DYNAMIC-RESPONSE OF COCHLEAR BLOOD-FLOW TO OCCLUSION OF ANTERIOR INFERIOR CEREBELLAR ARTERY IN GUINEA-PIGS

In this study we investigated the autoregulation and hemodynamics of c ochlear blood flow (CBF) as measured by laser-Doppler flowmetry. When the anterior inferior cerebellar artery was clamped, CBF decreased sim ilar to 40% (not to ''biological zero''), followed by a gradual increa se. When the clamp was released, CBF quickly increased to as much as 1 67% of the baseline level and then slowly returned to baseline. We ass ume that the dynamic CBF response to anterior inferior cerebellar arte ry clamping reflects primarily a combination of passive elastic proper ties of the cochlear vessels and active autoregulatory mechanisms. The decrease portion of the negative phase and the increase portion of th e positive phase reflect mainly passive behavior, static compliance, a nd resistance of vessels, whereas the slow exponential negative and po sitive changes indicate an active response of vessels: an autoregulato ry mechanism based on compensatory vascular dilation and constriction. Our preliminary data show a very strong CBF autoregulatory response t o a change in intravascular pressure. Sympathetic stimulation can enha nce this autoregulation, and CO2 inhalation promotes compensatory dila tion and inhibits compensatory vascular constriction.