VOLTAGE-DEPENDENT REVERSIBLE MOVEMENTS OF THE APEX IN ISOLATED GUINEA-PIG VESTIBULAR HAIR-CELLS

Type I vestibular hair cells isolated from guinea pig were placed in t he whole cell clamp configuration, and electrically stimulated by depo larizing voltage pulses. The voltage dependent reversible movements of the cell apex affected the length of the cell neck, the position of t he cuticular plate, and the tilting and bending of the stereocilia. Th e cell neck shortened when the membrane was depolarized by 10 mV while cuticular plate and the stereocilia tilting did not begin until 20 mV . The shortening was 0.5 to 1 mum, and the cuticular plate tilting was up to 15-degrees for depolarization amplitudes of 20-40 mV. These mov ements were reversed within a few seconds. More complex, larger moveme nts were induced by stronger depolarizations. The cuticular plate tilt ing and the hair bundle bending were always in the opposite direction to the kinocilium position. The small reversible movements of the mamm alian type I vestibular hair cells are discussed in terms of mechanica l adaptation processes and morphological features. It is suggested tha t such active movements of the vestibular hair cells occur in vivo.