Stereological Study Of The White Matter And The Myelinated Fibers In The White Matter Of CUS Resilient Rat

Objective: To investigate the changes of the white matter and the myelinated fibers in the white matter of stress resilient rats after chronic unpredictable stress(CUS)in order to further explore whether resilience to stress is related to the white matter change.Methods: Fifty male Sprague-Dawley(SD)rats(4-to 5-week-old)were randomly divided into the control group and the CUS group.A depression rat model was built using separation and four-week CUS.After four-week CUS procedure,the stress susceptible group and the stress resilient group were distinguished using the sucrose preference test(SPT).Meanwhile,the behaviors of each group were investigated using the open field test(OFT).The white matter volume,the total length of the myelinated fibers,the total volume of the myelinated fibers and the total volume of the myelin sheaths in the white matter were estimated using the stereological methods.Results: The sucrose preference of the stress susceptible group was significantly lower than the control group and the stress resilient group(p < 0.05).The total score of the OFT in the resilient group was significantly higher than the control group and the stress susceptible group(p < 0.05).The white matter volume,the total volumes of the myelinated fibers,the myelinated fiber axons and the myelin sheaths in the white matter,and the total length of the myelinated fibers in the white matter of stress susceptible group were significantly decreased when compared to the control group and the resilient group(p < 0.05).The white matter volume,the total volumes of the myelinated fibers and the myelinated fiber axons in the white matter were not significantly different between the control group and resilient group(p > 0.05),while the myelin sheath volume,and the total length of the myelinated fibers in the white matter of the resilient group were significantly higher than those in the control group(p < 0.05).Conclusions: The present results suggested that the changes in the white matter and the myelinated fibers in the white matter might be associated with susceptibility differences of depression.Myelinated nerve fibers in white matter might be one of the structural targets for the development of the new anti-depression treatment.