[Adaptive function of the sympathetic innervation of cerebral vessels following rapid changes in systemic arterial pressure].

Acute hemorrhagic hypotension followed by hypertension induced by rapid blood reinfusion was simulated in acute experiments on anesthesized rats with unilateral denervation of cerebral vessels (cervical sympathectomy). The quantity of hypertension-induced small hemorrhages in the denervated hemisphere was twice as large as in the intact one. No hemorrhages were obtained in both hemispheres in experiments without preliminary hypotension. Thus the reflector activation of the sympathetic neuronal system increases during hypotension the resistance of the brain vascular bed to the following hypertension.