Aloin attenuates chronic constriction injury-induced neuropathic pain in rats by inhibiting inflammatory cytokines and oxidative stress

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Objective: To investigate the effect of aloin against chronic constriction injury (CCI)-induced neuropathic pain in rats. Methods: Rats were randomly divided into 7 groups: Group I (normal control), Group II (sham-operated), Group III (CCI control) and Group IV, V, VI, and VII, which underwent CCI surgery and then were administered with aloin (5 mg/kg, p.o.; 25 mg/kg, p.o.; 125 mg/kg, p.o.) and gabapentin (50 mg/kg, p.o.), respectively for 14 days. Peripheral neuropathy was induced by silk ligatures (4-0) loosely placed around the sciatic nerve. Nociceptive thresholds against mechanical stimuli (Von-Frey filaments) and thermal stimuli (12 °C and 40 °C) were measured at mid-plantar paw region ipsilateral to the compressed nerve on day-3, 7, 11, and 14. The concentration of cytokines including tumor necrosis factor-α (TNF-α), interleukin-6, and interleukin-1β was estimated at day-7. At day 14, motor nerve conduction velocity was determined under urethane anesthesia (1.25 g/kg). Oxidative stress parameters (malondiadehyde, glutathione, catalase, and superoxide dismutase) were estimated in sciatic nerve homogenates at day 14. Representative nerve samples were processed for histological investigations. Results: Aloin significantly reduced CCI-induced mechanical and thermal allodynia. It also improved motor nerve conduction velocity and decreased oxidative stress in nerve tissues. In addition, it decreased pro-inflammatory cytokine levels and restored the histoarchitecture of compressed sciatic nerve. Conclusions: Aloin mitigates CCI-induced neuropathic pain in rats by inhibiting oxidative stress and pro-inflammatory cytokines in the afflicted sciatic nerve.