Autoradiographic and quantitative study of benzodiazepine-binding sites in human hippocampus

Benzodiazepine-binding sites were studied on frozen sections of 5 human hippocampi, using autoradiographic and biochemical techniques. The affinity, density, distribution and heterogeneity (two types) of sites were investigated using [3H]flunitrazepam as a ligand, clonazepam or C1 218872 as displacing agents. The autoradiographic images evidence a differential distribution of the binding sites in the histologic layers of the hippocampus. Subtypes I and II coexist in the same proportion in the three layers exhibiting the highest densities of binding sites (stratum granulosum and pyramidale, deep layer of stratum radiatum). The Kd, Bmax and Ki values found here are analogous to those described in animal studies, but the anatomical distribution of the sites in human hippocampus seems to differ slightly from that previously described in that of the rat.