Proceedings of The Physiological Society

Physiology 2014 (London, UK) (2014) Proc Physiol Soc 31, PCB069

Poster Communications

Opiates modulate thermosensation by internalizing cold receptor TRPM8

G. Shapovalov1, D. Gordienko1,5, D. Gkika1, M. Devilliers2,3, A. Kondratskyi1, J. Busserolles2,3, A. Bokhobza1, A. Eschalier2,4, R. Skryma1, N. Prevarskaya1

1. Laboratoire de physiologie cellulaire inserm u1003, Villeneuve d'Ascq, France. 2. Clermont Universit

Stimulation of μ-opioid receptors (OPRM) brings powerful pain relief, but it also leads to development of tolerance and addiction. Ensuing withdrawal in abstinent patients manifests itself with severe symptoms, including cold hyperalgesia, often preventing addicted patients from successfully completing the rehabilitation. Unsurprisingly, OPRMs have been a central point of many studies. Nonetheless, satisfactory understanding of the pathways leading to distorted sensory responses during opiate administration and abstinence is far from complete. Here we present a novel mechanism leading to modulation by OPRMs of one of the sensory responses - thermosensation; activation of OPRM1 leads to internalization of a cold sensor TRPM8, that can be reversed by a follow-up treatment with inverse OPRM agonist, naloxone. Thus, morphine (10 μM) inhibited menthol-evoked currents in TRPM8-expressing DRG neurons (~15% over 10 min) and HEK293 cells (~50% over 40 min) as well as significantly suppressed Ca2+ entry. These effects of morphine could be reversed by wash-out or a 10 μM naloxone treatment. Interestingly, no difference in single-channel kinetics could be observed when activity of individual channel proteins was analysed. Imunoprecipitation experiments have demonstrated co-localization of TRPM8 and OPRM1, while cell-surface biotinylation showed that morphine treatment led to a progressive removal of TRPM8 from plasma membrane in the cells expressing OPRM1 but not in the cells expressing TRPM8 alone. Addressing the physiological role of TRPM8 internalization, the knockout of TRPM8 protein leads to a decrease in morphine-induced cold analgesia in mice with the reduction of morphine analgesic effect ranging from 40% at 20°C to 89% at 10°C, as was evidenced by tail immersion test. Additionally, escape jump and cold-plate assays demonstrated a significant score decrease, indicating a clear suppresion of cold hyperalgesia during morphine withdrawal in KO mice. The proposed pathway represents a universal mechanism that is likely shared by regulatory pathways modulating general pain sensation in response to opioid treatment.

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