The role of NO in neuropathic pain is controversial. The aim of this study was to compare neuropathic pain behavior after a NOS inhibitor or NO donor treatment and to investigate NOS activity in the dorsal root ganglia (DRG) of young and adult rats after spinal nerve injury. Methods: The effect of L-nitroarginine methylester (L-NAME) or sodium nitroprusside (SNP) on allodynia was measured in a spinal nerve ligation model of neuropathic pain. A NADPH-diaphorase (NADPH-d) histochemistry was

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... med on the DRG in a spinal nerve ligation model of neuropathic pain. Results: Mechanical allodynia was increased after spinal nerve injury in both young and adult rats, especially more prominent in young rats. The NOS inhibitor, L-NAME, alleviated allodynia after spinal nerve ligation in young rats but not in adults. The NO donor, SNP, aggravated allodynia in a spinal nerve ligation model of neuropathic pain in young rats but not in adult rats. NOS activity increased prominently in the DRG after spinal nerve ligation in young rats in contrast to adult rats. Conclusions: Severe neuropathic pain behavior may be a result of an increase of NOS activity in the DRG of young rats after spinal nerve ligation, whereas NO production may not be significantly related to neuropathic pain behaviors in a spinal nerve ligation model of adult rats.