Hyperbaric oxygen pre-treatment impairs anoxic tolerance but improves hyperglycemic tolerance in peripheral nerve.

Abstract

Prior research has suggested that treatment with hyperbaric oxygen (HBO) may change energy metabolism in the peripheral nerve, potentially resulting in improved tolerance to hyperglycemia and anoxia. In this paper, the invitro rat sciatic nerve model was used to explore the effects of a single 90min treatment with either 1 or 3 atmospheres of: oxygen, nitrogen or air on the ability of the peripheral nerve to tolerate intermittent anoxia or hyperglycemia. After this treatment, the nerve was placed in a perfusion system where the nerve action potential (NAP) was continuously recorded over the duration of a 16h experiment. The amplitude, paired pulse response, velocity and duration of the NAP were used as markers of peripheral nerve function. The perfusate contained either 5mmol/L or 55mmol/L glucose and was either continuously oxygenated or intermittently replaced by an oxygen free solution of identical composition. HBO treatment primarily affected the amplitude and duration of the NAP. HBO improved the NAP in continuously oxygenated nerves exposed to the 55mmol/L glucose perfusate but not the 5mmol/L. However, it worsened the NAP in nerves exposed to intermittent anoxia and increased the rate at which the amplitude of the NAP declined during anoxia. Pressure had an effect on the NAP only for oxygen but not nitrogen or air. The effect of the HBO treatment persisted more than 1h after the end of the treatment.