Neurophysiologic responses of peripheral nerve to anoxia: effects of hypothermia and age.
OBJECTIVE
Quantify how temperature and age modulate the effects of multiple periods of anoxia on peripheral nerve.


METHODS
Nerve action potentials (NAP) recorded from rat sciatic nerve in vitro. Effects of multiple cycles of anoxia on the NAP are evaluated as functions of temperature and age. In some experiments, the nerve was held at constant temperature and others the nerve was hypothermic only during anoxia and returned to 36°C with restoration of oxygen.


RESULTS
Hypothermia mitigates the effect of anoxia on the NAP, an effect that increases with multiple cycles of anoxia. Preservation of the NAP waveform after 5 cycles of anoxia is best when hypothermia is delivered only during anoxia. Hypothermia reduces the rate at which the NAP disappears during anoxia but has a limited effect on the rate of recovery. With intermittent hypothermia the amplitude of the NAP is best preserved with temperatures of 15-22°C. Velocity and duration are best preserved below 25°C. The loss of the NAP during anoxia is slower in the older nerves.


CONCLUSIONS
Lower temperatures improve the recovery of the NAP from anoxia and increase the time it takes for the NAP to disappear during anoxia as does increasing age.


CONCLUSIONS
Document the effects of hypothermia on the anoxia response as a step toward understanding its nerve protectant effect.
Winthrop University Hospital, Mineola, NY 11530, USA. mmstecker@gmail.com
Mark
M
Stecker
Jacob
J
Wolfe
Matthew
M
Stevenson
D000200:Action Potentials / Q000502:physiology; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D007035:Hypothermia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D009431:Neural Conduction / Q000502:physiology; D010525:Peripheral Nerves / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012584:Sciatic Nerve / Q000502:physiology; D013696:Temperature