Deflection of the hair bundle changes the stereociliary calcium ion concentration and causes the hair bundle (using the myosin motor protein) to spring back, opposing the stimulus [ 182].
Upon deflection of the hair bundle toward the largest row of stereocilia, tension in the tip links increases.
Both myosin-1c and myosin VIIa have been implicated in the adaptation of mechanoelectrical transduction upon sustained deflection of the hair bundle (29, 30).
In a standard experimental protocol, adaptation is measured by the decrease in mechanotransduction current, which occurs during a sustained deflection of the hair bundle [ 42].
In the adaptation process driven by a sustained deflection of the hair bundle towards the tallest stereocilia, harmonin-b limits the reclosure of the transduction channels, likely by preventing the full relaxation of the tip-link tension (24).
In the cochlea, the relative motion between the sensory cells and their overlaying structure, the tectorial membrane, causes the deflection of the hair bundle and the opening of mechanotransduction channels, one of the few ion channels not yet conclusively identified [ 24].
It is thought that the hair cell receptor potential is caused by deflection of the hair bundle towards the tallest stereocilia, which increases the tension in the tip link causing the opening of mechanotransduction channels located at its bottom end [ 12].
Regarding the phase of the force generated by the OHC relative to the deflection of the hair bundle, a phase delay of 90 degrees is suggested in the high frequency range; this delay is probably resulting from low-pass filtering at the membrane due to membrane resistance and membrane capacitance [ 16] (see Appendix).
The fluid jet produces a uniform deflection of the hair bundle (Corns et al., 2014) and for IHCs, which are stimulated in vivo by fluid motion within the cochlear partition (Fettiplace and Kim, 2014), it provides a near-physiological stimulation without affecting their resting position.
DOI: http://dx.doi.org/10.7554/eLife.08177.008 The sinewave, 1 nA in amplitude and of varying frequency, was used to mimic the transducer current during the sound induced deflection of the hair bundle that would open and close the MT channels from their resting state.
