An in situ assay for determination of benzodiazepine binding

Benzodiazepine (BDZ) receptors have been demonstrated recently in a variety of mammalian tissues. However, assay methods for such receptors have required that disrupted tissues be used. We have developed an in situ assay for this receptor utilizing intact cells cultured from the cerebral cortices of fetal mice which is more sensitive and physiologic than those used previously. Results obtained with this assay differ in the following ways from those in which disrupted tissues are used: (1) total and specific BDZ binding was as much as 10-fold higher in the in situ assays; (2) Scatchard analysis of the binding data is consistently nonlinear, revealing at least two binding sites with KD values of 5.5 and 303 nM, and (3) presumed nonneuronal receptors were found in abundance.