• Monika Jeub, Omneya Taha, Thoralf Opitz, Ildiko Racz, Julika Pitsch, Albert Becker, and Heinz Beck.
• Department of Neurology, University of Bonn Medical Center, Bonn, Germany, monika.jeub@ukbonn.de.
• J Pain Res. 2019 Jan 1; 12: 635-647.

BackgroundNeuropathic pain resulting from peripheral nerve lesions is a common medical condition, but current analgesics are often insufficient. The identification of key molecules involved in pathological pain processing is a prerequisite for the development of new analgesic drugs. Hyperexcitability of nociceptive DRG-neurons due to regulation of voltage-gated ion-channels is generally assumed to contribute strongly to neuropathic pain. There is increasing evidence, that T-type Ca2+-currents and in particular the Cav3.2 T-type-channel isoform play an important role in neuropathic pain, but experimental results are contradicting.PurposeTo clarify the role of T-type Ca2+-channels and in particular the Cav3.2 T-type-channel isoform in neuropathic pain.MethodsThe effect of partial sciatic nerve ligation (PNL) on pain behavior and the properties of T-type-currents in nociceptive DRG-neurons was tested in wild-type and Cav3.2-deficient mice.ResultsIn wild-type mice, PNL of the sciatic nerve caused neuropathic pain and an increase of T-type Ca2+-currents in capsaicin-responsive neurons, while capsaicin-unresponsive neurons were unaffected. Pharmacological experiments revealed that this upregulation was due to an increase of a Ni2+-resistant Ca2+-current component, inconsistent with Cav3.2 up-regulation. Moreover, following PNL Cav3.2-deficient mice showed neuropathic pain behavior and an increase of T-Type Ca2+-currents indistinguishable to that of PNL treated wild-type mice.ConclusionThese data suggest that PNL induces an upregulation of T-Type Ca2+-currents in capsaicin-responsive DRG-neurons mediated by an increase of a Ni2+-insensitive current component (possibly Cav3.1 or Cav3.3). These findings provide relevance for the development of target specific analgesic drugs.

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