Hair cell regeneration in senescent quail

Hair cell regeneration was studied following exposure to an intense pure tone stimulus in young adult and senescent Coturnix quail. Three, 3-month old and four, 3-year old quail were continuously exposed to a 1500 Hz pure tone at 115 dB SPL for 12 h. Four quail were not noise exposed and were used as age-matched controls. Control and experimental birds received injections of [3H]thymidine daily for 10 days after noise exposure. Ten days after noise exposure birds were killed and their cochleae embedded, sectioned serially and processed through standard methods of autoradiography. Hair cell counts showed a discreet area of hair cell loss for both age groups in the proximal half of the papilla. Incorporation of [3H]thymidine was clearly seen over the nuclei of hair cells and support cells in the region of hair cell loss in both age groups. Incorporation of [3H]thymidine was also seen over the nuclei of hair cells and support cells in a very small area in two of the non-exposed control birds. These results demonstrate that the potential for hair cell regeneration is maintained throughout life in Coturnix quail. Further, they suggest that there may be some very low level of hair cell production in the normal adult quail ear which is activated in the absence of massive trauma.