Sensitivity, polarity, and conductance change in the response of vertebrate hair cells to controlled mechanical stimuli.

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Abstract
Hair cells, the primary receptors of the auditory, vestibular, and lateral-line sensory systems, produce electrical signals in response to mechanical stimulation of their apical hair bundles. An in vitro preparation and intracellular recording were employed to investigate the transduction mechanism of hair cells in the sacculus from the inner ear of the bullfrog (Rana catesbeiana). When stimulated directly by mechanical deflection of their hair bundles, these cells gave graded responses up to 15 mV in amplitude; the peak sensitivity was about 20 mV/.mu.m deflection. The depolarizing component of the receptor potential corresponded to stimuli directed towards the kinocilium. Depolarizing responses were associated with a membrane resistance decrease, the hyperpolarizing responses with a resistance increase. Action potentials, possibly C2+ spikes, were occasionally evoked in hair cells by mechanical or electrical stimulation.