Compressed air or a
nitrogen-
oxygen mixture produces from 0.3 MPa
nitrogen narcosis. The traditional view was that anaesthesia or
narcosis occurs when the volume of a hydrophobic site is caused to expand beyond a critical amount by the absorption of molecules of a
narcotic gas. The observation of the pressure reversal effect on general anaesthesia has for a long time supported the
lipid theory. However, recently,
protein theories are in increasing consideration since results have been interpreted as evidence for a direct anaesthetic-
protein interaction. The question is to know whether
inert gases act by binding processes on
proteins of
neurotransmitter receptors. Compression with breathing mixtures where
nitrogen is replaced by
helium which has a low
narcotic potency induces from 1 MPa, the
high pressure nervous syndrome which is related to neurochemical disturbances including changes of the
amino-acid and monoamine neurotransmissions. The use of
narcotic gas (
nitrogen or
hydrogen) added to a
helium-
oxygen mixture, reduced some symptoms of the
HPNS but also had some effects due to an additional effect of the
narcotic potency of the gas. The researches performed at the level of basal ganglia of the rat brain and particularly the nigro-striatal pathway involved in the control of the motor, locomotor and cognitive functions, disrupted by
narcosis or pressure, have indicated that GABAergic neurotransmission is implicated via GABAa receptors.