Inhibitory influences of mammalian FMRFamide (Phe-Met-Arg-Phe-amide)-related peptides on nociception and morphine- and stress-induced analgesia in mice.
The effects of two endogenous mammalian FMRFamide (Phe-Met-Arg-Phe-NH2)-related peptides, an octapeptide F8Fa (Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2) and an octadecapeptide A18Fa (Ala-Gly-Glu-Gly-Leu-Ser-Ser-Pro-Phe-Trp-Ser-Leu-Ala-Ala-Pro-Gln-Arg-Phe -NH2) on morphine- and restraint stress-induced analgesia and basal nociceptive sensitivity, as measured by the latency of a foot-lifting response to a warmed surface, were examined in male mice. Intracerebroventricular (i.c.v.) administrations of F8Fa and A18Fa (0.10-10 micrograms) during the day-time significantly reduced morphine (10 mg/kg) and restraint-induced analgesia at 30 min after administration, with F8Fa having a greater inhibitory effect than A18Fa. At night during the dark period i.c.v. F8Fa also significantly reduced the elevated nocturnal thermal response latency, while not affecting the shorter day-time nociceptive responses. Peripheral administrations of the prototypic opiate antagonist, naloxone (1.0 mg/kg), had similar inhibitory effects on morphine- and stress-induced analgesia, and the day-night rhythm of nociceptive sensitivity. These results indicate that F8Fa and A18Fa are involved in the modulation of opioid analgesia and suggest that these endogenous FMRFamide-related peptides may be associated with the expression of the day-night rhythm of opioid-mediated nociceptive sensitivity.
Kavaliers
M
M
Division of Oral Biology, Faculty of Denistry, University of Western Ontario, London, Canada.
D000595:Amino Acid Sequence; D000698:Analgesia; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology; D004723:Endorphins / Q000502:physiology*; D019835:FMRFamide; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009020:Morphine / Q000494:pharmacology*; D009479:Neuropeptides / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology* / Q000502:physiology; D010146:Pain / Q000378:metabolism* / Q000503:physiopathology; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000378:metabolism* / Q000503:physiopathology
D004723:Endorphins; D009479:Neuropeptides; D009842:Oligopeptides; D019835:FMRFamide; D009020:Morphine; C053651:phenylalanyl-leucyl-phenylalanyl-glutaminyl-prolyl-glutaminyl-arginyl-phenylalaninamide; C061209:A18Famide