Table 3

Potencies of WIN 55212-2 in stimulating [35S]GTPγS and displacing [3H]SR141716A binding

RegionWIN 55212-2 ED50vs.[35S]GTPγSWIN 55212-2 Kivs. [3H]SR141716AWIN55212-2Ki/ED50 Ratio
nM nM
Cerebellum156  ± 16a338  ± 85a2.39  ± 0.52a
Amygdala84  ± 20b87  ± 29b1.10  ± 0.27ab
Hypothalamus131  ± 13ab109  ± 28b0.86  ± 0.20b

ED50 values and IC50 values were determined for WIN 55212-2 stimulation of [35S]GTPγS binding and WIN 55212-2 displacement of [3H]SR141716A binding simultaneously by incubating membranes with either 0.05 nM [35S]GTPγS or 0.05 nM unlabeled GTPγS (for [3H]SR141716A), along with 30 μM GDP and 30 to 10,000 nM WIN 55212-2. K i values were calculated by the equation: K i = IC50/([L]/K D) + 1) (Cheng and Prusoff, 1973), where [L] was the concentration of [3H]SR141716A in each assay and K D values were those for [3H]SR141716A shown in table 1.K i/ED50 ratios were calculated for each assay of each region to obtain mean ± S.E.M. values from three to five determinations. Values that are not significantly different (by Tukey-Kramer test at P < .05) are denoted with the same single letter.