LACK OF SHORT-TERM AUTOREGULATION IN THE COCHLEAR MICROCIRCULATION INGUINEA-PIGS

To determine the relationship between the dynamics of mean arterial bl ood pressure (MABP) elevation and possible changes in the cochlear mic rocirculation the cochlear blood flow (CBF) was measured in guinea pig s by a laser Doppler method. The MABP was elevated at rates ranging fr om 0. 02 mm Hg/s to 4 mm Hg/s by intravenous infusions of norepinephri ne or epinephrine in various concentrations. A fall in MABP was induce d by exsanguination of the animals. The purpose of the experiments was to record the time of onset and course of an expected autregulation i n the cochlea in response to slow or rapid changes in MABP. The data s uggest that there is no short-term autoregulation in the cochlear micr ocirculation reflecting the increase of the MABP, but a slight compens ation occurs when the MABP declines. These latter changes could be att ributed to the high CO2 sensitivity of the cochlear blood vessels.