Autoradiographic localization of "peripheral-type" benzodiazepine binding sites in the rat brain, heart and kidney.

The localization of peripheral-type benzodiazepine binding sites has been accomplished using quantitative receptor autoradiography after labeling slide-mounted tissue sections with [3H]-RO 5-4864. Specific [3H]-RO 5-4864 binding sites were observed in the choroid plexus and ependyma cells within the brain. Lower levels of specific binding were seen in areas corresponding to the glomerular layer of the olfactory bulb. Stereotaxic administration of the excitotoxin, ibotenic acid, into the piriform cortex produced a dramatic increase in binding to the peripheral-type site in this brain region. Binding in the kidney was associated with the ascending limb of the loop of Henle and the distal convoluted tubule, while in the heart a more diffuse binding was found throughout the ventricle wall. The localization of peripheral-type benzodiazepine binding sites to areas involved in ion transport gives additional support to previously suggested physiological roles for these sites.