Effects of Cations and Anions on the Binding of 3 H-Diazepam to Rat Brain

Abstract

Summary

The effects of anions and cations on the specific binding of ³H-diazepam to rat brain were determined. Crude synaptic membranes from whole rat brain were prepared by differential centrifugation followed by hypo-osmotic shock and freezing. The monovalent cations (as their chloride salts) Li⁺, Na⁺, K⁺, and NH₄ ⁺ produced very slight enhancements of binding whereas Cs⁺ did not have any effect. The monovalent anions (as their sodium salts) F^- and I^- were inhibitory whereas Br^- produced a very slight enhancement. Divalent cations (as their chloride salts) produced marked enhancements of binding. Ni²⁺ caused the greatest increase which reached 86% at 5 mM. This increased binding was the result of enhanced affinity for the binding site; the total number of sites was not altered. The rank order of potency for stimulating binding at 0.1 mM cation concentration was Ni²⁺, Hg²⁺ > Cu²⁺, Zn²⁺ > Co²⁺ > Ba²⁺, Mg²⁺, Ca²⁺, Mn²⁺, Ni²⁺ did not affect the specific binding to brain homogenates of ³H-strychnine or of ³H-quinuclidinyl benzilate, but inhibited binding of ³H-naloxone.