Comparisons of oxygen metabolism and tissue po2in cortex and hippocampus of gerbil brain

Abstract

Recessed oxygen microelectrodes (tip diameter < 2 μm) were positioned stereo tactically into either the cerebral cortex or the hippocampus of sodium pentobarbital anesthetized gerbils(n = 21). The mean tissue P02 levels (± SEM) were not significantly different between cortex (35.4 ± 1.7 torr) and hippocampus (33.6 ± 1.4 torr) although differences in the tissue Po2distributions were seen. The disappearance rate for oxygen (- dPo2/dt) was measured after brief (< 15 seconds) bilateral carotid artery (total brain blood flow) occlusion. The mean (±SEM) disappearance rate was significantly higher (p<0.05) in the cortex (23.8 ± 1.5 torr/sec, 160 locations in 21 gerbils) than In the hippocampus (17.0 ± 0.7 torr/sec, 119 locations in 16 gerbils). The maximum oxygen consumption rates (VO2max) for Michaelis-Menten kinetics were calculated from the disappearance rates, correcting for gerbil oxyhemoglobin. The mean VO2max was 8.28 ± 0.51 and 6.13 ± 0.25 ml O2/100 g/min for the cortex and hippocampus, respectively. The apparent Michael is-Menten kinetic constants (Ko) for the 2 regions were not significantly different (overall mean 3.3 ± 0.4 torr). Differences in the recovery of tissue PO2 after releasing the occlusion were seen, with more hyperemic responses in the hippocampus. © 1987 American Heart Association, Inc.