Benzodiazepine receptor development in cultures of fetal mouse cerebral cortex mimics its development in vivo

Using a recently developed assay method which maintains cell integrity, we have performed a developmental study of the benzodiazepine (BDZ) receptor on cells of fetal mouse cortex in cultures which were either 'neuron-poor' or 'neuron-rich'. The developmental profile of the BDZ receptor in culture, when assayed on the intact cell, closely mimicked its development in vivo, reaching maximum values at 35-42 days after conception. Further, the time course of development paralleled that reported for GABA neurons both in vivo and in vitro. We have also shown that the relative delay in development of the clonazepam-displaceable portion of BDZ binding approximated a similar delay in the reported development of glutamic acid decarboxylase activity, both parameters presumably reflecting specific neuronal development. Thus, the ontogenesis of specific BDZ receptor binding in culture bears marked similarity to the time course of development of the GABAergic system.