Endothelin-1 and U46619 potentiate selectively the venous responses to nerve stimulation within the perfused superior mesenteric vascular bed of the rat

The effects were examined of endothelin-1 and U46619 on the responses to perivascular nerve stimulation of the simultaneously perfused arterial and venous vessels of the superior mesenteric arterial bed of the rat. Stimulation of the nerves at 4-16 Hz for 30 s caused frequency dependent constrictions of both the arterial and venous vessels similar to those produced by bolus doses of exogenous noradrenaline (0.1-10 nmol). Infusion of either endothelin-1 (0.1 nM) or U46619 (1-3 nM) caused small (less than or equal to 5 mmHg) increases in arterial and venous perfusion pressures and selectively potentiated the venous, but not arterial, responses to nerve stimulation. Conversely, endothelin-1 and U46619 potentiated the responses of both the arterial and venous vessels to exogenous noradrenaline. Thus, as reported previously for the arterial vessels of the rat mesentery, the isolated venous vessels constrict to perivascular nerve stimulation in a frequency dependent manner. In addition, endothelin-1 and U46619 potentiate selectively the effects of nerve stimulation on the veins.