Competitive interactions at [ 3H]1,3-DI(2-tolyl) guanidine (DTG)-defined σ recognition sites in guinea pig brain

Abstract

In saturation binding experiments, (+)pentazocine, (+)3-(3-hydroxyphenyl)-N-propylpiperidine (3-PPP), haloperidol and rimcazole did not inhibit the binding of [ 3H]DTG in a purely competitive fashion. Although Scatchard analysis indicated that [ 3H]DTG bound to a single site, the inhibition curves of some, but not all, reference compounds exhibited Hill coefficients of less than 0.8. The Scatchard data were consistent with a model of hyperbolic competitive inhibition of binding to the [ 3H]DTG-defined σ site, although other possibilities such as negative cooperativity or binding to two sites cannot be definitively excluded. Compounds from numerous pharmacological and structural classes inhibited the binding of [ 3H]DTG, suggesting that interactions of [ 3H]DTG with other receptors may have confounded the Scatchard analysis of the binding of [ 3H]DTG to σ recognition sites.