[3H]cocaine binding in brain is inhibited by tris (hydroxymethyl) aminomethane

High-affinity binding of [³H]cocaine to membranes of mouse cerebral cortex is inhibited by Tris (hydroxymethyl) aminomethane, the buffer commonly used in receptor binding assays. This inhibition is not due to an effect of ionic strength in general. Comparison of binding in Tris buffer with that in sodium phosphate buffer indicates a more than 4-fold higher K_d in the former buffer, with no differences in the B_max values.