Comparative effects of noradrenaline and serotonin in a central and a peripheral artery in vitro.

A comparative study was done on a central and a peripheral artery of the rabbit with noradrenaline, serotonin and K+ in vitro. The aorta was more sensitive to NA than to 5-HT whilst the cerebral artery responded better to 5-HT. In both vessels, K+ produced similar responses. The alpha-adrenoceptor antagonist, phentolamine, and the tryptaminergic receptor antagonists, methysergide and cyproheptadine reduced, competitively, the effects of the agonists. There was no significant difference in the degree of antagonism between the cerebral artery and the thoracic aorta. Potassium-induced contractions were also reversibly reduced by phentolamine but not by 5-HT antagonists. There was no cross-tolerance between 5-HT and noradrenaline and K+ in these arteries. These results indicate that there are differences in the sensitivities of these vessels to the vasoconstrictors. This is interesting in view of the fact that 5-HT has often been implicated in migraine, a central phenomenon.