Outer hair cells in vitro contract in response to various stimuli: electrical stimulation, K+-depolarization, elevation of intracellular calcium or osmotic changes of the extracellular medium. The characteristics of motile responses induced by K+-depolarization, osmotic changes, and calcium injection were compared in this study in order to delineate the underlying mechanisms. Slow shape changes...

Using histochemical technique, changes of nucleic acid activity in the cochlea resulting from white noise exposure were investigated. Forty-eight guinea pigs were used for this experiment. The results obtained were as follows: 1. The first sign of pathological changes in the organ of Corti due to exposure to white noise occurred in the outer hair cells. Temporary high metabolic rates of DNA wer...

Live outer hair cells were isolated from guinea pig, chinchilla, rat, mouse, and gerbil. The organ of Corti from selected turns of the cochlea was briefly incubated with collagenase and outer hair cells were separated from the tissue by micromanipulation under microscopic observation. Morphological criteria for cell viability were: cylindrical cell shape without swelling or distortion of the me...

The cochlea contains two types of sensory cells, the inner and outer hair cells. Sound-evoked deflection of outer hair cell stereocilia leads to fast force production that will enhance auditory sensitivity up to 1,000-fold. In contrast, inner hair cells are thought to have a purely receptive function. Deflection of their stereocilia produces receptor potentials, transmitter release, and action ...

Normal hearing depends on sound amplification within the mammalian cochlea. The amplification, without which the auditory system is effectively deaf, can be traced to the correct functioning of a group of motile sensory hair cells, the outer hair cells of the cochlea. Acting like motor cells, outer hair cells produce forces that are driven by graded changes in membrane potential. The forces dep...

The adult mammalian cochlea receives dual afferent innervation: the inner sensory hair cells are innervated exclusively by type I spiral ganglion neurons (SGN), whereas the sensory outer hair cells are innervated by type II SGN. We have characterized the spatiotemporal reorganization of the dual afferent innervation pattern as it is established in the developing mouse cochlea. This reorganizati...

Essential functions of neurotrophin 3 (NT-3) in regulating afferent and efferent innervation of the cochlea have been characterized by comparison of normal and NT-3 mutant mice. NT-3 deficiency has striking, region-specific effects, with complete loss of sensory neurons in the basal turn and dramatic but incomplete neuronal loss in the middle and apical turns. The sensory innervation of inner a...

Gap junctional intercellular communication (GJIC) plays a major role in cochlear function. Recent evidence suggests that connexin 26 (Cx26) and Cx30 are the major constituent proteins of cochlear gap junction channels, possibly in a unique heteromeric configuration. We investigated the functional and structural properties of native cochlear gap junctions in rats, from birth to the onset of hear...

The extra-cellular cochlear microphonic is believed to be generated predominantly by outer hair cells and therefore it would seem reasonable to assume that the presence of a cochlear microphonic excludes outer hair cell dysfunction. Indeed, a diagnosis of auditory neuropathy might be, and has been, made on the basis of a cochlear microphonic present with an abnormal auditory brainstem response....