Neurotropin inhibits neuronal activity through potentiation of sustained Kv currents in primary cultured DRG neurons

[Speaker] Hiroyuki Kawai:1
[Co-author] Nozomi Asaoka:1, Takahito Miyake:1, Kazuki Nagayasu:1, Hisashi Shirakawa:1, Shuji Kaneko:1
1:Department of Molecular Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, Japan

Neurotropin (NTP) is a non-protein extract from rabbit inflamed skin inoculated with vaccinia virus, which is widely used in Japan as an effective analgesic agent for neuropathic pain; however, the mechanisms underlying this effect remain poorly defined. Dorsal root ganglion (DRG) neurons transmit peripheral sensory inputs to the central nervous system, and DRG hyperactivity induces neuropathic pain. However, effects of NTP on DRG neurons remain to be investigated. In this study, I examined the effects of NTP on primary cultured rat DRG neurons by whole-cell patch-clamp recordings. In whole-cell current-clamp experiments, 3-day treatment with NTP reduced the number of action potentials evoked by current injection and increased current threshold. Additionally, whole-cell voltage-clamp recordings revealed that NTP potentiated voltage-gated potassium (Kv) channel currents, especially in its sustained component, which is important for modulating neuronal activity. On the other hand, NTP did not affect voltage-independent potassium currents. Taken together, these results suggest that NTP inhibits firing activity of DRG neurons through augmentation of sustained Kv currents.

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