Trophic influence of the sympathetic nervous system on the rat portal vein

Adrenergic denervation of the rat portal vein was produced in vivo by the sympatholytic agent 6-hydroxydopamine (6-OHDA). Treatment of rats with 6-OHDA decreased the responses of the portal veins to nerve stimulation, reduced 3H-norepinephrine (NE) uptake, and decreased catecholamine fluorescence, indicating that partial adrenergic denervation was achieved. The main findings of this study indicate that the in vivo denervation produced: (1) a (time-dependent) increase in sensitivity of the veins to NE, which was not of prejunctional origin, (2) an increase in sensitivity to BaC12, and (3) a partial depolarization of the myovascular cells. The results suggest that the in vivo denervation of the portal veins by 6-OHDA produces a postjunctional alteration, which may be due to the removal of a trophic influence of the sympathetic nervous system. It is proposed that the partial depolarization and associated ionic changes may be components of the mechanism. These results provide the first direct evidence that membrane excitability changes are involved in trophic nerve-muscle interactions in blood vessels.