EFFECTS OF CERVICAL SYMPATHETIC-NERVE STIMULATION ON THE CEREBRAL MICROCIRCULATION - POSSIBLE CLINICAL IMPLICATIONS

The action of bilateral cervical sympathetic nerve (CSN) stimulation o n mean cerebral blood flow (CBF) and on its rhythmical fluctuations wa s studied in normotensive rabbits by using laser-Doppler flowmetry (LD F). A reduction in mean CBF, mediated by a-adrenoceptors, was the pred ominant effect; it was more often present and larger in size in the va scular beds supplied by the carotid than in those supplied by the vert ebro-basilar system. This suggests that the sympathetic action facilit ates a redistribution of blood flow to the brain stem. The effect indu ced by CSN stimulation on CBF spontaneous oscillations was a consisten t decrease in amplitude and an increase in frequency, irrespective of the changes produced on the mean level of CBF. The possible implicatio ns of the sympathetic action on the state of the blood-brain barrier ( BBB) are discussed. Experimental and clinical data dealing with the in fluence of sympathetic activation on the cerebrovascular system have b een compared. As a result the possibility of analysing the spontaneous oscillations of CBF for clinical purposes is suggested.