Role of TRPV1 and ASIC3 in formalin-induced secondary allodynia and hyperalgesia

Background in the present study we determined the role of transient receptor potential v1 channel (trpv1) and acid-sensing ion channel 3 (asic3) in chronic nociception. methods 1% formalin was used to produce long-lasting secondary allodynia and hyperalgesia in rats. western blot was used to determine trpv1 and asic3 expression in dorsal root ganglia. results peripheral ipsilateral,but not contralateral,pre-treatment (-10 min) with the trpv1 receptor antagonists capsazepine (0.03-0.3 μm/paw) and a-784168 (0.01-1 μm/paw) prevented 1% formalin-induced secondary mechanical allodynia and hyperalgesia in the ipsilateral and contralateral paws. likewise,peripheral ipsilateral,but not contralateral,pre-treatment with the non-selective and selective asic3 blocker benzamil (0.1-10 μm/paw) and apetx2 (0.02-2 μm/paw),respectively,prevented 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. peripheral ipsilateral post-treatment (day 6 after formalin injection) with capsazepine (0.03-0.3 μm/paw) and a-784168 (0.01-1 μm/paw) reversed 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. in addition,peripheral ipsilateral post-treatment with benzamil (0.1-10 μm/paw) and apetx2 (0.02-2 μm/paw),respectively,reversed 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. trpv1 and asic3 proteins were expressed in dorsal root ganglion in normal conditions,and 1% formalin injection increased expression of both proteins in this location at 1 and 6 days compared to naive rats. conclusions data suggest that trpv1 and asic3 participate in the development and maintenance of long-lasting secondary allodynia and hyperalgesia induced by formalin in rats. the use of trpv1 and asic3 antagonists by peripheral administration could prove useful to treat chronic pain. © 2014 institute of pharmacology,polish academy of sciences.