The acute nociceptive signals induced by bradykinin in rat sensory neurons are mediated by inhibition of M-type K+ channels and activation of Ca2+-activated Cl– channels
Boyi Liu, … , Hailin Zhang, Nikita Gamper
Boyi Liu, … , Hailin Zhang, Nikita Gamper
Published March 24, 2010
Citation Information: J Clin Invest. 2010;120(4):1240-1252. https://doi.org/10.1172/JCI41084.
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Research Article

The acute nociceptive signals induced by bradykinin in rat sensory neurons are mediated by inhibition of M-type K+ channels and activation of Ca2+-activated Cl– channels

Abstract

Bradykinin (BK) is an inflammatory mediator and one of the most potent endogenous pain-inducing substances. When released at sites of tissue damage or inflammation, or applied exogenously, BK produces acute spontaneous pain and causes hyperalgesia (increased sensitivity to potentially painful stimuli). The mechanisms underlying spontaneous pain induced by BK are poorly understood. Here we report that in small nociceptive neurons from rat dorsal root ganglia, BK, acting through its B2 receptors, PLC, and release of calcium from intracellular stores, robustly inhibits M-type K+ channels and opens Ca2+-activated Cl– channels (CaCCs) encoded by Tmem16a (also known as Ano1). Summation of these two effects accounted for the depolarization and increase in AP firing induced by BK in DRG neurons. Local injection of inhibitors of CaCC and specific M-channel openers both strongly attenuated the nociceptive effect of local injections of BK in rats. These results provide a framework for understanding spontaneous inflammatory pain and may suggest new drug targets for treatment of such pain.

Authors

Boyi Liu, John E. Linley, Xiaona Du, Xuan Zhang, Lezanne Ooi, Hailin Zhang, Nikita Gamper

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Figure 5

CaCC current in DRG neurons depends on expression of TMEM16A.

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CaCC current in DRG neurons depends on expression of TMEM16A. (A) Curren...
(A) Current at –60 mV induced by BK (200 nM) in small DRG neurons is attenuated by Tmem16a siRNA (right trace) but not by the scrambled siRNA control (left trace). (B) Mean peak inward current amplitudes for experiments as in A, for cells transfected with 2 different scrambled oligos (scrambled 1 and 2), mock-transfected cells, and cells transfected with Tmem16a siRNA. *P ≤ 0.05; numbers of experiments are shown in the bars. (C–E) Tmem16a siRNA does not affect BK-induced inhibition of M current. Application of 200 nM BK to the neuron transfected with Tmem16a siRNA induced robust inhibition of M current, which was recorded by the voltage pulse from –30 mV to –60 mV (inset above the current traces in D). (E) Mean M current inhibition by BK in neurons transfected with scrambled oligos or Tmem16a siRNA. (F) Tmem16a mRNA levels (normalized to the housekeeping gene U6) in DRG cultures transfected with scrambled oligo (scrambled 1) or Tmem16a siRNA, as well as in untransfected culture and acutely dissociated DRG prep from an adult (8 weeks) rat; **P ≤ 0.01. (G) Western blot showing decrease in TMEM16A protein abundance (band at 116 kDa) in whole cell lysates of DRG cells transfected with Tmem16a siRNA (as compared with the scrambled oligo control 1) and whole protein lysate from acutely extracted DRG (no cell culture) of P7 rat; loading control was β-actin.