Benzodiazepine receptor development in murine glial cultures

Benzodiazepine (BDZ) receptor binding characteristics were determined from glial cultures prepared from the cerebral hemispheres of newborn mice. Receptor binding and saturation analyses were performed at various ages in culture on intact cells. Utilizing 5 nM 3H-diazepam at 0.4 degrees C, specific binding reached a plateau at 16-21 days after plating. A single high-affinity binding site was identified with Kd 25.3 +/- 2.6 nM and Bmax 7,575 +/- 410 fmol/mg protein. Inhibition studies utilizing clonazepam indicated that this ligand, thought to have affinity exclusively for neurons, displaces more than 20% of the specific BDZ binding at concentrations as low as 300 nM, although the IC50 was 1.5-2.0 microM. In contrast, the IC50 for Ro5-4864 was 10-20 nM.