Microdialysis study of striatal dopaminergic dysfunctions induced by 3 MPa of nitrogen- and helium-oxygen breathing mixtures in freely moving rats.
Previous studies have demonstrated opposite effects of high-pressure helium and nitrogen on extracellular dopamine (DA) levels, which may reflect disturbances on the synthesis, release or metabolic mechanisms. Intrastriatal microdialysis was used to measure the precursor (tyrosine), DA and its metabolites (DOPAC, HVA) levels under nitrogen- or helium- at pressure up to 3 MPa. Under 3 MPa of helium-oxygen breathing mixtures, the extracellular concentration of tyrosine is decreased while the extracellular concentration of DA is increased. On the contrary, nitrogen-oxygen breathing mixture at the same pressure increased extracellular tyrosine concentration and decreased DA release. Under both conditions, an increment of the DOPAC and HVA levels could be noted. Our results suggest that changes in DA release and metabolism during high-pressure helium exposure reflect the effect of the pressure per se, whereas the intrinsic effects of narcotic gases, although sensitive to pressure, would be revealed by hyperbaric nitrogen exposure.
Dedieu
David
D
Laboratoire de Physiopathologie et Action Thérapeutique des Gaz sous Pression, Faculté de Médecine Nord, Université de la Méditerranée et IMNSSA, E.A. 3280, IFR Jean Roche, 13916 Marseilles cedex 20, France.
Balon
Norbert
N
Weiss
Michel
M
Risso
Jean-Jacques
JJ
Kinkead
Richard
R
Rostain
Jean-Claude
JC
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000399:Air Pressure; D000818:Animals; D001923:Brain Chemistry; D002851:Chromatography, High Pressure Liquid; D003342:Corpus Striatum / Q000187:drug effects* / Q000503:physiopathology; D004298:Dopamine / Q000378:metabolism*; D006371:Helium / Q000494:pharmacology*; D006610:High Pressure Neurological Syndrome / Q000503:physiopathology; D006719:Homovanillic Acid / Q000378:metabolism; D007222:Inert Gas Narcosis / Q000503:physiopathology; D008297:Male; D017551:Microdialysis; D009068:Movement; D009584:Nitrogen / Q000494:pharmacology*; D010100:Oxygen; D051381:Rats; D017207:Rats, Sprague-Dawley
D015102:3,4-Dihydroxyphenylacetic Acid; D006371:Helium; D009584:Nitrogen; D010100:Oxygen; D004298:Dopamine; D006719:Homovanillic Acid