| Objective To investigate the effects of14-months treadmill running on theage-related changes of white matter and on the age-related changes of themyelinated nerve fibers and oligodendrocytes in SD rat white matter inorder to understand the morphological bases and mechanisms of theprotective effects of long-term treadmill running on aged brain.Methods Fourteen months (ten male and ten female) rats randomly selectedfrom each group were tested with morris water maze before treadmillrunning, after4months running and after14months running, respectively.Five male and five female rats were randomly selected from each group(running group,28months control group and18months control group).One hemisphere was randomly sampled from each rat, six white matterblocks (1.5mm×1.5mm×1.0mm) were randomly sampled for the sampled hemispheres. Ultrathin sections (60nm) were cut for transmissionelectron microscopy under electron microscope and with the magnificationof6000,6～8photographs were obtained from each white matter block.The other hemispheres were used for oligodendrocyte study. The totalvolume of white matter, total length of the myelinated nerve fibers, totalvolume of the myelinated nerve fibers, proportion of degenerative myelinsheath and number of oligodendrocyte were obtained with the stereologicalmethods.Results1. Compared to escaped latency of both male and female SD ratsbefore exercise, the escaped latency of both male and female SD rats weresignificantly improved after4month treadmill running (p<0.05). There wasno significant difference of the escaped latency of both male and femalerats between28months running group and before running group (14months old)(p＞0.05). There was no significant difference of escapedlatency between28months running group and28months control group (p>0.05).2. The proportions of degenerative nerve fibers in female SD ratbrain among28months running group, control group (18months) andcontrol group (28months old) were21.2±11.04%,35.8±9.78%and49.2±2.56%, respectively. The proportions of nerve fibers with age-relatedchanges in male rat brain among running group, control group (18months)and control group (28months old) were24.9±9.62%,50.80±3.64%and44.1±10.30%, respectively. Age-related changes of myelin sheath in both male and female running group were significantly reduced after14monthtraining (p<0.05).3. Compared to the control group (28months), the totalwhite matter volumes of male and female rats in28months running groupwere significantly larger by56.5%and43.3%, respectively (p<0.01).Compared to the control group (18months), the total white matter volumeof female rats in28months running group were significantly larger(p<0.01). There was no significant difference in the total white mattervolume of male rats between28months running group and control group(18months)(p>0.05).4. Compared to the control group (28months), thetotal length of the myelinated nerve fibers in male and female rats inrunning group were significantly longer by45.48%and34.83%,respectively (p<0.01). Compared to the control group (18months), the totallength of the myelinated fibers in the white matter of female rats in runninggroup were significantly larger48.20%(p<0.01). There was no significantdifference in the total length of the myelinated fibers in the white matter ofmale rats between28months running group and control group (18months)(p>0.05).5. Compared to the control group (28months), the total volumeof the myelinated fibers in the white matter of male and female rats inrunning group were significantly longer by55.98%and46.84%,respectively (p<0.01). Compared to the control group (18months), the totalvolume of female rats in running group were significantly larger by44.07%(p<0.01). There was no significant difference of the total volume of the myelinated fibers in the white matter of male rats between running groupand control group (18months)(p>0.05).6. The number of CNPase+oligodendrocytes in the white matter of male and female rats in runninggroups were (12.48±0.63)×106and (12.59±1.96)×106, respectively.The number of CNPase+oligodendrocytes in the white matter of male andfemale rats in control groups (28months) were (5.05±1.31)×106and(6.48±0.84)×106, respectively. The number of oligodendrocytes inrunning groups were significantly higher than that in the control group (28months)(p<0.01). There was no significant difference of theoligodendrocytes number in the white matter of male rats between runninggroup and control group (18months)(p>0.05).Conclusions1. Long-term treadmill running had protective effects on thespatial learning and memory ability of aged rats.2. Long-term treadmillrunning can effectively reduce the proportion of degenerative myelinsheath and significantly delay the age-related changes the white mattervolume, the total length of the myelinated fiber, the total volume of themyelinated fibers and the number of oligodendrocytes in the white matter.In male rats the related parameters of the white matter in28monthsrunning group were in the same level as those in18months control group.In female rats the related parameters of the white matter of28monthsrunning group were significantly higher than those in18months controlgroup. Objective To investigate the effect of long-term treadmill running onage-related changes of capillaries in white matter in order to reveal themechanisms for the protection of long-term treadmill running on the agedwhite matter.Methods Five male and five female rats were randomly selected from eachgroup (28months running group,28months control group and18monthscontrol group). One hemisphere was randomly selected from each rat. Thewhite mater was taken out and embedded by O.C.T.5μm sections were cutaccording to the isector principle. Capillaries were labeled with collagen IVantibody. Under light microscope with the magnification of1000, the viewof visopms were sampled the total length, total surface area and the volumeof the capillaries in white matter were obtained with the stereologedmethods. Results1. The total length of the capillaries in the subcortical white matterof female and male28months running rats were36.92±4.65m and33.68±3.91m, respectively. The total length of the capillaries in the subcorticalwhite matter of female and male28months the control group were22.55±5.39m and18.42±2.55m, respectively. The total length of the capillariesin the subcortical white matter of female and male18months the controlgroup were29.31±2.97m and30.76±5.46m, respectively. Compared tothe28months control group and18months control group, the total lengthof the capillaries in the white matter of the female running of rats weresignificantly longer by63.73%(p<0.01) and25.96%(p<0.01), respectively.Compared to the28months control group and18months control group, thetotal length of the capillaries in the white matter of the male running ratswere longer by82.84%(p<0.01) and by9.49%(p>0.05), respectively.2.The total surface area of capillaries in subcortical white matter of femaleand male28months running rats were by6.35±0.99cm2and8.79±1.22cm2, respectively. The total surface area of capillaries in subcortical whitematter of female and male28months control group were by4.29±0.59cm2and3.34±0.51cm2, respectively. The total surface area of capillariesin subcortical white matter of female and male18months control groupwere by8.08±1.96cm2, and6.79±1.53cm2, respectively. Compared tothe28months control group and18months control group, the total surfacearea of capillaries in the white matter of the female running rats were larger by48.02%(p<0.01) and21.41%(p>0.05), respectively. Compared to the28months control group and18months control group, the total surfacearea of capillaries in the white matter of the male running rats were largerby163.17%(p<0.01) and29.46%(p>0.05), respectively.3. The totalvolumes of capillaries in subcortical white matter of female and male28months running rats were0.66±0.14mm3and and0.83±0.20mm3,respectively. The total volumes of capillaries in subcortical white matter offemale and male28months control rats were0.69±0.24mm3and1.06±0.29mm3, respectively. The total volumes of capillaries in subcorticalwhite matter of female and male18months running rats were0.51±0.23mm3and1.03±0.37mm3, respectively. Compared to the28monthscontrol group and18months control group, the total volume of capillariesin the white matter of the female running rats were larger by4.35%(p>0.05) and37.74%(p<0.05), respectively. Compared to the28monthscontrol group and18months control group, the total volume of capillariesin the white matter of the male running rats were larger by62.75%(p <0.05)and19.42%(p>0.05), respectively.Conclusion1. long-terrm exercise had protective effects on the total length,total surface area, and total volume of capillaries in aged white matter. Thevarious parameters of the capillaries in the white matter of28months malerunning rats were significantly higher than those in the28months malecontrol rats. There were no significant difference in the various parameters of the capillaries in the white matter between28month male running ratsand18months male control rats. The various parameters of the capillariesin the white matter of28months female running rats were significantlyhigher than those in the28months female control rats and18monthsfemale control rats. Objectives To investigate the effects of long-term treadmill running onthe factors associated with the nerve and vascular growth in blood andsubcortical white matter in order to reveal the possible target andmechanism for the protection for long-term treadmill running on agedwhite matter.Methods Five male SD rats were randomly selected from each group(running group and control group), respectively. Blood and white matterwere obtained after30min exercise. The factors associated with the nerve and vascular growth in blood and white matter homogenate were detectedby the BCA method and Elisa kits.Results1. BDNF content in running group and control group were154.0±8.7ng/L and124.9±10.3ng/L, respectively. Compared to the controlgroup, the BDNF content in the running group was significantly increased(p<0.01). There was no significant difference of FGF, IGF-1, VEGF andNGF between the running group and the control group (p>0.05),respectively.2. Factor contents of BDNF, NGF, GDNF and NOGO-A were675.2±93.9pg/mg,371.6±48.0pg/mg,543.8±67.1pg/mg and925.4±131.2pg/mg in the white matter of the control group, respectively.Factor contents of BDNF, NGF, GDNF and NOGO-A were466.3±59.2pg/mg,295.7±79.4pg/mg,171.6±44.2pg/mg and334.9±61.3pg/mgin the white matter of the running group, respectively. All the factorcontents of the running group were significantly lower than those in thecontrol group (p <0.01).Conclusions1. Long-term treadmill running significantly increasedBDNF content in blood and reduced factor contents associated with nerveand vascular growth in the white matter.2.The relationship between theeffects of long-term running exercise on the related nerve growth factorsand the related vascular growth factors and the protective effects oflong-term exercise on aged white matter and on the capillaries of agedwhite matter needs to be further investigated.
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