Evidence for potassium-induced motility in type I vestibular hair cells in the guinea pig.

In higher vertebrates, vestibular epithelia contain two types of hair cells, type I and type II cells. Physiological properties of single nerve units have been correlated to the corresponding hair cell type and a better knowledge of the hair cell static and dynamic properties should help in understanding transduction and coding in the vestibular system. For the auditory system, isolated outer cochlear hair cells (OHCs) have provided a useful approach for electrophysiological studies and for observations of motile processes involved in the active control of cochlear micromechanics. The present study tests the hypothesis of motile properties in guinea-pig vestibular hair cells, using stimuli known to elicit motile events in OHCs. After exposure to a medium containing a high concentration in potassium (125 mM or 80 mM KCl), 19 of 26 type I hair cells showed an irreversible tilt of the neck region often accompanied by an obvious swelling of the cell body. In contrast, no shape changes were detected in type II cells. In response to extracellular electrical stimulation, no motility was observed in either type I or type II cells.