Altered gene expression in the brain of senescence accelerated mouse SAMP8

Senescence-accelerated mouse (SAM) with special references to neurodegeneration models, SAMP8 and SAMP10 mice

The SAM strains, a group of related inbred strains consisting of senescence-prone inbred strains (SAMP) and senescence-resistant inbred strains (SAMR), have been successfully developed by selective inbreeding of the AKR/J strain of mice donated by the Jackson laboratory in 1968. The characteristic feature of aging common to the SAMP and SAMR is accelerated senescence and normal aging, respectively. Furthermore, SAMP and SAMR strains of mice manifest various pathobiological phenotypes spontaneously. Among SAMP strains, SAMP8 and SAMP10 mice show age-related behavioral deterioration such as deficits in learning and memory, emotional disorders (reduced anxiety-like behavior and depressive behavior) and altered circadian rhythm associated with certain pathological, biochemical and pharmacological changes. Here, the previous and recent literature on SAM mice are reviewed with an emphasis on SAMP8 and SAMP10 mice. A spontaneous model like SAM with distinct advantages over the gene-modified model is hoped by investigators to be used more widely as a biogerontological resource to explore the etiopathogenesis of accelerated senescence and neurodegenerative disorders.

Age-related expression of calcium/calmodulin-dependent protein kinase II A in the hippocampus and cerebral cortex of senescence accelerated mouse prone/8 mice is modulated by anti-Alzheimer's disease drugs

Senescence-accelerated mouse (SAM) prone/8 (SAMP8) is a good animal model to investigate the fundamental mechanisms of age-related learning and memory deficits such as Alzheimer's disease (AD) at the gene and protein levels, and SAM resistant/1 (SAMR1) is its normal control. Calcium/calmodulin-dependent protein kinase II-alpha (CaMKIIalpha) is one of the most abundant subunits of calcium/calmodulin-dependent protein kinase II in cerebral cortex and hippocampus, and is closely linked to AD. In this study, we used real time fluorescence quantitative PCR (RT-PCR) and Western blot techniques to examine the expression of CaMKIIalpha mRNA and protein in the cerebral cortex and hippocampus of SAMP8 both with aging and following treatment with anti-AD drugs (for example, natural product huperzine A (HupA) and traditional Chinese medicinal prescription Liu-Wei-Di-Huang decoction (LW), Ba-Wei-Di-Huang decoction (BW), Huang-Lian-Jie-Du decoction (HL), Dang-Gui-Shao-Yao-San (DSS) and Tiao-Xin-Fang decoction (TXF)). The results showed that the levels of both CaMKIIalpha mRNA and protein decreased significantly in the cerebral cortex of SAMR1 with aging, but increased significantly in the cerebral cortex of SAMP8. Compared with age-matched SAMR1, the expression of mRNA and protein of CaMKIIalpha significantly increased in the cerebral cortex and hippocampus of SAMP8 after 10 months of age. After SAMP8 was treated with the previously mentioned drugs, the abnormally high expression of CaMKIIalpha was relatively down-regulated. These results indicated that the expression of CaMKIIalpha in the brain of SAMP8 was abnormal and that this abnormality could be reversed with anti-AD drugs. These data suggest that CaMKIIalpha may play an important role in the age-related cognitive deterioration in AD, and may be a potential targets for anti-AD drugs.

Effect of Dietary Restriction on Learning and Memory Impairment and Histologic Alterations of Brain Stem in Senescence-Accelerated Mouse (SAM) P8 Strain

The age-associated spontaneous spongy degeneration in the brain stem of senescence-accelerated mouse (SAM) P8 strain has been suggested to be closely associated with the ability to learn and memorize. In this study, we investigated the effects of dietary restriction (DR) initiated from weaning on learning and memory and histologic changes of the brain stem in P8 and control R1 mice. Although no effect of DR was observed in the retention of the passive-avoidance response in both the P8 and R1 mice, the acquisition of the task was significantly improved by DR in P8 mice. On the other hand, the total area and number of vacuoles in the brain stem was significantly higher in ad libitum-fed (AD)-P8 mice than in AD-R1 mice. However, no significant effect was observed on the vacuole formation in the brain stem of P8 mice by DR. These observations suggest that the improvement of the acquisition of the task by DR in P8 mice is possibly due to changes in neuronal function rather than histologic alteration in brain stem.