Evidence for more than two central benzodiazepine receptors in rat spinal cord

Competitive binding assays were performed in rat spinal cord membranes at 0 degrees C against [3H]Ro15-1788. The displacement curves of Ro15-1788 and alpidem produced pseudo-Hill slopes of 1.0 and 0.5, respectively. In addition, 5-10% of the specifically bound [3H]Ro15-1788 could not be displaced by greater than 100 microM of alpidem. These two pieces of evidence strongly suggest the presence of at least three central benzodiazepine binding sites in the spinal cord.