Neuroprotective effect of saponin rich extract of Acorus calamus L. in rat model of chronic constriction injury (CCI) of sciatic nerve-induced neuropathic pain

Traditionally, Acorus calamus has been used for the treatment and management of headache, migraine, body ache and severe inflammatory pain in the Unani, Ayurveda and Indian system of medicine. Present study focuses on the evaluation of saponin rich extract of Acorus calamus (SRE-AC) in chronic constriction injury (CCI) of sciatic nerve induced neuropathic pain and neuronal functional changes in rats. The pain sensitive tests, i.e., thermal and mechanical hyperalgesia and sciatic functional index test, were performed on the different days, i.e., days 0, 1, 7, 14, and 21. The motor and sensory nerve conduction velocity was also measured on the 21st day. Tissue total protein, superoxide anion generation, total calcium, myeloperoxidase and TNF-α levels were estimated to assess biochemical changes. Histopathological evaluations were also performed. SRE-AC (20 and 40 mg/kg) and pregabalin (10 mg/kg, serving as a positive control) were administered orally for 14 consecutive days from the day of surgery. CCI produced significant (P<0.05) increase in thermal and mechanical hyperalgesia, rise in sciatic functional index, decrease in nerve conduction velocity, along with biochemical and histopathological changes. Oral administration of SRE-AC and pregabalin significantly (P<0.05) ameliorated CCI-induced nociceptive pain threshold, sciatic functional and electrophysiological changes in a dose dependent manner. Further, tissue biochemical and histopathological changes were also attenuated. SRE-AC has shown ameliorative effect in CCI-induced neuropathic pain which may be attributed to its multiple actions including anti-oxidative, anti-inflammatory and neuroprotective actions.