Cannabidiol and mitragynine exhibit differential interactive effects in the attenuation of paclitaxel-induced mechanical allodynia, acute antinociception, and schedule-controlled responding in mice.

Abstract

For many chemotherapy patients peripheral neuropathy is a debilitating side effect. Mitragyna speciosa (kratom) contains the alkaloid mitragynine (MG), which produces analgesia in multiple preclinical pain models. In humans, anecdotal reports suggest cannabidiol (CBD) may enhance kratom-related analgesia. We examined the interactive activity of MG and CBD in a mouse chemotherapy-induced peripheral neuropathy (CIPN) model. We also examined MG + CBD in acute antinociception and schedule-controlled responding assays, as well as examined underlying receptor mechanisms. Male and female C57BL/6J mice received a cycle of intraperitoneal (ip) paclitaxel injections (cumulative dose 32mg/kg). The von Frey assay was utilized to assess CIPN allodynia. In paclitaxel-naïve mice, schedule-controlled responding for food was conducted under a fixed ratio (FR)-10, and hot plate antinociception was examined. MG dose-relatedly attenuated CIPN allodynia (ED50 102.96mg/kg, ip), reduced schedule-controlled responding (ED50 46.04mg/kg, ip), and produced antinociception (ED50 68.83mg/kg, ip). CBD attenuated allodynia (ED50 85.14mg/kg, ip) but did not decrease schedule-controlled responding or produce antinociception. Isobolographic analysis revealed 1:1, 3:1 MG + CBD mixture ratios additively attenuated CIPN allodynia. All combinations decreased schedule-controlled responding and produced antinociception. WAY-100635 (serotonin 5-HT1A receptor antagonist) pretreatment (0.01mg/kg, ip) antagonized CBD anti-allodynia. Naltrexone (pan opioid receptor antagonist) pretreatment (0.032mg/kg, ip) antagonized MG anti-allodynia and acute antinociception but produced no change in MG-induced decreased schedule-controlled behavior. Yohimbine (α2 receptor antagonist) pretreatment (3.2mg/kg, ip) antagonized MG anti-allodynia and produced no change in MG-induced acute antinociception or decreased schedule-controlled behavior. Although more optimization is needed, these data suggest CBD combined with MG may be useful as a novel CIPN therapeutic.