Neuropathic pain is associated with severe chronic sensory disturbances characterized by spontaneous pain, increased responsiveness to painful stimuli (hyperalgesia) and pain perceived in response to non-noxious stimuli (allodynia). Morphine is effective treatment for neuropathic pain but produces tolerance on chronic use. The present study was designed to explore the anti-nociceptive and anti-hyperalgesic effect of grape seed extract using sciatic nerve ligation-induced neuropathic pain in rats.
Chronic constructive injury (CCI) was performed under anesthesia, on one side leg exposed by making a skin incision, and chromic gut ligatures were tied loosely around the sciatic nerve at 1 mm intervals. The treatment with grape seed proanthocyanidin extract (GSPE) (100 and 200 mg/kg, p.o.) was initiated on 7th day post-surgery and continued for next 14 days. Morphine (10 mg/kg, s.c.) alone and morphine in combination with GSPE (100 mg/kg, p.o.) were administered in CCI rats for 5 days starting from 7th day. On 3rd, 7th, 14th and 21st day, behavioral parameters (mechanical allodynia and thermal hyperalgesia) were assessed. Then the animals were killed on 22nd day and biochemical parameters [reduced glutathione (GSH), lipid peroxidation (LPO), catalase, nitrite, superoxide dismutase (SOD)] were assessed.
Ligation of the sciatic nerve significantly induced mechanical allodynia and thermal hyperalgesia and induces oxidative stress (increase in LPO and nitrite) and decline of anti-oxidant enzyme levels (catalase, SOD, GSH) in sciatic nerve homogenate. GSPE (100 and 200 mg/kg, p.o.) attenuated all the behavioural and biochemical parameters. Morphine also significantly reversed the symptoms of neuropathic pain but produced tolerance after 5 days. Further, co-treatment of GSPE (100 mg/kg) with morphine (10 mg/kg, s.c.) in CCI rats significantly reversed the morphine tolerance and enhanced its anti-hyperalgesic effect as compared to the morphine-alone-treated group.
In the present set of experiments, GSPE showed a significant anti-hyperalgesic and anti-nociceptive effect in rats.