Abstract Details

Title Effects of Anoxia on the Time Course of Changes in the Nerve Action Potential Produced by Hyperkalemia

Topic Peripheral Nerve

Presentation(s) P02 - (-)

Poster/Presentation
Number 185

Objective

Background BACKGROUND: A large number of changes occur in peripheral nerve with anoxia. These include changes in myelin, metabolic pathways, and ion channels. Previous studies have demonstrated that the nerve action potential (NAP) can provide important information on the effects of anoxia.

Design/Methods DESIGN/METHODS: Paired constant-current stimuli at 15mA, 0.01msec and 5Hz are applied to in-vitro rat sciatic nerve while the NAP is recorded. Computer controlled perfusate, either fully oxygenated with KCL=3.9 mM or KCL=25mM or fully deoxygenated with KCL=3.9 mM. Automated abstraction of NAP parameters with experimenter auditing is used and the time course of changes in response to high KCL is recorded before and after a 90 minute period of anoxia followed by a 90 minute recovery period in normal oxygenated perfusate.

Results RESULTS: On exposure to the high potassium concentrations, the amplitude of the nerve action potential declines gradually, conduction velocity decreases while the duration of the NAP increases. The paired pulse response initially decreases and then increases. Although the time it takes for the NAP to drop to half baseline value after being exposed to the high potassium solution is similar both before and after anoxia, the shape of the curve is very different (F(19,190)=2.4,p<.001) when a repeated measures ANOVA is used for analysis. The Mann-Whitney test applied to each time point shows significant differences at the first (p <.005 second p<0.02, and 19th data points p<.01). Recovery from anoxia is impaired in high potassium solutions.

Conclusions CONCLUSIONS: The course of changes in the NAP after exposure to high concentrations of potassium has potential to help understand the changes induced in peripheral nerve by anoxia.

Authors/Disclosures
Mark M. Stecker, MD, FAAN PRESENTER	No disclosure on file
Volker Limmroth, MD, PhD (City of Cologne / Cologne General Hospital (Merheim))	No disclosure on file
Grazia Dell'Agnello, MD (Dept of Neuroscience/Univ of Pisa)	No disclosure on file

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