11.7 T MR Imaging Revealed Dilatation of Virchow-Robin Spaces within Hippocampus in Maternally Lipopolysaccharide-exposed Rats

Increased hippocampal fissure width is a sensitive indicator of rat hippocampal atrophy

OBJECTIVES

Volume loss within the hippocampus is known as the most replicated finding of structural brain imaging studies of neuropsychiatric diseases. Although voxel-based auto or semi-auto volumetric measurements are widely used in the determination of the human hippocampus, the detection of hippocampal atrophy in rats is still a dilemma as it relies on a relatively primitive and complex approach. In this study, we aimed to develop a convenient way to measure the atrophy of the hippocampus in rats.

METHODS

Twenty-four male Wistar rats were exposed to chronic unpredictable mild stress (CUMS) and a wheel running test (WRT) to simulate the conditions of hippocampal volume atrophy and improvement. The hippocampal volume and hippocampal fissure (HiF) width were dynamically measured using 7 T structural magnetic resonance imaging (MRI) with the grayscale method at week 0, 2, 4, and 8. The changes in the hippocampal volume and HiF width in rats were compared. In addition, hematoxylin-eosin (HE) staining of the HiF was used to verify the MRI findings.

RESULTS

The hippocampal volume and the HiF width presented opposite trends based on the MRI findings and the histology data. The atrophy of the hippocampal subfields was closely related to the corresponding increase in the HiF width.

CONCLUSION

Determination of the HiF width may serve as a sensitive and convenient indicator of rat hippocampal atrophy.

Dilated Virchow-Robin spaces in the hippocampus impact behaviors and effects of anti-depressant treatment in model of depressed rats

The occurrences of dilated Virchow-Robin spaces (dVRSs) and inflammatory factors were closely related with development of depression and antidepressants. The present study indicated accumulation of inflammatory factors in dVRSs played a practical role in behaviors and the treatment-resistant in rats with depression. Eighty-one male Wistar rats were exposed to chronic unpredictable mild stress (CUMS) until the model was successfully established. According to the detection of dVRSs on 7 T structural magnetic resonance imaging (MRI), rats were divided into two groups (45 CUMS^non-dVRSs rats and 36 CUMS^dVRSs rats). Subsequently, different antidepressant treatment (nontreat, aspirin, fluoxetine, fluoxetine+aspirin) was given to the two groups, respectively. Sucrose preference test (SPT), forced swim test (FST) and morris water maze (MWM) was used to test the behaviors of rats. ELISA and Western blot was used to determine the levels of inflammatory factors. Compared with the negative control (NC) group, there were obvious behavioral abnormalities and increased inflammatory factors in the CUMS^non-dVRSs rats. Interestingly, these changes were more significant in the CUMS^dVRSs rats. In addition, the efficacy of fluoxetine was only found in CUMS^non-dVRSs rats rather than CUMS^dVRSs rats. Meanwhile, behaviors and levels of inflammatory factor in hippocampus were ameliorated in the aspirin group of CUMS^dVRSs rats, and these effects were significantly enhanced in the fluoxetine+aspirin group. The dVRSs in the hippocampus might exacerbate depression-like behaviors and the effects of antidepressant treatment in depressed rats by increasing the levels of inflammatory factors.