Solubilization and characterization of benzodiazepine receptors in frontal cortex of rabbit brain

[3H]Flunitrazepam binding to benzodiazepine receptors solubilized by the detergent 3-[(3-cholamidopropyl)-dimethyl-ammonio]-l-propanesulfonate (CHAPS) was saturable and showed non-linear Scatchard plot with KD1 0.31 nmol/L and KD2 6.7 nmol/L. The affinities of soluble receptors to benzodiazepine were consistent with P2 membrane. One radioactive zone was found by SDS-PAGE after photoaffinity labelling of soluble membrane and the apparent molecular weight of 55,000 was reported. [3H]Flunitrazepam binding to soluble receptors was enhanced by GABA, NaCl or KCl and barbiturates, but inhibited by bicuculline and picrotoxinin. The enhancement of GABA on [3H]flunitrazepam binding was amplified by NaCl or KCl and antagonized by bicuculline and picrotoxinin. These results suggest that the benzodiazepine receptors solubilized by CHAPS have their pharmacological properties and are still associated with GABA receptors and chloride channel.