EFFECT OF DENERVATION ON ENDOTHELIUM-DERIVED RELAXING FACTOR-DEPENDENT RELAXATION IN THE RAT CREMASTER MUSCLE

Endothelium-derived relaxation mediated primarily by endothelium-deriv ed relaxing factor/nitric oxide (EDRF/NO) is essential in the maintena nce of vascular tone. However, little is known about the effects of de nervation on EDRF-mediated relaxation in the microcirculation after re implantation. Using intravital videomicroscopy in the rat cremaster mo del, this study assessed the effect of acute and chronic denervation o f the muscle, produced by severing the genitofemoral nerve, on EDRF-me diated vasorelaxation. The results demonstrated that acetylcholine-ind uced EDRF relaxation (10(-6)M) significantly relieved norepinephrine-i nduced vasoconstriction in small arteries (40-80 mum diameter) in both the acute and chronic denervated muscles. There was no significant di fference in the relaxant response between the denervated or innervated controls in each group or between the acute or chronic groups. This r elaxation was prevented by methylene blue (10(-4) M). These findings s uggest that EDRF-mediated relaxation in the microcirculation is not de pendent on tissue innervation. Thus the use of potent endothelial depe ndent agonists may be of use in cases of vasospasm postreimplantation. (C) 1993 Wiley-Liss, Inc.