Nitric oxide production in rat dorsal root ganglia and spinal cord after sciatic nerve lesion

M.F. CORONEL; P.L. MUSOLINO; M.J. VILLAR

San Diego, USA

Congreso; Society for Neuroscience; 2004

Society for Neuroscience

Recent studies have analyzed the role of nitric oxide (NO) in pain modulation in several models of sciatic nerve injury. In the present study we have investigated NO production in lumbar dorsal root ganglia (DRG) and spinal cord (SC) over time in a model of peripheral neuropathy. A correlation with neuronal nitric oxide synthase (nNOS) -like immunoreactivity (LI) was also done. Animals subjected to peripheral axotomy were decapitated after different survival times (1, 7, 14, 28 days) and the ipsilateral and contralateral L4-5 DRGs, as well as the corresponding levels of the SC, were removed and homogenized in 20mM Tris-ClH (pH=7,4) with 0.32M sucrose and 2mM EDTA. The homogenates were centrifuged at 10000 X g for 10 min at 4°C. In the supernatants, NO production was evaluated by measuring nitrite (NO2-) and nitrate (NO3-), the stable degradation products of NO, using the NO Analyser 280 (Sievers). Animals destined for determination of nNOS-LI were perfused following similar survival times and their DRGs and SC processed for standard ABC immunohistochemistry using nNOS antibodies. Nerve section induced a progressive increase in NO production in the ipsilateral DRGs and SC in a pattern that correlated with nNOS-LI: this increase was gradual after 7 days of survival time, more pronounced after 14 days and reached a peak 28 days after the axotomy. This study shows that nNOS expression and, in consequence, the amount of NO produced, are increased in DRGs and SC after peripheral nerve lesion. These findings support the idea of NO participation in the mechanisms of neuropathic pain.