Differential responses of rat aorta and mesenteric artery to norepinephrine and serotonin in vitro

The differences in the responses of isolated ring segments of aorta and mesenteric artery of rat have been investigated. The aortic rings showed higher sensitivity to norepinephrine than the mesenteric artery rings. On the other hand, the sensitivity of the mesenteric artery to serotonin was 17 times greater than that of the aortic ring segments. However, there was no difference between the sensitivity of the aorta and the mesenteric artery to potassium chloride stimulation. There was also no difference in the contractile responses of the aorta and the mesenteric artery to calcium chloride either during norepinephrine stimulation or during stimulation with serotonin. The phasic contraction of the aorta to norepinephrine was greater than the phasic contraction of the mesenteric artery to this agonist while the magnitude of phasic contraction of the aorta to serotonin was lower than that of the mesenteric artery. These results suggest that the differences in the contractile responses of the rat aorta and the mesenteric artery to norepinephrine and serotonin are dependent on the ability of these agonists to mobilise calcium from intracellular stores.