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 2

BK inhibits M current in DRG neurons.

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BK inhibits M current in DRG neurons. (A) Time course for the effect of ...
(A) Time course for the effect of 200 nM BK on M current amplitude (Ideac, the amplitude of the deactivating tail current at –60 mV; see Methods). A specific M channel blocker, XE991 (3 μM), was applied at the end of the recording. Drugs were applied during the periods indicated by the bars. The lower inset shows the current traces recorded at the times indicated by the letters; the dotted line indicates a zero current level. The voltage protocol is depicted in the inset above. (B) Concentration dependency of the inhibitory effect of BK on M current. The curve represents the fit of data to a logistic equation (see Methods). The n number for each data point is given in parentheses. (C–E) As in A, but neurons were pretreated with (C) the specific B2R antagonist Hoe-140 (100 nM), (D) PLC inhibitor edelfosine (10 μM), or (E) IP3 receptor blocker xestospongin C (Xe-C, 1 μM). (F) Summary of the pharmacology of BK-induced M current inhibition. Bars show percentage M current inhibition by 200 nM BK (Control); BK + 100 nM Hoe-140; BK + 10 μM edelfosine; BK + 1 μM Xe-C; BK + 2 μM thapsigargin (Thap); BK + high BAPTA pipette solution; BK + 100 nM bisindolylmaleimide (BIM); and BK + 10 μM quinacrine (Quin). The number of experiments is given above each bar; **P ≤ 0.01.