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M2 Receptors Exert Analgesic Action on DRG Sensory Neurons by Negatively Modulating VR1 Activity
Author(s) -
De Angelis Federica,
Marinelli Sara,
Fioretti Bernard,
Catacuzzeno Luigi,
Franciolini Fabio,
Pavone Flaminia,
Maria Tata Ada
Publication year - 2014
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.24499
Subject(s) - agonist , receptor , trpv1 , stimulation , hyperalgesia , chemistry , pharmacology , capsaicin , nociception , dorsal root ganglion , endocrinology , microbiology and biotechnology , sensory system , transient receptor potential channel , medicine , biology , neuroscience , biochemistry
Abstract The peripheral application of the M2 cholinergic agonist arecaidine on sensory nerve endings shows anti‐nociceptive properties. In this work, we analyze in vitro, the mechanisms downstream M2 receptor activation causing the analgesic effects, and in vivo the effects produced by M2 agonist arecaidine administration on nociceptive responses in a murine model of nerve growth factor (NGF)‐induced pain. Cultured DRG neurons treated with arecaidine showed a decreased level of VR1 and SP transcripts. Conversely, we found an increased expression of VR1 and SP transcripts in DRG from M2/M4 −/− mice compared to WT and M1 −/− mice, confirming the inhibitory effect in particular of M2 receptors on SP and VR1 expression. Patch‐clamp experiments in the whole‐cell configuration showed that arecaidine treatment caused a reduction of the fraction of capsaicin‐responsive cells, without altering the mean capsaicin‐activated current in responsive cells. We also demonstrated that arecaidine prevents PKCϵ translocation to the plasma membrane after inflammatory agent stimulation, mainly in medium–small sensory neurons. Finally, in mice, we have observed that intraperitoneal injection of arecaidine reduces VR1 expression blocking hyperalgesia and allodynia caused by NGF intraplantar administration. In conclusion, our data demonstrate that in vivo M2 receptor activation induces desensitization to mechanical and heat stimuli by a down‐regulation of VR1 expression and by the inhibition of PKCϵ activity hindering its translocation to the plasma membrane, as suggested by in vitro experiments. J. Cell. Physiol. 229: 783–790, 2014. © 2013 Wiley Periodicals, Inc.