Neurophysiologic responses of peripheral nerve to repeated episodes of anoxia

ObjectiveDetermine the effects of serial episodes of anoxia in an in vitro peripheral nerve preparation.MethodsThe nerve action potential (NAP) from rat sciatic nerve was recorded during 5 cycles of anoxia and reperfusion. Multiple NAP parameters were analyzed as well as stimulus response curves.ResultsThe amplitude of the NAP declined to half baseline in 865 s on the first cycle of anoxia and recovered to half baseline during recovery in 470 s. These times increased with successive cycles of anoxia. The current required to produce a half maximal NAP showed a variable initial decrease before increasing with anoxia. The paired-pulse response showed a decline at 2–3 ms interstimulus interval during anoxia but was less dependent of interstimulus interval during recovery. NAP amplitude and velocity decrease over successive cycles of anoxia at a rate greater than in the absence of anoxia.ConclusionsThe NAP declines slowly when peripheral nerve is exposed to anoxia but returns at least twice as quickly when re-exposed to oxygen. Short periods of anoxia produce long lasting changes in the nerve suggesting greater resistance to anoxia. With serial episodes of anoxia there is gradual NAP amplitude reduction and increase in duration and latency.SignificanceAnoxic-preconditioning appears in isolated peripheral nerve.

► The NAP declines slowly when the peripheral nerve is exposed to anoxia but returns at least twice as quickly when re-exposed to oxygen.
► Changes in the NAP during anoxia/recovery are strongly dependent on the previous history of exposure to anoxia. Anoxic preconditioning occurs in isolated peripheral nerve.
► Different parameters of the NAP respond differently to repetitive episodes of anoxia.