Prenatal benzodiazepine immunosuppression: possible involvement of peripheral benzodiazepine site.

Treatment of pregnant Long Evans rats with a low dose of diazepam (1.25 mg/kg from gestational day 14-20) produced offspring suffering from suppression of cellular immune responses. Analogous effects were produced by clonazepam, a benzodiazepine (BDZ) with high affinity for the central-type, and Ro 5-4864, a BDZ with selective affinity for the peripheral-type BDZ receptor. Peripheral-type BDZ receptors are found to develop early in fetal life in peripheral organs including primary (thymus) and secondary (spleen) lymphoid organs, in the central nervous system and on immune cells (lymphocytes). In prenatally diazepam-exposed offspring the affinity constant is significantly changed. BDZ and PK 11195 also inhibit mitogen and alloantigen-induced T and B cell proliferation in vitro in adult murine lymphocytes. Diazepam, Ro 5-4864 and PK 11195 were found to be the most active compounds.