Pharmacological manipulation of vascular endothelium function in non-diabetic and streptozotocin-diabetic rats: effects on nerve conduction, hypoxic resistance and endoneurial capillarization

Abstract

We examined the potential for some of the abnormalities of vascular endothelium found in diabetes mellitus to cause neuropathic changes. Non-diabetic rats were treated for 2 months with the cyclo-oxygenase inhibitor flurbiprofen (5 mg·kg⁻¹·day⁻¹) to reduce prostacyclin production, the nitric oxide synthase inhibitor N^G-nitro-L-arginine (5 or 25 mg·kg⁻¹·day⁻¹), or combined treatment. There were dose-dependent reductions in sciatic motor and saphenous sensory conduction velocity. The two inhibitors acted synergistically, thus, the 5–6% motor conduction deficits (pG-nitro-l-arginine (5 mg·kg⁻¹·day⁻¹) increased to 17% (pG-nitro-l-arginine (25 mg·kg⁻¹·day⁻¹) and flurbiprofen, motor and sensory conduction velocity were reduced by 23% (ppG-nitro-l-arginine (25 mg·kg⁻¹·day⁻¹) and flurbiprofen together produced a 13% prolongation of the time taken for 80% hypoxic conduction failure in vitro (pG-nitro-L-arginine (5 mg·kg⁻¹·day⁻¹) would prevent nerve dysfunction. However, rather than prophylaxis during 2-month streptozotocin diabetes, treatment exacerbated nerve abnormalities. Thus, N^G-nitro-L-arginine worsened (8%,ppp<0.01). We conclude that overproduction of nitric oxide is unlikely to be involved in the aetiology of experimental diabetic neuropathy. However, endothelial dysfunction resulting in impaired nitric oxide and prostacyclin synthesis could make a substantial contribution.