Dissociation of the opioid receptor mechanisms that control mechanical and heat pain.
Delta and mu opioid receptors (DORs and MORs) are inhibitory G protein-coupled receptors that reportedly cooperatively regulate the transmission of pain messages by substance P and TRPV1-expressing pain fibers. Using a DOReGFP reporter mouse we now show that the DOR and MOR are, in fact, expressed by different subsets of primary afferents. The MOR is expressed in peptidergic pain fibers, the DOR in myelinated and nonpeptidergic afferents. Contrary to the prevailing view, we demonstrate that the DOR is trafficked to the cell surface under resting conditions, independently of substance P, and internalized following activation by DOR agonists. Finally, we show that the segregated DOR and MOR distribution is paralleled by a remarkably selective functional contribution of the two receptors to the control of mechanical and heat pain, respectively. These results demonstrate that behaviorally relevant pain modalities can be selectively regulated through the targeting of distinct subsets of primary afferent pain fibers.
Scherrer
Grégory
G
Department of Anatomy and Physiology and WM Keck Center for Integrative Neuroscience, University of California, San Francisco, CA 94158, USA.
Imamachi
Noritaka
N
Cao
Yu-Qing
YQ
Contet
Candice
C
Mennicken
Françoise
F
O'Donnell
Dajan
D
Kieffer
Brigitte L
BL
Basbaum
Allan I
AI
D000698:Analgesia; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D055879:Gene Knock-In Techniques; D006358:Hot Temperature; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009020:Morphine / Q000494:pharmacology; D009619:Nociceptors / Q000502:physiology; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology*; D017465:Receptors, Opioid, delta / Q000819:agonists / Q000502:physiology*; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000502:physiology*; D013116:Spinal Cord / Q000473:pathology / Q000502:physiology; D013373:Substance P / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism
D000701:Analgesics, Opioid; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D013373:Substance P; D009020:Morphine