title: Distinct functions of opioid-related peptides and gastrin-releasing peptide in regulating itch and pain in the spinal cord of primates.
abstract: How neuropeptides in the primate spinal cord regulate itch and pain is largely unknown. Here we elucidate the sensory functions of spinal opioid-related peptides and gastrin-releasing peptide (GRP) in awake, behaving monkeys. Following intrathecal administration, β-endorphin (10-100 nmol) and GRP (1-10 nmol) dose-dependently elicit the same degree of robust itch scratching, which can be inhibited by mu-opioid peptide (MOP) receptor and GRP receptor (BB2) antagonists, respectively. Unlike β-endorphin, which produces itch and attenuates inflammatory pain, GRP only elicits itch without affecting pain. In contrast, enkephalins (100-1000 nmol) and nociceptin-orphanin FQ (3-30 nmol) only inhibit pain without eliciting itch. More intriguingly, dynorphin A(1-17) (10-100 nmol) dose-dependently attenuates both β-endorphin- and GRP-elicited robust scratching without affecting pain processing. The anti-itch effects of dynorphin A can be reversed by a kappa-opioid peptide (KOP) receptor antagonist nor-binaltorphimine. These nonhuman primate behavioral models with spinal delivery of ligands advance our understanding of distinct functions of neuropeptides for modulating itch and pain. In particular, we demonstrate causal links for itch-eliciting effects by β-endorphin-MOP receptor and GRP-BB2 receptor systems and itch-inhibiting effects by the dynorphin A-KOP receptor system. These studies will facilitate transforming discoveries of novel ligand-receptor systems into future therapies as antipruritics and/or analgesics in humans.
authors.affiliation: Department of Anesthesiology &Pain Medicine, School of Medicine, Ewha Womans University, Seoul 158-710, South Korea.
authors.forename: Heeseung
authors.initials: H
authors.lastname: Lee
authors.affiliation: 1] Department of Physiology &Pharmacology, Wake Forest University, Winston-Salem, NC 27157, USA [2] Department of Dermatology, Wake Forest University, Winston-Salem, NC 27157, USA [3] Center for Comparative Medicine Research, School of Medicine, Wake Forest University, Winston-Salem, NC 27157, USA.
authors.forename: Mei-Chuan
authors.initials: MC
authors.lastname: Ko
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D001522:Behavior, Animal; D004399:Dynorphins / Q000494:pharmacology; D005260:Female; D019886:Gastrin-Releasing Peptide / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D006930:Hyperalgesia / Q000188:drug therapy; D007278:Injections, Spinal; D008253:Macaca mulatta; D008297:Male; D009479:Neuropeptides / Q000494:pharmacology / Q000627:therapeutic use*; D010146:Pain / Q000150:complications / Q000188:drug therapy*; D011537:Pruritus / Q000150:complications / Q000188:drug therapy*; D013116:Spinal Cord / Q000187:drug effects / Q000473:pathology*; D001615:beta-Endorphin / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; D009479:Neuropeptides; D001615:beta-Endorphin; D004399:Dynorphins; D019886:Gastrin-Releasing Peptide