[abstract] BRAIN SAMPLES FROM SUDDEN INTRACRANIAL DECOMPRESSION AND HEMODYNAMIC AND METABOLIC FACTORS DURING SEIZURES FROM OXYGEN AT HIGH PRESSURE

Abstract

In the present study a brain freeze-blowing technique was developed to permit sampling of the rat brain by explosive decompression of the cranium. Thus brain samples were instantaneously collected and frozen during grand ma1 seizures. This study was performed in order to determine brain glucose and GABA levels during seizures and to measure blood pressure and heart rate. Blood samples were also obtained for analysis of glucose and circulating catecholamines. In 100% oxygen at 6 ATA systemic blood pressure in 8 rats gradually increased from 127å± mm Hg just prior to compression, 134å± after (P<0.01), to 158å± (P<0.001) just prior to a grand ma1 seizure and 189å±1 (P<0.001) during the seizure. Heart rate was 374å±2 before compression, 363å±1 after, 303215 just prior to grand ma1 seizure (P<0.01) and 389å±1 (P<0.001) during the seizure. Pretreatment of 6 rats with phenoxybenzamine did not prevent the rise in blood pressure with compression, 10823 to 120å± (P<0.01) or during exposure to OHP, 135å± (P<0.01) suggesting a local central sympathetic regulatory mechanism. However, these pretreated rats showed a fall (11523) in blood pressure during seizures. Blood glucose values in 8 rats were 15525 mg% before exposure and 241å±2 (P<0.01) after a series of minor seizures. In a separate series blood glucose in 10 rats was 16126 prior to exposure and 214å±2 (P<0.05) during the initial stages of a grand ma1 seizure. Brain GABA levels during seizures averaged 2.5 micromoles per g brain tissue. Blood pressure increases were attributed to autoregulation prior to convulsions and to sympathetic activity during severe seizures.