INCREASED NITRIC-OXIDE SYNTHASE IMMUNOREACTIVITY IN RAT DORSAL-ROOT GANGLIA IN A NEUROPATHIC PAIN MODEL

In rats, tight ligation of L5 and L6 spinal nerves produces symptoms o f thermal hyperalgesia and mechanical allodynia, mimicking the symptom s which characterise painful peripheral neuropathies in humans. Immuno reactivity for nitric oxide synthase (NOS) was investigated in lumbar (L1, L4, L5 and L6) dorsal root ganglia from naive controls and from r ats surviving for 3, 7, and 14 days after unilateral ligation of the L 5 and L6 spinal nerves. Quantitative analysis revealed significant inc reases in the percentage of NOS-immunoreactive cell profiles in L5 and L6 ganglia on the operated side at all time points, with the number o f labelled profiles increasing with time following ligation, but L1 an d L4 ganglia were unaffected. These findings suggest that nitric oxide may have a role in the generation and/or maintenance of neuropathic p ain.