Feng Z C, Sick T J, Rosenthal M
Department of Neurology, University of Miami School of Medicine, Florida 33101.
Am J Physiol. 1988 Sep;255(3 Pt 2):R485-91. doi: 10.1152/ajpregu.1988.255.3.R485.
Recent evidence suggests that suppression of electrical activity, with the likely reduction of energy use, provides a necessary strategy for prolonged anoxic tolerance of turtle brain. The present study was aimed toward defining mechanisms underlying anoxia-induced suppression of electrical activity in turtle brain. Goals were to determine whether effects of anoxia were selective to excitatory or inhibitory processes and to test the hypothesis that enhanced inhibition underlies suppression of orthodromic field potentials in olfactory bulb. Amplitudes of "conditioning" and "test" responses, provoked by pairs of stimulus pulses to the olfactory nerve, were evaluated before, during, and after anoxic insults in the brains of turtles anesthetized with pentobarbital sodium. Suppression of conditioning responses was proportionally greater than that of test responses, indicating that inhibition was decreased and that enhanced inhibitory activity is not responsible for suppression of field potentials in turtle olfactory bulb during anoxia. When normoxia was restored, conditioning responses recovered but test responses remained suppressed. These data confirm that the inhibitory effect of a conditioning pulse on responses to a second pulse of stimulation results from a recurrent circuit and suggest that anoxia-induced changes in field potentials are independent of this recurrent circuit. Enhanced inhibition during the early period of recovery after anoxic insults may provide advantages for restoring energy status and cell physiology by suppressing electrical activity and energy use.
最近的证据表明，抑制电活动并可能减少能量消耗，为延长海龟大脑的缺氧耐受性提供了一种必要策略。本研究旨在确定海龟大脑中缺氧诱导的电活动抑制的潜在机制。目标是确定缺氧的影响是否对兴奋性或抑制性过程具有选择性，并检验以下假设：增强的抑制作用是嗅球中顺行场电位抑制的基础。在用戊巴比妥钠麻醉的海龟大脑中，在缺氧损伤之前、期间和之后，评估由成对的刺激脉冲刺激嗅神经所引发的“条件”和“测试”反应的幅度。条件反应的抑制比测试反应的抑制更大，这表明抑制作用减弱，并且增强的抑制活性不是缺氧期间海龟嗅球中场电位抑制的原因。当恢复常氧时，条件反应恢复，但测试反应仍然受到抑制。这些数据证实，条件脉冲对第二次刺激脉冲反应的抑制作用是由一个反复回路产生的，并表明缺氧诱导的场电位变化与这个反复回路无关。缺氧损伤后早期增强的抑制作用可能通过抑制电活动和能量消耗为恢复能量状态和细胞生理提供优势。
