Evidence of Piezoelectric Resonance in Isolated Outer
Hair Cells
Richard D. Rabbitt 1*, Harold E. Ayliffe 1, Doug Christensen 1, Kranti Pamarthy 1, Carl Durney 1, Sarah Clifford 1 and William E. Brownell 2
1 University of Utah
2 Baylor College of Medicine
* To whom correspondence should be addressed. E-mail: r.rabbitt{at}utah.edu.
Submitted on August 3, 2004
Revised on September 16, 2004
Accepted on 3 December 2004
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Abstract |
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Present results demonstrate high-frequency electrical resonances in outer hair cells (OHCs), isolated from the apical turn of the cochlea, exhibiting features analogous to classical piezoelectric transducers. The fundamental (1st) resonance frequency averaged fn~13kHz (Q~1.7). Higher-order resonances were also observed. Resonances were ultrasonic relative to the characteristic best frequencies in the region of the cochlea from which the cells were isolated. To obtain these results, OHCs were positioned in a custom micro-chamber and subjected to stimulating electric fields along the axis of the cells (1-100kHz, 4-16mV/80µm). Electrodes embedded in the side-walls of the micro-chamber were used in a voltage-divider configuration to estimate the electrical admittance of the top portion of the cell-loaded chamber (containing the electro-motile lateral wall) relative to the lower portion (containing the basal plasma membrane). This ratio exhibited resonance-like tuning. Resonance was also detected independently using a secondary 1MHz radio-frequency (RF) interrogation signal applied transverse across the cell diameter. The RF interrogation revealed changes in the transverse electric impedance modulated by the axial stimulus. Modulation of the transverse electric impedance was particularly pronounced near the resonant frequencies. Experimental results are in qualitative agreement with simple single-mode (SM) and more complex length-thickness-extension (LTE) piezoelectric models of the OHC.
Key Words:
Cochlea, Flexoelectric, Motility, Prestin
