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[Ischemic and hypoxic depolarization in the rat neocortex]
V I Koroleva1, L V Vinogradova
1Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow.
Zhurnal Vysshei Nervnoi Deiatelnosti Imeni I P Pavlova
|September 14, 2000
Summary
Ischemia and hypoxia cause cortical negative DC potential shifts. Ischemic depolarization damages nervous tissue, unlike hypoxic depolarization, suggesting different origins and mechanisms.
Area of Science:
- Neuroscience
- Cerebrovascular Research
- Electrophysiology
Background:
- Cortical negative DC potential shifts are key indicators of neuronal function and dysfunction.
- Investigating these shifts during ischemia and hypoxia provides insights into brain injury mechanisms.
- Understanding the differential effects of these insults is crucial for developing targeted therapies.
Purpose of the Study:
- To compare the characteristics and functional consequences of cortical negative DC potential shifts during focal cortical ischemia and systemic hypoxia.
- To elucidate the underlying mechanisms differentiating ischemic depolarization (ID) from hypoxic depolarization (HD).
Main Methods:
- Focal cortical ischemia induced by photothrombotic occlusion of the middle cerebral artery (dMCA) in an experimental model.
- Systemic hypoxia induced by combined bilateral common carotid artery ligation and carbon monoxide (CO) breathing.
- Electrophysiological recordings of DC potential shifts, cortical spreading depression (SD), and persistent negative potential (PNP).
Main Results:
- Ischemic depolarization (ID) reached 28-33 mV, declined gradually, and caused significant tissue damage, evidenced by reduced SD amplitude and increased PNP.
- Hypoxic depolarization (HD) did not exceed 20 mV, remained stable, and did not alter SD or PNP characteristics.
- ID resulted in a 1.5-2 fold increase in perifocal PNP amplitude, indicating substantial functional disruption.
Conclusions:
- Focal cortical ischemia and systemic hypoxia induce distinct cortical negative DC potential shifts with differing functional consequences.
- Ischemic depolarization leads to neuronal damage, while hypoxic depolarization appears to be a reversible, non-damaging phenomenon.
- The distinct outcomes suggest that ID involves neuronal membrane dysfunction and excitotoxicity, whereas HD may be primarily related to blood-brain barrier changes and vasospasm.