Benzodiazepine receptors in the human cerebellar cortex: a quantitative autoradiographic and pharmacological study demonstrating the predominance of type I receptors.

The anatomical localization of benzodiazepine receptors in the human cerebellar cortex was studied using quantitative autoradiography following in vitro labelling of cryostat sections with [3H]flunitrazepam ([3H]FNZ), and the pharmacology of these receptors has been characterized by computerized, non-linear least squares regression analysis of [3H]FNZ displacement by FNZ, CL218,872 and ethyl beta-carboline-3-carboxylate (ECC) binding to membranes. The autoradiograms demonstrated that benzodiazepine receptors were present throughout all layers of the human cerebellar cortex; high concentrations of receptors were present in the molecular layer, moderate concentrations were present in the granular layer and a much lower density of receptors was seen in the intervening Purkinje cell layer. The pharmacological studies indicated that the human cerebellar cortex contained a high concentration of homogeneous benzodiazepine receptors which have high affinity for FNZ, ECC and CL218,872, i.e. type I sites.