Actin, myosin and alpha-actinin containing filament bundles in hyaline cells of the caiman cochlea

Hyaline cells of the auditory organ of the spectacled caiman contain smooth muscle-like filament bundles within their basal cell pole. These bundles were heavily labeled with antibodies to actin, myosin and alpha-actinin (muscular Z-line protein). Since hyaline cells are firmly attached to the basilar membrane these cells may actively modify the stiffness of the basilar membrane. A contractile mechanism in hyaline cells might affect frequency tuning of primary auditory afferents. This frequency tuning has been shown to be a temperature-dependent process in caimans and other submammalian species. The presence of synaptic contacts between efferent nerve fibres and hyaline cells suggests neural control of hyaline cell activity.