Pressure, temperature, and repetitive impulse generation in crustacean axons.

ABSTRACT

Increases in nerve axon excitability, including repetitive activity, have from time to time been reported in nerves subjected to high hydrostatic pressure. With the description of the high-pressure nervous syndrome (HPNS) in human divers and experimental animals, this phenomenon is of interest as a possible basis for the hyperexcitability associated with HPNS. The present study was designed to define the relationships between temperature, pressure, and repetitive activity in isolated crayfish axons. Crayfish claw nerves were exposed to helium pressures between 1 and 200 atmospheres absolute (ATA) in a temperature-controlled recording chamber. Repetitive and spontaneous impulses were reliably evoked on compression. The probability of repetitive response was increased by low temperature and high pressure; the frequency of the repetitive activity was increased by high temperature and pressure. Repetitive activity appeared spontaneously in the unstimulated preparation but could be entrained by the stimulus. The results are consistent with a mechanism involving changes in nerve membrane lipid fluidity and in the time course of membrane ionic channel state changes, including those involved in repolarization and accommodation.