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Signaling Potentiates Voltage-Dependent Sodium Currents in Trigeminal Nociceptive Neurons
1Departments of Anesthesiology, 2Neurobiology and Center of Neuroengineering, and 3Neurology, and 4Center for Translational Neuroscience, Duke University Medical Center, Durham, North Carolina
Submitted 16 May 2005; accepted in final form 19 November 2005
The proinflammatory cytokine interleukin-1
(IL-1
) mediates inflammation and hyperalgesia, although the underlying mechanisms remain elusive. To better understand such molecular and cellular mechanisms, we investigated how IL-1
modulates the total voltage-dependent sodium currents (INa) and its tetrodotoxin-resistant (TTX-R) component in capsaicin-sensitive trigeminal nociceptive neurons, both after a brief (5-min) and after a chronic exposure (24-h) of 20 ng/ml IL-1
. A brief exposure led to a 28% specific (receptor-mediated) reduction of INa in these neurons, which were found to contain type I IL-1 receptors (IL-1RI+) on both their soma and nerve endings. In marked contrast, after a 24-h exposure, the total sodium current was specifically increased by 67%, without significantly affecting the TTX-R component. This potentiation of INa was suppressed in the presence of selective inhibitors of protein kinase C and G-proteincoupled signaling pathways, thereby suggesting that INa can be modulated through multiple pathways. In summary, the potentiation of INa through chronic IL-1
signaling in nociceptive sensory neurons may be a critical component of inflammatory-associated hyperalgesia.
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