ABSTRACT
Aim To assess the effects of Trillium Tschonoskii Maxim ( TTM ) decoction on Tau protein phosphorylation and synaptic development in AD model rats induced by high activity GSK-3β. Methods The SD rats were divided into five groups of ten animals, named sham-operated group ( blank group) , AD model group, TTM group (0. 5, 0. 25, 0. 125 g·kg-1 · d-1 ) . Treatment group received gavage once a day for seven days with TTM decoction, while other groups by gavage once a day for seven days with drinking water. On 2nd day by gavage, Morris water maze test was used to assess the spatial learning and memory ability of the rats. After five days' training, rats in the treat-ment groups and AD model group were injected wort-mannin ( WT, PI3K specific inhibitor ) and GF-109203X (GFX, PKC specific inhibitor) (100 μmol ·L-1 of each, total volume of 10 μL) into the right lateral ventricle. Western blot was used to detect the levels of phosphorylation Tau protein at multiple sites and the expression level of PI3K, Akt, PKC, GSK-3β(S9, T216) and synapse-associated proteins. Immu-nohistochemical method was used to detect the hyper-phosphorylation of Tau protein in hippocampus of rats. Golgi staining was applied to detect the number and morphological changes of synaptic development and dendritic spines. Nissl' s staining was employed to ob-serve the development of neonatal neurons in hippo-campus and cortex. Results Western blot showed that the phosphorylation level of Tau in hippocampus increased in model group, and the activity of GSK-3βwas up-regulated. Among them, however, in middle dose TTM group, the phosphorylation level of Tau in hippocampus decreased and the activity of GSK-3βde-creased. The expression levels of p-PKC and p-Akt in low and middle dose treatment group were higher than those in model group, thus increasing the activity of PKC and Akt to inhibit the activity of GSK-3β kinase. Immunohistochemistry also indicated that TTM could decrease the biological effects of Tau phosphorylation in hippocampus of AD rats. Western blot showed that TTM could increase the expression levels of synapsin-1 , syn-aptophysin and GluR-1 in hippocampus of AD rats. Nissl staining showed that the number of Nissl bodies in hippocampal neurons of AD model group were signif-icantly fewer than those of sham operation group, which could be increased by TTM middle and high dose group, and the complexity and dendritic spine density of hippocampal neurons in AD rats could be en-hanced as well. Conclusion TTM can effectively im-prove the cognitive function of AD rats induced by the increase of GSK-3β activity, and its possible mecha-nism may be via down-regulating the activity of GSK-3β and inhibiting the phosphorylation of tau protein and promoting the development of neurons.
ABSTRACT
The calyx of Held, a specialized synaptic terminal in the medial nucleus of the trapezoid body, undergoes a series of changes during postnatal development that prepares this synapse for reliable high frequency firing. These changes reduce short-term synaptic depression during tetanic stimulation and thereby prevent action potential failures during a stimulus train. We measured presynaptic membrane capacitance changes in calyces from young postnatal day 5-7 (p5-7) or older (p10-12) rat pups to examine the effect of calcium buffer capacity on vesicle pool size and the efficiency of exocytosis. Vesicle pool size was sensitive to the choice and concentration of exogenous Ca2+ buffer, and this sensitivity was much stronger in younger animals. Pool size and exocytosis efficiency in p5-7 calyces were depressed by 0.2 mM EGTA to a greater extent than with 0.05 mM BAPTA, even though BAPTA is a 100-fold faster Ca2+ buffer. However, this was not the case for p10-12 calyces. With 5 mM EGTA, exocytosis efficiency was reduced to a much larger extent in young calyces compared to older calyces. Depression of exocytosis using pairs of 10-ms depolarizations was reduced by 0.2 mM EGTA compared to 0.05 mM BAPTA to a similar extent in both age groups. These results indicate a developmentally regulated heterogeneity in the sensitivity of different vesicle pools to Ca2+ buffer capacity. We propose that, during development, a population of vesicles that are tightly coupled to Ca2+ channels expands at the expense of vesicles more distant from Ca2+ channels.