[paperplane]

this question also helped me understand why for an experiment to show the permissive effect of cortisol they hypophysectomized the animals before administering norepinephrine alone and then norepinephrine with cortisol pretreatment. the graph showed higher vascular responsiveness with pretreatment.This is permissiveness not synergism because cortisol has no vasoconstrictive effect all on its own. That's why a hypotensive crisis occurs when there is adrenal insufficiency! there is no cortisol to potentiate the effects of the catecholamines (which are less too ,I guess) and of the angiotensin2.