Loss of Does Not Affect Hearing and Balance.

Although estrogen affects the structure and function of the nervous system and brain and has a number of effects on cognition, its roles in the auditory and vestibular systems remain unclear. The actions of estrogen are mediated predominately through two classical nuclear estrogen receptors, estrogen receptor 1 (ESR1) and estrogen receptor 2 (ESR2). In the current study, we investigated the roles of ESR1 in normal auditory function and balance performance using 3-month-old wild-type (WT) and knockout (KO) mice on a CBA/CaJ background, a normal-hearing strain. As expected, body weight of KO females was lower than that of KO males. Body weight of KO females was higher than that of WT females, while there was no difference in body weight between WT and KO males. Similarly, head diameter was higher in KO vs. WT females. Contrary to our expectations, there were no differences in auditory brainstem response (ABR) thresholds, ABR waves I-V amplitudes and ABR waves I-V latencies at 8, 16, 32, and 48 kHz, distortion product otoacoustic emission (DPOAE) thresholds and amplitudes at 8, 16, and 32 kHz, and rotarod balance performance (latency to fall) between WT and KO mice. Furthermore, there were no sex differences in ABRs, DPOAEs, and rotarod balance performance in KO mice. Taken together, our findings show that deficiency does not affect auditory function or balance performance in normal hearing mice, and suggest that loss of is likely compensated by ESR2 or other estrogen receptors to maintain the structure and function of the auditory and vestibular systems under normal physiological conditions.