Sympathetic innervation and cerebral hemodynamics in the rat ; Innervation sympathique et hémodynamique cérébrale chez le rat

The goal of the present work was to determine, in conscious rats, the role of the sympathetic innervation in the control of cerebral hemodynamics 1/ during a baseline period lasting ~4 h, and 2/ during an acute increase in blood pressure (BP) evoked by an emotional stressor (jet of air). Blood flows in internal carotid arteries (CaBF) were recorded with Doppler flow probes chronically implanted in intact rats and in rats that underwent unilateral excision of the superior cervical ganglion. Stress induced a large and brisk increase in BP which was accompanied by hyperemia and vasodilatation that were much stronger on the denervated than on the intact side. Spectral analysis demonstrated an overall enhancement of CaBF variability on the denervated side. Coherence between the two CaBFs, which provides an index of linear correlation in the frequency domain, was computed before (ordinary coherence) and after (partial coherence) mathematically eliminating the influence of BP. Both ordinary and partial coherences were lowered by unilateral sympathectomy in the 0.01-0.1 Hz frequency range, which suggests an important modulatory role for sympathetic innervation with respect to these slow CaBF fluctuations. These results indicate that in the conscious rat, sympathetic innervation plays a protective role of the cerebral circulation in the face of stress-induced increases in BP. On the other hand, this innervation modulates slow, spontaneous fluctuations of cerebral blood flow which are not directly related to BP fluctuations. ; Ce travail avait pour but de déterminer, chez le rat vigil, le rôle de l’innervation sympathique dans le contrôle de l’hémodynamique cérébrale 1/ au cours d’une période d’activité normale d’environ 4 heures, et 2/ lors d’une augmentation aiguë de la pression artérielle (PA) induite par un stress émotionnel (jet d’air). Les débits sanguins dans les artères carotides internes (DSCa) ont été mesurés grâce à des sondes Doppler chroniquement implantées, chez des rats intacts ou ayant subi l’exérèse ...