Table 3

Reversibility of SCH-202676's action on the α2a-adrenergic and the D1 dopaminergic receptors

Treatmentα2a-Adrenergic ReceptorD1 Dopaminergic Receptor, [3H]SCH-23390
[3H]Yohimbine[3H]UK-14,304
KDBmaxKDBmaxKDBmax
nM fmol/mg nM fmol/mg nM pmol/mg
Control5.56420.57250.91.6
SCH-2026765.46550.66361.12.1

HT-29 cell membranes expressing the α2a-adrenergic receptor and CHO cell membranes expressing the dopaminergic D1 receptor were incubated with 10 μM SCH-202676 or vehicle (control) for 1 h at room temperature in buffer containing 50 mM Tris-HCl, pH 7.4, 10 mM MgCl2, and 1 mM EGTA. Then, reaction mixtures were centrifuged for 30 min at 100,000g and pellets were washed twice with same buffer. Final pellets were resuspended in assay buffer (50 mM HEPES, pH 7.4, 10 mM NaCl, 1 mM MgCl2, and 2.5 mM CaCl2) and were used for saturation binding and protein determination assays as described under Experimental Procedures.