ABSTRACT
Objective To observe the effect of epigallocatechin gallate (EGCG) on the spatial learning memory deficit in amyloid procursor protein (APP) / presenilin-1 (PS1) double transgenic mice, synaptic ultrastructure and expression of neural cell adhesion molecule in hippocampal CA1 region. Methods Eight weeks old male APP / PS1 double transgenic mice were selected as Alzheimer’s disease (AD) model and divided into the model group, the EGCG group and the donepezil hydrochloride group, 12 in each group.Besides,normal mice of the same brood (with no transgene) were recruited as a normal group (n = 12). Related indices were detected after 6 months continuous gastrogavage. The spatial learning-memory deficit of APP / PS1 double transgenic mice was detected by Morris water maze test. The synaptic ultrastructure of hippocampal CA1 region was observed by transmission electron microscopy. The expression levels of neural cell adhesion molecule (NCAM) and polysialyltranseferase α2,8-polysialic acid (ST8Sia Ⅱ) protein in hippocampal CA1 region of APP / PS1 transgenic mice were detected by immunofluorescence and Western blotting. Results Compared with the normal group, the mean value of escape latency in the model group was extended, and compared with the model group, the mean value of escape latency in the EGCG group and donepezil hydrochloride group were increased (P < 0. 05) . The result of electron microscope showed that the changes of synaptic interface curvature of EGCG group and donepezil hydrochloride group were not obvious. Compared with the model group, the width of the synaptic gap becomes narrower and the thickness of the post-synaptic compact were increases (P < 0. 05) . Immunofluorescence showed that the expression of NCAM and ST8Sia Ⅱ proteins in the hippocampus CA1 region was expressed in the cytoplasm of neurons, the expressions of NCAM and ST8Sia Ⅱ in hippocampal CA1 region were significantly increased in EGCG group and donepezil hydrochloride group (P< 0. 05) . Their contents also showed higher levels of expression in Western blotting (P < 0. 05) . Conclusion EGCG shows improvement on the spatial learning-memory deficit in APP / PS1 double transgenic mice,which may be associated with affecting the synaptic structure of hippocampus and improving the expressions of neural cell adhesion molecule.
ABSTRACT
BACKGROUND: The inducible forebrain-specific cholecystokinin receptor-2 (CCKR-2) double transgenic (tTA/tetO-CCKR-2 tg, abbreviated as dtg) mice are an ideal model of anxiety-related diseases. However, there is still a lack of model identification and life related data OBJECTIVE: To identify the genomic DNA of the offspring and the specific expression of CCKR-2 transgene in the forebrain, and to analyze the survival probability of dtg mice. METHODS: α-CaMKII/tTA single transgenic mice and tetO-CCKR-2 single transgenic mice were cross-fertilized to construct a dtg mouse model. The genomic DNA was extracted from the tail of the offspring, and the genotypes were detected by PCR and agarose gel electrophoresis. Wild-type (WT) mice were used as controls. In situ hybridization was used to detect the expression of CCKR-2. Survival of dtg mice and WT mice (30 females and 30 males) was observed and recorded within 2 years. The study protocol was approved by the Experimental Animal Ethics Committee of Southwest Medical University, with an approval No. 20150068. RESULTS AND CONCLUSION: Agarose gel electrophoresis results showed the molecular weight of the PCR products of dtg mice was consistent with the expected target gene fragment. In situ hybridization results showed a strong signal of CCKR-2 was detected in the forebrain of dtg mice, but hardly present in the WT mice. The median survival time of dtg mice was 76 weeks in females and 77 weeks in males. The survival probability was decreased with age in dtg mice. The survival probability of WT mice was significantly better than that of dtg mice (P < 0.001). There was no significant sex difference between males and females of dtg mice (P=0.577). Therefore, the specific expression of CCKR-2 transgene in the forebrain can be identified using PCR amplification, genomic DNA extraction, agarose gel electrophoresis, and in situ hybridization. tTA/tetO-CCKR-2 double transgenic induction may shorten the survival time of mice, but no significant difference is observed between the females and males of dtg mice.