Effect of anticonvulsant drugs on peripheral benzodiazepine receptors of human lymphocytes

Anticonvulsant drugs, such as carbamazepine, may exert some of their effects through peripheral benzodiazepine receptors (PBR), which are present in glial cells and regulate the synthesis of neurosteroids. PBR have also been demonstrated in human lymphocytes, where they might be used as peripheral markers of anticonvulsant drug effects. In the present paper we investigated the interaction of various antiepileptic drugs with PBR of human lymphocytes and evaluated possible effects of acute and chronic treatment with these drugs. At normal therapeutic concentrations, diazepam, carbamazepine and phenobarbital occupy respectively 70, 30 and 10% of PBR sites in human lymphocytes. Although no change of receptor density or affinity was observed after acute in vitro treatment, in epileptic patients chronically treated with carbamazepine, phenobarbital and valproic acid, PBR B_max was increased with respect to controls and untreated epileptics. Since PBR of human lymphocytes may be affected by anticonvulsant drug treatment, we suggest that they might be involved in the immunological alterations reported in these patients and might be used as peripheral markers of drug effects on the central nervous system.