Effect of indomethacin on the responses of resistance and capacitance vessels to noradrenaline in working skeletal muscles in the dog (1) (2).

The effect of indomethacin upon the responses of resistance and capacitance vessels to noradrenaline (NA) in working skeletal muscles of the dog's hind leg was investigated. Responses of the resistance and the capacitance vessels of NA (0,1-0,5 microgram/kg injected into the femoral artery--i.f.a) were reflected as the changes in peripheral vascular resistance and in tissue volume respectively, and determined during and following exercise before and after indomethacin (1-1,5 mg/kg i.f.a.). Muscular exercise was induced by sciatic nerve stimulation of 6 min duration. The results show that indomethacin potentiates constrictor effects of NA in both pre-and postcapillary sections of the muscular vascular bed during and following exercise. An augmentation of NA effects is significantly greater in the capacitance than in the resistance vessels. Potentiated constrictor responses to NA are also maintained longer in the capacitance than in the resistance segment during the postexercise period. The results suggest that endogenous prostaglandings are involved in a local vascular response to exercise within both pre-and postcapillary segments of the muscular vascular bed. Their role in the capacitance vessels of the limb may be related to a local inhibiton of sympathetic activity, reduction of postcapillary resistance and facilitation of the venous outflow.