HRR 009X5 Differences in the distribution of F-actin in outer hair cells along the organ

There is evidence of differences in the structure. innervation and phystological responses between outer hair cells (OHCs) of the basal and apical turns of the mammalian cochlea. In this study we have used rhodamine-labelled phalloidtn to investigate the differential distribution of F-actin in OHCs along the organ of Corti of the guinea pig. Isolated OHCs and surface preparations and cryosectmns of the organ of Corti were studied. F-actin was ohserved in stereocilia and the cuticular plate of all OHCa. In addition. some OHCs had a network of F-actin extending from the cuticular plate towards the nucleus. This infracuticular network was observed in most OHCs of the apical cochlear turns but was not seen in any OHCs of the basal turn. These microstructural differences between OHCs of the base and apex could be related to differences in OHC function between the apical and basal portions of the cochlea. Rhodamine-lahelled phalloidin; F-actin; Organ of Corti: Hair cell. outer introduction There is an increasing body of literature dem-onstrating that the outer hair cells (OHCs) of the mammalian cochlea do not comprise a homoge-neous cell population, but that substantial dif-ferences exist in the structure and physiological responses of these cells from the base to apex of the organ of Corti. Structural differences that have been noted in OHCs along the organ of Corti include the length of the cell body (Smith, 1968). and the number, length (Strelioff and Flock, 1984: Wright, 1984) and stiffness of stereocilia (Strelioff and Flock. 1984). OHCs in the base also have a substantial efferent innervation and this di-minishes apically where OHCs receive more affer-ent nerve fibres (Spoendlin. 1979). There are also temporal differences in the development of th