ABSTRACT
Objective:To explore the effect of foraging exercise (FE) on the behavior of rats with post-stroke depression (PSD) and the expression of 5-Hydroxytryptamine 1A (5-HT1A) receptor and transforming growth factor β1 (TGF-β1) in their frontal lobes.Methods:Thirty-six healthy male Sprague-Dawley rats were randomly divided into an ischemia-reperfusion (I/R) group, a PSD group and a PSD+ FE (FE) group, each of 12. The right middle cerebral artery of each was occluded using the thread occlusion method with 1.5h of ischemia. In the PSD and FE groups, mild stimulation was administered at unpredictable intervals over 3 weeks beginning 1 week after the successful modeling. The rats in the I/R group were raised in a group. Those in the PSD group were raised in individual cages. Those in the FE group were raised in a single cage and foraged freely for a total of 4 weeks. Four and eight weeks after the modeling, the body weights were measured, and the open field, social interaction (SIT) and sugar preference tests were administered to all of the groups. Four weeks later, all of the rats were sacrificed and their brains were sliced and stained. The expression of 5-HT1A receptor and TGF-β1 in the frontal lobe was detected using western blotting.Results:One week after modeling, there was no significant difference in average body weight or the average behavioral scores among the three groups. After four weeks the PSD and FE groups had significantly lower average body weight than the I/R group, fewer counts of rearing and grid crossing, longer SIT latency, less interaction time and lower average sugar preference (all significant differences). After eight weeks the average body weight had increased in each group. SIT latency had shortened and interaction time had increased in the FE group, and the rearing and grid crossing counts and sugar preference had increased in the PSD and FE groups. At that point the FE group had significantly greater average body weight than the PSD group, more counts of rearing and grid crossing, shorter SIT latency, increased interaction time, and greater sugar preference. The ratio of residual brain volume in the right hemisphere of the PSD and FE groups was significantly lower on average than in the I/R group. However, there was no significant difference in the right residual brain volume ratio between the PSD and FE groups. Staining revealed that the pathological changes in the frontal lobes of the FE group had been significantly relieved compared with the PSD group. Eight weeks after the operation the increases in average 5-HT 1A receptor and TGF-β1 levels in the FE group were significantly greater than in the PSD group.Conclusion:Foraging can relieve the depressive symptoms of rats modeling post-stoke depression. The mechanism may be related to alleviating the pathological damage and increasing the expression of 5-HT1AR and TGF-β1 in the frontal lobe. Early chronic stress may increase the volume of cerebral infarction, at least in rats.
ABSTRACT
Objective:To explore the effects of foraging exercise (FE) on depressive-like behaviors and expression of transforming growth factor-β1 (TGF-β1) in hippocampus of rats with ischemic stroke after chronic stress.Methods:The right middle cerebral artery occlusion (MCAO) model was used in 30 male adult clean grade SD rats by suture method.According to the body weight, rats were evenly divided into stroke group ( n=10) and chronic unpredictable mild stimulation (CUMS) group ( n=20). Rats of CUMS group received stress induction 1 week after operation and lasted for 3 weeks. Then, according to random number generator of SPSS 24.0 software, the depression rats were divided into post-stroke depression (PSD) group( n=10) and FE groups ( n=10). The FE group received free FE intervention for 4 weeks. Body weight, water maze test, novelty inhibition feeding test (NSFT) and sucrose preference test (SPT) were performed at the end of the 1st, 4th and 8th week, respectively. The expression of TGF-β1 in hippocampus was detected by Immunohistochemistry (IHC) and Western blot (WB), and the levels of TGF-β1 and TNF-α in serum were detected by ELISA. SPSS 24.0 software was used for statistical analysis. The behavioral data were compared by two factor repeated measurement analysis of variance. One way ANOVA was used for comparison among groups, and LSD test was used for further pairwise comparison. Results:(1) The interaction between group and time had statistical significance on body weight, latency and food intake of NSFT and sucrose preference index(SPI) ( F=2.936-12.098, all P<0.05). After 4 weeks, compared with the stroke group((343.80±19.34)g, (12.10±6.97)s, (0.75±0.09)%), the body weight((307.80±17.23)g, (305.30±24.39)g), and SPI((0.52±0.06)%, (0.53±0.07)%) of PSD group and FE group were lower and the NSFT latency((21.70±7.02)s, (22.40±0.84)s) was longer (all P<0.05). After 8 weeks, SPI in FE group was higher than that in PSD group ( P=0.045). There were significant differences in body weight of three groups, NSFT latency and SPI of PSD group and FE group, and food intake of stroke and FE group ( F=8.478-196.548, all P<0.05). There was no interaction between group and time in the water maze test. Main effect of time ( P=0.034) and main effect of group ( P<0.01) had statistical significance on escape latency. The escape latency after 4 weeks was longer than that after 1 week ( P=0.003). The latency of PSD group was longer than that of stroke group ( P=0.005), and latency of FE group was shorter than that of the PSD group ( P<0.01). The main effect of group had statistical significance in the number of crossing quadrant ( P<0.01). The number of crossing quadrant of FE group was less than that of PSD group ( P<0.01). (2) Immunohistoche mistry staining showed that compared with the stroke group, the expression of TGF-β1 was down-regulated in 3 areas of hippocampus of PSD group (CA1, CA3 and DG) ( t=5.449-9.353, all P<0.01). Compared with stroke group, the expression of TGF-β1 of CA1 ( t=7.433, P<0.01) in FE group was down-regulated, but was up-regulated in CA3 ( t=3.342, P<0.05) of FE group. Compared with the PSD group, the expression of TGF-β1 was up-regulated in CA3 and DG of FE group ( t=7.811, 8.790, both P<0.01). (3) Western blot results: Compared with stroke group, the expression of TGF-β1 in hippocampus of PSD group was down-regulated ( t=3.255, P<0.01). Compared with the PSD group, the expression of TGF-β1 in hippocampus of FE group was up-regulated ( t=2.906, P<0.05). (4) ELISA detection showed that compared with the stroke group, the levels of TGF-β1 decreased ( t=2.224, P<0.05), but TNF-α increased ( t=6.127, P<0.01) in PSD group.Compared with the PSD group, the expression of TGF-β1 in FE group increased significantly ( t=4.417, P<0.01). Conclusion:Foraging exercise can improve the depressive behavior symptoms of ischemic stroke rats after chronic stress, and its mechanism may be related to the increasing expression of TGF-β1, which can alleviate the inflammatory reaction in hippocampus.