title: Mechanical relaxation of the hair bundle mediates adaptation in mechanoelectrical transduction by the bullfrog's saccular hair cell.
abstract: Mechanoelectrical transduction by hair cells of the frog's internal ear displays adaptation: the electrical response to a maintained deflection of the hair bundle declines over a period of tens of milliseconds. We investigated the role of mechanics in adaptation by measuring changes in hair-bundle stiffness following the application of force stimuli. Following step stimulation with a glass fiber, the hair bundle of a saccular hair cell initially had a stiffness of approximately equal to 1 mN X m-1. The stiffness then declined to a steady-state level near 0.6 mN X m-1 with a time course comparable to that of adaptation in the receptor current. The hair bundle may be modeled as the parallel combination of a spring, which represents the rotational stiffness of the stereocilia, and a series spring and dashpot, which respectively, represent the elastic element responsible for channel gating and the apparatus for adaptation.
mesh_terms: D000064:Acclimatization; D000818:Animals; D004553:Electric Conductivity; D004558:Electric Stimulation; D006198:Hair Cells, Auditory / Q000502:physiology*; D008564:Membrane Potentials; D008839:Microelectrodes; D010812:Physical Stimulation; D011892:Rana catesbeiana; D012444:Saccule and Utricle / Q000502:physiology*