Spatial Learning Ability Of Mice Research Articles

Atrophy of lacunosum moleculare layer is important for learning and memory in APP/PS1 transgenic mice

Changes in the hippocampus are closely associated with learning and memory in Alzheimer's disease; however, it is not clear which morphological and cellular and subcellular changes are essential for learning and memory. Here, we accurately quantitatively studied the hippocampal microstructure changes in Alzheimer's disease model mice and analyzed the relationship between the hippocampal microstructure changes and learning and memory. Ten-month-old male APP/PS1 transgenic mice and age-matched nontransgenic littermate mice were randomly selected. The spatial learning and memory abilities were assessed using the Morris water maze. The volumes of each layer and numbers of neurons, dendritic spines and oligodendrocytes in the hippocampal subregions were investigated using unbiased stereological techniques. The APP/PS1 transgenic mice showed a decline in hippocampus-dependent spatial learning and memory abilities, smaller volumes of each layer (other than stratum radiatum) and fewer numbers of neurons, dendritic spine synapses and mature oligodendrocytes in the hippocampal subregions than nontransgenic mice. In particular, the decline of spatial learning ability was significantly correlated with the atrophy of lacunosum moleculare layer (LMol) and the decrease of hippocampal neurons and mature oligodendrocytes rather than dendritic spines. The CA1-3 fields (including LMol) atrophy was significantly correlated with the decrease both of neurons, dendritic spines and mature oligodendrocytes. However, the dentate gyrus atrophy was significantly correlated with the decrease of neurons and mature oligodendrocytes rather than dendritic spines. The loss of neurons, dendritic spines synapses and mature oligodendrocytes together caused the LMol atrophy and then led to a decline in hippocampus-dependent spatial learning ability in mice with Alzheimer's disease.

Geniposidic acid ameliorates spatial learning and memory deficits and alleviates neuroinflammation via inhibiting HMGB-1 and downregulating TLR4/2 signaling pathway in APP/PS1 mice

Geniposidic acid (GPA) is an extract from Eucommia ulmoides Oliv. Bark (Eucommiaceae). Accumulating evidences have reported GPA has anti-aging, anti-oxidative stress, anti-inflammatory and neurotrophic effects on neurons. However, whether GPA could alleviate memory deficits in Alzheimer's disease animal models is not clear. We aimed to investigate the effect of GPA treatment on cognitive performance, Aβ deposition and glial cells activation in the transgenic mouse model of AD. 6–7 months APP/PS1 mice were given GPA for 90 days; behavioral experiments were executed to estimate the memory and spatial learning abilities of mice, and the mechanism of neuroprotective effect of GPA was investigated with a focus on amyloid-β deposition, astrocytes and microglia activation and neuroinflammation. GPA treatment significantly improved the spatial learning and memory abilities and also decreased cerebral amyloid-β deposition in APP/PS1 mice. Via HE staining, we found that GPA could ameliorate histopathological changes in cerebrum. We also found that GPA treatment inhibited the activation of astrocytes and microglia, down-regulated the expression of pro-inflammatory cytokines and iNOS, and up-regulated the expression of anti-inflammatory cytokines and Arg-1. In addition, GPA down-regulated the gene expression of HMGB-1 receptors (TLR2, TLR4 and RAGE) then mediated MyD88, TRAF6 and phospho-ERK1/2, subsequently modulated the expression of key AP-1 and NF-κB family members (c-Fos, c-Jun and p65). The reversal of the pro-inflammatory state suggested GPA can serves as a multi-target candidate by alleviating Aβ deposition and neuroinflammation for the auxiliary therapy of Alzheimer's disease.

Effects of developmental arsenite exposure on hippocampal synapses in mouse offspring.

Arsenic exposure through drinking water can impair the learning and memory ability of children in China and other countries. Synaptic plasticity plays a key role in the process of learning and memory. Alterations in the expression of presynaptic and postsynaptic proteins can be used to evaluate synaptic plasticity, and further to evaluate impairment in learning and memory ability. Thereby, the aim of this study was to explore the mechanisms underlying arsenic neurotoxicity by focusing on alterations in the hippocampal synapses of mouse offspring induced by developmental arsenite exposure. Mother mice and their offspring were exposed to 0, 25, 50 or 100 mg L-1 arsenite via drinking water from the first day of gestation until postnatal day (PND) 35. The spatial learning and memory ability of PND 35 mice was evaluated using a Morris water maze. The levels of speciated arsenicals in the brain of PND 7, 14, 21 and 35 mice were analyzed by hydride generation coupled with atomic absorption spectrophotometry. Synaptic structure and protein expression of postsynaptic density protein-95 (PSD-95) and synaptophysin (SYP) in the hippocampus of PND 7, 14, 21 and 35 mice were examined. The findings from this study disclosed that the spatial learning ability of mice could be impaired by exposure to 25 mg L-1 arsenite; however spatial memory ability could not be impaired until exposure to 100 mg L-1 arsenite. The thickness of the postsynaptic density (PSD) decreased, whereas the width of the synaptic cleft widened significantly in arsenite exposure groups. Moreover, protein expression of both PSD-95 and SYP decreased significantly in arsenite exposure groups. In conclusion, the results of this study demonstrated that developmental arsenite exposure could depress the expression of synaptic proteins, subsequently cause alteration in synaptic structures, and finally contribute to arsenite-induced deficits in spatial learning and memory ability in mouse offspring.

Systems genetic analysis of hippocampal neuroanatomy and spatial learning in mice.

Variation in hippocampal neuroanatomy correlates well with spatial learning ability in mice. Here, we have studied both hippocampal neuroanatomy and behavior in 53 isogenic BXD recombinant strains derived from C57BL/6J and DBA/2J parents. A combination of experimental, neuroinformatic and systems genetics methods was used to test the genetic bases of variation and covariation among traits. Data were collected on seven hippocampal subregions in CA3 and CA4 after testing spatial memory in an eight-arm radial maze task. Quantitative trait loci were identified for hippocampal structure, including the areas of the intra- and infrapyramidal mossy fibers (IIPMFs), stratum radiatum and stratum pyramidale, and for a spatial learning parameter, error rate. We identified multiple loci and gene variants linked to either structural differences or behavior. Gpc4 and Tenm2 are strong candidate genes that may modulate IIPMF areas. Analysis of gene expression networks and trait correlations highlight several processes influencing morphometrical variation and spatial learning.

Effects of lead exposure on D-serine metabolism in the hippocampus of mice at the early developmental stages.

The aim of this study was to explore the mechanisms of lead neurotoxicity by focusing on the alteration of D-serine metabolism in the hippocampus of mice at the early life. Mother mice and their offspring were exposed to 0, 0.5, 1.0 and 2.0 g/L lead in lead acetate via drinking water from the first day of gestation until the postnatal day (PND) 40. Morris water maze was used to measure the spatial learning and memory ability of PND 40 mice. Expressions of serine racemase (SR), D-amino acid oxidase (DAAO), alanine-serine- cysteine transporter-1 (asc-1) and subunits of N-methyl-D-aspartate receptor (NMDAR) in the hippocampus of PND 10, 20 and 40 mice were examined by western blot and real time RT-PCR. Findings from this study disclosed that the spatial learning ability of mice tested by place trial could be significantly impaired by 0.5 g/L lead exposure, and the spatial memory ability tested by probe trail could be impaired by 1.0 g/L lead exposure. Exposure to 2.0 g/L lead in the water could significantly inhibit the protein and mRNA expression of SR; conversely enhance the expression of DAAO protein and mRNA in the hippocampus during the early developmental stages. However, the protein expressions of DAAO and asc-1 in the hippocampus were significantly enhanced by 0.5 g/L lead exposure at different developmental stages. On the other hand, the protein and mRNA expressions of both NR1 and NR2A were inhibited significantly by 1.0 g/L lead exposure since PND 10, and by 0.5 g/L lead exposure since PND 20. Noteworthy, the protein expression of NR2B was inhibited significantly by 0.5 g/L lead exposure in PND 10 mice, and by 1.0 g/L lead exposure in PND 20 mice, but there was no significant group difference in PND 40 mice. Meanwhile, expressions of asc-1 and NR2B mRNA were not affected obviously by lead exposure. In conclusion, chronic lead exposure during brain development might affect D-serine metabolism by enhancing its degradation, which might be related to the inhibited expression of NMDAR subunits, and furthermore contribute to deficits in learning and memory ability in mice.

Improvement of memory and cognitive function by alantolactone and isoalantolactone in mouse model (629.9)

Our previous study demonstrated that alantolactone and its isoform isolated from Inula helenium had neuroprotective and antioxidative effects in primary cortical neurons. This study was conducted to assess the preventive effect of both sesquiterpenes from the impairment of memory and cognitive function in scopolamine‐induced mice. ICR mice (5 week‐old, male) were injected i.p. with 1 mg/kg body weight of scopolamine to induce amnesia. The memory and spatial learning ability of mice were evaluated by passive avoidance test, Y‐maze test, and Morris water maze test. We found that these two sesquiterpenes improved the cognitive function of mice injected with scopolamine in a dose‐dependent manner. In particular, the group treated with 1 mg isoalantolactone per kg body weight showed the longer latency time than positive control group. Moreover, isoalantolactone reversed the scopolamine‐induced spatial memory impairment of mice as assessed by Y‐maze test. The inhibition of acetylcholine esterase in hippocampus and cerebral cortex was postulated as the potential mechanism of the memory improvement by the compound. In conclusion, these results suggest that sesquiterpenes attenuate scopolamine‐induced memory impairment maybe through enhancement of the cholinergic nervous system via acetylcholinesterase inhibition.Grant Funding Source: Supported by NRF‐2010‐0027204 and 2011‐0009782 and IPET (High Value‐added Food TechnologyDevelopment Program, 2012, 112066‐3), S. Korea

Mice undernourished before, but not after, weaning perform better in motor coordination and spatial learning tasks than well-fed controls

Undernutrition of rodents has been claimed to result in long-term behavioural deficits in motor coordination and spatial learning ability, although the literature on this is somewhat conflicting. We have recently been engaged in a study of the effects of either pre- or post-weaning undernutrition on longevity in mice. As part of this ageing study, we have also assessed the effects of such nutritional regimes on motor coordination and spatial learning ability of mice. Motor coordination was tested in 21-week-old control and previously undernourished mice by assessing their ability to remain on a revolving drum. We have found that mice previously undernourished either during the pre- or post-weaning period performed better than controls during some, but not all, of the test days. Spatial learning was tested in 50–58-week-old mice using the Morris water maze. In this instance we found that mice previously undernourished during the pre-weaning period performed better at this task than either controls or mice undernourished for a period after weaning. It seems that undernutrition during the pre-weaning period may, paradoxically, improve the performance of mice in these behavioural tasks compared to controls. Undernutrition after weaning had little or no effect on these behavioural measures. The exact mechanisms involved in causing the observed long-term changes in functional capacity due to a period of undernutrition from conception until weaning age of the mice in our study remain unknown.

Toxicity and Oxidative Stress Induced by Organic Arsenical Diphenylarsinic Acid and Inorganic Arsenicals and Their Effects on Spatial Learning Ability in Mice

In the present study, we investigated the oxidative stress induced by arsenical compounds in mice. Catalase (CAT) activity in the liver was decreased significantly when an organic arsenical compound, diphenylarsinic acid (DPAA), was administered to mice for 7 and 28 consecutive days. Reduced glutathione (GSH) was decreased significantly in the blood of the mice treated for 7 days with another organic arsenical, phenylmethyl arsonic acid (PMAA), and an inorganic arsenical, Na2HAsO4, as well as DPAA. GSH was also decreased significantly in the brain of the mice treated for 28 days with DPAA. Arsenic concentrations in the brain of the mice administered DPAA for 7 or 28 days were 1.6-3.0 times higher than those in the livers of these mice. The levels were about 3.0-14 times higher than those in the brains of mice administered inorganic arsenicals, suggesting that organic arsenicals tended to be more highly accumulated in the brain than inorganic arsenicals. The Morris water maze test supported these results, i.e., the latency time of the mice administered DPAA was significantly longer than that of the mice administered Na2HAsO4 or NaAsO2, as well as that of controls without arsenical. These results showed that DPAA decreased GSH in the blood, liver and brain, and that DPAA was more easily transferred to the brain. It was suggested that spatial learning ability was depressed by the accumulation of DPAA in the brain.

The role of dietary niacin intake and the adenosine-5′-diphosphate-ribosyl cyclase enzyme CD38 in spatial learning ability: is cyclic adenosine diphosphate ribose the link between diet and behaviour?

The pyridine nucleotide NAD+ is derived from dietary niacin and serves as the substrate for the synthesis of cyclic ADP-ribose (cADPR), an intracellular Ca signalling molecule that plays an important role in synaptic plasticity in the hippocampus, a region of the brain involved in spatial learning. cADPR is formed in part via the activity of the ADP-ribosyl cyclase enzyme CD38, which is widespread throughout the brain. In the present review, current evidence of the relationship between dietary niacin and behaviour is presented following investigations of the effect of niacin deficiency, pharmacological nicotinamide supplementation and CD38 gene deletion on brain nucleotides and spatial learning ability in mice and rats. In young male rats, both niacin deficiency and nicotinamide supplementation significantly altered brain NAD+ and cADPR, both of which were inversely correlated with spatial learning ability. These results were consistent across three different models of niacin deficiency (pair feeding, partially restricted feeding and niacin recovery). Similar changes in spatial learning ability were observed in Cd38- / - mice, which also showed decreases in brain cADPR. These findings suggest an inverse relationship between spatial learning ability, dietary niacin intake and cADPR, although a direct link between cADPR and spatial learning ability is still missing. Dietary niacin may therefore play a role in the molecular events regulating learning performance, and further investigations of niacin intake, CD38 and cADPR may help identify potential molecular targets for clinical intervention to enhance learning and prevent or reverse cognitive decline.

Assessment of spatial learning abilities of mice in a new circular maze

In the present study, we tested the spatial learning behavior of four different mouse strains (129/Sv, BALB/c, C57BL and Swiss) in a newly developed circular maze. The maze was based on the circular Barnes maze, which was initially developed for rats. Since mice do not readily enter holes in floor, additional reinforcers (positive and negative) or pretraining procedures have been used to train the animals. Because these methods are not always desirable, we examined whether mice are more willing to enter escape holes (12), which were located in the rim of the apparatus. C57BL mice appeared to improve their performance on three different measures of spatial learning: latency to find escape hole, distance to escape hole and errors (visit to other holes). The other strains also improved their performance although this was only seen for one parameter (i.e. 129/Sv and BALB/c on latency, and Swiss on distance). When the animals were trained to find another location, it was found that only the performance of the C57BL mice was transiently impaired. The C57BL mice were also very efficient in improving their performance in a repeated acquisition paradigm (six trials per day on four successive days). Applying a probe trial procedure, a clear preference for the goal location was found. These findings indicate that these mice used a spatial search strategy. Although this circular maze can be used as an additional tool to assess spatial learning in (genetically modified) mice, it is noted that strain differences in spatial learning seem to be independent of task. Further, our data with different strains indicate that different measures of behavior should be evaluated to assess the spatial learning performance of mice.