MULTIPLE [H-3] DTG BINDING-SITES IN GUINEA-PIG CEREBELLUM - EVIDENCE FOR THE PRESENCE OF NONSPECIFIC-BINDING

The characteristics of the low affinity component of 1,3-di(2-[5-H-3]tolyl)guanidine binding to the guinea pig cerebellum were investigated. Saturation binding assays where a, receptors were masked with dextrallorphan indicated that 1,3-di(2-[5(3)H]tolyl)guanidine bound to cerebellar membranes in a fashion best described by a 1 site + non-specific binding model with a low density of specific binding sites (B-max approximate to 200 fmol/mg protein). Boiling the cerebellar membranes before addition to the saturation assay had no effect on the density of 1,3-di(2-[5-H-3]tolyl)guanidine binding. In contrast, both the K-d and B-max for 1,3-di(2-[5- H-3]tolyl)guanidine binding to liver membranes was significantly reduced by boiling, as was the density of [H-3](+)-pentazocine binding to cerebellum and liver. Thus, a substantial component of 1,3-di(2-[5- 3 H]tolyl)guanidine binding in the guinea pig cerebellum is to non-specific, proteinaceous binding sites with some of the pharmacological characteristics of the sigma(2) binding site.