TABLE 5

Potencies of histaprodifens acting as antagonists at hH₁R, h_gpE2H₁R, and h_gpNgpE2H₁R determined in the steady-state GTPase assay at Sf9 cell membranes expressing hH₁R, h_gpE2H₁R, or h_gpNgpE2H₁R, and RGS4 The potencies of 4S, 6R, and 6S were determined in the steady-state GTPase assay as described under Materials and Methods. Each assay tube additionally contained 1 μM histamine. Data were analyzed by nonlinear regression and were best fit to sigmoidal concentration-response curves. The pK_B values were calculated according to Cheng and Prusoff (1973) method. Data shown are means ± S.E.M. of at least three experiments, each one performed in duplicate or triplicate. Membranes were used from independent membrane preparations.