Effect of CBDA (0.01, 0.1, 1.0, 10, 100, 1000 nM) on 8-OH-DPAT-induced stimulation of [35S]GTPγS binding to rat brainstem membranes. Symbols represent mean values ± SEM (n = 6 or 7). Mean Emax and EC50 values for 8-OH-DPAT in panels (A)–(F) that were determined in the presence of VEH (DMSO) or CBDA, together with the 95% confidence limits of these values, are listed in Table 1.