title: Opposing effects of narcotic gases and pressure on the striatal dopamine release in rats.
abstract: Nitrogen-oxygen breathing mixtures, for pressures higher than 0.5 MPa, decrease the release of dopamine in the rat striatum, due to the narcotic potency of nitrogen. In contrast, high pressures of helium-oxygen breathing mixtures of more than 1-2 MPa induce an increase of the striatal dopamine release and an enhancement of motor activity, referred to as the high pressure nervous syndrome (HPNS), and attributed to the effect of pressure per se. It has been demonstrated that the effect of pressure could be antagonized by narcotic gas in a ternary mixture, but most of the narcotic gas studies measuring DA release were executed below the threshold for pressure effect. To examine the effect of narcotic gases at pressure on the rat striatal dopamine release, we have used two gases, with different narcotic potency, at sublethargic pressure, nitrogen at 3 MPa and argon at 2 MPa. In addition, to dissociate the effect of the pressure, we have used nitrous oxide at 0.1 MPa to induce narcosis at very low pressure, and helium at 8 MPa to study the effect of pressure per se. In all the narcotic conditions we have recorded a decrease of the striatal dopamine release. In contrast, helium pressure induced an increase of DA release. For the pressures used, the results suggest that the decrease of dopamine release was independent of such an effect of the pressure. However, for the same narcotic gas, the measurements of the extracellular DA performed in the striatum seem to reflect an opposing effect of pressure, since the decrease in DA release is lower with increasing pressure.
authors.affiliation: Université de la Méditerranée et IMNSSA, E.A. 3280, Laboratoire de Physiopathologie et Action Thérapeutique des Gaz sous Pression, Faculté de Médecine Nord, IFR Jean Roche, 13916 Marseille cedex 20, France.
authors.forename: Norbert
authors.initials: N
authors.lastname: Balon
authors.forename: Badreddine
authors.initials: B
authors.lastname: Kriem
authors.forename: Erick
authors.initials: E
authors.lastname: Dousset
authors.forename: Michel
authors.initials: M
authors.lastname: Weiss
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Rostain
mesh_terms: D000818:Animals; D001128:Argon / Q000494:pharmacology*; D001274:Atmospheric Pressure; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D006371:Helium / Q000494:pharmacology; D008297:Male; D009294:Narcotics / Q000494:pharmacology*; D009584:Nitrogen / Q000494:pharmacology*; D009609:Nitrous Oxide / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D009294:Narcotics; D006371:Helium; D001128:Argon; D009609:Nitrous Oxide; D009584:Nitrogen; D004298:Dopamine