morin and Neuralgia

Vincristine is a toxic chemotherapeutic agent which often triggers neuropathic pain through inflammation. Morin isolated from figs (Ficus carica) exerts anti-inflammatory and neuroprotective activities. We investigated whether morin ameliorates vincristine-induced neuropathic pain and the underlying mechanism. Vincristine was injected i.p. for 10 days (day 1-5 and day 8-12). Morin was orally administered every other day from day 1 to 21. The pain behaviors were determined by measuring paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). The axons of sciatic nerves were stained with toluidine blue to study the histological abnormality. Function deficit of sciatic nerves was evaluated by sciatic functional index and the sciatic nerve conduction velocity. Neuronal excitability was assessed electrophysiologically and inflammatory mediators were detected using western blotting in dorsal root ganglia. The vincristine-induced reduction in PWT, PWL, and body weight gain was attenuated by morin. Morin restored the sciatic nerve deficits both histologically and functionally in vincristine-injected rats. The vincristine-induced neuronal hyperexcitability and increase in the expression of IL-6, NF-κB, and pNF-κB were abolished after morin administration. This study suggests that morin treatment suppressed vincristine-induced neuropathic pain by protecting the sciatic nerve and inhibiting inflammation through NF-κB pathway.

Topics: Animals; Flavonoids; Ganglia, Spinal; Inflammation; Inflammation Mediators; Male; Neuralgia; Neuroprotective Agents; NF-kappa B; Rats, Sprague-Dawley; Sciatic Nerve; Signal Transduction; Vincristine

As inflammatory and immune responses are involved in pathophysiology of debilitating neuropathic pain, reagents that can modulate these two responses may have therapeutic potential. Morin, derived from the moraceae family of plants, benefits inflammation-related diseases, but its antinociceptive effects on cancer pain remain elusive. In the present study, we investigated antinociceptive effects of morin on bone cancer pain using a rat model, where rats were subject to implantation of Walker 256 mammary gland carcinoma cells into the tibia. Morin (5-20 mg/kg) dose-dependently attenuated behavioral hypersensitivities, including mechanical allodynia and free movement pain, which was accompanied by downregulation of astrocyte marker glial fibrillary acidic protein in the spinal cord in cancer-bearing rats. Treatment with morin also induced reduction of pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 and upregulation of an antiinflammatory cytokine IL-10. Furthermore, intrathecal injection of AM630 (an antagonist of cannabinoid receptor 2, CB

Topics: Animals; Astrocytes; Bone Neoplasms; Cancer Pain; Cytokines; Female; Flavonoids; Glial Fibrillary Acidic Protein; Hyperalgesia; Indoles; Inflammation; Injections, Spinal; Interleukin-10; Interleukin-1beta; Interleukin-6; Neoplasm Transplantation; Neuralgia; Pain Measurement; Rats; Rats, Sprague-Dawley; Spinal Cord; Tumor Necrosis Factor-alpha

Neuropathic pain is initiated or caused due to the primary lesion or dysfunction in the nervous system and is proposed to be linked to a cascade of events including excitotoxicity, oxidative stress, neuroinflammation and apoptosis. Oxidative/nitrosative stress aggravates the neuroinflammation and neurodegeneration through poly (ADP) ribose polymerase (PARP) overactivation. Hence, the present study investigated the antioxidant and anti-inflammatory effects of the phytoconstituent; morin in chronic constriction injury (CCI) induced neuropathy. Neuropathic pain was induced by chronic constriction of the left sciatic nerve in rats, and the effect of morin (15 and 30 mg/kg, p.o.) was evaluated by measuring behavioural and biochemical changes. Mechanical, chemical and thermal stimuli confirmed the CCI-induced neuropathic pain and treatment with morin significantly improved these behavioural deficits and improved the sciatic functional index by the 14th day after CCI induction. After 14 days of CCI induction, oxidative/nitrosative stress and inflammatory markers were elevated in rat lumbar spinal cord. Oxidative stress induced PARP overactivation resulted in depleted levels of ATP and elevated levels of poly (ADP) ribose (PAR). Treatment with morin reduced the levels of nitrites, restored glutathione levels and abrogated the oxidant induced DNA damage. It also mitigated the increased levels of TNF-α and IL-6. Protein expression studies confirmed the PARP inhibition and anti-inflammatory activity of morin. Findings of this study suggest that morin, by virtue of its antioxidant properties, limited PARP overactivation and neuroinflammation and protected against CCI induced functional, behavioural and biochemical deficits.

Topics: Animals; Antioxidants; Constriction; Flavonoids; Inflammation; Inflammation Mediators; Male; Neuralgia; Oxidative Stress; Poly(ADP-ribose) Polymerases; Random Allocation; Rats; Rats, Sprague-Dawley; Sciatic Neuropathy