Binding characteristics of 3Hflunitrazepam in pentobarbital-withdrawal rats

摘要

The effects of chronic pentobarbital (PB) treatment on the binding characteristics of 3Hflunitrazepam (FLU) in rat brain were examined. Saline or sodium PB (500 μg/10μl/hr) was infused into the lateral cerebral ventricles of rats for 6 days using osmotic pumps. Immediately before withdrawal, there were no significant differences in 3HFLU binding constants (KDand Bmax) between saline and PB groups. However, 24 hr withdrawal caused an increase in Bmaxwith no changes in KD. The enhancement of 3HFLU binding by in vitro addition of chloride ions and PB was not affected after the PB infusion. The PB enhancement of 3HFLU binding was inhibited by the convulsant, picrotoxicin. PB withdrawal did not cause significant differences in the binding constants of 3HRo 15-1788, a benzodiazepine (BZ) antagonist, between the saline and PB groups. Pretreatment of membranes with 0.02 mM of 3-(3-cholamidopropyl)-dimethylammonio-1-propanesulfonate (CHAPS), a zwitterionic detergent, caused decreases in both KDand Bmaxin FLU binding in PB-withdrawal membrane, but not in the saline-treated membrane. The enhancement of 3HFLU binding by chloride ions and PB was not affected by the CHAPS treatment. These results suggest that the change in BZ receptors induced by PB withdrawal is functionally linked to the GABA-BZ-barbiturate receptor complex and that PB withdrawal induces some conformational changes in BZ receptor