[3H]propyl-6-azido-beta-carboline-3-carboxylate: a new photoaffinity label for the GABAA-benzodiazepine receptor.

[3H]Propyl-6-azido-beta-carboline-3-carboxylate ([3H]ACCP) exhibited a high affinity for GABAA receptors affinity purified from the brains of adult rats, and binding of this compound could be inhibited by several ligands of the benzodiazepine binding site of GABAA receptors. On irradiation with UV light, [3H]ACCP, similarly to [3H]flunitrazepam, irreversibly labeled a protein with an apparent molecular weight of 51 kDa in affinity-purified GABAA receptors, and this labeling could be inhibited in the presence of diazepam. These data indicate that [3H]ACCP can be used as a photoaffinity label for GABAA receptors.