To evaluate the direct effects of a barbiturate on cerebral functions without its influence on brain perfusion pressure, circulatory hormones and metabolites, the electroencephalogram (EEG) was studied in the isolated rat head. Male Wistar rats were anesthetized, and EEG electrodes were inserted into the cranium. A Krebs-Ringer bicarbonate buffer solution containing heparinized rat whole blood, 20 mmol/l glucose, 200 mmol/l mannitol and 0.1 mg/ml dexamethasone was used for the perfusate. The bilateral common carotid arteries were cannulated, pumped at a rate of 6 ml/min and the head was isolated. The venous effluent was reoxygenated and recirculated into the brain. Twenty-five min after isolation of the heads pentobarbital was added to the perfusate at concentrations of 0.1, 0.5 and 2.5 mg/ml. EEG was recorded before and during perfusion. EEG activity could be recorded for more than 25 min after the beginning of perfusion. EEG activity gradually declined from 42±5 μV before perfusion (in vivo) to 4±1 μV at 25 min after the beginning of perfusion. Then, 3 min after the addition of pentobarbital, the EEG activity became significantly higher in the high dose groups; 12±3 μV in the 0.5 mg/ml group (p<0.05) and 12±1 μV in 2.5 mg/ml group (p<0.05) compared with the group without pentobarbital (2±2 μV). The present study suggests that a barbiturate has mitigating effects on the brain damage induced by the in vitro brain perfusion., A. Tagawa, O. Mokuda, Y. Sakamoto, N. Shimizu., and Obsahuje bibliografii
Antagonists of GABA B receptors are expected to have proconvulsant acti on also in developing brain. Two antagonists (CGP55845 and CGP46381) were tested in a model of cortical epileptic afterdischarges (ADs) in 12-, 18- and 25-day-old rat pups with implanted electrodes. CGP55845 was dissolved in dimethylsulfoxide and the results demonstrated marked proconvulsant action of this solvent which masked possible action of the antagonist. Water soluble antagonist CGP46381 led to marked potentiation of ADs in 12-day-old animals, its action decreased with age, it was negligible in 25-day-old rats. Our results demonstrated important inhibitory role of GABA B receptors at very early stages of maturation., P. Mareš., and Obsahuje bibliografii a bibliografické odkazy