title: An opioid basis for early-phase isoflurane-induced hypotension in rats.
abstract: This study was conducted to more clearly delineate the possible role of endogenous opioid receptors and opioid peptides in general anesthesia-associated hypotension in rats. Exposure to 2% isoflurane in oxygen produced a triphasic change in mean arterial pressure (MAP), including an early phase in which MAP fell by -28.4 +/- 2.2%. The magnitude of this early-phase hypotension was attenuated in rats pretreated with intravenous (i.v.) mu-subtype-selective doses of either naloxone or methylnaloxone but not central doses of the selective mu-opioid antagonist beta-funaltrexamine. This early hypotensive phase was also reduced following i.v. pretreatment with antiserum against methionine-enkephalin but not beta-endorphin. These findings suggest that early-phase isoflurane-induced hypotension may be due to activation of peripheral mu-opioid receptors by an endogenous opioid peptide, possibly related to methionine-enkephalin.
authors.affiliation: Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Ellenberger
authors.forename: Heather L
authors.initials: HL
authors.lastname: Lucas
authors.forename: John M
authors.initials: JM
authors.lastname: Russo
authors.forename: Janet L
authors.initials: JL
authors.lastname: Mueller
authors.forename: Peggy L
authors.initials: PL
authors.lastname: Barrington
authors.forename: Leon F
authors.initials: LF
authors.lastname: Tseng
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Quock
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004723:Endorphins / Q000037:antagonists & inhibitors / Q000502:physiology*; D004744:Enkephalin, Methionine / Q000494:pharmacology; D006358:Hot Temperature; D007022:Hypotension / Q000139:chemically induced*; D007276:Injections, Intraventricular; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology; D009271:Naltrexone / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010147:Pain Measurement / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D011957:Receptors, Opioid / Q000502:physiology*; D014520:Urethane / Q000494:pharmacology; D001615:beta-Endorphin / Q000494:pharmacology
chemical_list: D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D019138:Antibodies, Blocking; D004723:Endorphins; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D009270:Naloxone; D014520:Urethane; D004744:Enkephalin, Methionine; D009271:Naltrexone; D001615:beta-Endorphin; C024524:beta-funaltrexamine; D007530:Isoflurane