Photoaffinity labeling of the benzodiazepine receptor in bovine cerebral cortex

Clonazepam, nitrazepam and flunitrazepam were found to engage in an irreversible interaction with benzodiazepine binding sites in bovine cerebral cortex homogenates upon irradiation with ultraviolet light. Photoaffinity labeling with ³H]flunitrazepam could be substantially (approx. 85%) inhibited by a number of different benzodiazepines, including clonazepam, lorazepam, Ro5-3027, and non-radioactive flunitrazepam. Spiroperidol, atropine, naltrexone, propranolol and GABA had no effect on irreversible ³H]flunitrazepam binding, indicating that this binding is to the benzodiazepine receptor as defined in previous studies.