Secondary hyperalgesia in the rat first degree burn model is independent of spinal cyclooxygenase and nitric oxide synthase

Spinal pretreatment with cyclooxygenase (10 and 30 μg (S)-(+)-ibuprofen; and 3 and 30 μg ketorolac) and nitric oxide synthase (33 and 100 μg NG Nitro-l-arginine methyl ester hydrochloride (l-NAME) and 10 μg thiocitrulline) inhibitors resulted in no specific anti-allodynia. In contrast, ziconotide (0.3, 1.0 and 3 μg), the N-type voltage gated calcium channel antagonist was very effective in blocking burn-induced sensitivity at all doses used. l-type (Diltiazam 230 μg) and P-type (Agatoxin IVA 0.3 μg) calcium channel blockers produced intermediate effects. Thus, cyclooxygenase and nitric oxide synthase are assumed not to be downstream of Ca2++ permeable AMPA receptors. Voltage gated calcium channels blockers could exert their effects either pre- or post-synaptically.