Nonlinear stochastic dynamics of hair cells
Sensory hair cells are mechanoreceptors transducing mechanical stimuli to electrical signals in auditory and vestibular periphery in vertebrates. In amphibians, hair cells may exhibit spontaneous oscillations of their hair bundles and membrane potentials, reflecting two distinct active amplification mechanisms employed in these peripheral mechanosensors. We use a two-compartment model of bullfrog's saccular hair cell to study how the interaction between its mechanical and electrical compartments affects the emergence of distinct dynamical regimes, and the role of this interaction in shaping the response of the hair cell to weak mechanical stimuli. The model employs a Hodgkin-Huxley type system for the basolateral electrical compartment and a nonlinear stochastic hair bundle oscillator for the mechanical compartment, which are coupled bidirectionally. In effect, the hair cell system can be represented by two bidirectionally coupled unequally noisy oscillators. Consistent with experiments, the model demonstrates that dynamical regimes of the hair bundle change in response to variations in the conductances of basolateral ion channels. We show that the sensitivity of the hair cell to weak mechanical stimuli can be maximized by varying coupling strength.