Passive Compliance and Active Force Generation in the Guinea Pig Outer Hair
Cell.
Hallworth, Richard.
Department of Otolaryngology - Head and Neck Surgery, University of Texas
Health Science Center, San Antonio, Texas 78284, USA.
APStracts 2:0229N, 1995.
SUMMARY AND CONCLUSIONS
1. Cochlear outer hair cells, 20 to 80 [mu]m in length, were compressed
axially in vitro using calibrated glass fibers mounted on a piezoelectric
actuator. 2 . When driven by rectangular pulses in the compression direction,
the motion of the fiber tip consisted of a rapid initial compression that was
complete in 10-20 ms, followed by a smaller compression of slower time course.
3. The initial fiber deflections were found to be linear in amplitude for
compressions up to 400 nm. The axial compliances of outer hair cells were
calculated from the difference between the fiber tip motions when unattached
and when in contact with a cell. Axial compliances were found to be in the
range 0.04 - 1.2 km/N for 149 cells. The axial compliance was an increasing
function of cell length. 4. The peak force generated by electrically-
stimulated outer hair cells was measured from the deflection of a glass fiber
when the cell was stimulated by sinusoidal voltage commands. The slope gain of
force generation (force generated per mV of command at the cell membrane) was
estimated to range from 0.01 to 100 pN/mV. Most of the results fell in the
range 0.1 to 20 pN/mV. 5. When the apparent stiffness of the fiber was
increased, by moving the cell closer to the fiber base, the peak amplitude of
the fiber deflection generated by the cell decreased, and the peak force
increased, for the same sinusoidal voltage command. 6. The results of the
previous experiment were interpreted in the light of a model of outer hair
cell motility in which an ideal extension-generating element is in series with
an internal stiffness element. This internal stiffness was then calculated for
13 cells. 7. The internal stiffnesses of cells calculated by the above
procedure were found to be positively correlated with the axial stiffness
measurements obtained for the same cells. 8. The implications of the above
results for the effectiveness of outer hair cell motility in vivo are
discussed.
Received 10 March 1995; accepted in final form 30 July 1995.
APS Manuscript Number J159-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.