Hyperthermia-Induced Seizures Modify the GABAA and Benzodiazepine Receptor Binding in Immature Rat Brain

Effects of hyperthermia-induced seizures (HS) on GABAA and benzodiazepine (BDZ) receptor binding in immature rat brain were evaluated using in vitro autoradiography. HS were induced in 10-day-old rats by a regulated stream of moderately heated air directed 50 cm above the animals. Rats were killed 30 min, 24 h, or 20 days after HS and their brains were used for in vitro autoradiography experiments to determine GABAA and BDZ receptor binding. GABAA binding was significantly enhanced in all brain areas evaluated 30 min after HS, an effect that endures 24 h and 20 days after seizures. Concerning BDZ receptor binding, a significant increase was detected in entorhinal and perirhinal cortices and decreased in basolateral amygdala 30 min following HS. One day after HS, animals demonstrated enhanced BDZ binding in the cingulate, frontal, posterior parietal, entorhinal, temporal, and perirhinal cortices; striatum, accumbens, substantia nigra pars compacta, and amygdala nuclei. Twenty days after HS enhanced BDZ binding was restricted in the cingulated, frontal, anterior and posterior parietal cortices, as well as in substantia nigra pars reticulata, whereas decreased values were found in accumbens nucleus and substantia nigra pars compacta. Our data indicate differential effects of HS in GABAA and BDZ binding in immature brain. HS-induced GABAA and BDZ changes are different from those previously described in experimental models of temporal lobe epilepsy in adult animals.