Prenatal Diazepam Exposure Affects β‐Adrenergic Receptors in Brain Regions of Adult Rat Offspring

The postnatal development of [ 3 H]dihydro‐alprenolol binding to β‐adrenergic receptors has been studied in frontal cortex, cerebellum, striatum, and hypothalamus of the rat after prenatal and perinatal exposure to diazepam. Dams were injected subcutaneously with single daily doses of 1 mg of diazepam/kg from day 7 to 20 of gestation or from day 15 of gestation to day 6 after birth. Prenatal exposure had no effect on litter size or length of gestation or on the postnatal development of body and brain weights of the progeny. However, a reduced mortality of the pups was observed in relation to vehicle‐treated controls until postnatal day 10. Prenatal diazepam administration decreased [ 3 H]dihydroalprenolol binding in frontal cortex, striatum, and hypothalamus but not in cerebellum. This decrease in β‐adrenergic receptor binding was due to a decrease in receptor density rather than in receptor affinity. In contrast, perinatal diazepam exposure led to a transient decrease in [ 3 H]dihydroalprenolol binding limited to the frontal cortex. The permanent reduction in number of β‐adrenergic receptors, which depends on the scaling and duration of the drug application period, points to the necessity of a prolonged evaluation of effects of exposure to psychotropic drugs in early stages of brain development.