Solubilization of histamine H-1, GABA and benzodiazepine receptors

Binding sites for histamine H-1, GABA and benzodiazepine receptors have been solubilized from mammalian brain membranes using, as detergents, digitonin for benzodiazepine and H-1 receptors and lysolecithin for GABA receptors. The dissociation constants for ³H-mepyramine at histamine H-1 (1.5 nM), ³H-muscimol at GABA (7 nM, 24 nM) and ³H-flunitrazepam at benzodiazepine receptors (1.5 nM) are similar to values in membrane preparations. The relative and absolute potencies of various drugs in competing for ³H-ligand binding to the three receptors are closely similar in the soluble and membrane bound states, indicating that the conformation of the receptor recognition site is maintained during solubilization. Maximal numbers of binding sites are about 50% of corresponding levels in the membrane bound state.