Differential effect of spironolactone in chronic constriction injury and vincristine-induced neuropathic pain in rats

The present study was designed to investigate the ameliorative potential of spironolactone in chronic constriction injury and vincristine-induced neuropathic pain in rats. The chronic constriction injury was induced by placing four loose ligatures around the sciatic nerve, while vincristine (50 mu g/kg) was administered for 10 days to induce chemotherapy-induced neuropathic pain. Acetone drop, pin-prick, hot plate and paint brush tests were performed to assess cold allodynia; mechanical and heat hyperalgesia; dynamic mechanical allodynia, respectively. The spontaneous pain and postural index in terms of foot deformity was also assessed. The levels of TNF-alpha were measured in the sciatic nerve as an index of inflammation. Chronic constriction injury led to significant development of cold allodynia; mechanical and heat hyperalgesia; dynamic mechanical allodynia; spontaneous pain and foot deformity along with rise in the levels of TNF-alpha. Administration of vincristine was associated with the development of allodynia and hyperalgesia without spontaneous pain, foot deformity and elevation in the levels of TNF-alpha. Administration of spironolactone (10 and 20 mg/kg) significantly attenuated chronic constriction injury-induced pain related behaviour and foot deformity along with attenuation of TNF-alpha levels, without modulating vincristine-induced neuropathic pain. The attenuating effect of spironolactone in chronic constriction injury may be due to its anti-inflammatory properties and ability to decrease pro-inflammatory cytokines, while involvement of noninflammatory mechanisms in the pathogenesis of vincristine-induced pain may probably explain its lack of beneficial effect in chemotherapy associated pain. Published by Elsevier B.V.