Journal of Applied Physiology, Vol 76, Issue 1 212-217, Copyright © 1994 by American Physiological Society
Dynamic response of cochlear blood flow to occlusion of anterior inferior cerebellar artery in guinea pigs
T. Ren, G. B. Avinash, A. L. Nuttall, J. M. Miller, E. A. Laurikainen and W. S. Quirk
Kresge Hearing Research Institute, University of Michigan Medical School, Ann Arbor 48109-0506.
In this study we investigated the autoregulation and hemodynamics of
cochlear blood flow (CBF) as measured by laser-Doppler flowmetry. When the
anterior inferior cerebellar artery was clamped, CBF decreased
approximately 40% (not to "biological zero"), followed by a gradual
increase. When the clamp was released, CBF quickly increased to as much as
167% of the baseline level and then slowly returned to baseline. We assume
that the dynamic CBF response to anterior inferior cerebellar artery
clamping reflects primarily a combination of passive elastic properties of
the cochlear vessels and active autoregulatory mechanisms. The decrease
portion of the negative phase and the increase portion of the positive
phase reflect mainly passive behavior, static compliance, and resistance of
vessels, whereas the slow exponential negative and positive changes
indicate an active response of vessels: an autoregulatory mechanism based
on compensatory vascular dilation and constriction. Our preliminary data
show a very strong CBF autoregulatory response to a change in intravascular
pressure. Sympathetic stimulation can enhance this autoregulation, and CO2
inhalation promotes compensatory dilation and inhibits compensatory
vascular constriction.
