Acupuncture has long been used to relieve some inner ear diseases such as deafness and tinnitus. The present study examined the effect of electroacupuncture on noise-induced hearing loss (NIHL) in animals. A NIHL rat model was established. Electroacupuncture pretreatment at 2 Hz or posttreatment at the right Zhongzhu (TE3) acupoint was applied for 1 hour. Auditory thresholds were measured using auditory brainstem responses (ABRs), and histopathology of the cochlea was examined.
The results indicated that the baseline auditory threshold of ABR was not significantly different between the control (no noise), electroacupuncture-only (only electroacupuncture without noise), noise (noise exposure only), pre-electroacupuncture (pretreating electroacupuncture then noise), and post-electroacupuncture (noise exposure then posttreating with electroacupuncture) groups. Significant auditory threshold shifts were found in the noise, pre-electroacupuncture, and post-electroacupuncture groups in the immediate period after noise exposure, whereas auditory recovery was better in the pre-electroacupuncture and post-electroacupuncture groups than that in the noise group at the three days, one week (W1), two weeks (W2), three weeks (W3), and four weeks(W4) after noise stimulation.
Histopathological examination revealed greater loss of the density of spiral ganglion neurons in the noise group than in the control group at W1 and W2. Although significant loss of spiral ganglion loss happened in pre-electroacupuncture and post-electroacupuncture groups, such loss was less than the loss of the noise group, especially W1.
These results indicate that either pretreatment or posttreatment with electroacupuncture may facilitate auditory recovery after NIHL. The detailed mechanism through which electroacupuncture alleviates NIHL requires further study.