Table 3

Affinity of D1, D2, and chimeric dopamine receptors for dopamine in the presence and absence of GTP

 One site in absence of3.810040.081003
200 μM GTP5.360.1249.9  (7.6–13)67.3  (5.7–9.4)6
Addition of(4.0–7.0)(0.09–0.14)

K i values for the binding of [3H]spiperone to chimeric and D2 dopamine receptors and binding of [3H]SCH23390 to D1receptors determined as described in Experimental Procedures. Affinity values (μm) represent geometric mean values for the number of independent experiments indicated (n) with the limits defined by the asymmetrical standard error given in parentheses. The proportion of sites in the high and low affinity classes is also indicated (%).