Central and peripheral anti-hyperalgesic effects of diosmin in a neuropathic pain model in rats

Flavonoids are natural compounds showing anti-hyperalgesic activity in models of pain. Diosmin is a compound poorly studied in the treatment of neuropathic pain. This study evaluates the anti-hyperalgesic actions of diosmin and possible mechanisms of action involved by using a neuropathic pain model in rats. Experimental neuropathic pain was induced by chronic constriction injury (CCI) in male Wistar rats, then aesthesiometric index and plantar tests were assessed to evaluate mechanical and thermal hyperalgesia, respectively, in order to explore the analgesic effects of acute and sub-chronic treatment with diosmin. The GABAA, 5-HT1A, D2-like and opioid receptors participation, as well as levels of TNF-alpha, IL-1 beta and IL-6, were evaluated in the spinal cord and sciatic nerve tissues after acute and subchronic diosmin administration. In addition, the presence of diosmin on cerebral samples was determined by UHPLC-MS analysis. Acute and sub-chronic treatment with diosmin significantly diminished the mechanical and thermal hyperalgesia induced by CCI in rats. This anti-hyperalgesic effects of diosmin were modified in the presence of naloxone (1 mg/kg, i.p.) and haloperidol (0.1 mg/kg, i.p.), but not by GABAA and 5-HT1A receptor antagonists. The anti-hyperalgesic effects of diosmin were also linked with reduced levels of TNF-alpha, IL-1 beta and IL-6. The presence of diosmin in the cerebral samples was confirmed by chromatographic analysis. In conclusion, our results provide evidence that diosmin produces significant anti-hyperalgesic effects acting at central level by an opioid and D-2 dopaminergic receptors participation, and at peripheral level by reducing proinflammatory cytokines.