Electrophysiological evidence for long_term depression in the contralateral, intact brain following transient focal cerebral ischemia in rats

E. Jian Lee, Sheng Yang Huang, Yu Hsiang Kuan, Tsung Ying Chen, Hung Yi Chen, Tian Shung Wu

Research output: Contribution to journalArticle

Abstract

Introduction: Focal brain injury may induce synapto-functional, metabolic and electrophysiological dysfunction in the contralateral areas [1]. We hypothesize that contralateral electrophysiological diaschisis may represent a form of long-term depression after injury. Methods: Male Sprque-Dawley rats, weighing 240-280 gm, were subjected to intraluminal suture occlusion for 60 minutes or sham-occlusion. Physiological parameters, including core temperature, local cortical perfusion and arterial blood gases, were measured, whereas the somatosensory potentials (SSEPs) evoked from individual forepaw and hindpaw regions were recorded prior to the ischemic insult and at 1, 3, 7, 21 or 28 days after reperfusion. Postmortem brain ischemic damage was determined by quantitative image analysis of Nissl-stained sections. Results: The sham-operated group did not cause a significant change in the physiological parameters or the SSEP waveforms recorded either in the ipsilateral or the contralateral brain hemispheres at various intervals of recording. There was no difference in brain infarction volumes among each time interval of the ischemic groups (p > 0.05). Relative to the baseline data, at 24-72 hours of reperfusion the SSEPs recorded from ischemic fore- and hindpaw cortical fields were depressed and the amplitudes decreased to 36.4-41.3% and 41.9-44.5% of baseline, respectively (p < 0.001). On contrast, the SSEPs recorded from non-ischemic fore- and hindpaw cortical fields decreased. The amplitudes decreased to 76.0-83.0% and 74.5-81.8% of baseline, respectively (p < 0.001). At 7-28 days of reperfusion improved SSEPs recorded from ischemic fore- and hindpaw cortical fields were noted. The amplitudes recovered to 49.9-54.7% and 45.5-58.5% of baseline, respectively (p < 0.001). On contrast, the SSEPs recorded from non-ischemic fore- and hindpaw cortical fields were also noted to improve. The amplitudes recovered to 88.6-96.2% and 85.5-96.3% of baseline, respectively (p < 0.001 up to 21 days of reperfusion). Relative to the pooled sham-operated controls, the amplitudes of SSEPs recorded from both ischemic fore-and hindpaw cortical field in the ischemic animals significantly but gradually improved by 18.3% (p < 0.001) and 16.6% (p < 0.001) of baselines, respectively, during a course of 28-day recovery. On contrast, the amplitudes of SSEPs recorded from both non-ischemic fore- and hindpaw cortical field in the ischemic animals also significantly improved by 17.9% (p < 0.001) and 10.4% (p < 0.001) of baselines, respectively, up to 21 days of reperfusion. Conclusions: Cerebral ischemia-reperfusion induces time-dependent electrophysiological depression not only in the ischemic, but also in the contralateral, intact brain, and both the events, however, improve over time. This electrophysiological evidence suggests long-term depression in the contralateral, intact brain and functional re-organization following cerebral ischemia-reperfusion.

Original languageEnglish
Pages (from-to)BP18-05W
JournalJournal of Cerebral Blood Flow and Metabolism
Volume27
Issue numberSUPPL. 1
Publication statusPublished - 2007 Nov 13

All Science Journal Classification (ASJC) codes

  • Neurology
  • Clinical Neurology
  • Cardiology and Cardiovascular Medicine

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