MODULATION OF OUTER HAIR CELL COMPLIANCE AND FORCE BY AGENTS THAT AFFECT HEARING

Force generated by outer hair cells is thought to be an essential sour ce of mechanical input to the normal cochlea. Many disease processes i n the inner ear act via outer hair cells. It is therefore plausible th at such disease processes modulate outer hair cell force generation. T he force generated by an isolated, electrically stimulated outer hair cell against a load may be represented by an intrinsic motor and a pas sive axial stiffness in series. Thus modulation of outer hair cell for ce generation may occur either by action on the motor or indirectly by an action on cell stiffness. In this study, the effects of agents tha t affect hearing on outer hair cell stiffness and force generation hav e been examined. Overstimulation and hypoosmotic challenge caused cell s to decrease in length and increase In stiffness. The force generated by a constant voltage stimulus increased consequent to the stiffness increase. Hyperosmotic challenge elicited a stiffness decrease and a f orce decrease. In contrast, salicylate caused a decrease in force with out stiffness change. The results suggest that outer hair cell force g eneration in vivo may be modulated in at least two ways. (C) 1997 Else vier Science B.V.