (143–229) | |
| Δsodium | 13 | 13 | 4 | 4 | |
| Sulpiride | +sodium | 33 (26–44) | 17 (13–21) | 126 (89–178)3-a | 300 (229–394)3-a |
| − sodium | 1440 (1030–2030) | 1810 (1310–2510) | 898 (740–1090) | 1260 (990–1610) | |
| Δsodium | 44 | 106 | 7 | 4 | |
Apparent affinity (K I) values for the indicated drugs were determined by inhibition of the binding of [3H]spiperone, as described under Experimental Procedures. Each value is the geometric mean of three to five independent experiments, followed in parentheses by the limits defined by the asymmetrical S.E. The fold change in affinity resulting from the presence or absence of sodium (Δsodium) is also given.
↵3-a P < 0.05 compared with the affinity of D2L for that drug.