Antagonist binding to membranes of Sf9 cells expressing the D2L receptor and various G proteins. The binding of (+)-butaclamol, haloperidol, clozapine, and raclopride to the D2L receptor co-expressed with Gi1 (a), Gi2 (b), Gi3 (c) or Go (d) was determined in competition vs [3H]-spiperone binding as described in the Methods section. Data shown are representative experiments replicated two to three times and the curves are the best fit curves to a one binding site model. Mean Ki values (nM) for the different compounds are as follows: (+)-butaclamol (0.25, 0.30, 0.33, 0.31); haloperidol (3.9, 2.4, 4.0, 1.8); clozapine (87, 93, 100, 115); raclopride (417, 372, 447, 240) in D2Gi1, D2Gi2, D2Gi3, D2Go, respectively.