[Effects of conditioning noise exposure on the expression of F-actin].

Objective: To obtain more information on the distribution of F-actin in the guinea pig cochlea, to observe the effects of conditioning noise exposure on the expression of F-actin and to study this "toughening" phenomenon mechanisms.

Method: An octave band noise centered at 1 kHz at 95 dB SPL for 8 hours a day was used as conditioning noise. Animals were killed at different time points after different conditioning noise exposure. The organs of Corti were labelled by FITC-phalloidin and examined using laser scanning confocal microscopy following cochlear preparation.

Result: High intensity labeling of F-actin was seen in both inner and outer hair cells, specifically in stereocilia, cuticular plates. In the circumferential rings around the apical periphery of each cell, the head plates of the pillar cells, the lowest portion of OHC bodies, which represented the Deiters cup and in the phalangeal processes of Deiters cell, the strong labelling of F-actin was also seen. F-actin was found in the out pillar cells' body. F-actin labelling of OHCs in differently conditioning exposed animals was different.

Conclusion: (1) Conditioning exposure can change the expression of F-actin in guinea pig cochlea. (2) In the organ of Corti of guinea pig, F-actin distributes not only in the portions previously reported, but also in the out pillar cell' s body. (3) A reduced expression of F-actin in out hair cell after conditioning exposure may be connected to the "toughening" phenomenon.