Four-month treadmill exercise prevents the decline in spatial learning and memory abilities and the loss of spinophilin-immunoreactive puncta in the hippocampus of APP/PS1 transgenic mice.

BACKGROUND: Previous studies have reported that exercise could improve the plasticity of hippocampal synapses. However, the effects of exercise on synapses in the hippocampus in Alzheimer's disease (AD) are not completely known. METHODS: In this study, thirty 12-month-old male APP/PS1 double transgenic mice were randomly divided into a sedentary group (n = 15) and a running group (n = 15). Fifteen 12-month-old male wild-type littermates were assigned to the control group (n = 15). While running mice were assigned to treadmill running for four months, the control mice and sedentary mice did not run during the study period. After Morris water maze testing, five mice in each group were randomly selected for a stereological assessment of spinophilin-immunoreactive puncta in the CA1, CA2-3 and dentate gyrus (DG) of the hippocampus. RESULTS: Morris water maze testing revealed that while the learning and memory abilities in sedentary APP/PS1 mice were significantly worse than those in wild-type control mice, the learning and memory abilities in running APP/PS1 mice were significantly better than those in sedentary APP/PS1 mice. The stereological results showed that the spinophilin-immunoreactive puncta numbers of the CA1, CA2-3 and DG in the hippocampus of sedentary APP/PS1 mice were significantly lower than those of wild-type control mice and that the numbers of these spines in the CA1, CA2-3 and DG in the hippocampus of running APP/PS1 mice were significantly higher than those of sedentary APP/PS1 mice. Moreover, a running-induced improvement in spatial learning and memory abilities was significantly correlated with running-induced increases in the spinophilin-immunoreactive puncta numbers in the CA1 and DG of the hippocampus. CONCLUSIONS: Four-month treadmill exercise induced a significant improvement in spatial learning and memory abilities and a significant increase in the number of spinophilin-immunoreactive puncta of the CA1, CA2-3 and DG in the hippocampus of APP/PS1 mice. Running-induced improvements in spatial learning and memory abilities were significantly correlated with running-induced increases in the spinophilin-immunoreactive puncta numbers in the CA1 and DG of the hippocampus.

Exercise more efficiently regulates the maturation of newborn neurons and synaptic plasticity than fluoxetine in a CUS-induced depression mouse model.

Depression, a common and important cause of morbidity and mortality worldwide, is commonly treated with antidepressants, electric shock and psychotherapy. Recently, increasing evidence has shown that exercise can effectively alleviate depression. To determine the difference in efficacy between exercise and the classic antidepressant fluoxetine in treating depression, we established four groups: the Control, chronic unpredictable stress (CUS/STD), running (CUS/RUN) and fluoxetine (CUS/FLX) groups. The sucrose preference test (SPT), the forced swimming test (FST), the tail suspension test (TST), immunohistochemistry, immunofluorescence and stereological analyses were used to clarify the difference in therapeutic efficacy and mechanism between exercise and fluoxetine in the treatment of depression. In the seventh week, the sucrose preference of the CUS/RUN group was significantly higher than that of the CUS/STD group, while the sucrose preference of the CUS/FLX group did not differ from that of the CUS/STD group until the eighth week. Exercise reduced the immobility time in the FST and TST, while fluoxetine only reduced immobility time in the TST. Hippocampal structure analysis showed that the CUS/STD group exhibited an increase in immature neurons and a decrease in mature neurons. Exercise reduced the number of immature neurons and increased the number of mature neurons, but no increase in the number of mature neurons was observed after fluoxetine treatment. In addition, both running and fluoxetine reversed the decrease in the number of MAP2+ dendrites in depressed mice. Exercise increased the number of spinophilin-positive (Sp+) dendritic spines in the hippocampal CA1, CA3, and dentate gyrus (DG) regions, whereas fluoxetine only increased the number of SP+ spines in the DG. In summary, exercise promoted newborn neuron maturation in the DG and regulated neuronal plasticity in three hippocampal subregions, which might explain why running exerts earlier and more comprehensive antidepressant effects than fluoxetine.

Anti-Lingo-1 antibody ameliorates spatial memory and synapse loss induced by chronic stress.

Chronic stress can induce cognitive impairment, and synapse number was significantly decreased in the hippocampus of rats suffering from chronic stress. Lingo-1 is a potent negative regulator of axonal outgrowth and synaptic plasticity. In the current study, the effects of anti-Lingo-1 antibody on the spatial learning and memory abilities and hippocampal synapses of stressed rats were investigated. After 4 weeks of stress exposure, the model group was randomly divided into a chronic stress group and an anti-Lingo-1 group. Then, the anti-Lingo-1 group rats were treated with anti-Lingo-1 antibody (8 mg/kg) for 3 weeks. The effects of anti-Lingo-1 antibody on the spatial learning and memory abilities were investigated with the Morris water maze test. Immunohistological staining and an unbiased stereological method were used to estimate the total number of dendritic spine synapses in the hippocampus. At the behavioral level, after 3 weeks of treatment, the anti-Lingo-1 group rats displayed significantly more platform location crossings in the Morris water maze test than the chronic stress group rats. Anti-Lingo-1 significantly prevented the declines in dendritic spine synapses and postsynaptic density protein-95 (PSD-95) expression in the dentate gyrus and the CA1 and CA3 regions of the hippocampus. The present results indicated that anti-Lingo-1 antibody may be a safe and effective drug for alleviating memory impairment in rats after chronic stress and protecting synapses in the hippocampus of stressed rats.

Exercise improves depressive symptoms by increasing the number of excitatory synapses in the hippocampus of CUS-Induced depression model rats.

Exercise has been considered for the treatment of depression, but the mechanism by which exercise improves depression is still unclear. To clarify the mechanism, rats were randomly divided into the control, chronic unpredictable stress (CUS)/standard and CUS/running groups. The rats in the CUS/running group ran for four weeks. In this study, a sucrose preference test (SPT) was used to evaluate the depression-like symptoms in the rats, and western blot, immunohistochemical and stereological analyses were performed to study the expression of synaptic-related proteins in the hippocampus and the changes in excitatory synapses in each sub-region. The results show that sucrose preference in the CUS/standard group was significantly lower than that in the control group, but in the CUS/running group, sucrose preference was higher than that in the CUS/standard group. Surprisingly, there was no difference in the synaptic-related proteins in the hippocampus among groups. The CUS/standard group exhibited fewer spinophilin+ (Sp+) dendritic spines representing excitatory synapses in CA1, CA3 and dentate gyrus (DG) of the hippocampus than the control group, whereas the CUS/running group exhibited significantly more Sp+ dendritic spines in these regions than the CUS/standard group, indicating that excitatory synapses were reduced in depressed rats and that running exercises could reverse this change. We hypothesize that the changes in the number of excitatory synapses better reflect the changes in depressive symptoms than the level of synaptic proteins and that the effect of exercise on excitatory synapses in the sub-regions of the hippocampus may be an important structural indicator of the improvement of depressive symptoms.

Changes in white matter and the effects of fluoxetine on such changes in the CUS rat model of depression.

OBJECTIVE: To explore the pathogenesis of depression and the possible mechanism of the effects of selective serotonin reuptake inhibitors (SSRIs) on the myelinated fibers and myelin sheaths in the white matter during the antidepressant action of fluoxetine. METHODS: In this study, Sprague Dawley (SD) rats were divided into a Control group, a group treated with CUS and no drugs (CUS/Standard group) and a group treated with CUS and fluoxetine (CUS/FLX group). The CUS/FLX group was treated with fluoxetine at dose of 5 mg/kg for 21 days. The white matter volume, the myelinated fiber parameters and the myelin sheath volume in the white matter were calculated from transmission electron microscope images through unbiased stereological methods. RESULTS: The total volume and total length of myelinated fibers;and mean volume of white matter of the CUS/Standard group were significantly decreased compared to values from the control group (p = 0.025, p = 0.007, p = 0.000), whereas no significant differences in these stereological parameters were found between the CUS/Standard and CUS/FLX groups (p > 0.05). CONCLUSIONS: Fluoxetine successfully treated depression-like behavior but had no effects on the white matter or its component myelinated fibers in the CUS rat model of depression.