Characterization of benzodiazepine receptor binding in immature rat brain after kainic acid administration

To evaluate the effects of status epilepticus on benzodiazepine (BDZ) receptor binding in immature rat brain.

Twenty-four immature (15 days old) and six adult (90 days old) rats were used in this study. Status epilepticus was induced in immature animals by administration of kainic acid (7 mg/kg intraperitoneal), whereas adults rats received saline. Animals were killed 72 hours or 35 days after treatment, and their brains were used for in vitro autoradiography experiments to determine BDZ binding.

In basal conditions and compared with the adult group, immature animals presented reduced BDZ binding in the entorhinal cortex, substantia nigra pars reticulata, and periaqueductal gray. Seventy-two hours after kainic acid-induced status epilepticus, immature rats showed significantly increased BDZ in the frontal (48%), cingulate (39%), sensorimotor (39%), piriform (57%), and entorhinal (59%) cortices, the medial (84%) and basolateral (27%) amygdaloid nuclei, the dentate gyrus (51%), and the substantia nigra pars reticulata (43%). Thirty-five days after status epilepticus, immature rats displayed decreased BDZ binding in the entorhinal cortex (48%), dentate gyrus (36%), and fields CA1, CA2, and CA3 of Ammon's horn (30%).

The present study demonstrates that status epilepticus and temporal lobe epilepsy produce a characteristic pattern of BDZ binding changes in the immature rat brain that differs from the one previously seen in adults.