title: Inflammation enhances Y1 receptor signaling, neuropeptide Y-mediated inhibition of hyperalgesia, and substance P release from primary afferent neurons.
abstract: Neuropeptide Y (NPY) is present in the superficial laminae of the dorsal horn and inhibits spinal nociceptive processing, but the mechanisms underlying its anti-hyperalgesic actions are unclear. We hypothesized that NPY acts at neuropeptide Y1 receptors in the dorsal horn to decrease nociception by inhibiting substance P (SP) release, and that these effects are enhanced by inflammation. To evaluate SP release, we used microdialysis and neurokinin 1 receptor (NK1R) internalization in rat. NPY decreased capsaicin-evoked SP-like immunoreactivity in the microdialysate of the dorsal horn. NPY also decreased non-noxious stimulus (paw brush)-evoked NK1R internalization (as well as mechanical hyperalgesia and mechanical and cold allodynia) after intraplantar injection of carrageenan. Similarly, in rat spinal cord slices with dorsal root attached, [Leu(31), Pro(34)]-NPY inhibited dorsal root stimulus-evoked NK1R internalization. In rat dorsal root ganglion neurons, Y1 receptors colocalized extensively with calcitonin gene-related peptide (CGRP). In dorsal horn neurons, Y1 receptors were extensively expressed and this may have masked the detection of terminal co-localization with CGRP or SP. To determine whether the pain inhibitory actions of Y1 receptors are enhanced by inflammation, we administered [Leu(31), Pro(34)]-NPY after intraplantar injection of complete Freund's adjuvant (CFA) in rat. We found that [Leu(31), Pro(34)]-NPY reduced paw clamp-induced NK1R internalization in CFA rats but not uninjured controls. To determine the contribution of increased Y1 receptor-G protein coupling, we measured [(35)S]GTPγS binding simulated by [Leu(31), Pro(34)]-NPY in mouse dorsal horn. CFA inflammation increased the affinity of Y1 receptor G-protein coupling. We conclude that Y1 receptors contribute to the anti-hyperalgesic effects of NPY by mediating the inhibition of SP release, and that Y1 receptor signaling in the dorsal horn is enhanced during inflammatory nociception.
authors.affiliation: Department of Physiology, School of Medicine, University of Kentucky Medical Center, Lexington, KY 40536, USA. Electronic address: brad.taylor@uky.edu.
authors.forename: B K
authors.initials: BK
authors.lastname: Taylor
authors.affiliation: Department of Physiology, School of Medicine, University of Kentucky Medical Center, Lexington, KY 40536, USA.
authors.forename: W
authors.initials: W
authors.lastname: Fu
authors.affiliation: Division of Pharmacology, University of Missouri-Kansas City, Kansas City, MO, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Kuphal
authors.affiliation: Department of Medicine, Division of Clinical Pharmacology, Karolinska Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: C-O
authors.initials: CO
authors.lastname: Stiller
authors.affiliation: Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160, USA.
authors.forename: M K
authors.initials: MK
authors.lastname: Winter
authors.affiliation: Veteran Affairs Greater Los Angeles Healthcare System and Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA, USA.
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Physiology, School of Medicine, University of Kentucky Medical Center, Lexington, KY 40536, USA.
authors.forename: G F
authors.initials: GF
authors.lastname: Corder
authors.affiliation: Department of Physiology and Biophysics, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Urban
authors.affiliation: Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: McCarson
authors.affiliation: Veteran Affairs Greater Los Angeles Healthcare System and Division of Digestive Diseases, Department of Medicine, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, CA, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Marvizon
mesh_terms: D000818:Animals; D005620:Freund's Adjuvant / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000493:pharmacokinetics; D006930:Hyperalgesia / Q000209:etiology* / Q000473:pathology; D066298:In Vitro Techniques; D007249:Inflammation / Q000139:chemically induced / Q000150:complications* / Q000473:pathology; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D009478:Neuropeptide Y / Q000378:metabolism*; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D017476:Receptors, Neuropeptide Y / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013116:Spinal Cord / Q000473:pathology*; D013126:Spinal Nerve Roots / Q000502:physiology; D013373:Substance P / Q000378:metabolism*; D013460:Sulfur Isotopes / Q000493:pharmacokinetics
chemical_list: D009478:Neuropeptide Y; D018040:Receptors, Neurokinin-1; D017476:Receptors, Neuropeptide Y; D013460:Sulfur Isotopes; D013373:Substance P; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D005620:Freund's Adjuvant
keywords: 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid; ANOVA; CFA; CGRP; DRG; G-protein; HEPES; IB4; NK1R; NPY; PBS; RIA; SP; SP-LI; SP-like immunoreactivity; aCSF; analysis of variance; artificial cerebrospinal fluid; calcitonin gene-related peptide; capsaicin; complete Freund’s adjuvant; dorsal root ganglion; isolectin B4; isolectin-B4; neurokinin 1 receptor; neurokinin-1 receptor; neuropeptide Y; pain; phosphate-buffered saline; radioimmunoassay; substance P