Friday, April 14, 2006

An Elegant Article: What Really Happens to Neurons When Exposed to CO2, Oxygen and Nitrogen at depth?



Neuronal sensitivity to hyperoxia, hypercapnia, and inert gases at hyperbaric pressures.

Dean JB, Mulkey DK, Garcia AJ 3rd, Putnam RW, Henderson RA 3rd.
Department of Anatomy and Physiology, Wright State University, Dayton, OH 45435, USA. jay.dean@wright.edu

Free Full Article can be seen at http://jap.physiology.org/cgi/content/full/95/3/883

ABSTRACT
As ambient pressure increases, hydrostatic compression of the central nervous system, combined with increasing levels of inspired PO2, PCO2, and N2 partial pressure, has deleterious effects on neuronal function, resulting in O2 toxicity, CO2 toxicity, N2 narcosis, and high-pressure nervous syndrome. The cellular mechanisms responsible for each disorder have been difficult to study by using classic in vitro electrophysiological methods, due to the physical barrier imposed by the sealed pressure chamber and mechanical disturbances during tissue compression. Improved chamber designs and methods have made such experiments feasible in mammalian neurons, especially at ambient pressures <5 atmospheres absolute (ATA). Here we summarize these methods, the physiologically relevant test pressures, potential research applications, and results of previous research, focusing on the significance of electrophysiological studies at <5 ATA. Intracellular recordings and tissue PO2 measurements in slices of rat brain demonstrate how to differentiate the neuronal effects of increased gas pressures from pressure per se. Examples also highlight the use of hyperoxia (<=3 ATA O2) as a model for studying the cellular mechanisms of oxidative stress in the mammalian central nervous system.

anesthesia; carbon dioxide toxicity; free radicals; high-pressure nervous syndrome; membrane potential; nitrogen narcosis; oxidative stress; oxygen toxicity; polarographic oxygen electrode

TOP
ABSTRACT
Glossary
OVERVIEW OF BARO-RELATED...
CENTRAL EFFECTS OF PRESSURE...
NARCOTIC AND TOXIC PROPERTIES...
RESEARCH APPLICATION: HYPEROXIA...
PERSPECTIVE
APPENDIXES A-D: HYPERBARIC...
REFERENCES

See also on our web site:
Problems Due to Gases and Pressure