title: Intracerebroventricular administration of 26RFa produces an analgesic effect in the rat formalin test.
abstract: GPR103 is one of the orphan G protein-coupled receptors. Recently, an endogenous ligand for GPR103, 26RFa, was identified. Many 26RFa binding sites have been observed in various nuclei of the brain involved in the processing of pain such as the parafascicular thalamic nucleus, the locus coeruleus, the dorsal raphe nucleus, and the parabrachial nucleus. In the present study, the effects of intracerebroventricular injection of 26RFa were tested in the rat. Intracerebroventricular injection of 26RFa significantly decreased the number of both phase 1 and phase 2 agitation behaviors induced by paw formalin injection. This analgesic effect of 26RFa on the phase 1 response, but not phase 2 response, was antagonized by BIBP3226, a mixed antagonist of neuropeptide Y Y1 and neuropeptide FF receptors. Intracerebroventricular injection of 26RFa has no effect in the 52.5 degrees C hot plate test. Intracerebroventricular injection of 26RFa had no effect on the expression of Fos-like immunoreactivity induced by paw formalin injection in the superficial layers of the spinal dorsal horn. These data suggest that (1) 26RFa modulates nociceptive transmission at the supraspinal site during a formalin test, (2) the mechanism 26RFa uses to produce an analgesic effect on the phase 1 response is different from that on the phase 2 response, and (3) intracerebroventricularly injected 26RFa dose not directly inhibit the nociceptive input to the spinal cord.
authors.affiliation: Department of Anesthesiology, Graduate School of Medical Science, Kumamoto University, 1-1-1 Honjo, Kumamoto-shi, Kumamoto, Japan. yamamotot@fc.kuh.kumamoto-u.ac.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Rika
authors.initials: R
authors.lastname: Miyazaki
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yamada
mesh_terms: D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D014151:Anti-Anxiety Agents / Q000008:administration & dosage / Q000494:pharmacology; D001120:Arginine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D005557:Formaldehyde / Q000494:pharmacology; D006358:Hot Temperature; D007276:Injections, Intraventricular; D008297:Male; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D009478:Neuropeptide Y / Q000008:administration & dosage / Q000494:pharmacology; D009479:Neuropeptides / Q000008:administration & dosage / Q000494:pharmacology* / Q000502:physiology; D009842:Oligopeptides / Q000008:administration & dosage / Q000494:pharmacology; D010146:Pain / Q000139:chemically induced*; D010147:Pain Measurement / Q000187:drug effects*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000502:physiology; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism
chemical_list: D018712:Analgesics, Non-Narcotic; D014151:Anti-Anxiety Agents; C092926:BIBP 3226; D009292:Narcotic Antagonists; D009478:Neuropeptide Y; D009479:Neuropeptides; D009842:Oligopeptides; D016760:Proto-Oncogene Proteins c-fos; C516486:Qrfpr protein, rat; D043562:Receptors, G-Protein-Coupled; C480638:prepro-26RFa protein, human; D005557:Formaldehyde; D001120:Arginine; C053651:phenylalanyl-leucyl-phenylalanyl-glutaminyl-prolyl-glutaminyl-arginyl-phenylalaninamide