Aging: effect on ex-vivo benzodiazepine binding after a diazepam injection.

Ex vivo [3H]flunitrazepam receptor occupation was determined in the brain of young, mature and old male Fischer 344 rats after a single intravenous injection of a low dose of diazepam. The two benzodiazepine receptor subtypes or conformations (BZ1 and BZ2) were differentiated by the displacement of [3H]flunitrazepam specific binding with the triazolopyridazine, CL 218,872. The acute diazepam injection decreased ex vivo [3H]flunitrazepam binding in only the senescent rats. The [3H]flunitrazepam binding at both the BZ1 and BZ2 receptor or receptor conformation was significantly reduced in the old rats.