Anti-allodynic effect of intrathecal processed Aconitum jaluense is associated with the inhibition of microglial activation and P2X7 receptor expression in spinal cord.

BACKGROUND: For their analgesic and anti-arthritic effects, Aconitum species have been used in folk medicine in some East Asian countries. Although their analgesic effect is attributed to its action on voltage-dependent sodium channels, they also suppress purinergic receptor expression in dorsal root ganglion neurons in rats with neuropathic pain. In vitro study also demonstrated that the Aconitum suppresses ATP-induced P2X7 receptor (P2X7R)-mediated inflammatory responses in microglial cell lines. Herein, we examined the effect of intrathecal administration of thermally processed Aconitum jaluense (PA) on pain behavior, P2X7R expression and microglial activation in a rat spinal nerve ligation (SNL) model. METHODS: Mechanical allodynia induced by L5 SNL in Sprague-Dawley rats was measured using the von Frey test to evaluate the effect of intrathecal injection of PA. Changes in the expression of P2X7R in the spinal cord were examined using RT-PCR and Western blot analysis. In addition, the effect of intrathecal PA on microglial activation was evaluated by immunofluorescence. RESULTS: Intrathecal PA attenuated mechanical allodynia in a dose-dependent manner showing both acute and chronic effects with 65 % of the maximal possible effect. The expression and production of spinal P2X7R was increased five days after SNL, but daily intrathecal PA injection significantly inhibited the increase to the level of naïve animals. Immunofluorescence of the spinal cord revealed a significant increase in P2X7R expression and activation of microglia in the dorsal horn, which was inhibited by intrathecal PA treatment. P2X7R co-localized with microglia marker, but not neurons. CONCLUSIONS: Intrathecal PA exerts anti-allodynic effects in neuropathic pain, possibly by suppressing P2X7R production and expression as well as reducing microglial activation in the spinal cord.

An exploratory study on the effectiveness of "Calmare therapy" in patients with cancer-related neuropathic pain: A pilot study.

PURPOSE: Calmare therapy (CT) has been suggested as a novel treatment for managing chronic pain. Recently, it was reported to show a positive therapeutic outcome for managing neuropathic pain condition. We performed an exploratory prospective study on the effectiveness of CT in patients with various types of cancer-related neuropathic pain (CNP). METHOD: We performed an open-labeled, single-arm, exploratory study on the effectiveness of CT in patients with various types of cancer-related neuropathic pain (CNP). The primary endpoint was a comparison of the 11-point Numerical Rating Scale (NRS) pain score at one month with the baseline score in each patient. Brief Pain Inventory (BPI) and consumption of opioid were also evaluated during follow-up period. RESULTS: CT significantly decreased NRS pain score at one month from baseline (p < 0.001) in 20 patients with chemotherapy-induced peripheral neuropathy (n = 6), metastatic bone pain (n = 7), and post-surgical neuropathic pain (n = 7). It also improved overall BPI scores, decreased consumption of rescue opioid (p = 0.050), and was found satisfactory by a half of patients (n = 10, 50.0%). CONCLUSIONS: Our preliminary results suggest that CT may be considered for cancer patients with various types of CNP. Large studies are necessary to confirm our findings and ascertain which additional CNP show positive response to CT.