Differences between cerebral and cerebellar autoregulation during progressive hypotension in rats

Autoregulation in the brain is essential to the maintenance of perfusion an d hence to the normal functioning of the organism in the face of various he modynamic challenges. The existence of prodromal symptoms preceding faintin g suggests that cerebellar autoregulation could be altered earlier than cer ebral autoregulation during the development of hypotension. The purpose of this study was to compare cerebral and cerebellar autoregulatory responses to hypotension induced by two rates of hemorrhage 1.5 and 2.0 ml/min. Corti cal blood flows were measured simultaneously using laser Doppler flowmetry in rats. With increasing rate of hemorrhage, the kinetics of autoregulation were maintained in the cerebrum, whereas it caused a progressive loss in t he efficacy of autoregulation in the cerebellum. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.