From Simple to Complex: Pressure and Inert Gas Modulation of Nerve Cell Membrane Properties

Abstract

When subjected to high hydrostatic or helium pressure of approximately 2 – 1 0 MPA (20 – 100 atmospheres), vertebrates display symptoms of heightened neural excitation manifested as the High Pressure Neurological (or Nervous) Syndrome (HPNS) (Brauer, 1984). The syndrome includes, among other manifestations, tremors and convulsions. In anesthetized animals, an additional stimulatory effect of pressure is manifested as an increase in the amount of anesthetic required to prevent mobility (Miller, 1977). There are actually four different CNS responses to inert gases and pressure: (1) anesthesia (and inert gas narcosis); (2) the convulsions and tremors of the HPNS (3) the anti-anesthetic effects of pressure, and (4) the anti-HPNS effects of anesthetics. The cellular and molecular sites of HPNS and of pressure reversal of anesthesia are considered to be different because of dissimilarities in pharmacology and in pressure-anesthetic dose/response curves (Halsey, 1982), and because of the limited window of anesthetic and pressure exposure in which animals are both awake and seizure-free (Miller 1977). For neither phenomenon is the cellular basis known