title: The spinal antinociceptive effect of FR140423 is mediated through kyotorphin receptors.
abstract: We investigated the antinociceptive effect of a novel anti-inflammatory and analgesic drug, 3-(difluoromethyl)-1-(4-methoxyphenyl)-5-[4-(methylsulfinyl)phenyl]pyraz ole (FR140423), in the tail-pinch test in mice, and evaluated the mechanism of action of FR140423 using L-leucyl-L-arginine (Leu-Arg), a kyotorphin (endogenous Met-enkephalin releaser) receptor antagonist, L-NG-nitroarginine methylester (L-NAME), an inhibitor of nitric oxide (NO) synthase, and methylene blue (MB), an inhibitor of activation of guanylate cyclase. Oral administration of FR140423, at doses of 5-80 mg/kg, produced a dose-dependent antinociceptive effect with an ED50 value of 18 mg/kg. This antinociception was reversed by intrathecal (i.t.) (10 microg/mouse), but not by intracerebroventricular (i.c.v.) (100 microg/mouse), injection of Leu-Arg. Moreover, the antinociceptive effect of i.t. injection of FR140423 with an ED50 value of 3.7 microg/mouse was completely antagonized by co-administered Leu-Arg 10 microg/mouse. However, L-NAME (2000 mg/kg s.c.) and MB (200 mg/kg s.c.) did not antagonize the antinociception of FR140423. These findings suggest that FR140423 plays a role in nociceptive modulation in the spinal cord, being antinociceptive via the kyotorphin-Met-enkephalin pathway but not via the peripheral NO-cyclic GMP pathway.
authors.affiliation: Department of Immunology and Inflammation, Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co., Ltd., Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ochi
authors.forename: Y
authors.initials: Y
authors.lastname: Motoyama
authors.forename: T
authors.initials: T
authors.lastname: Goto
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects; D004151:Dipeptides / Q000008:administration & dosage / Q000494:pharmacology; D004723:Endorphins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D007279:Injections, Subcutaneous; D008297:Male; D008751:Methylene Blue / Q000008:administration & dosage / Q000494:pharmacology; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010147:Pain Measurement / Q000187:drug effects; D011720:Pyrazoles / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000187:drug effects* / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects*; D013454:Sulfoxides
chemical_list: D000701:Analgesics, Opioid; D000894:Anti-Inflammatory Agents, Non-Steroidal; D004151:Dipeptides; D004723:Endorphins; D004791:Enzyme Inhibitors; D011720:Pyrazoles; D011957:Receptors, Opioid; D013454:Sulfoxides; C019448:kyotorphin; C108904:3-(difluoromethyl)-1-(4-methoxyphenyl)-5-(4-(methylsulfinyl)phenyl)pyrazole; C078789:leucylarginine; D009020:Morphine; D019001:Nitric Oxide Synthase; D006162:Guanylate Cyclase; D008751:Methylene Blue; D019331:NG-Nitroarginine Methyl Ester