title: Exposure to nitrous oxide stimulates a nitric oxide-dependent neuronal release of beta-endorphin in ventricular-cisternally-perfused rats.
abstract: We have previously shown that the antinociceptive effect of nitrous oxide (N(2)O) in the rat hot plate test is sensitive to antagonism by antisera against the endogenous opioid peptide beta-endorphin. Moreover, N(2)O-induced antinociception is reduced by inhibition of nitric oxide (NO) production in the brain. To test the hypothesis that N(2)O might stimulate an NO-dependent neuronal release of beta-endorphin, we conducted a ventricular-cisternal perfusion with artificial cerebrospinal fluid (aCSF) in urethane-anesthetized Sprague-Dawley rats. Ten-minute fractions of aCSF perfusate were collected from separate groups of room air-exposed rats, N(2)O-exposed rats, and L-NAME-pretreated, N(2)O-exposed rats; they were then analyzed for their content of NO metabolites and beta-endorphin. Compared to room air control, exposure to 70% N(2)O increased perfusate levels of the NO metabolites nitrite and nitrate as well as beta-endorphin. Pretreatment of rats with L-N(G)-nitro arginine methyl ester, an inhibitor of NO synthase, prevented the N(2)O-induced increases in nitrite, nitrate and beta-endorphin. These findings demonstrate in an in vivo rat model that N(2)O may stimulate an NO-dependent neuronal release of beta-endorphin.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, P.O. Box 646534, Pullman, WA 99164, USA.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Zelinski
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ohgami
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Quock
mesh_terms: D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage; D000704:Analysis of Variance; D000818:Animals; D002408:Catheters, Indwelling; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009609:Nitrous Oxide / Q000008:administration & dosage* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D001615:beta-Endorphin / Q000134:cerebrospinal fluid*
chemical_list: D018712:Analgesics, Non-Narcotic; D004791:Enzyme Inhibitors; D009566:Nitrates; D009573:Nitrites; D001615:beta-Endorphin; D009609:Nitrous Oxide; D019331:NG-Nitroarginine Methyl Ester