Effects of Acute Nitric Oxide Synthase Inhibition on Lower Leg Vascular Function in Chronic Tetraplegia

Background/Objective:

To improve our understanding of the lower-leg vascular responses of nitric oxide synthase inhibition in persons with tetraplegia.

Participants:

Six people with chronic tetraplegia and 6 age-matched controls.

Methods:

Lower-leg relative vascular resistance and venous volume variation were obtained by venous occlusion plethysmography and blood pressure by auscultation at baseline. Postintravenous infusion of the nitric oxide synthase inhibitor N^G-nitro-l-arginine-methyl-ester (1 mg·kg⁻¹) or placebo on separate days.

Results:

At baseline in the group with tetraplegia compared with controls, mean arterial pressure and relative vascular resistance of the leg were significantly lower. After nitric oxide synthase inhibition, mean arterial pressure and lower leg vascular resistance were significantly elevated in both groups. There were no group or intervention differences in venous volume variation.

Conclusion:

These preliminary results suggest that nitric oxide synthase inhibition with 1 mg·kg⁻¹ N^G-nitro-l-arginine-methyl-ester normalizes seated blood pressure and lower leg vascular resistance to control group baseline levels.