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 (10-100a €‰nmol) and GRP (1-10a €‰nmol) dose-dependently elicit the same degree of robust itch scratching, which can be inhibited by mu-opioid peptide (MOP) receptor and GRP receptor (BB 2) antagonists, respectively. Unlike β-endorphin, which produces itch and attenuates inflammatory pain, GRP only elicits itch without affecting pain. In contrast, enkephalins (100-1000a €‰nmol) and nociceptin-orphanin FQ (3-30a €‰nmol) only inhibit pain without eliciting itch. More intriguingly, dynorphin A(1-17) (10-100a €‰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-BB 2 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.
| Original language | English |
|---|---|
| Article number | 11676 |
| Journal | Scientific Reports |
| Volume | 5 |
| DOIs | |
| State | Published - 29 Jun 2015 |
Bibliographical note
Funding Information:The authors thank Eric Hu, Kathryn Wladischkin, Colette Cremeans, Erin Gruley, and Kelly Tuzi for excellent technical assistance. Research reported in this publication was supported by the U.S. National Institutes of Health, NIAMS (R01-AR059193 and R21-AR064456) and NIDA (R01-DA032568 and R21-DA035359), and the U.S. Department of Defense (W81XWH-13-2-0045). The content is solely the responsibility of the authors and does not necessarily represent the official views of the U.S. federal agencies.