The binding of diazepam in the mitochondria of Tetrahymena pyriformis as detected by quantitative high resolution autoradiography

Tritiated diazepam accumulates mainly in the mitochondria of the unicellular Tetrahymena. This is the case in both a single (the first encounter) and a repeated (one day or a week after the first) administration of the drug. When imprinting of Tetrahymena by diazepam (the first encounter) is followed a week later by the administration of the labelled drug, the membranes of the vesicles, too, show the appearance of label. Regarding the studies presented here, the unicellular Tetrahymena also contain diazepam receptors in the mitochondria as suggested for cells of higher rank animals.

Diazepam receptors on mouse astrocytes in primary cultures: displacement by pharmacologically active concentrations of benzodiazepines or barbiturates

Astrocytes in primary cultures were found to bind large amounts of [3H]diazepam. More than 90% of the total binding is specific, i.e., displaceable by an excess of nonlabeled diazepam. At saturation the specific binding amounts to about 20 pmol/mg protein and the Kd value is 30 nM. Clonazepam and flurazepam displace [3H]diazepam from its specific binding sites; 20–30% displacement is brought about by 0.1–0.3 μM clonazepam, which is similar to the plasma concentrations encountered in epileptic patients treated with this drug. Barbiturates have a similar effect, but considerably higher concentrations are required.