Long term memory deficits in adult rats due to postnatal malnutrition

Rats who suffered zinc deficiency in early infancy were significantly retarded in the development of their long term memory. Other rats who suffered undernutrition during the same time period did not suffer impaired memory. It was hypothesized that zinc deficiency interfered with the normal development of the brain structures which are necessary for mediating long term memory.     

GRK5 deficiency leads to early Alzheimer-like pathology and working memory impairment

G-protein coupled receptor kinase-5 (GRK5) deficiency has been linked to early Alzheimer's disease in humans and mouse models of the disease. To determine potential roles of GRK5 in the disease pathogenesis, the GRK5 knockout mouse was evaluated at pathological and behavioral levels. We found that these mice displayed an age-dependent increase in hippocampal axonal defects characterized by clusters of axonal swellings that accumulated abnormal amounts of molecular motor proteins, microtubule-associated proteins, intracellular β-amyloid, and subcellular organelles. In severe cases, extracellular β-amyloid fibrillar deposits were occasionally observed, along with degenerating axonal components, and were tightly surrounded by reactive astrocytes. Moreover, significant loss of synaptic proteins and early signs of cholinoceptive neurodegeneration were evident in the hippocampus as well. Consistent with the moderate level of pathologic change, aged GRK5 knockout mice displayed selective working memory impairment, with other cognitive domains unaffected. Taken together, these findings not only strongly support an important role of GRK5 deficiency in early Alzheimer's pathogenesis, but also promote the GRK5 knockout mouse as an additional model for early Alzheimer-related studies.     

Enhanced zinc consumption causes memory deficits and increased brain levels of zinc

Zinc deficiency has been shown to impair cognitive functioning, but little work has been done on the effects of elevated zinc. This research examined the effect on memory of raising Sprague-Dawley rats on enhanced levels of zinc (10 ppm ZnCO3; 0.153 mM) in the drinking water for periods of 3 or 9 months, both pre- and postnatally. Controls were raised on lab water. Memory was tested in a series of Morris Water Maze (MWM) experiments, and zinc-treated rats were found to have impairments in both reference and working memory. They were significantly slower to find a stationary platform and showed greater thigmotaxicity, a measure of anxiety. On a working memory task, where the platform was moved each day, zinc-treated animals had longer latencies over both trials and days, swam further from the platform, and showed greater thigmotaxicity. On trials using an Atlantis platform, which remained in one place but was lowered on probe trials, the zinc-treated animals had significantly fewer platform crossings, spent less time in the target quadrant, and did not swim as close to the platform position. They had significantly greater latency on nonprobe trials. Microprobe synchrotron X-ray fluorescence (microSXRF) confirmed that brain zinc levels were increased by adding ZnCO3 to the drinking water. These data show that long-term dietary administration of zinc can lead to impairments in cognitive function.     

Programmed cell death (apoptosis) in lymphoid and myeloid cell lines during zinc deficiency.

Three human cell lines of lymphoid (Molt-3 and Raji) or myeloid (HL-60) origin were maintained in vitro under zinc-sufficient or zinc-deficient conditions. Under these conditions, cell proliferation, viability and mode of death (apoptotic or necrotic) were assessed. All three cell types decreased their proliferative capacity and viability under conditions of zinc deficiency. Cell death in the HL-60 and Raji cultures occurred primarily via apoptosis, while most cells in zinc-deficient Molt-3 cultures died via necrosis. Apoptosis in zinc-deficient cultures of HL-60 and Raji cells was characterized by a slow decline in culture viability as cells with condensed and fragmented nuclear DNA appeared. These morphological changes were accompanied by an increase in cell buoyant density, which allowed separation of viable apoptotic cells from their non-apoptotic counterparts by means of percoll stepdensity gradients. Necrosis in zinc-deficient Molt-3 cultures was characterized by rapid loss of cell culture viability as these cells underwent direct lysis. Intact necrotic cells were easily identified by the flocculated state of their chromatin as well as the decreased basophilia of their cytoplasm. Analysis of DNA from apoptotic HL-60 and Raji cells revealed that internucleosomal DNA degradation, indicative of endogenous endonuclease activation, had occurred, whereas the nuclear DNA of necrotic Molt-3 cells remained relatively unfragmented. The different modes of cell death evoked may reflect the relative sensitivities of cells of these lineages to zinc levels in vivo.     

N-acetyl cysteine supplementation prevents impairment of spatial working memory functions in rats following exposure to hypobaric hypoxia

Exposure to high altitude (HA), especially extreme altitude, is associated with impairment of cognitive functions including memory and increased oxidative stress. However, the underlying mechanisms involved are not well understood. It is hypothesized that HA induced oxidative stress may be one of the factors underlying hypoxia induced memory impairment. The aim of the present study was to investigate the effect of hypobaric hypoxia (HH) on spatial working and reference memory functions, oxidative stress markers in rats and effect of supplementation of N-acetyl cysteine (NAC). The rats were divided into four groups. Group I served as normoxic (n=6), Group II served as hypoxic (n=6), Group III as hypoxia group treated with NAC (n=6) and Group IV served as normoxic group treated with NAC (n=6). Group II & III were exposed to HH for 3 days equivalent to 6100 m and received oral NAC supplementation (750 mg/kg) daily. Rats from all the groups were trained in Morris Water Maze (MWM) task for 8 consecutive days. Spatial working and reference memory were tested immediately after the termination of HH and then the rats were sacrificed for estimation of oxidative stress markers in hippocampus. Rats displayed significant deficits in spatial working memory, and increased oxidative stress along with decrease in antioxidant status on hypoxic exposure. Supplementation with NAC in hypoxia-exposed group improved spatial memory performance, and decreased oxidative stress. These findings indicate that hypoxic exposure is associated with increased oxidative stress, which may have caused memory deficit in rats exposed to simulated HA.     

Regulation of cognitive resources during sustained attention and working memory in 10-year-olds and adults

We examined differences between 10-year-olds and young adults in resource recruitment and regulation during tasks of sustained attention and spatial working memory. We administered participants spatial 0- and 1-back tasks and used pupillary dilation as a measure of resource recruitment. Repeated administration of 0-back led to smaller pupillary dilations and greater response time (RT) variability, revealing a vigilance decrement. Effects of repeated administration of 0-back and differences between 0- and 1-back in d' and RTs were similar between ages. Results further suggested that the children may not have been as effective as adults in extracting frequency information. Thus, on simple tasks of sustained attention and working memory, children recruit resources in a manner similar to adults. Finally, d' was correlated with RT variability on both tasks at both ages, highlighting the role of attentional fluctuations on both tasks.     

Effects of prenatal nutritional deficiency on affiliation and aggression in rats

Adult male rats were allowed to choose between two different target rats in a T-maze. The experimental animals and targets experienced prenatal zinc deficiency (Z), undernutrition, or normal nutrition (A) via their mother's diet during the last third of pregnancy. In social encounters between the experimental and target animals, the Z animals were the most aggressive rats. The choice data indicated that animals preferred to affiliate with the A targets. The Z target rats were the social partners most often avoided. The results suggest long-term effects of early nutritional deprivation on social behavior, specifically affiliation and aggression.     

Electroacupuncture restores learning and memory impairment induced by both diabetes mellitus and cerebral ischemia in rats

Previous investigations have demonstrated that electroacupunctural stimulation can ameliorate primary and secondary symptoms such as peripheral neuropathy and diabetic encephalopathy in diabetic rats. In this study, we investigated whether electroacupuncture could improve learning and memory which was typically impaired in diabetic rats with cerebral ischemia. Furthermore, we investigated the mechanisms underlying its effects using passive avoidance test, active avoidance test, Morris water maze and electrophysiology. Electroacupuncture increased the step-down latency in passive avoidance test and accurate rate in active avoidance test, decreased the escape latency in Morris water maze. After electroacupuncture treatment, the long-term potentiation (LTP) impaired by both diabetes and cerebral ischemia was restored significantly. These results suggest that electroacupuncture can ameliorate learning and memory capacity impaired by hyperglycemia and ischemia. LTP plays a very important role in this beneficial effect.     

High altitude memory impairment is due to neuronal apoptosis in hippocampus, cortex and striatum

Cognitive and neuropsychological functions have been impaired at high altitude and the effects depend on altitude and duration of stay. However, the neurobiological mechanism of this impairment is poorly understood especially exposure to different duration. Aim of the present study was to investigate the changes of behavior, biochemistry and morphology after exposure to different duration of hypobaric hypoxia. The rats were exposed continuously to a simulated high altitude of 6100 m for 3, 7, 14 and 21 days in an animal decompression chamber. Spatial reference memory was tested by Morris water maze. The oxidative stress markers like free radicals, NO, lipid peroxidation, LDH activity and antioxidant systems like GSH, GSSG, GPx, GR, SOD were estimated from cortex, hippocampus and striatum. The morphological changes, neurodegeneration, DNA fragmentation and mode of cell death have also been studied. It was observed that the spatial reference memory was significantly affected after exposure to hypobaric hypoxia. Increased oxidative stress markers along with decreased effectiveness of antioxidant system were also observed in hypoxia-exposed animals. Further pyknotic, shrunken, tangle-like neurons were observed in all these regions after hypoxia and neurodegeneration, DNA fragmentation and apoptosis were also observed in all the three regions. But after 21 days of exposure, the spatial memory was improved along with improvement of antioxidant activities. Our result suggests that the apoptotic death may be involved in HA-induced memory impairment and after 7 days of exposure the effect was more pronounced but after 21 days of exposure recovery was observed.     

空间辨别性学习记忆活动与大鼠海马结构基质细胞衍生因子 1表达的关系

目的 探讨大鼠空间辨别性学习记忆活动与趋化因子基质细胞衍生因子.1(SDF-1)的关系. 方法用免疫组织化学方法、免疫印迹法和RT-PCR方法对获得空间辨别性学习记忆大鼠海马结构内SDF-1表达进行研究,并与游水组和对照组比较.结果 1.免疫组织化学方法显示,对照组大鼠海马结构内趋化因子SDF-1阳性细胞分布在海马结构各亚区和各层.阳性细胞的形态以圆形为主,少见锥体形和梭形.阳性产物主要分布在细胞膜上;游水组大鼠海马结构内SDF-1阳性细胞的形态和分布与对照组相比未见组间差异;训练组大鼠海马结构内SDF-1免疫阳性细胞的数量比对照组增多(P<0.01).阳性细胞的形态以锥体形和三角形居多,在分布上有向齿状回聚集的趋势.2.免疫印迹方法检测训练组大鼠海马结构内SDF-1蛋白质的表达明显高于对照组(P<0.01).而且在训练组内则随着训练时间的延长表达量随之增加.3.RT-PCR方法检测训练组大鼠海马结构内SDF-1mRNA的量明显高于对照组(P<0.01),且随着训练时间的延长表达增加.在水盆中漫游的游水组大鼠,不论是免疫组织化学方法,还是免疫印迹法以及RT-PCR方法获得的结果与对照组相比均未见组间差异. 结论 经水迷宫训练使大鼠获得空间辨别性学习记忆功能,致使海马结构内细胞导向因子SDF-1表达上调,上调的SDF-1蛋白质可能与所获功能需要的形态基础.神经微环路的形成有关.     

Learning and memory dissociation in rats with lesions to the subthalamic nucleus or to the dorsal striatum

The striatum and the subthalamic nucleus (STN) are the two main cortical inputs to the basal ganglia. Both structures are involved in motor and cognitive functions, particularly executive functions, known to rely mainly on fronto-basal ganglia circuits. The present work investigated the respective role of the dorsal part of the striatum (dST) and the STN by studying their involvement in learning and memory processes in two separate experiments. In a first experiment, rats with lesions to the STN or to the dST were trained in a light-tone discrimination task. When the learning criterion was reached, rats were then trained to the reversed discrimination. In a second experiment, surgery was done when the learning criterion had been reached. Three weeks after surgery, animals were then subjected to two relearning sessions and then to either a reversal learning or a working memory task. When surgery was done before learning, dysfunction of the dorsal striatum induced slight difficulties in acquisition, whereas dysfunction of the STN induced no difficulties during the initial learning but induced a more rapid inhibition of responses to the first lever press following the presentation of the tone during the reversed discrimination. In the second experiment, dST-lesioned rats showed long-term memory deficit in contrast to STN-lesioned rats which showed no difficulties during relearning but deficits in working memory. These results indicate a clear dissociation in cognitive functions in which STN and dorsal striatum are involved, suggesting that the fronto-striatal circuit and the fronto-STN circuit support, at least in part, different cognitive functions.     

Effects of prenatal nutrition on learning and motivation in rats.

The results of two learning experiments revealed that adult male rats whose dams suffered either prenatal zinc deficiency or undernutrition showed, as compared to rats whose dams were fed ad lib, normal diets during pregnancy (1) more resistance to extinction following partial reinforcement, and (2) a faster occurring negative contrast effect when shifted from large to small reward. An incentive-motivation interpretation of the data suggests that the nutritionally deprived and normal animals differ with respect to the incentive value of the consummatory reward. This effect appears to be long-term.     

Variations in the content of some trace elements and macroelements in the hippocampus of rats during learning and memory retrieval after destruction of the entorhinal cortex

We studied variations in the concentration of Na, K, Ca, and Mg in the hippocampus of rats with damaged entorhinal cortex. The concentration of Mg, Na, K, and Ca remained practically unchanged, while the content of Zn and Cu increased during learning and memory retrieval in animals with damaged entorhinal cortex. Our results indicate that Zn and Cu, constituents of metalloproteins and metalloenzymes, play an important role in hippocampal function. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 143, No. 6, pp. 608–610, June, 2007     

Nitric oxide contributes to learning and memory deficits observed in hypothyroid rats during neonatal and juvenile growth

INTRODUCTION:

Severe cognitive impairment follows thyroid hormone deficiency during the neonatal period. The role of nitric oxide (NO) in learning and memory has been widely investigated.

METHODS:

This study aimed to investigate the effect of hypothyroidism during neonatal and juvenile periods on NO metabolites in the hippocampi of rats and on learning and memory. Animals were divided into two groups and treated for 60 days from the first day of lactation. The control group received regular water, whereas animals in a separate group were given water supplemented with 0.03% methimazole to induce hypothyroidism. Male offspring were selected and tested in the Morris water maze. Samples of blood were collected to measure the metabolites of NO, NO₂, NO₃ and thyroxine. The animals were then sacrificed, and their hippocampi were removed to measure the tissue concentrations of NO₂ and NO₃.

DISCUSSION:

Compared to the control group''s offspring, serum thyroxine levels in the methimazole group''s offspring were significantly lower (P<0.01). In addition, the swim distance and time latency were significantly higher in the methimazole group (P<0.001), and the time spent by this group in the target quadrant (Q1) during the probe trial was significantly lower (P<0.001). There was no significant difference in the plasma levels of NO metabolites between the two groups; however, significantly higher NO metabolite levels in the hippocampi of the methimazole group were observed compared to controls (P<0.05).

CONCLUSION:

These results suggest that the increased NO level in the hippocampus may play a role in the learning and memory deficits observed in childhood hypothyroidism; however, the precise underlying mechanism(s) remains to be elucidated.     

Impairment of inflammatory response in adult rats submitted to maternal undernutrition during early lactation: Role of insulin and glucocorticoid

Objective: Early nutritional environment may program permanent metabolic alterations, predisposing to later diseases. We have investigated the interference of maternal malnutrition during lactation with the development of acute inflammation in adult rats. Materials and methods: Adult rats, offspring of dams fed with either protein-free diet (UN group) or 22% protein diet (C group) during the first 10 days of lactation, were submitted to pleurisy with carrageenan (500 g/cavity). Pleural edema, neutrophil migration and ICAM expression, were evaluated 4 h after and correlated with alterations in plasma insulin and corticosterone. Leukocyte-endothelium interactions were evaluated by intravital microscopy 1 h after inflammation. Results: Compared to controls, UN rats showed a decrease in pleural edema formation (50%), neutrophil migration (50%), endothelial ICAM-1 expression on pulmonary tissue, and impairment in leukocyte adhesion (50%) and migration (80%) through endothelium. Circulating insulin was lower (42%) and corticosterone was higher (34%) in UN, compared to controls. Pre-treatment of UN with insulin (5 IU/day) or RU486 (20 mg/kg/day), inhibitor of glucocorticoid receptor, restored leukocyte functions and ICAM-1 expression. Conclusion: Postnatal maternal malnutrition, programming for permanent alterations in insulin and glucocorticoid secretion in progeny, that were unable to properly mount an inflammatory response, probably predisposes to chronic diseases in adult life.Received 5 December 2002; returned for revision 6 June 2003; accepted by I. Ahnfelt-Rønne 28 June 2003     

大建中汤对脾阳虚腹痛大鼠大脑皮质三磷酸腺苷含量和三磷酸腺苷酶活性的影响

目的:通过观察大建中汤对脾阳虚腹痛大鼠皮质ATP含量以及钠钾ATP酶和钙镁ATP酶活性的影响,探讨大建中汤对脾阳虚腹痛大鼠的镇痛机制。方法:将大鼠随机分为正常对照组,模型对照组,大建中汤大、小剂量组。用饮食失调、劳倦过度加苦寒泻下的方法,建立脾阳虚腹痛大鼠模型后分别给予相应治疗。取大脑皮质处理后,采用高效液相色谱法测定各组大鼠皮质ATP含量的变化;采用无机磷法测定钠钾-三磷酸腺苷酶和钙镁-三磷酸腺苷酶活性。结果:与正常对照组相比,脾阳虚腹痛模型组大鼠大脑皮质ATP含量明显升高,钠钾ATP酶和钙镁ATP酶活性显著降低;与模型组相比,大建中汤能显著减少脾阳虚腹痛大鼠大脑皮质ATP含量,增加钠钾ATP酶和钙镁ATP酶活性。结论:脾阳虚腹痛症能使大脑皮质ATP含量升高,钠钾ATP酶和钙镁ATP酶活性降低,大建中汤能下调脾阳虚症动物大脑皮质ATP及上调钠钾ATP酶和钙镁ATP酶活性,这可能是其治疗脾阳虚腹痛的作用机制之一。