Editing Nitrogen narcosis (section)

== Mechanism ==
[[File:Lipid bilayer section.gif|thumb|Illustration of a lipid bilayer, typical of a cell membrane, showing the [[hydrophilic]] heads on the outside and [[hydrophobic]] tails inside|alt=Representation of tall molecules lined up in two rows, one above the other. The top ends of the molecules in the upper row coloured red, as are the bottom ends of those in the bottom row]]
The precise mechanism is not well understood, but it appears to be the direct effect of gas dissolving into nerve membranes and causing temporary disruption in nerve transmissions. While the effect was first observed with air, other gases including argon, krypton and hydrogen cause very similar effects at higher than atmospheric pressure.<!--http://www.deep-six.com/page74.htm-->{{sfnp|Bennett|Rostain|2003|p=304}} Some of these effects may be due to [[Receptor antagonist|antagonism]] at [[NMDA]] receptors and [[wikt:potentiation|potentiation]] of [[GABAA receptor|GABA<sub>A</sub>]] receptors,{{r |Hapfelmeier2000}} similar to the mechanism of [[nonpolar]] anesthetics such [[diethyl ether]] or [[ethylene]].{{r |Hamilton1995}} However, their reproduction by the very chemically inactive gas argon makes them unlikely to be a strictly chemical bonding to receptors in the usual sense of a [[chemical bond]]. An indirect physical effect&nbsp;– such as a change in membrane volume&nbsp;– would therefore be needed to affect the [[ligand-gated ion channel]]s of nerve cells.{{r |Franks1994}} Trudell ''et al.'' have suggested non-chemical binding due to the attractive [[van der Waals force]] between proteins and inert gases.{{r |Trudell1998}}

Similar to the mechanism of [[ethanol]]'s effect, the increase of gas dissolved in nerve cell membranes may cause altered ion [[Semipermeable membrane|permeability]] properties of the [[neural]] cells' [[lipid]] bilayers. The [[partial pressure]] of a gas required to cause a measured degree of impairment correlates well with the lipid solubility of the gas: the greater the solubility, the less partial pressure is needed.{{r |Franks1994}}

An early theory, the [[Minimum alveolar concentration#Meyer-Overton hypothesis|Meyer-Overton hypothesis]], suggested that narcosis happens when the gas penetrates the lipids of the brain's nerve cells, causing direct mechanical interference with the transmission of signals from one nerve cell to another.{{sfnp|Bennett|Rostain|2003|p=308}}{{r |Paton1975 |Hamilton1985}} More recently, specific types of chemically gated receptors in nerve cells have been identified as being involved with anesthesia and narcosis. However, the basic and most general underlying idea, that nerve transmission is altered in many diffuse areas of the brain as a result of gas molecules dissolved in the nerve cells' fatty membranes, remains largely unchallenged.{{r |Rostain2006 |Smith1986}}