[Correlation between age-related hearing loss and impairment of cognition in C57BL/6J mice].

OBJECTIVE

To explore the correlation of age-related hearing loss and cognition impairment in C57BL/6J mice by observing hearing, cognitive function and synapses.

METHODS

C57BL/6J and CBA/CaJ mice were divided into 3 groups. The hearing and cognitive functions of each animal was tested. And the ultrastructure of synapses was simultaneously observed for C57BL/6J mice.

RESULTS

The 24-26-week-old C57BL/6J mice developed moderate hearing loss while the 42-44-week-old C57BL/6J counterparts suffered profound hearing loss. Whereas excellent hearing was maintained in 3 groups of CBA/CaJ mice within 44 weeks. During cognitive test, the performance of 42-44-week-old C57BL/6J mice was significantly worse than CBA/CaJ mice. During probe test, the number of platform crossing of 42-44-week-old C57BL/6J mice was smaller than that of CBA/CaJ mice (0.5 ± 0.6 vs 1.9 ± 1.6; P < 0.05). The 42-44-week-old C57BL/6J mice had a wider synaptic cleft and a thinner postsynaptic density than the 24-26-week-old C57BL/6J counterparts [synaptic cleft: (19.4 ± 0.5) nm vs (11.9 ± 0.7) nm; postsynaptic density: (15.2 ± 0.5) nm vs (27.8 ± 2.0) nm; both P < 0.05]. Furthermore, the degeneration of synapses in hippocampus CA3 area of C57BL/6J mice were clearly observed at 42 - 44 weeks of age, but not seen in CBA/CaJ mice.

CONCLUSION

Age-related hearing loss might impact on the cognition impairment in C57BL/6J mice.