Anti-inflammatory and central and peripheral anti-nociceptive activities of α-asarone through the inhibition of TNF-α production, leukocyte recruitment and iNOS expression, and participation of the adenosinergic and opioidergic systems.

Alpha-asarone has been found to possess many pharmacological activities, which can improve cognitive function and exert anti-oxidant, anxiolytic, anti-epileptic and protective effects against endothelial cell injury. The anti-inflammatory activity of α-asarone was evaluated using lipopolysaccharide (LPS)-induced paw oedema. Moreover, leukocyte migration, inducible nitric oxide synthase (iNOS) expression and tumour necrosis factor-alpha (TNF-α) levels were quantified in footpads. Formalin and LPS-induced thermal hyperalgesia models were generated using adenosinergic, opioidergic, serotonergic and muscarinic receptor antagonists. The effects on motor coordination were evaluated by means of the rota-rod test. Oral treatment (p.o.) with α-asarone (3 mg/kg) significantly inhibited paw oedema by 62.12 and 72.22%, 2 and 4 h post LPS injection, respectively. Alpha-asarone (3 mg/kg, p.o.) attenuated the inflammatory infiltrate 1, 3 and 6 h after LPS injection. Furthermore, α-asarone (3 mg/kg, p.o.) suppressed iNOS expression and TNF-α production, 6 and 1 h after inflammatory stimulus, respectively. Alpha-asarone (3, 10 and 30 mg/kg, p.o.) inhibited both phases of formalin-induced licking. In the hot-plate test, α-asarone (10 and 30 mg/kg, p.o.) increased the latency to response 3 and 5 h post LPS stimulus. Caffeine and naloxone abolished the central anti-nociceptive effect of α-asarone (neurogenic phase of formalin and hot plate tests), suggesting the participation of the adenosinergic and opioidergic systems. Furthermore, naloxone reversed the peripheral activity of α-asarone (inflammatory phase of formalin test), indicating the possible involvement of the opioidergic pathway. In the rota-rod test, α-asarone did not change motor coordination. These findings suggest that α-asarone has anti-inflammatory, peripheral and central anti-nociceptive effects and could represent a promising agent for future research.