Pressure (< or=4 ATA) increases membrane conductance and firing rate in the rat solitary complex.

Abstract

Neuronal sensitivity to pressure, barosensitivity, is illustrated by high-pressure nervous syndrome, which manifests as increased central nervous system excitability when heliox or trimix is breathed at >15 atmospheres absolute (ATA). We have tested the hypothesis that smaller levels of pressure (<or=4 ATA) also increase neuronal excitability. The effect of hyperbaric helium, which mimics increased hydrostatic pressure, was determined on putative CO2/H+-chemoreceptor neurons in the solitary complex in rat brain stem slices by intracellular recording. Pressure stimulated firing rate in 31% of neurons (barosensitivity) and decreased input resistance. Barosensitivity was retained during synaptic blockade and was unaffected by antioxidants. Barosensitivity was distributed among CO2/H+-chemosensitive and -insensitive neurons; in CO2/H+-chemosensitive neurons, pressure did not significantly reduce neuronal chemosensitivity. We conclude that moderate pressure stimulates certain solitary complex neurons by a mechanism that possibly involves an increased cation conductance, but that does not involve free radicals. Neuronal barosensitivity to <or=4 ATA may represent a physiological adaptive response to increased pressure or a pathophysiological response that is the early manifestation of high-pressure nervous syndrome.

• Authors: Daniel K Mulkey, Richard A Henderson 3rd, Robert W Putnam, Jay B Dean
• Journal: Journal of applied physiology (Bethesda, Md. : 1985) (J Appl Physiol (1985)) Vol. 95 Issue 3 Pg. 922-30 (Sep 2003) ISSN: 8750-7587 [Print] United States
• PMID: 12704095 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antioxidants
• Free Radicals
• Magnesium
• Calcium

Topics

• Acidosis (physiopathology)
• Animals
• Antioxidants (pharmacology)
• Atmospheric Pressure
• Calcium (pharmacology)
• Electrophysiology
• Free Radicals
• High Pressure Neurological Syndrome (physiopathology)
• Hyperbaric Oxygenation
• Hypercapnia (physiopathology)
• In Vitro Techniques
• Magnesium (pharmacology)
• Membrane Potentials (drug effects, physiology)
• Microelectrodes
• Neurons (drug effects, physiology)
• Rats
• Solitary Nucleus (cytology, drug effects, physiology)
• Synapses (drug effects, physiology)
• Synaptic Transmission (drug effects, physiology)