An infracuticular network is not required for outer hair cell shortening.

The presence and distribution of filamentous actin was documented in normal and shortened isolated outer hair cells by use of fluorescently labeled phalloidin. In hair cells isolated from the guinea pig cochlea, an infracuticular network containing organized bundles of actin filaments is present in some, but not all, control cells and in some, but not all, cells after shortening. An infracuticular network of organized bundles of actin filaments is not present in control outer hair cells isolated from chinchilla or gerbil cochleas and it is never observed in any outer hair cells from these species even after shortening. Thus shortening of isolated outer hair cells is not correlated with the presence or the formation of organized bundles of actin filaments in an infracuticular network.