Chih C P, Feng Z C, Rosenthal M, Lutz P L, Sick T J
Department of Neurology, University of Miami, School of Medicine 33101.
Am J Physiol. 1989 Oct;257(4 Pt 2):R854-60. doi: 10.1152/ajpregu.1989.257.4.R854.
Unlike the mammalian brain, the turtle brain maintains ion homeostasis and avoids anoxic depolarization during prolonged anoxia. The mechanisms by which turtle brains avoid and recover from anoxic depolarization were investigated by relating changes in cellular ATP levels to extracellular K+ (K+o) and evoked potential activities after 6 h of anoxia and during anoxic depolarization induced by superfusion of the brain surface with iodoacetate during anoxia. ATP levels were maintained during 6 h of anoxia despite marked decreases in energy production, but ATP was lowered during inhibition of both oxidative phosphorylation and glycolysis. K+o activity was unchanged during 6 h of anoxia but increased when ATP levels decreased. Ion homeostasis in the turtle brain appears to be linked to ATP levels but is unaffected by rate of energy production. In contrast, amplitudes of evoked potentials decreased when ATP levels were maintained, but rate of energy production declined. ATP and K+o levels recovered after anoxic depolarization, but evoked potential activity was not restored. These data suggest that the basic strategy for turtle brain to survive anoxia is to avoid anoxic depolarization by maintaining ATP levels.
与哺乳动物的大脑不同，乌龟的大脑在长时间缺氧期间能维持离子稳态并避免缺氧去极化。通过将细胞ATP水平的变化与缺氧6小时后以及在缺氧期间用碘乙酸盐灌注脑表面诱导缺氧去极化期间的细胞外K +（K + o）和诱发电位活动相关联，研究了乌龟大脑避免和从缺氧去极化中恢复的机制。尽管能量产生明显减少，但在缺氧6小时期间ATP水平仍得以维持，但在氧化磷酸化和糖酵解均受到抑制时ATP水平降低。在缺氧6小时期间K + o活性未发生变化，但当ATP水平降低时K + o活性增加。乌龟大脑中的离子稳态似乎与ATP水平相关，但不受能量产生速率的影响。相反，当ATP水平维持时诱发电位的幅度降低，但能量产生速率下降。缺氧去极化后ATP和K + o水平恢复，但诱发电位活动未恢复。这些数据表明，乌龟大脑在缺氧中存活的基本策略是通过维持ATP水平来避免缺氧去极化。
