NITRIC-OXIDE MEDIATES BEHAVIORAL SIGNS OF NEUROPATHIC PAIN IN AN EXPERIMENTAL RAT MODEL

THIS study was conducted to determine whether nitric oxide (NO) is inv olved in the maintenance of behavioral signs of neuropathic pain induc ed by tightly ligating the left L5 and L6 spinal nerves. Neuropathic r ats showed behavioral signs representing mechanical allodynia, cold al lodynia and cold-stress exacerbated ongoing pain. Mechanical allodynia was suppressed by N-omega-nitro-L-arginine methyl ester (L-NAME; 200, 100, 50, 10 mu M/kg, i.p.), a nitric oxide synthase inhibitor, in a d ose-dependent manner. Cold allodynia and cold-stress exacerbated ongoi ng pain was also attenuated by L-NAME. Neither N-omega-nitro-D-arginin e methyl ester (D-NAME; 200 mu M/kg) nor saline changed any of the neu ropathic pain behaviors. These results suggested that NO plays an impo rtant role in the maintenance of the behavioral signs of neuropathic p ain and is involved in common steps in the maintenance of the differen t modalities of pain such as mechanical allodynia and cold allodynia. (C) 1998 Rapid Science Ltd.