| Objective:To investigate the regularity and correlation between the changes of auditory function and glucose metabolism in cochlear nucleus,and the role of positron emission tomography/computed tomography（PET/CT）in the early warning of auditory function degradation and cochlear nucleus aging in guinea pigs.Methods:1.Animal groups.48 3-month-old guinea pigs were randomly divided into control and D-galactose model groups,and 8 18-month-old guinea pigs were used as elderly group.D-galactose(300mg·kg-1·d-1)were injected subcutaneously once a day in guinea pigs of D-galactose model group.Moreover,the model group was divided into 1,2,3,4,5 and 6weeks groups according to different time points of drug injection.Guinea pigs were fed naturally without any treatment in the control and elderly groups.2.Detection of ABR in guinea pig.Auditory brainstem response（ABR）examination was performed before and after drug injection.Guinea pigs were anesthetized intraperitoneally with 10%chloral hydrate（350 mg/kg）,and ABR was detected.When the intensity of sound stimulation was 131d B SPL,the latency of ABR waveⅢwas observed in each group.3.Micro PET/CT examination of guinea pig.After anesthetized,guinea pigs were injected intraperitoneally with 1.5mic/kg18F-fluorodeoxyglucose（18F-FDG）.50 minutes after injection of imaging agent,PET/CT scanning was performed to observe the imaging agent uptake of guinea pigs in each group.The interest areas of bilateral cochlear nucleus and cerebellar were delineated on the same plane,and the maximum standard uptake value（SUVmax）of 18F-FDG was measured automatically by computer.The results were analyzed by the average ratio of the maximum standard uptake between the cochlear nucleus and cerebellum.4.Correlation analysis was performed between auditory function and glucose metabolism in cochlear nucleus.5.Statistical methods.The data obtained from this experiment were statistically analyzed by SPSS26.0 software.All values are expressed as mean±standard deviation.One-way ANOVA was used as the statistical method to analyze the experimental data.When variance was homogeneous,LSD method was used for inter group comparison.On the contrary,the differences between groups were analyzed by Tamhane’s T2 test.Pearson correlation analysis was used for correlation analysis.Results:1.Appearance and activity.Dull fur,and severe depilation appeared in the model and elderly groups.Moreover,there were mental malaise,poor diet,autonomous activities,slow movement and loose skin in model group at the 4th week.However,there were no changes in appearance and activity in the control group.2.Changes of weight.The average of weight was 274.31±30.20,291.69±44.93,271.06±25.13,270.00±35.75,305.13±28.86,286.13±28.13 and 301.06±13.61 respectively in the control and model groups,and there were no significant differences in the weight between the control and model groups before the experiment（P>0.05）.Moreover,the average of weight was 436.88±63.21,351.88±53.88,385.06±55.62,381.75±59.79,428.50±64.57,452.81±44.43 and 464.88±37.02respectively in the 6th week of the control and model groups,and there were no significant differences in the weight between the control and model groups after the experiment（P>0.05）.3.The latency of ABR III wave.The average latency of ABR III wave was 2.45±0.08,2.53±0.05,2.58±0.09,2.59±0.06,2.64±0.05,2.69±0.04 and 2.81±0.08 respectively in the control group,and 1,2,3,4,5 and 6 weeks group.The latency of ABR III wave was 2.78±0.07 in the elderly group.There were significant differences in the average latencies of ABR III waves among the control group,the model group and the elderly group（F=27.120,P<0.001）.Compared with the control group,the average latency of III wave increased in 1,2,3,4,5 and 6weeks group,and the difference is statistically significant（P<0.05）.Moreover,compared with the control group,there were statistical increase in the average latency of III wave in the elderly group（F=78.867,P<0.001）.Additionally,the average latency of III wave reduced in 1,2,3,4 and 5 weeks in comparison with the elderly group（P<0.05）.However,There was no significant difference in the latency of III wave between the 6 week and the elderly group（P>0.05）.4.The change in glucose metabolism of cochlear nucleus in each group.The average ratio of SUVmax between cochlear nucleus and cerebellum was 0.88±0.05,0.87±0.03,0.86±0.04,0.84±0.09,0.82±0.07,0.76±0.06 and 0.69±0.05respectively in the control group,and 1,2,3,4,5 and 6 weeks group.The average ratio of SUVmax between cochlear nucleus and cerebellum was0.68±0.03 in the elderly group.There were significant differences in the average ratio of SUVmax between cochlear nucleus and cerebellum among control group,model group and elderly group（F=12.294,P<0.001）.Compared with the control group,the average ratio of SUVmax between cochlear nucleus and cerebellum increased in model group.However,the average ratio of SUVmax between cochlear nucleus and cerebellum in 5 and6 weeks group was significantly lower than that in control group（P<0.05）.Moreover,the average ratio of SUVmax between cochlear nucleus and cerebellum reduced in the elderly group in comparison with the control group（F=68.266,P<0.001）.Furthermore,compared with the elderly group,the average ratio of SUVmax between cochlear nucleus and cerebellum increased in 1,2,3,4 and 5 weeks group（P<0.05）,and there was no significant difference in the 6 week group（P>0.05）.5.The correlation between auditory function and glucose metabolism.There was a negative correlation between the auditory function and glucose metabolism in cochlear nucleus between cerebellum（r=-0.733,P<0.001）.Conclusion:1.The hearing function and glucose metabolism of cochlear nucleus decreased gradually in guinea pigs during the occurrence and development of age-related hearing loss.2.There were significant correlations in the time sequence between hearing loss and glucose metabolism in cochlear nucleus of guinea pigs with age-related hearing loss.3.PET/CT may be a means in the early warning of auditory function degradation and cochlear nucleus aging in guinea pigs. |
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