Tolerance and morphine-induced cross-tolerance are not shown to Tyr-W-MIF-1 analgesia.
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.
Bell
R L
RL
Department of Psychology, University of New Orleans, LA 70148, USA. ribell@iupui.edu
Vaccarino
A L
AL
Olson
R D
RD
Olson
G A
GA
Nores
W L
WL
Cambre
J G
JG
Zadina
J E
JE
Kastin
A J
AJ
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
D009292:Narcotic Antagonists; C077532:tyrosyl-prolyl-tryptophyl-glycinamide; D009020:Morphine; D009075:MSH Release-Inhibiting Hormone