title: Tolerance and morphine-induced cross-tolerance are not shown to Tyr-W-MIF-1 analgesia.
abstract: Tolerance and cross-tolerance between Tyr-W-MIF-1, a mixed micro-agonist/antagonist, and morphine were examined. Opiate dependence also was examined. Rats were pretreated with Tyr-W-MIF-1, morphine, or saline for 4 days. On day 5, the animals were tested for Tyr-W-MIF-1 analgesia, morphine analgesia, or naloxone-precipitated withdrawal. Tyr-W-MIF-1- and morphine-pretreated animals showed similar levels of dependence. Animals pretreated with Tyr-W-MIF-1 failed to express tolerance to Tyr-W-MIF-1 analgesia but did display cross-tolerance to morphine analgesia. Animals pretreated with morphine displayed tolerance to morphine analgesia but did not express cross-tolerance to Tyr-W-MIF-1 analgesia. Therefore, tolerance and morphine-induced cross-tolerance were not expressed to Tyr-W-MIF-1 analgesia.
authors.affiliation: Department of Psychology, University of New Orleans, LA 70148, USA. ribell@iupui.edu
authors.forename: R L
authors.initials: RL
authors.lastname: Bell
authors.forename: A L
authors.initials: AL
authors.lastname: Vaccarino
authors.forename: R D
authors.initials: RD
authors.lastname: Olson
authors.forename: G A
authors.initials: GA
authors.lastname: Olson
authors.forename: W L
authors.initials: WL
authors.lastname: Nores
authors.forename: J G
authors.initials: JG
authors.lastname: Cambre
authors.forename: J E
authors.initials: JE
authors.lastname: Zadina
authors.forename: A J
authors.initials: AJ
authors.lastname: Kastin
mesh_terms: D000818:Animals; D004361:Drug Tolerance; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D009292:Narcotic Antagonists; C077532:tyrosyl-prolyl-tryptophyl-glycinamide; D009020:Morphine; D009075:MSH Release-Inhibiting Hormone