Involvement of nuclear factor κB and descending pain pathways in the anti-hyperalgesic effect of ß-citronellol, a food ingredient, complexed in ß-cyclodextrin in a model of complex regional pain syndrome - Type 1.

Complex regional pain syndrome type 1 (CRPS-1) is a painful syndrome without effective treatment. In order to explore possible new treatments, we used an animal model of CRPS-1 to examine the effects of ß-Citronellol (ßCT), a monoterpene found in a variety of plants that has been shown to have analgesic effects. We aimed to assess its effects alone, and complexed with ß-cyclodextrin (ßCD), which has been previously used to enhance the effects of a number of medicines. The ßCT-ßCD was characterized physiochemically using high performance liquid chromatography (HPLC) and differential scanning calorimetry (DSC) and shown to have 80% efficiency. In the animal model, Swiss mice were treated with ßCT, ßCT-ßCD, vehicle, pregabalin or sham and evaluated for hyperalgesia and motor coordination. Inflammatory mediators were measured by Western blot or ELISA and the descending pain pathway by immunofluorescence. ßCT was shown to have an anti-hyperalgesic effect (without affecting motor coordination) that reduced inflammatory mediators and activated the descending pain pathway, and these effects were increased with complexation in ßCD. Our results showed ßCT-ßCD to be a promising treatment for CRPS-1.

p-Cymene attenuates cancer pain via inhibitory pathways and modulation of calcium currents.

BACKGROUND: Oncological pain is one of the most prevalent and difficult-to-treat symptoms in patients with cancer. p-Cymene (PC) is a monoterpene found in more than 100 different plant species, endowed with various pharmacological properties-particularly antinociceptive. HYPOTHESIS/PURPOSE: PC has antinociceptive effect in a model of oncologic pain due to the activation of the descending inhibitory pathway of pain. STUDY DESIGN: A pre-clinical, longitudinal, blind and randomized study. METHODS: Male Swiss mice were induced with S180 cells in the right hind paw, then treated daily with PC (12.5, 25 and 50 mg/kg, s.c.) and screened for mechanical hyperalgesia, spontaneous nociception, nociception induced by non-noxious palpation, tumor growth, changes in the neuromuscular function and existence of bone degradation in the tumor area. The effect of PC on Ca2+ currents (electrophysiological records), histological and neurochemical changes (immunofluorescence for Fos) were also evaluated. RESULTS: PC reduced (p < 0.05) the mechanical hyperalgesia, the spontaneous (p < 0.001) and non-noxious palpation (p < 0.001) nociceptions, not changing the tumor development, neuromuscular function or histopathological aspects of the paw affected. PC reduced Fos expression in the spinal cord (p < 0.001) and increased this expression in the PAG (p < 0.05) and in the NRM (p < 0.01). PC decreased the density of calcium channel currents (p < 0.05). CONCLUSION: These results suggest the antinociceptive effect of PC on oncologic pain, probably acting in both ascending and descending pain pathways, and modulating the calcium channel currents in order to exert its effects.