Effects And Mechanisms Of Electroacupuncture At Tinggong And Yifeng On Aging Of Auditory Center In Guinea Pig Following D-galactose-induced Age-related Hearing Loss

Objective: To investigate the role of NR2A, GAD, BDNF,GAP-43in the pathogenesis of age-related hearing loss (AHL), and theeffects and mechanisms of electroacupuncture on aging of auditory centerin guinea pigs. Methods:1.There was4groups.30adult guinea pigswere randomly divided into3groups, including the control group (CG,n=10), D-galactose group (DG, n=10), and D-galactose andelectroacupuncture group (DEG, n=10).18months old guinea pigs wereused as the elderly group (EG, n=10). Guinea pigs of the DG were givensubcutaneous injection of D-galactose at300㎎/㎏per day for six weeks,the CG were treated with equal physiological saline. Given the sametreatment as the DG, guinea pigs of the DEG were electroacupunctured atTinggong and Yifeng acupoint for six weeks at the same time. The EGrejected any treatments.2. After ABR were tested, brain-derivedneurotrophic factor (BDNF), and growth and plasticity-associated protein(GAP-43) protein expression using Western-blotting, N-methyl-D-aspartate receptor2A (NR2A) and Glutamic acid decarboxylase (GAD)mRNA using quantitative real time PCR were detected. The changes inultrastructures of neurons and synapses of the dorsal cochlear nucleus (DCN) were observed by transmission electron microscope. Results:1.The average latent period of the third wave was2.66±0.19、2.88±0.25、2.74±0.14、2.84±0.15in the CG、DG、DEG and the EG. There were asignificant prolongation in latent period of the third wave of ABR in theDG and the EG (P＜0.05, compared with the CG), a curtailment in DEG(P＜0.05, compared with the DG), and no statistical differences betweenthe DMG and EG (P＞0.05).2. The fold change in NR2A mRNA was1.18±0.25、1.52±0.53、1.29±0.54respectively in the DG, DEG and EG.There were no significant differences in all groups (F=1.456, P=0.264).Moreover, the fold change in GAD mRNA was1.07±0.19、1.45±0.38、1.08±0.21respectively in the DG, DEG, and EG, and there was asignificant increase in the DEG (P＜0.05, compared with the DG).3.There was a significant upregulation of BDNF and GAP-43proteinexpression in the DEG (P＜0.05,compared with the DG). In addition,there was a significant downregulation of BDNF and GAP-43proteinexpression in the DG in comparion with the CG (P＜0.05). And then,there was no significant difference of GAP-43protein expressionbetween the DMG and EG (P＞0.05), but BDNF protein expression inthe DG was lower than that of the EG (P＜0.05).4. The averagethickness of the postsynaptic density (PSD) was58.89±9.82、33.77±10.79、44.99±15.27and31.95±4.32nm in the CG, DG, DEG andEG. In comparison with the CG, there was a significant decrease in the thickness of the PSD in the DG and EG (P＜0.001). Next, there was alsoa significant increase in the thickness of the PSD in the DEG (P＜0.05,compared with DG). Finally, there was no statistical difference betweenthe DG and EG (P＞0.05). Conclusions:1. It is an effective way toinduce aging of auditory cortex and DCN by subcutaneous injection ofD-galactose at300㎎/㎏per day for six weeks.2. The decrease ofplasticity caused by the decrease of BDNF and GAP-43proteinexpression may join in the aging of auditory cortex in guinea pigs.3.Acupuncturing at Tinggong and Yifeng acupoint can result in the increaseof BDNF and GAP-43expression, and partly delay the aging processinduced by D-galactose in the auditory cortex of guinea pig.4. The agingof the DCN may be related with the decrease of GAD expression. Theincrease of GAD expression induced by acupuncturing at Tinggong andYifeng acupoint may enhance the inhibitory action of GABA, and therebydelay the aging process of DCN.5. Acupuncturing at Tinggong andYifeng acupoint can regulate the neuronal and synaptic plasticity,effectively resist the aging of DCN and delay the development of AHLinduced by D-galactose.