| Aging is an inevitable biological process. As the coming of global population aging, aging has become a central question that the scientists have to face. How to improve brain plasticity and delay the aging process? With imaging techniques, such as MRI and PET, some researches have shown that running exercise increases brain volume (mainly in the brain's frontal and temporal lobes), induces brain angiogenesis and improves regional cerebral blood flow. Quite a number of studies have demonstrated that long-term scientific and regular running exercise can stimulate neurogenesis, increase resistance to brain insult, improve brain fitness and plasticity and reduce the elderly cognitive decline. Some studies have also indicated that running exercise increases levels of BDNF and other growth factors, enhances synaptic activity, elicits compensatory angiogenesis and increases the density of blood vessels. It can be seen from these studies that exercise is a simple strategy to delay the progress of brain function decline with aging. Previous imaging studies confirmed that running training can increase cerebral blood flow. However, there have been no reports on the changes of total volume and total length of the cerebral capillaries accompanied by increasing cerebral blood flow after running interference. Stereological methods are a series of accurate methods to obtain quantitative information of three-dimensional microstructure, based on the observations of two-dimensional images. Therefore, we used the unbiased stereological methods, three-dimensional quantitative techniques, to quantitatively investigate the capillaries in the white matter. In order to explore whether running exercise intervention induced capillaries changes of the white matter, middle-aged Sprague-Dawley rats were used. After 4 months running exercise, the white matter volume, the total length, the total volume and the total surface area of the capillaries in the white matter were investigated with immunohistochemistry and stereological techniques. The results will help us further understand the mechanism for the fact that exercise delays the progress of brain aging.1. Materials and methods1.1 Twenty Sprague-Dawley rats (14-month-old) were used. Body weight is 280±20 g. Rats were randomly divided into exercise group (5 females and 5 males) and control group (5 females and 5 males).1.2 Rats in the exercise group were made to run on treadmills for 20 min once daily for 5 consecutive days in a week. Running exercise started at nine o'clock in the morning. The exercise load consisted of running at a speed of 10 m/min in the first week, at 15 m/min in the second week, and at 20 m/min from the third week to the end of the fourth month. Rats in the control group were not subject to any exercises.1.3 After 4 months running exercise, the rats were anaesthetized and perfusion-fixed. One hemisphere was sampled from each rat brain and then cut into 2-mm-thick consecutive slabs. A 4-μm isotropic, uniform random section was cut from each slab. The sections were stained with immunohistochemistry technique. Under an oil objective lens (100×), 4~6 fields of vision were captured from the entire region of the white matter on each section. On average, 30 photographs were obtained per rat white matter.1.4 The white matter volume, the length density and the total length, the volume density and total volume, the surface area density and the total surface area of the capillaries in the white matter were estimated with the new stereological methods.2. Results2.1 The volume of the white matter in female control group was 84.8±10.2 mm3. The volume of the white matter in male control group was 98.3±10.1 mm3. The difference between female control group and male control group was non-significant (p>0.05).2.2 The total length, the total volume and the total surface area of the capillaries in the white matter in female control group were 15.9±2.70 m, 0.49±0.06 mm3, 2.84±0.48 cm2, respectively. The total length, the total volume and the total surface area of the capillaries in the white matter in male control group were 19.9±4.10 m, 0.57±0.15 mm3, 3.46±0.82 cm2, respectively. The stereological data of the capillaries in the white matter were both no significant difference between male control group and female control group (p>0.05).2.3 After running exercise, the volume of the white matter in female exercise group was 112±14.9 mm3. The total length, the total volume and the total surface area of the capillaries in the white matter in female exercise group were 20.6±3.40 m, 0.57±0.12 mm3, 3.54±0.53 cm2, respectively. The volume of the white matter and the total length of the capillaries in the white matter in female exercise group were significantly higher than those of female control group (p<0.01 and p<0.05, respectively).2.4 After running exercise, the volume of the white matter in male exercise group was 98.6±13.5 mm3. The total length, the total volume and the total surface area of the capillaries in the white matter in male exercise group were 26.1±4.20 m, 0.60±0.10 mm3, 4.11±0.76 cm2, respectively. The length density and the total length of the capillaries in the white matter in female exercise group were significantly higher than those of female control group (p<0.05).General Conclusions1. The present study for the first time found that the total volume of the white matter in middle-aged female Sprague-Dawley rats was significantly increased after short-term running.2. The present study for the first time found that the total length of the capillaries in the white matter of middle-aged female and male Sprague-Dawley rats was significantly increased after short-term running.3. Short-term running exercise have positive effects on the white matter volume of middle-aged female rats and the total length of the capillaries in the white matter of middle-aged female and male rats. These results provided important scientific bases for seeking drugs and behavioral strategies to prevent or delay the progress of brain function decline with aging. |
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