[Changes in the hydration of the cerebral interstitial space and their role in the development of vascular...

Augmentation of the cerebral venous pressure in anesthetized cats whose brain was naturally perfused under the constant arterial pressure, caused a transvascular filtration of fluid into the brain tissue. Capillary filtration coefficient was 0.099 +/- 0.18 ml/mm Hg/min/100 g, i.e. near the values obtained earlier under perfusion of the hemodynamically isolated brain with constant blood flow. A new hypothesis is advanced on the modulating role of extracellular space hydration in actualization of opposite effects of neuro-humoral and metabolic factors on the vascular system. The augmentation of the cerebral tissue hydration was shown to evoke an increasing cerebrovascular resistance response to injection of increasing doses of noradrenaline into the cerebral arterial system. The lowering of the brain tissue hydration reduces the dose response to the noradrenaline.