β-caryophyllene, a dietary cannabinoid, complexed with β-cyclodextrin produced anti-hyperalgesic effect involving the inhibition of Fos expression in superficial dorsal horn

AimsEvaluate the anti-hyperalgesic effect of the complex containing β-caryophyllene (βCP) and β-cyclodextrin (βCD) in a non-inflammatory chronic muscle pain mice model and investigated its action on superficial dorsal horn of the lumbar spinal cord.Main methodsThe βCP-βCD complex were prepared and characterized through the DSC, TG/DTG, FTIR, XRD and SEM. The model of chronic muscle pain was induced by two injections of pH 4.0 saline (20 μL) into left gastrocnemius 5 days apart. After confirming hyperalgesia, male mice were treated with βCP-βCD (10 or 20 mg/kg; p.o.) or vehicle (saline 0.9%, p.o.) daily for 9 days. 1 h after, the mechanical hyperalgesia, muscle withdrawal thresholds and motor performance were evaluated. To evaluate the βCP-βCD action on spinal cord, animals induced with chronic muscle pain were treated with βCP-βCD (20 mg/kg; p.o.) or vehicle (saline 0.9%, p.o.) and 90 min. after, were perfused, the lumbar spinal cord collected, crioprotected, cut and submitted in an immunofluorescence protocol for Fos protein.Key findingsThe characterization tests indicated that βCP were efficiently incorporated into βCD. The oral treatment with βCP-βCD, at all doses tested, produced a significant (p < 0.05) reduction on mechanical hyperalgesia and a significant (p < 0.05) increase in muscle withdrawal thresholds, without produce any alteration in force. In addition, βCP-βCD was able to significantly (p < 0.05) decrease Fos expression in the superficial dorsal horn.SignificanceThus, βCP-βCD attenuates the non-inflammatory chronic muscle pain in mice and inhibits the Fos expression in the lumbar spinal cord.