Effects of Temperature on Evoked Electrical Activity and Anoxic Injury in CNS White Matter

Author:

Stys Peter K.1,Waxman Stephen G.1,Ransom Bruce R.1

Affiliation:

1. Department of Neurology, Yale University School of Medicine, New Haven, and PVA/EPVA Center for Neuroscience and Regeneration Research, VA Medical Center, West Haven, Connecticut, U.S.A.

Abstract

Temperature is known to influence the extent of anoxic/ischemic injury in gray matter of the brain. We tested the hypothesis that small changes in temperature during anoxic exposure could affect the degree of functional injury seen in white matter, using the isolated rat optic nerve, a typical CNS white matter tract (Foster et al., 1982). Functional recovery after anoxia was monitored by quantitative assessment of the compound action potential (CAP) area. Small changes in ambient temperature, within a range of 32 to 42°C, mildly affected the CAP of the optic nerve under normoxic conditions. Reducing the temperature to <37°C caused a reversible increase in the CAP area and in the latencies of all three CAP peaks; increasing the temperature to >37°C had opposite effects. Functional recovery of white matter following 60 min of anoxia was strongly influenced by temperature during the period of anoxia. The average recovery of the CAP, relative to control, after 60 min of anoxia administered at 37°C was 35.4 ± 7%; when the temperature was lowered by 2.5°C (i.e., to 34.5°C) for the period of anoxic exposure, the extent of functional recovery improved to 64.6 ± 15% ( p < 0.00001). Lowering the temperature to 32°C during anoxic exposure for 60 min resulted in even greater functional recovery (100.5 ± 14% of the control CAP area). Conversely, if temperature was increased to >37°C during anoxia, the functional outcome worsened, e.g., CAP recovery at 42°C was 8.5 ± 7% ( p < 0.00001). Hypothermia (i.e., 32°C) for 30 min immediately following anoxia at 37°C did not improve the functional outcome. Many processes within the brain are temperature sensitive, including O2 consumption, and it is not clear which of these is most relevant to the observed effects of temperature on recovery of white matter from anoxic injury. Unlike the situation in gray matter, the temperature dependency of anoxic injury cannot be related to reduced release of excitotoxins like glutamate, because neurotransmitters play no role in the pathophysiology of anoxic damage in white matter (Ransom et al., 1990 a). It is more likely that temperature affects the rate of ion transport by the Na+–Ca2+ exchanger, the transporter responsible for intracellular Ca2+ loading during anoxia in white matter, and/or the rate of some destructive intracellular enzymatic mechanism(s) activated by pathological increases in intracellular Ca2+.

Publisher

SAGE Publications

Subject

Cardiology and Cardiovascular Medicine,Neurology (clinical),Neurology

Cited by 33 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3