Sex differences in the effects of Tyr-MIF-1 on morphine- and stress-induced analgesia.
There is evidence suggesting that the endogenous tetrapeptide, Tyr-MIF-1 (Tyr-Prol-Leu-Gly-amide), has antagonistic or modulatory effects on opioid-mediated analgesia. There is also substantial evidence for sex differences in opioid effects, whereby male rodents display greater levels of opioid-mediated analgesia than females. In the present study, determinations were made of the effects of Tyr-MIF-1 on morphine- and restraint stress-induced opioid analgesia in adult male and female deer mice, Peromyscus maniculatus. Intraperitoneal treatment with Tyr-MIF-1 (0.10-10 mg/kg) reduced morphine- and stress-induced analgesia in both male and female mice, with Tyr-MIF-1 having markedly greater antagonistic effects in male than female mice. These results indicate that there are sex differences in the modulatory (antiopiate) effects of Tyr-MIF-1 on opioid-mediated analgesia.
Division of Oral Biology, Faculty of Dentistry, University of Western Ontario, London, Canada.
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D000595:Amino Acid Sequence; D000698:Analgesia; D000818:Animals; D005260:Female; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D009020:Morphine / Q000037:antagonists & inhibitors*; D010542:Peromyscus; D012149:Restraint, Physical; D012727:Sex Characteristics; D013312:Stress, Physiological / Q000503:physiopathology*
D009020:Morphine; C036930:tyrosyl-prolyl-leucyl-glycinamide; D009075:MSH Release-Inhibiting Hormone