The effects of choline supplementation in mothers with hypothyroidism on the alteration of cognitive-behavioral, long-term potentiation, morphology, and apoptosis in the hippocampus of pre-pubertal offspring rats

The mother's thyroid hormone status during gestation and the first few months after delivery can play a crucial role in maturation during the brain development of the child. Transient abnormalities in thyroid function at birth indicate developmental and cognitive disorders in adulthood. Choline supplementation during gestation and the perinatal period in rats causes long-lasting memory improvement in the offspring. However, it remains unclear whether choline is able to restore the deficits in rats with maternal hypothyroidism. The aim of this study was to evaluate the effects of choline supplementation on the alteration of cognitive-behavioral function, long-term potentiation (LTP), and morphological changes as well as apoptosis in pre-pubertal offspring rats. To induce hypothyroidism, 6-propyl-2-thiouracil was added to the drinking water from the 6th day of gestation to the 21st postnatal day (PND). Choline treatment was started twice a day on the first day of the gestation until PND 21 via gavage. LTP recording and Morris water maze (MWM) test were conducted at PND 28. Then, the rats were sacrificed to assess their brains. The results revealed that developmental thyroid hormone deficiency impaired spatial learning and memory and reduced LTP (both: P < 0.001). Choline treatment alleviated LTP (P < 0.001), as well as learning and memory deficits (P < 0.01) in both male and female hypothyroid rats. However, no significant changes were observed in the number of caspase-3 stained cells in choline-receiving hypothyroid groups. The results revealed that developmental thyroid hormone deficiency impaired spatial learning and memory and reduced LTP. Choline treatment alleviated LTP, as well as learning and memory deficits in both male and female hypothyroid rats.

Positive modulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors differentially alters spatial learning and memory in juvenile rats younger and older than three weeks

Remarkable performance improvements occur at the end of the third postnatal week in rodents tested in various tasks that require navigation according to spatial context. While alterations in hippocampal function at least partially subserve this cognitive advancement, physiological explanations remain incomplete. Previously, we discovered that developmental modifications to hippocampal glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in juvenile rats was related to more mature spontaneous alternation behavior in a symmetrical Y-maze. Moreover, a positive allosteric modulator of AMPA receptors enabled immature rats to alternate at rates seen in older animals, suggesting an excitatory synaptic limitation to hippocampal maturation. We then validated the Barnes maze for juvenile rats in order to test the effects of positive AMPA receptor modulation on a goal-directed spatial memory task. Here we report the effects of the AMPA receptor modulator, CX614, on spatial learning and memory in the Barnes maze. Similar to our prior report, animals just over 3 weeks of age display substantial improvements in learning and memory performance parameters compared to animals just under 3 weeks of age. A moderate dose of CX614 enabled immature animals to move more directly to the goal location, but only after 1 day of training. This performance improvement was observed on the second day of training with drug delivery or during a memory probe trial performed without drug delivery after the second day of training. Higher doses created more search errors, especially in more mature animals. Overall, CX614 provided modest performance benefits for immature rats in a goal-directed spatial memory task.

Repeated pre-exposure to morphine inhibited the amnesic effect of ethanol on spatial memory: Involvement of CaMKII and BDNF

Evidence has suggested that addiction and memory systems are related, but the signaling cascades underlying this interaction have not been completelyealed yet. The importance of calcium-calmodulin-dependent protein kinase II (CaMKII) and brain-derived neurotrophic factor (BDNF) in the memory processes and also in drug addiction has been previously established. In this present investigation, we examined the effects of repeated morphine pretreatment on impairment of spatial learning and memory acquisition induced by systemic ethanol administration in adult male rats. Also, we assessed how these drug exposures influence the expression level of CaMKII and BDNF in the hippocampus and amygdala. Animals were trained by a single training session of 8 trials, and a probe test containing a 60-s free-swim without a platform was administered 24 h later. Before training trials, rats were treated with a once-daily subcutaneous morphine injection for 3 days followed by a 5-day washout period. The results showed that pre-training ethanol (1 g/kg) impaired spatial learning and memory acquisition and down-regulated the mRNA expression of CaMKII and BDNF. The amnesic effect of ethanol was suppressed in morphine- (15 mg/kg/day) pretreated animals. Furthermore, the mRNA expression level of CaMKII and BDNF increased significantly following ethanol administration in morphine-pretreated rats. Conversely, this improvement in spatial memory acquisition was prevented by daily subcutaneous administration of naloxone (2 mg/kg) 15 min prior to morphine administration. Our findings suggest that sub-chronic morphine treatment reverses ethanol-induced spatial memory impairment, which could be explained by modulating CaMKII and BDNF mRNA expressions in the hippocampus and amygdala.

Antioxidant theranostic copolymer-mediated reduction in oxidative stress following traumatic brain injury improves outcome in a mouse model

Following a traumatic brain injury (TBI), excess reactive oxygen species (ROS) and lipid peroxidation products (LPOx) are generated and lead to secondary injury beyond the primary insult. A major limitation of current treatments is poor target engagement, which has prevented success in clinical trials. Thus, nanoparticle-based treatments have received recent attention because of their ability to increase accumulation and retention in damaged brain. Theranostic neuroprotective copolymers (NPC3) containing thiol functional groups can neutralize ROS and LPOx. Immediate administration of NPC3 following injury in a controlled cortical impact (CCI) mouse model provides a therapeutic window in reducing ROS levels at 2.08-20.83 mg/kg in males and 5.52-27.62 mg/kg in females. This NPC3-mediated reduction in oxidative stress improves spatial learning and memory in males, while females show minimal improvement. Notably, NPC3-mediated reduction in oxidative stress prevents the bilateral spread of necrosis in male mice, which was not observed in female mice and likely accounts for the sex-based spatial learning and memory differences. Overall, these findings suggest sex-based differences to oxidative stress scavenger nanoparticle treatments, and a possible upper threshold of antioxidant activity that provides therapeutic benefit in injured brain since female mice benefit from NPC3 treatment to a lesser extent than male mice.

Prevention of neurotoxicity and cognitive impairment induced by zinc nanoparticles by oral administration of saffron extract

The accumulation of relatively higher dose of zinc oxide nanoparticles in brain was reported to produce neurotoxicity. Indeed, nanoparticles have a high ability to penetrate biological membranes and be uptaken by cells, which may cause cell disorders and physiological dysfunctions. The aim of the current study was to evaluate, whether oral administration of saffron extract, in rats, can protect from neurotoxicity and behavioural disturbances induced by chronic administration of ZnO-NPs. Daily oral administration of ZnO-NPs was performed for 21 consecutive days to induce oxidative stress-like situation. Then after the saffron extract was concomitantly administrated in several rat groups to overcome the nanotoxicological effect induced by ZnO-NPs. In the frontal cortex, the hippocampus and the cerebellum, ZnO-NPs induced a H2 O2 -oxydative stress-like effect reflected in reduced enzymatic activities of catalase, superoxide dismutase and glutathione S-transferase, and decreased acetylcholinesterase activity. In addition, increased levels of proinflammatory interleukins IL-6 and IL-1-⍺ occurred in the hippocampus, reveal the existence of brain inflammation. The concomitant administration of saffron extract to animals exposed to ZnO-NPs prevented the enhanced anxiety-related to the behaviour in the elevated plus-maze test, the open field test and preserved spatial learning abilities in the Morris water maze. Moreover, animals exposed to ZnO-NPs and saffron showed abnormal activity of several antioxidant enzymes as well as acetylcholinesterase activity, an effect that may underly the preserved anxiety-like behaviour and spatial learning abilities observed in these animals. Saffron extract has a potential beneficial therapeutic effect: antioxidant, anti-inflammatory and neuroprotective agent.

Inhibition of Anaplastic Lymphoma Kinase (Alk) as Therapeutic Target to Improve Brain Function in Neurofibromatosis Type 1 (Nf1)

Neurofibromatosis type 1 (Nf1) is a neurodevelopmental disorder and tumor syndrome caused by loss of function mutations in the neurofibromin gene (Nf1) and is estimated to affect 100,000 people in the US. Behavioral alterations and cognitive deficits have been found in 50-70% of children with Nf1 and include specific problems with attention, visual perception, language, learning, attention, and executive function. These behavioral alterations and cognitive deficits are observed in the absence of tumors or macroscopic structural abnormalities in the central nervous system. No effective treatments for the behavioral and cognitive disabilities of Nf1 exist. Inhibition of the anaplastic lymphoma kinase (Alk), a kinase which is negatively regulated by neurofibromin, allows for testing the hypothesis that this inhibition may be therapeutically beneficial in Nf1. In this review, we discuss this area of research and directions for the development of alternative therapeutic strategies to inhibit Alk. Even if the incidence of adverse reactions of currently available Alk inhibitors was reduced to half the dose, we anticipate that a long-term treatment would pose challenges for efficacy, safety, and tolerability. Therefore, future efforts are warranted to investigate alternative, potentially less toxic and more specific strategies to inhibit Alk function.

Tirzepatide ameliorates spatial learning and memory impairment through modulation of aberrant insulin resistance and inflammation response in diabetic rats

Background: One of the typical symptoms of diabetes mellitus patients was memory impairment, which was followed by gradual cognitive deterioration and for which there is no efficient treatment. The anti-diabetic incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) were demonstrated to have highly neuroprotective benefits in animal models of AD. We wanted to find out how the GLP-1/GIP dual agonist tirzepatide affected diabetes's impairment of spatial learning memory. Methods: High fat diet and streptozotocin injection-induced diabetic rats were injected intraperitoneally with Tirzepatide (1.35 mg/kg) once a week. The protective effects were assessed using the Morris water maze test, immunofluorescence, and Western blot analysis. Golgi staining was adopted for quantified dendritic spines. Results: Tirzepatide significantly improved impaired glucose tolerance, fasting blood glucose level, and insulin level in diabetic rats. Then, tirzepatide dramatically alleviated spatial learning and memory impairment, inhibited Aβ accumulation, prevented structural damage, boosted the synthesis of synaptic proteins and increased dendritic spines formation in diabetic hippocampus. Furthermore, some aberrant changes in signal molecules concerning inflammation signaling pathways were normalized after tirzepatide treatment in diabetic rats. Finally, PI3K/Akt/GSK3β signaling pathway was restored by tirzepatide. Conclusion: Tirzepatide obviously exerts a protective effect against spatial learning and memory impairment, potentially through regulating abnormal insulin resistance and inflammatory responses.

Long-Term Effect of Moderate Hypoxia and Chronic Administration of Fluoxetine during the Neonatal Period on Cognitive and Stress-Hormonal Functions in Adult Male Rats

We studied the effect of moderate neonatal normobaric hypoxia on the indicators of spatial learning, memory, and reactivity of the hypothalamic-pituitary-adrenocortical system in adult male Wistar rats. The pharmacological effect of chronic injections of the serotonin reuptake inhibitor fluoxetine during the neonatal period on the studied behavioral and the physiological indices was evaluated. Hypoxia impaired spatial training, increased the short-term memory performance, but did not change long-term memory and stress indicator in response to its testing. The use of fluoxetine normalized learning, but did not change memory indicators and the stress-induced level of corticosterone in blood plasma in the hypoxic rats and control animals. New results indicate a protective effect of fluoxetine in the neonatal period under conditions of moderate normobaric hypoxia.

Investigations on learning and memory function in extended one-generation reproductive toxicity studies - when considered needed and based on what?

To justify investigations on learning and memory (L&M) function in extended one-generation reproductive toxicity studies (EOGRTS; Organization for Economic Co-operation and Development (OECD) test guideline (TG) 443) for registration under Registration, Evaluation, Authorization, and Restriction of Chemical (REACH), the European Chemicals Agency has referred to three publications based on which the Agency concluded that "perturbation of thyroid hormone signaling in offspring affects spatial cognitive abilities (learning and memory)" and "Therefore, it is necessary to conduct spatial learning and memory tests for F1 animals". In this paper, the inclusion of the requested L&M tests in an EOGRTS is challenged. In addition, next to the question on the validity of rodent models in general for testing thyroid hormone-dependent perturbations in brain development, the reliability of the publications specifically relied upon by the agency is questioned as these contain numerous fundamental errors in study methodology, design, and data reporting, provide contradicting results, lack crucial information to validate the results and exclude confounding factors, and finally show no causal relationship. Therefore, in our opinion, these publications cannot be used to substantiate, support, or conclude that decreases in blood thyroid (T4) hormone level on their own would result in impaired L&M in rats and are thus not adequate to use as fundament to ask for L&M testing as part of an EOGRTS.

The RNA cargo in small extracellular vesicles from chicken eggs is bioactive in C57BL/6 J mice and human peripheral blood mononuclear cells ex vivo

Small extracellular vesicles (sEVs) and their RNA cargo in milk are bioavailable in humans, pigs, and mice, and their dietary depletion and supplementation elicits phenotypes. Little is known about the content and biological activity of sEVs in foods of animal origin other than milk. Here we tested the hypothesis that sEVs in chicken eggs (Gallus gallus) facilitate the transfer of RNA cargo from an avian species to humans and mice, and their dietary depletion elicits phenotypes. sEVs were purified from raw egg yolk by ultracentrifugation and authenticated by transmission electron microscopy, nano-tracking device, and immunoblots. The miRNA profile was assessed by RNA-sequencing. Bioavailability of these miRNAs in humans was assessed by egg feeding study in adults, and by culturing human peripheral blood mononuclear cells (PBMCs) with fluorophore-labeled egg sEVs ex vivo. To further assess bioavailability, fluorophore-labeled miRNAs, encapsulated in egg sEVs, were administered to C57BL/6 J mice by oral gavage. Phenotypes of sEV RNA cargo depletion were assessed by feeding egg sEV and RNA-defined diets to mice and using spatial learning and memory in the Barnes and water mazes as experimental readouts. Egg yolk contained 6.30 × 10¹⁰ ± 6.06 × 10⁹ sEVs/mL, which harbored eighty-three distinct miRNAs. Human PBMCs internalized sEVs and their RNA cargo. Egg sEVs, loaded with fluorophore-labeled RNA and administered orally to mice, accumulated primarily in brain, intestine and lungs. Spatial learning and memory (SLM) was compromised in mice fed on egg sEV- and RNA-depleted diet compared to controls. Egg consumption elicited an increase of miRNAs in human plasma. We conclude that egg sEVs and their RNA cargo probably are bioavailable. The human study is registered as a clinical trial and accessible at https://www.isrctn.com/ISRCTN77867213.

Prenatal Exposure to Δ9-Tetrahydrocannabinol Affects Hippocampus-Related Cognitive Functions in the Adolescent Rat Offspring: Focus on Specific Markers of Neuroplasticity

Previous evidence suggests that prenatal exposure to THC (pTHC) derails the neurodevelopmental trajectories towards a vulnerable phenotype for impaired emotional regulation and limbic memory. Here we aimed to investigate pTHC effect on hippocampus-related cognitive functions and markers of neuroplasticity in adolescent male offspring. Wistar rats were exposed to THC (2 mg/kg) from gestational day 5 to 20 and tested for spatial memory, object recognition memory and reversal learning in the reinforce-motivated Can test and in the aversion-driven Barnes maze test; locomotor activity and exploration, anxiety-like behaviour, and response to natural reward were assessed in the open field, elevated plus maze, and sucrose preference tests, respectively. The gene expression levels of NMDA NR1-2A subunits, mGluR5, and their respective scaffold proteins PSD95 and Homer1, as well as CB1R and the neuromodulatory protein HINT1, were measured in the hippocampus. pTHC offspring exhibited deficits in spatial and object recognition memory and reversal learning, increased locomotor activity, increased NR1-, decreased NR2A- and PSD95-, increased mGluR5- and Homer1-, and augmented CB1R- and HINT1-hippocampal mRNA levels. Our data shows that pTHC is associated with specific impairment in spatial cognitive processing and effectors of hippocampal neuroplasticity and suggests novel targets for future pharmacological challenges.

Altered cognition and anxiety in adolescent offspring whose mothers underwent different-pattern maternal sleep deprivation, and cognition link to hippocampal expressions of Bdnf and Syt-1

Background

Inadequate sleep during pregnancy negatively affects the neural development of offspring. Previous studies have focused on the continuous sleep deprivation (CSD) paradigm, but the sleep pattern during late pregnancy is usually fragmented.

Objective

To compare the effects of CSD and fragmented sleep deprivation (FSD) in late pregnancy on emotion, cognition, and expression of synaptic plasticity-related proteins in offspring mice.

Methods

Pregnant CD-1 mice were either subjected to 3/6 h of CSD/FSD during gestation days 15-21, while those in the control group were left untreated. After delivery, the offspring were divided into five groups, i.e., control (CON), short or long CSD (CSD3h, CSD6h), and short or long FSD (FSD3h, FSD6h). When the offspring were 2 months old, the anxiety-like behavior level was tested using the open field (OF) and elevated plus maze (EPM) test, and spatial learning and memory were evaluated using the Morris water maze (MWM) test. The expression of hippocampal of brain-derived neurotrophic factor (Bdnf) and synaptotagmin-1 (Syt-1) was determined using RT-PCR and western blotting.

Results

The CSD6h, FSD3h, and FSD6h had longer latency, fewer center times in the OF test, less open arms time and fewer numbers of entries in the open arms of the EPM, longer learning distance swam and lower memory percentage of distance swam in the target quadrant in the MWM test, and decreased BDNF and increased Syt-1 mRNA and protein levels in the hippocampus. Compared to the CSD6h, the FSD3h and FSD6h had longer distance swam, a lower percentage of distance swam in the target quadrant, decreased BDNF, and increased Syt-1 mRNA and protein levels in the hippocampus.

Conclusion

The results suggested that maternal sleep deprivation during late pregnancy impairs emotion and cognition in offspring, and FSD worsened the cognitive performance to a higher extent than CSD. The observed cognitive impairment could be associated with the expression of altered hippocampal of Bdnf and Syt-1 genes.

Etomidate affects spatial learning and memory and neuronal apoptosis of rats via MAPK/ERK pathway

OBJECTIVE

To observe the effect of etomidate on spatial learning and memory and neuronal apoptosis in rats of different ages.

METHODS

The rats of different ages were divided into 3 age groups: juvenile (21-day old), adult (~3-months old) and elderly (~19-months old). Then, rats with similar age within a group were randomly divided into three subgroups, with 10 rats in each group. The experimental subgroups were intraperitoneally injected with etomidate (emulsion formulated, i.p. injection) at a dose of 5 mg/kg; the solvent control subgroups were given intraperitoneal injection of vehicle emulsion; and blank control subgroups received laparoscopic injection of normal saline. The rats' learning and memory ability was tested by Morris water maze. The tissue sections of each group's hippocampus were analyzed by H&E staining. The apoptosis of hippocampal cells was detected by TUNEL staining. MAPK expression in hippocampus was tested by Western blot.

RESULTS

Etomidate significantly extended the escape latency and reduced the platform crossings and the swimming time at original platform of juvenile rats, indicating that the spatial learning and memory function of juvenile rats can be affected by etomidate. However, etomidate had no effect on spatial learning and memory in adult and elderly rats. There were no obvious abnormalities in number of neurons and morphology of vertebral cells in the hippocampus of all experimental subgroups when compared with those of corresponding blank control subgroups. There was no statistically significant difference in apoptosis index of the hippocampal tissue between the experimental subgroups and corresponding blank control subgroups (P>0.05). Within juvenile group, the expression of p-ERK in the hippocampus of experimental subgroup was remarkably lower than that of solvent control subgroup and blank control subgroup (P<0.05), while there were no significant differences in p-p38 and p-JNK expressions among the three subgroups of juvenile rats (P>0.05). The expressions of p-ERK, p-p38 and p-JNK in adult and elderly rats were not affected by etomidate.

CONCLUSION

Etomidate may have certain effects on spatial learning and memory in juvenile rats but not in adult and elderly rats. Etomidate affects neither the number of neurons in the CA1 area of the hippocampus nor the morphology of vertebral cells and did not cause the apoptosis of nerve cells. The mechanism of etomidate influence on the spatial learning and memory function of young rats may connect with the inhibition of MAPK/ERK pathway.

Loss of Ca(V)1.3 RNA editing enhances mouse hippocampal plasticity, learning, and memory

L-type Ca_V1.3 calcium channels are expressed on the dendrites and soma of neurons, and there is a paucity of information about its role in hippocampal plasticity. Here, by genetic targeting to ablate Ca_V1.3 RNA editing, we demonstrate that unedited Ca_V1.3^ΔECS mice exhibited improved learning and enhanced long-term memory, supporting a functional role of RNA editing in behavior. Significantly, the editing paradox that functional recoding of Ca_V1.3 RNA editing sites slows Ca²⁺-dependent inactivation to increase Ca²⁺ influx but reduces channel open probability to decrease Ca²⁺ influx was resolved. Mechanistically, using hippocampal slice recordings, we provide evidence that unedited Ca_V1.3 channels permitted larger Ca²⁺ influx into the hippocampal pyramidal neurons to bolster neuronal excitability, synaptic transmission, late long-term potentiation, and increased dendritic arborization. Of note, RNA editing of the Ca_V1.3 IQ-domain was found to be evolutionarily conserved in mammals, which lends support to the importance of the functional recoding of the Ca_V1.3 channel in brain function.

Examining the Effect of Increased Aerobic Exercise in Moderately Fit Adults on Psychological State and Cognitive Function

Regular physical exercise can decrease the risk for obesity, diabetes, and cardiovascular disease, increase life expectancy, and promote psychological health and neurocognitive functioning. Cross-sectional studies show that cardiorespiratory fitness level (VO2 max) is associated with enhanced brain health, including improved mood state and heightened cognitive performance. Interventional studies are consistent with these cross-sectional studies, but most have focused on low-fit populations. Few such studies have asked if increasing levels of physical activity in moderately fit people can significantly enhance mood, motivation, and cognition. Therefore, the current study investigated the effects of increasing aerobic exercise in moderately fit individuals on psychological state and cognitive performance. We randomly assigned moderately fit healthy adults, 25-59 years of age, who were engaged in one or two aerobic exercise sessions per week to either maintain their exercise regimen (n = 41) or increase their exercise regimen (i.e., 4-7 aerobic workouts per week; n = 39) for a duration of 3 months. Both before and after the intervention, we assessed aerobic capacity using a modified cardiorespiratory fitness test, and hippocampal functioning via various neuropsychological assessments including a spatial navigation task and the Mnemonic Similarity Task as well as self-reported measures including the Positive and Negative Affect Scale, Beck Anxiety Inventory, State-Trait Anxiety Inventory, Perceived Stress Scale, Rumination Scale, Eating Disorders Examination, Eating Attitudes Test, Body Attitudes Test, and Behavioral Regulation of Exercise Questionnaire. Consistent with our initial working hypotheses, we found that increasing exercise significantly decreased measures of negative affect, including fear, sadness, guilt, and hostility, as well as improved body image. Further, we found that the total number of workouts was significantly associated with improved spatial navigation abilities and body image as well as reduced anxiety, general negative affect, fear, sadness, hostility, rumination, and disordered eating. In addition, increases in fitness levels were significantly associated with improved episodic memory and exercise motivation as well as decreased stress and disordered eating. Our findings are some of the first to indicate that in middle-aged moderately-fit adults, continuing to increase exercise levels in an already ongoing fitness regimen is associated with additional benefits for both psychological and cognitive health.

Spatial Learning Promotes Adult Neurogenesis in Specific Regions of the Zebrafish Pallium

Adult neurogenesis could be considered as a homeostatic mechanism that accompanies the continuous growth of teleost fish. As an alternative but not excluding hypothesis, adult neurogenesis would provide a form of plasticity necessary to adapt the brain to environmental challenges. The zebrafish pallium is a brain structure involved in the processing of various cognitive functions and exhibits extended neurogenic niches throughout the periventricular zone. The involvement of neuronal addition as a learning-related plastic mechanism has not been explored in this model, yet. In this work, we trained adult zebrafish in a spatial behavioral paradigm and evaluated the neurogenic dynamics in different pallial niches. We found that adult zebrafish improved their performance in a cue-guided rhomboid maze throughout five daily sessions, being the fish able to relearn the task after a rule change. This cognitive activity increased cell proliferation exclusively in two pallial regions: the caudal lateral pallium (cLP) and the rostral medial pallium (rMP). To assessed whether learning impinges on pallial adult neurogenesis, mitotic cells were labeled by BrdU administration, and then fish were trained at different periods of adult-born neuron maturation. Our results indicate that adult-born neurons are being produced on demand in rMP and cLP during the learning process, but with distinct critical periods among these regions. Next, we evaluated the time course of adult neurogenesis by pulse and chase experiments. We found that labeled cells decreased between 4 and 32 dpl in both learning-sensitive regions, whereas a fraction of them continues proliferating over time. By modeling the population dynamics of neural stem cells (NSC), we propose that learning increases adult neurogenesis by two mechanisms: driving a chained proliferation of labeled NSC and rescuing newborn neurons from death. Our findings highlight adult neurogenesis as a conserved source of brain plasticity and shed light on a rostro-caudal specialization of pallial neurogenic niches in adult zebrafish.

Decoupling astrocytes in adult mice impairs synaptic plasticity and spatial learning

The mechanisms by which astrocytes modulate neural homeostasis, synaptic plasticity, and memory are still poorly explored. Astrocytes form large intercellular networks by gap junction coupling, mainly composed of two gap junction channel proteins, connexin 30 (Cx30) and connexin 43 (Cx43). To circumvent developmental perturbations and to test whether astrocytic gap junction coupling is required for hippocampal neural circuit function and behavior, we generate and study inducible, astrocyte-specific Cx30 and Cx43 double knockouts. Surprisingly, disrupting astrocytic coupling in adult mice results in broad activation of astrocytes and microglia, without obvious signs of pathology. We show that hippocampal CA1 neuron excitability, excitatory synaptic transmission, and long-term potentiation are significantly affected. Moreover, behavioral inspection reveals deficits in sensorimotor performance and a complete lack of spatial learning and memory. Together, our findings establish that astrocytic connexins and an intact astroglial network in the adult brain are vital for neural homeostasis, plasticity, and spatial cognition.

Tau Pathology Profile Across a Parietal-Hippocampal Brain Network Is Associated With Spatial Reorientation Learning and Memory Performance in the 3xTg-AD Mouse

In early Alzheimer's disease (AD) spatial navigation is one of the first impairments to emerge; however, the precise cause of this impairment is unclear. Previously, we showed that, in a mouse model of tau and amyloid beta (Aβ) aggregation, getting lost represents, at least in part, a failure to use distal cues to get oriented in space and that impaired parietal-hippocampal network level plasticity during sleep may underlie this spatial disorientation. However, the relationship between tau and amyloid beta aggregation in this brain network and impaired spatial orientation has not been assessed. Therefore, we used several approaches, including canonical correlation analysis and independent components analysis tools, to examine the relationship between pathology profile across the parietal-hippocampal brain network and spatial reorientation learning and memory performance. We found that consistent with the exclusive impairment in 3xTg-AD 6-month female mice, only 6-month female mice had an ICA identified pattern of tau pathology across the parietal-hippocampal network that were positively correlated with behavior. Specifically, a higher density of pTau positive cells predicted worse spatial learning and memory. Surprisingly, despite a lack of impairment relative to controls, 3-month female, as well as 6- and 12- month male mice all had patterns of tau pathology across the parietal-hippocampal brain network that are predictive of spatial learning and memory performance. However, the direction of the effect was opposite, a negative correlation, meaning that a higher density of pTau positive cells predicted better performance. Finally, there were not significant group or region differences in M78 density at any of the ages examined and ICA analyses were not able to identify any patterns of 6E10 staining across brain regions that were significant predictors of behavioral performance. Thus, the pattern of pTau staining across the parietal-hippocampal network is a strong predictor of spatial learning and memory performance, even for mice with low levels of tau accumulation and intact spatial re-orientation learning and memory. This suggests that AD may cause spatial disorientation as a result of early tau accumulation in the parietal-hippocampal network.

Behavioural Functions and Cerebral Blood Flow in a P301S Tauopathy Mouse Model: A Time-Course Study

Tauopathies refer to a group of neurodegenerative diseases with intracellular accumulation of hyperphosphorylated and aggregated microtubule-associated protein tau (MAPT) in neurons and glial cells. PS19 mice bearing the MAPT P301S mutation have been used to mimic human frontotemporal lobar degeneration. The present study was designed to systematically investigate how behavioural functions, resting cerebral blood flow (CBF) and tau pathology change in PS19 mice at 2, 4, 6, 8 and 12 months of age in a single study under one experimental condition, allowing for the cumulative assessment of age- and genotype-dependent changes. PS19 mice displayed hyperactivity and reduced anxiety levels with age, early and persistent spatial working memory deficits and reduced resting neocortical CBF. Immunoblotting and immunohistochemistry revealed age-related increases in phosphorylated tau in the brain of PS19 mice. In conclusion, the present study, for the first time, cumulatively demonstrated the time-course of changes in behavioural functions, resting CBF and tau pathology in a P301S tauopathy mouse model through their developmental span. This information provides further evidence for the utility of this model to study neurodegenerative events associated with tauopathy and tau dysfunction.

Oxidized Milk Induces Spatial Learning and Memory Impairment by Altering Gut Microbiota in Offspring Mice during Pregnancy and Lactation

Early adverse diet exposures are known to be associated with increased risk of learning and memory injury in offspring, yet whether oxidized milk is involved in such an effect has been largely unknown. Here, we focused on oxidized milk intake in mice during pregnancy and lactation to measure the changes in the learning and memory ability in offspring and also probed into the relevant association with gut microbiota. Milk was oxidized with H₂O₂-Cu or HClO, resulting in different degrees of oxidative damage. KM female mice were fed H₂O₂-Cu, HClO, or normal control diets immediately after caging until their offspring were 3-weeks old. Behavioral tests were then performed to test the learning and memory ability, and 16S rRNA sequencing was completed with harvested fecal contents. As analyzed, fecal microflora in mice with oxidized milk was affected, mainly reflected in decreased mucin-degrading bacteria, Akkermansia and Lactobacillus, and in reversely increased pro-inflammatory bacteria Shigella, pathobiont Mucispirillum, nervous associated bacteria Ruminococcus, Escherichia, and Desulfovibrio. In the meantime, the inflammation developed in mice was aggravated accompanied by increased expression of relevant genes, while the genes and proteins associated with the learning and memory ability were down-regulated. Further behavioral tests proved impairment of the learning and memory ability in offspring. In general, milk of oxidative damage is a risk factor of the impaired transgenerational ability in learning and memory, which is associated with gut microbiota and intestinal mucosa conditions. This finding may help support the potential of early adverse diet as a harmful factor in learning and memory.

Activation of a hippocampal CREB-pCREB-miRNA-MEF2 axis modulates individual variation of spatial learning and memory capability

Phenotypic variation is a fundamental prerequisite for cell and organism evolution by natural selection. Whereas the role of stochastic gene expression in phenotypic diversity of genetically identical cells is well studied, not much is known regarding the relationship between stochastic gene expression and individual behavioral variation in animals. We demonstrate that a specific miRNA (miR-466f-3p) is upregulated in the hippocampus of a portion of individual inbred mice upon a Morris water maze task. Significantly, miR-466f-3p positively regulates the neuron morphology, function and spatial learning, and memory capability of mice. Mechanistically, miR-466f-3p represses translation of MEF2A, a negative regulator of learning/memory. Finally, we show that varied upregulation of hippocampal miR-466f-3p results from randomized phosphorylation of hippocampal cyclic AMP (cAMP)-response element binding (CREB) in individuals. This finding of modulation of spatial learning and memory via a randomized hippocampal signaling axis upon neuronal stimulation represents a demonstration of how variation in tissue gene expression lead to varied animal behavior.

Effects of fish oil supplementation on spatial memory in rats with pilocarpine-induced epilepsy assessed using the Morris Water Maze test

OBJECTIVE

Patients with temporal lobe epilepsy (TLE) are at high risk of experiencing cognitive impairment. Such dysfunction is also observed in an animal model of TLE, the rat model of pilocarpine-induced epilepsy.

METHODS

We investigated the effects of fish oil supplementation on spatial memory in rats with pilocarpine-induced epilepsy using the Morris Water Maze (MWM) test.

RESULTS

Although rats with pilocarpine-induced epilepsy treated with fish oil learned the platform location significantly faster by Day 7 of the acquisition phase, spatial memory performance of these rats was unaffected by fish oil supplementation during probe trials.

SIGNIFICANCE

Our study provides insights into the importance of considering nutraceutical strategies for enhancing cognitive abilities in patients with TLE.

Attractin Gene Deficiency in Rats Leads to Impairments in Both Activity and Spatial Learning and Memory

Attractin (ATRN), an autosomal recessive gene that is widely distributed in the brain, is involved in the execution of a variety of brain functions and associated with certain neuropsychiatric disorders. Here, we introduce a novel rat strain harboring a mutation in ATRN that was generated by knocking in ATRN-G505C via the CRISPR/Cas9 system. We assessed the behavioral performance of these mutant ATRN knock-in rats. The G505C mutation was introduced into exon 9, and a synthetic primer was inserted into introns 8-9 for genotyping. The 505th amino acid, a Gly (G) residue, was mutated to a Cys (C) residue, i.e., GGC was mutated to TGC. Behavioral experiments showed that homozygous ATRN rats spent significantly more time searching for the escape platform in the acquisition trial and significantly less time in the target area in the probe trial in the Morris water maze (MWM) test and traveled a significantly shorter distance in the open field test (OFT) than wild-type rats. In addition, Western blot analysis and immunohistochemistry showed that rats with the mutant ATRN gene exhibited significantly reduced expression of brain-derived neurotrophic factor (BDNF). In summary, our results indicate that mutations in the ATRN gene directly lead to learning and memory impairments and slight motor deficits. These findings provide new clues for the mechanism by which mutant ATRN induces neurodegenerative changes.

Sedentary Life and Reduced Mastication Impair Spatial Learning and Memory and Differentially Affect Dentate Gyrus Astrocyte Subtypes in the Aged Mice

To explore the impact of reduced mastication and a sedentary lifestyle on spatial learning and memory in the aged mice, as well as on the morphology of astrocytes in the molecular layer of dentate gyrus (MolDG), different masticatory regimens were imposed. Control mice received a pellet-type hard diet, while the reduced masticatory activity group received a pellet diet followed by a powdered diet, and the masticatory rehabilitation group received a pellet diet, followed by powder diet and then a pellet again. To mimic sedentary or active lifestyles, mice were housed in an impoverished environment of standard cages or in an enriched environment. The Morris Water Maze (MWM) test showed that masticatory-deprived group, regardless of environment, was not able to learn and remember the hidden platform location, but masticatory rehabilitation combined with enriched environment recovered such disabilities. Microscopic three-dimensional reconstructions of 1,800 glial fibrillary acidic protein (GFAP)-immunolabeled astrocytes from the external third of the MolDG were generated using a stereological systematic and random sampling approach. Hierarchical cluster analysis allowed the characterization into two main groups of astrocytes with greater and lower morphological complexities, respectively, AST1 and AST2. When compared to compared to the hard diet group subjected to impoverished environment, deprived animals maintained in the same environment for 6 months showed remarkable shrinkage of astrocyte branches. However, the long-term environmental enrichment (18-month-old) applied to the deprived group reversed the shrinkage effect, with significant increase in the morphological complexity of AST1 and AST2, when in an impoverished or enriched environment. During housing under enriched environment, complexity of branches of AST1 and AST2 was reduced by the powder diet (pellet followed by powder regimes) in young but not in old mice, where it was reversed by pellet diet (pellet followed by powder and pellet regime again). The same was not true for mice housed under impoverished environment. Interestingly, we were unable to find any correlation between MWM data and astrocyte morphological changes. Our findings indicate that both young and aged mice subjected to environmental enrichment, and under normal or rehabilitated masticatory activity, preserve spatial learning and memory. Nonetheless, data suggest that an impoverished environment and reduced mastication synergize to aggravate age-related cognitive decline; however, the association with morphological diversity of AST1 and AST2 at the MolDG requires further investigation.

Specialized spatial cognition is associated with reduced cognitive senescence in a food-caching bird

Senescence, the gradual reduction and loss of function as organisms age, is a widespread process that is especially pronounced in cognitive abilities. Senescence appears to have a genetic basis and can be affected by evolutionary processes. If cognitive senescence is shaped by natural selection, it may be linked with selection on cognitive abilities needed for survival and reproduction, such that species where fitness is directly related to cognitive abilities should evolve delayed cognitive senescence likely resulting in higher lifetime fitness. We used wild food-caching mountain chickadees, which rely on specialized spatial cognition to recover thousands of food caches annually, to test for cognitive senescence in spatial learning and memory and reversal spatial learning and memory abilities. We detected no signs of age-related senescence in spatial cognitive performance on either task in birds ranging from 1 to 6 years old; older birds actually performed better on spatial learning and memory tasks. Our results therefore suggest that cognitive senescence may be either delayed (potentially appearing after 6 years) or negligible in species with strong selection on cognitive abilities and that food-caching species may present a useful model to investigate mechanisms associated with cognitive senescence.

Comparison between touchscreen operant chambers and water maze to detect early prefrontal dysfunction in mice

The relative lack of sensitive and clinically valid tests of rodent behavior might be one of the reasons for the limited success of the clinical translation of preclinical Alzheimer's disease (AD) research findings. There is a general interest in innovative behavioral methodology, and protocols have been proposed for touchscreen operant chambers that might be superior to existing cognitive assessment methods. We assessed and analyzed touchscreen performance in several novel ways to examine the possible occurrence of early signs of prefrontal (PFC) functional decline in the APP/PS1 mouse model of AD. Touchscreen learning performance was compared between APP/PS1-21 mice and wildtype littermates on a C57BL/6J background at 3, 6 and 12 months of age in parallel to the assessment of spatial learning, memory and cognitive flexibility in the Morris water maze (MWM). We found that older mice generally needed more training sessions to complete the touchscreen protocol than younger ones. Older mice also displayed defects in MWM working memory performance, but touchscreen protocols detected functional changes beginning at 3 months of age. Histological changes in PFC of APP/PS1 mice indeed occurred as early as 3 months. Our results suggest that touchscreen operant protocols are more sensitive to PFC dysfunction, which is of relevance to the use of these tasks and devices in preclinical AD research and experimental pharmacology.

Prenatal urban traffic noise exposure impairs spatial learning and memory and reduces glucocorticoid receptor expression in the hippocampus of male rat offspring

Introduction

Exposure to noise stress during early life may permanently affect the structure and function of the central nervous system. The aim of this study was to evaluate the effects of prenatal exposure to urban traffic noise on the spatial learning and memory of the rats' offspring and the expression of glucocorticoid receptors (GRs) in their hippocampi.

Methods

Three g\roups of pregnant rats were exposed to recorded urban traffic noise for 1, 2 or 4 h/day during the last week of pregnancy. At the age of 45 days, their male offspring were introduced to the Morris water maze (MWM) for assessment of spatial learning and memory. The corticosterone levels were measured in the offspring's sera by radioimmunoassay, and the relative expression of glucocorticoid and mineralocorticoid receptors (MRs) in their hippocampi was evaluated via RT-PCR.

Results

Facing urban traffic noise for 2 and 4 h/day during the third trimester of pregnancy caused the offspring to spend more time and to travel a larger distance than the controls to find the target platform. Analogously, these two groups were inferior to their control counterparts in the probe test. Also, prenatal noise stress elevated the corticosterone concentration in the sera of the rats' offspring and dose-dependently decreased the relative expression of the mRNA of both GRs and MRs in their hippocampi.

Conclusions

Urban traffic noise exposure during the last trimester of pregnancy impairs spatial learning and memory of rat offspring and reduces GRs and MRs gene expression in the hippocampus.

Over-expressed MST1 impaired spatial memory via disturbing neural oscillation patterns in mice

The activated mammalian Ste20-like serine/threonine kinases 1 (MST1) was found in the central nervous system diseases, such as cerebral ischemia, stroke and ALS, which were related with cognitions. The aim of this study was to examine the effect of elevated MST1 on memory functions in C57BL/6J mice. We also explored the underlying mechanism about the pattern alteration of neural oscillations, closely associated with cognitive dysfunctions, at different physiological rhythms, which were related to a wide range of basic and higher-level cognitive activities. A mouse model of the adeno-associated virus (AAV)-mediated overexpression of MST1 was established. The behavioral experiments showed that spatial memory was significantly damaged in MST1 mice. The distribution of either theta or gamma power was clearly disturbed in MST1 animals. Moreover, the synchronization in both theta and gamma rhythms, and theta-gamma cross-frequency coupling were significantly weakened in MST1 mice. In addition, the expressions of GABAA receptor, GAD67 and parvalbumin (PV) were obviously increased in MST1 mice. Meanwhile, blocking MST1 activity could inhibit the activation of FOXO3a and YAP. The above data suggest that MST1-overexpression may induce memory impairments via disturbing the patterns of neural activities, which is possibly associated with the abnormal GABAergic expression level.

Anodal Transcranial Direct Current Stimulation Can Improve Spatial Learning and Memory and Attenuate Aβ42 Burden at the Early Stage of Alzheimer's Disease in APP/PS1 Transgenic Mice

Alzheimer’s disease (AD) is an irreversible progressive neurodegenerative disease. Intervention in the early stage of AD is a new path for AD treatment that is being explored. The behavioral and pathological effects of anodal transcranial direct current stimulation (AtDCS) at the early stage of AD in the mouse model, amyloid precursor protein (APP)/presenilin-1 (PS1) transgenic mice, were investigated based on our previous studies. Thirty-three 6-month-old male APP/PS1 mice were randomly divided into the model group (AD group), model + sham stimulation group (ADST group) and stimulation group (ADT group). Eleven 6-month-old male C57 wild-type mice were randomly selected as a control group (CTL group). The ADT group received 10 AtDCS sessions. The Morris water maze (MWM) task and novel object recognition (NOR) task were used to test mouse memory. Nissl staining, Western blot (WB), immunohistochemistry and immunofluorescence staining of β-amyloid (Aβ₄₂), glial fibrillary acidic protein (GFAP) and NF200 were conducted for pathological analysis. The ADT group and the CTL group had a shorter escape latency and more platform-region crossings than the AD group and ADST group in the MWM. There was no significant difference in the discrimination index among the groups in the NOR task. Pathological analysis showed visible differences between the AD group and ADT group. This study revealed that early-stage APP/PS1 transgenic mice did not show recognition memory impairment. AtDCS effectively improved spatial learning and memory in the early-stage APP/PS1 transgenic mouse model of AD, alleviating Aβ burden and having a protective effect on neurons. AtDCS could improve AD-related symptoms by activating many glial cells to promote the degradation and clearance of Aβ or directly affecting production and degradation of Aβ to reduce glial activation. AtDCS is an effective means of early intervention in the early stage of AD.

3,4,5-Tricaffeoylquinic acid induces adult neurogenesis and improves deficit of learning and memory in aging model senescence-accelerated prone 8 mice

Caffeoylquinic acid (CQA) is a natural polyphenol with evidence of antioxidant and neuroprotective effects and prevention of deficits in spatial learning and memory. We studied the cognitive-enhancing effect of 3,4,5-tricaffeoylquinic acid (TCQA) and explored its cellular and molecular mechanism in the senescence-accelerated mouse prone 8 (SAMP8) model of aging and Alzheimer's disease as well as in human neural stem cells (hNSCs). Mice were fed with 5 mg/kg of TCQA for 30 days and were tested in the Morris water maze (MWM). Brain tissues were collected for immunohistochemical detection of bromodeoxyuridine (BrdU) to detect activated stem cells and newborn neurons. TCQA-treated SAMP8 exhibited significantly improved cognitive performance in MWM compared to water-treated SAMP8. TCQA-treated SAMP8 mice also had significantly higher numbers of BrdU+/glial fibrillary acidic protein (GFAP+) and BrdU+/Neuronal nuclei (NeuN+) cells in the dentate gyrus (DG) neurogenic niche compared with untreated SAMP8. In hNSCs, TCQA induced cell cycle arrest at G0/G1, actin cytoskeleton organization, chromatin remodeling, neuronal differentiation, and bone morphogenetic protein signaling. The neurogenesis promoting effect of TCQA in the DG of SAMP8 mice might explain the cognition-enhancing influence of TCQA observed in our study, and our hNSCs in aggregate suggest a therapeutic potential for TCQA in aging-associated diseases.

Genomic and Phenotypic Analyses Reveal Mechanisms Underlying Homing Ability in Pigeon

The homing pigeon was selectively bred from the domestic pigeon for a homing ability over long distances, a very fascinating but complex behavioral trait. Here, we generate a total of 95 whole genomes from diverse pigeon breeds. Comparing the genomes from the homing pigeon population with those from other breeds identifies candidate positively selected genes, including many genes involved in the central nervous system, particularly spatial learning and memory such as LRP8. Expression profiling reveals many neuronal genes displaying differential expression in the hippocampus, which is the key organ for memory and navigation and exhibits significantly larger size in the homing pigeon. In addition, we uncover a candidate gene GSR (encoding glutathione-disulfide reductase) experiencing positive selection in the homing pigeon. Expression profiling finds that GSR is highly expressed in the wattle and visual pigment cell layer, and displays increased expression levels in the homing pigeon. In vitro, a magnetic field stimulates increases in calcium ion concentration in cells expressing pigeon GSR. These findings support the importance of the hippocampus (functioning in spatial memory and navigation) for homing ability, and the potential involvement of GSR in pigeon magnetoreception.

Sevoflurane postconditioning improves spatial learning and memory ability involving mitochondrial permeability transition pore in hemorrhagic shock and resuscitation rats

BACKGROUND

Hemorrhagic shock induces the cognitive deficiency. Sevoflurane postconditioning has been documented to provide neuroprotection against ischemic-reperfusion injury by suppressing apoptosis. Mitochondrial permeability transition pore (mPTP) plays an important role in apoptosis, but it is unknown if the protective effect of sevoflurane postconditioning on hemorrhagic shock and resuscitation is associated with the change of mPTP opening. Hence, the aim of the study was to find out the precise mechanism of the sevoflurane postconditioning.

METHODS

Sprague Dawley rats were subjected to hemorrhage shock for 60 min and then exposed to 2.4% sevoflurane for 30 min at the instant of reperfusion. Additionally, an opener (atractyloside) or an inhibitor (cyclosporine A) of mPTP was used in the animal model before sevoflurane postconditioning. Rats were randomly assigned into groups of Sham, Shock, Shock+Sevoflurane, Shock+Atractyloside, Shock+Sevoflurane+Atractyloside, Shock+Cyclosporin A, and Shock+Sevoflurane+Cyclosporin A treatment. Rat behavior was assessed for 5 days by Morris water maze 72 hr after surgery, and then hippocampus CA1 region was immunohistochemically stained. Brains were harvested 24 hr after surgery to detect the protein expression levels of Bcl-2, Bax, and cytochrome C by Western blot, the changes of mPTP opening, and mitochondrial membrane potential (MMP).

RESULTS

We found that sevoflurane postconditioning significantly improved rats' spatial learning and memory ability, down-regulated the expression of Bax, cytochrome C, and caspase-3, up-regulated the expression of Bcl-2, decreased the mPTP opening, and increased the MMP. The neuroprotective effect of sevoflurane postconditioning was abolished by atractyloside, but cyclosporin A played the similar protective role as sevoflurane postconditioning.

CONCLUSION

These findings proved that sevoflurane postconditioning improved spatial learning and memory ability in hemorrhage shock and resuscitation rats, the mechanism of which may be related to block mPTP opening, increase MMP, and reduce neuron apoptosis in the hippocampus.

Dexmedetomidine Promotes Hippocampal Neurogenesis and Improves Spatial Learning and Memory in Neonatal Rats

Background

Dexmedetomidine (Dex) is a highly selective α2-adrenoceptor agonist used as an off-label medication for pediatric sedation and analgesia. Recently, Dex was reported to exhibit neuroprotective efficacy in several brain injury models. Here we investigate whether neonatal Dex administration promotes hippocampal neurogenesis and enhances hippocampus-dependent spatial learning and memory under physiological conditions.

Methods

Postnatal day 7 (P7) pups were administered saline (vehicle control) or Dex (10, 20, or 40 µg/kg) by intraperitoneal injection. Neurogenesis and astrogenesis were examined in brain slices by BrdU immunostaining on P8 and changes in the expression levels of GDNF, NCAM, CREB, PSD95, and GAP43 were assessed by Western blotting on P35, respectively. Open field and Morris water maze (MWM) tests were conducted from P28 to P36 in order to assess effects on general motor activity and spatial learning, respectively.

Results

Dexmedetomidine at 20 µg/kg significantly enhanced neurogenesis and astrogenesis in hippocampus and upregulated GDNF, NCAM, CREB, PSD95, and GAP43 compared to vehicle and other Dex doses. Moreover, 20 µg/kg Dex-injected rats showed no changes in motor or anxiety-like behavior but performed better in the MWM test compared to all other groups.

Conclusion

Neonatal injection of Dex (20 µg/kg) enhances spatial learning and memory in rat pups, potentially by promoting hippocampal neurogenesis and synaptic plasticity via activation of GDNF/NCAM/CREB signaling.

The effect of preventive exercise on the neuroprotection in 6-hydroxydopamine-lesioned rat brain

Parkinson's disease is characterized by neurodegeneration and learning deficiency. Physical exercise can alleviate these symptoms by increasing the expression of some effective and relevant factors. The preventive effect of 16-week treadmill running in a rat model of Parkinson's disease, before 6-hydroxydopamine (6-OHDA) induction, was assessed. Experimental groups consisted of sedentary (SED), SED+6-OHDA, exercised (EX), and EX+6-OHDA rats. Forty-eight hours after the last session of exercise, 6-OHDA was injected into the medial forebrain bundle (MFB). One week after the injection, behavioral tests, including spatial learning and memory, were assessed through Morris water maze (MWM) and apomorphine-induced rotation. Three weeks after the injection, mRNA expression and protein levels of the transcriptional co-activator peroxisome-proliferator-activated receptor-γ co-activator-1α (PGC-1α), fibronectin type III domain-containing protein 5 (FNDC5), brain-derived neurotrophic factor (BDNF), and tyrosine hydroxylase (TH) were measured in the striatum and the hippocampus of rats by applying real-time PCR and Western blotting. The findings indicate that exposure to 6-OHDA leads to impairments in behavioral and molecular functions. Exercise training prevents and reduces the symptoms caused by dopamine toxins. The results suggest that treadmill running can exert neuroprotective and have preventive effects to reduce Parkinson's disease symptoms. Novelty Parkinson's disease impairs spatial learning and memory. Parkinson's disease reduced levels of PGC-1α, FNDC5, and BDNF and increased neurodegeneration in the striatum and the hippocampus. Treadmill running before disease attenuated 6-OHDA-induced memory deficit and elevated neuroprotection. Exercise has multiple effects on memory and biochemical factors.

Prenatal exposure to artificial food colorings alters NMDA receptor subunit concentrations in rat hippocampus

Exposure to artificial food color additives (AFCAs) has been implicated in the etiology of certain childhood hyperactivity and learning disabilities. N-methyl-D-aspartate receptors and alpha-7 nicotinic acetylcholine receptor (α7 nAChR) are involved in learning and memory. We administered a mixture of AFCAs (erythrosine, ponceau 4R, allura red AC, sunset yellow FCF, tartrazine, amaranth, brilliant blue, azorubine, and indigotine) to female rats during gestation to investigate the effects of prenatal exposure to AFCAs on neurobehavior, spatial learning, and memory in their offspring. We also investigated whether AFCAs modulate NR2A, NR2B, and α7 nAChR protein levels in their offsprings' hippocampi. Although spatial learning and memory were not altered, the offspring of rats exposed to AFCAs exhibited decreased motivation and increased despair-related behavior. NR2A and NR2B protein levels were significantly reduced in female offspring in the experimental group (p < 0.05), whereas α7 nAChR level was not significantly altered. Our results suggest that prenatal exposure to AFCAs may lead to sex-dependent alterations in glutamatergic signaling which may continue into adolescence.

The Growing Evidence for the Importance of the Otoliths in Spatial Memory

Many studies have demonstrated that vestibular sensory input is important for spatial learning and memory. However, it has been unclear what contributions the different parts of the vestibular system - the semi-circular canals and otoliths - make to these processes. The advent of mutant otolith-deficient mice has made it possible to isolate the relative contributions of the otoliths, the utricle and saccule. A number of studies have now indicated that the loss of otolithic function impairs normal spatial memory and also impairs the normal function of head direction cells in the thalamus and place cells in the hippocampus. Epidemiological studies have also provided evidence that spatial memory impairment with aging, may be linked to saccular function. The otoliths may be important in spatial cognition because of their evolutionary age as a sensory detector of orientation and the fact that velocity storage is important to the way that the brain encodes its place in space.

Berberine Ameliorates Spatial Learning Memory Impairment and Modulates Cholinergic Anti-Inflammatory Pathway in Diabetic Rats

Background: Cognitive impairment caused by diabetes has been recognized. Berberine is well known for its resistance to peripheral lesions, but it is rarely used for the treatment of spatial learning and memory caused by diabetes. This study explored the mechanism of berberine to alleviate cognitive impairment via the cholinergic anti-inflammatory and insulin signaling pathways.

Methods: Morris water maze was used to appraise spatial learning and memory. Positron-emission tomography (PET) imaging was adopted to detect the transport of glucose, and blood/cerebrospinal fluid (CSF) glucose was checked using commercial blood glucose meter. Insulin level was measured by ELISA kit and β-Amyloid (Aβ) formation was observed by Congo red staining. Western-blot was performed to appraise protein expression.

Results: We found that berberine rectified some aberrant changes in signal molecules concerning inflammation, and cholinergic and insulin signaling pathways in the hippocampus. Furthermore, CSF/blood glucose, inflammatory response or acetyl cholinesterase enzyme (AChE) activity were reduced by berberine. Additionally, acetylcholine levels were enhanced after berberine treatment in diabetic rats. Finally, Aβ formation in diabetic hippocampus was inhibited and spatial learning memory was ameliorated by berberine.

Discussion: In conclusion, berberine clears Aβ deposit and consequently ameliorates spatial learning memory impairment via the activation of the cholinergic anti-inflammatory and insulin signaling pathways in diabetic rats.

Transplantation of Mesenchymal Stem Cells Overexpressing Fibroblast Growth Factor 21 Facilitates Cognitive Recovery and Enhances Neurogenesis in a Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a progressive and complex pathological condition that results in multiple adverse consequences, including impaired learning and memory. Transplantation of mesenchymal stem cells (MSCs) has produced limited benefits in experimental TBI models. Fibroblast growth factor 21 (FGF21) is a novel metabolic regulator that has neuroprotective effects, promotes remyelination, enhances angiogenesis, and elongates astrocytic processes. In this study, MSCs were genetically engineered to overexpress FGF21 in order to improve their efficacy in TBI. MSCs overexpressing FGF21 (MSC-FGF21) were transplanted to mouse brain by intracerebroventricular injection 24 h after TBI was induced by controlled cortical impact (CCI). Hippocampus-dependent spatial learning and memory, assessed by the Morris water maze test, was markedly decreased 3-4 weeks after TBI, a deficit that was robustly recovered by treatment with MSC-FGF21, but not MSC-mCherry control. Hippocampus-independent learning and memory, assessed by the novel object recognition test, was also impaired; these effects were blocked by treatment with both MSC-FGF21 and MSC-mCherry control. FGF21 protein levels in the ipsilateral hippocampus were drastically reduced 4 weeks post-TBI, a loss that was restored by treatment with MSC-FGF21, but not MSC-mCherry. MSC-FGF21 treatment also partially restored TBI-induced deficits in neurogenesis and maturation of immature hippocampal neurons, whereas MSC-mCherry was less effective. Finally, MSC-FGF21 treatment also normalized TBI-induced impairments in dendritic arborization of hippocampal neurons. Taken together, the results indicate that MSC-FGF21 treatment significantly improved TBI-induced spatial memory deficits, impaired hippocampal neurogenesis, and abnormal dendritic morphology. Future clinical investigations using MSC-FGF21 to improve post-TBI outcomes are warranted.

Spatial Learning and Memory Impairment in Growing Mice Induced by Major Oxidized Tyrosine Product Dityrosine

This study focused on the effects of oxidized tyrosine products (OTPs) and major component dityrosine (DT) on the brain and behavior of growing mice. Male and female mice were treated with daily intragastric administration of either tyrosine (Tyr; 420 μg/kg body weight), DT (420 μg/kg body weight), or OTPs (1909 μg/kg body weight) for 35 days. We found that pure DT and OTPs caused redox state imbalance, elevated levels of inflammatory factors, hippocampal oxidative damage, and neurotransmitter disorders while activating the mitochondrial apoptosis pathway in the hippocampus and downregulating the genes associated with learning and memory. These events eventually led to growing mice learning and memory impairment, lagging responses, and anxiety-like behaviors. Furthermore, the male mice exhibited slightly more oxidative damage than the females. These findings imply that contemporary diets and food-processing strategies of the modern world should be modified to reduce oxidized protein intake.

M1 Muscarinic Receptor Activation Rescues β-Amyloid-Induced Cognitive Impairment through AMPA Receptor GluA1 Subunit

M1 muscarinic receptors have long been identified as a potential therapeutic target for the treatment of cognitive impairment in Alzheimer's disease (AD). Our previous study has shown that M1 receptors promote membrane insertion and synaptic delivery of AMPA receptor GluA1 subunit. In this study, we sought to determine whether activation of M1 receptor would rescue the cognitive impairment in AD model mice through modulation of GluA1 subunit. For the mice injected with aggregated β-amyloid (Aβ) fragments to impair learning and memory, activation of M1 receptors could rescue it by reducing the latency to find the platform and spending more time in the target quadrant in the probe test in the Morris water maze. However, such an effect was ablated in mice with Ser845 residue of GluA1 mutated to alanine. Furthermore, the activation of M1 receptors enhanced the expression of GluA1 and its phosphorylation at Ser845 and drove GluA1 to incorporate with PSD95, a postsynaptic marker, in the hippocampi from Aβ-injected wild type mice but not from the mutant mice. Moreover, for 9-month-old APP/PS1 transgenic AD model mice, which may resemble the late AD, M1 receptor activation could not improve the cognitive impairment significantly. In addition, the enhancement of GluA1 expression and its phosphorylation at Ser845 were not observed in their hippocampi. Taken together, the study indicated that M1 receptor activation rescued the cognitive deficit through modulating the trafficking of GluA1-containing AMPA receptors and the therapeutics targeting M1 receptors should aim at mild AD or even pre-AD.

Bicuculline Reduces Neuroinflammation in Hippocampus and Improves Spatial Learning and Anxiety in Hyperammonemic Rats. Role of Glutamate Receptors

Patients with liver cirrhosis may develop minimal hepatic encephalopathy (MHE) with mild cognitive impairment. Hyperammonemia is a main contributor to cognitive impairment in MHE, which is mediated by neuroinflammation. GABAergic neurotransmission is altered in hyperammonemic rats. We hypothesized that, in hyperammonemic rats, (a) enhanced GABAergic tone would contribute to induce neuroinflammation, which would be improved by reducing GABAergic tone by chronic bicuculline treatment; (b) this would improve spatial learning and memory impairment; and (c) modulation of glutamatergic neurotransmission would mediate this cognitive improvement. The aim of this work was to assess the above hypotheses. Bicuculline was administrated intraperitoneally once a day for 4 weeks to control and hyperammonemic rats. The effects of bicuculline on microglia and astrocyte activation, IL-1β content, on membrane expression of AMPA and NMDA glutamate receptors subunits in the hippocampus and on spatial learning and memory as well as anxiety were assessed. Treatment with bicuculline reduces astrocyte activation and IL-1β but not microglia activation in the hippocampus of hyperammonemic rats. Bicuculline reverses the changes in membrane expression of AMPA receptor subunits GluA1 and GluA2 and of the NR2B (but not NR1 and NR2A) subunit of NMDA receptors. Bicuculline improves spatial learning and working memory and decreases anxiety in hyperammonemic rats. In hyperammonemia, enhanced activation of GABAA receptors in the hippocampus contributes to some but not all aspects of neuroinflammation, to altered glutamatergic neurotransmission and to impairment of spatial learning and memory as well as anxiety, all of which are reversed by reducing activation of GABAA receptors with bicuculline.

Effect of enriched environment during adolescence on spatial learning and memory, and voluntary consumption of morphine in maternally separated rats in adulthood

This study was designed to examine the effect of environmental enrichment (EE) during adolescence on spatial learning and memory and voluntary morphine consumption in maternally separated (MS) male and female rats in adulthood. Male Wistar rats were allowed to mate with female virgin Wistar rats. Pups were separated from the dams daily for 180 min during postnatal days 2-14. All pups were weaned on day 21. The pups of both sexes were reared in a standard (SE) or enriched (EE) environment during postnatal days 21-50. Then, adulthood rats were tested for spatial learning and memory (Morris Water Maze), and voluntary consumption of morphine using a two-bottle choice paradigm (TBC). We found that the MS/SE rats showed longer escape latencies to find the platform on the third (the male) and fourth (the female) days of training than No MS/SE rats. Also, exposure to EE shortened the latency to escape in the male and female MS rats as training progressed than MS/SE rats. Moreover, the No MS/EE and MS/EE male rats spent significantly more time in the target zone compared with the SE control groups in the probe test. We also found that voluntary morphine consumption was higher in the male and female MS/SE than No MS/SE rats, while it was lower in the male and female MS/EE rats. The present results have shown that EE treatment may have potential therapeutic application for the prevention of the development of drug addiction and recovery from cognitive deficits following neonatal MS during adulthood.

Time-dependent effect of oligomeric amyloid-β (1-42)-induced hippocampal neurodegeneration in rat model of Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD) is characterized with an abnormal deposition of insoluble amyloid-beta (Aβ) peptide plaques, tangles formation and synaptic dysfunction. These result in impaired functioning of neuronal circuits and alter the behavioral response owing to activation of neurotransmitter receptors. Recently, it has been implicated that Aβ influences N-methyl d-aspartate (NMDA) receptor activation in AD; however, the molecular mechanism underlying remains unclear. Thus, emerged specific aim to study the time-course effect of oligomeric Aβ_(1-42) (oAβ_1-42) on the mRNA expression of genes encoding NMDA and acetylcholine receptors in the rat model of AD.

METHODS

 Aggregated forms of synthetic Aβ peptides were injected bilaterally into the intrahippocampal region of rat brain using stereotaxic surgery. Behavioral analysis was performed using eight-arm Radial Arm Maze task at the end of experimental period. Euthanized rat brain hippocampal tissue was used to study the mRNA expression of glutamatergic and cholinergic receptor using semiquantitative reverse transcription-polymerase chain reaction.

RESULTS

oAβ_1-42 decreased the gene expression level of α7-nicotinic acetylcholine receptor and increased the mRNA expression of NMDA receptor 2A, and -2B subunits. In particular, oAβ_1-42 aggregates increased the retention time and altered the behavioral response in rats after 15 days of injection. Further, amyloid-β_1-42 are highly expressed in 15 days after postinjection in hippocampus of adult rats.

CONCLUSION

Acute exposure of oAβ_1-42 modulated differential gene expression of glutamatergic and cholinergic receptors in hippocampus of adult rats and is duration dependent reflecting changes in hippocampal circuitry system underlying learning and memory impairments.

ABBREVIATIONS

AD: Alzheimer's disease, Aβ: amyloid-β; oAβ_1-42: oligomeric amyloid-β 1-42 full length peptide; CAM: calmodulin; CNS: central nervous system; CR: Congo red; DG: dentate gyrus; EC: entorhinal cortex; HFIP: 1,1,1,3,3,3-hexafluoro-2-propanol; IBO: ibotenic acid; NMDA: N-methyl d-aspartate; NMDAR: N-methyl d-aspartate receptor; NR2A: N-methyl d-aspartate receptor 2A; NR2B: N-methyl d-aspartate receptor 2B; ACh: acetylcholine; α7-nAChR: α7-nicotinic acetylcholine receptor; PBS: phosphate buffered saline; RAM: Radial Arm Maze; ThT: thioflavin T.

A Developmental Study of Abnormal Behaviors and Altered GABAergic Signaling in the VPA-Treated Rat Model of Autism

Although studies have investigated the role of gamma-aminobutyric acid (GABA)ergic signaling in rodent neural development and behaviors relevant to autism, behavioral ontogeny, as underlain by the changes in GABAergic system, is poorly characterized in different brain regions. Here, we employed a valproic acid (VPA) rat model of autism to investigate the autism-like behaviors and GABAergic glutamic acid decarboxylase 67 (GAD67) expression underlying these altered behaviors in multiple brain areas at different developmental stages from birth to adulthood. We found that VPA-treated rats exhibited behavioral abnormalities relevant to autism, including delayed nervous reflex development, altered motor coordination, delayed sensory development, autistic-like and anxiety behaviors and impaired spatial learning and memory. We also found that VPA rats had the decreased expression of GAD67 in the hippocampus (HC) and cerebellum from childhood to adulthood, while decreased GAD67 expression of the temporal cortex (TC) was only observed in adulthood. Conversely, GAD67 expression was increased in the prefrontal cortex (PFC) from adolescence to adulthood. The dysregulated GAD67 expression could alter the excitatory-inhibitory balance in the cerebral cortex, HC and cerebellum. Our findings indicate an impaired GABAergic system could be a major etiological factor occurring in the cerebral cortex, HC and cerebellum of human cases of autism, which suggests enhancement of GABA signaling would be a promising therapeutic target for its treatment.

Chimeric Peptide Tat-HA-NR2B9c Improves Regenerative Repair after Transient Global Ischemia

Transient global ischemia (TGI) is a major public health problem, and it heightens the need of effective treatments. The present study was undertaken to investigate whether recombinant polypeptide Tat-HA-NR2B9c improves spatial learning and memory deficits in rats after TGI. Rats were subjected to 20-min ischemia induced by four-vessel occlusion (4-VO) method and daily injected with Tat-HA-NR2B9c (1.12 mg/kg) for 1 week. Tat-HA-NR2B9c increased CREB activity, upregulated B-cell lymphoma-2 (Bcl-2) expression after treated for 24 h. There was a significant increase in dendrite spine density in hippocampal CA1 region and BrdU-positive cells and BrdU/NeuN-positive cells in the dentate gyrus after Tat-HA-NR2B9c treatment, compared with ischemia group at postischemic day 28. Inhibition of the CREB activation by recombinant lentivirus, LV-CREB133-GFP, abolished the upregulation effects of Tat-HA-NR2B9c on Bcl-2 expression. Moreover, Tat-HA-NR2B9c improved the impaired spatial learning and memory ability in Morris water maze. These results suggest that Tat-HA-NR2B9c substantially ameliorated the TGI-induced loss of dendrite spine in hippocampal CA1, increased neurogenesis in dentate gyrus, and significantly improved cognitive abilities by the CREB pathway in rats after transient global cerebral ischemia. It may be served as a treatment for TGI.

Low-Frequency Repetitive Transcranial Magnetic Stimulation Ameliorates Cognitive Function and Synaptic Plasticity in APP23/PS45 Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disease leading to dementia, which is characterized by progressive memory loss and other cognitive dysfunctions. Recent studies have attested that noninvasive repetitive transcranial magnetic stimulation (rTMS) may help improve cognitive function in patients with AD. However, the majority of these studies have focused on the effects of high-frequency rTMS on cognitive function, and little is known about low-frequency rTMS in AD treatment. Furthermore, the potential mechanisms of rTMS on the improvement of learning and memory also remain poorly understood. In the present study, we reported that severe deficits in spatial learning and memory were observed in APP23/PS45 double transgenic mice, a well known mouse model of AD. Furthermore, these behavioral changes were accompanied by the impairment of long-term potentiation (LTP) in the CA1 region of hippocampus, a brain region vital to spatial learning and memory. More importantly, 2-week low-frequency rTMS treatment markedly reversed the impairment of spatial learning and memory as well as hippocampal CA1 LTP. In addition, low-frequency rTMS dramatically reduced amyloid-β precursor protein (APP) and its C-terminal fragments (CTFs) including C99 and C89, as well as β-site APP-cleaving enzyme 1 (BACE1) in the hippocampus. These results indicate that low-frequency rTMS noninvasively and effectively ameliorates cognitive and synaptic functions in a mouse model of AD, and the potential mechanisms may be attributed to rTMS-induced reduction in Aβ neuropathology.

Effects of Housing on Methamphetamine-Induced Neurotoxicity and Spatial Learning and Memory

Severe stress potentiates methamphetamine (MA) neurotoxicity. However, whether moderate stress increases or decreases the neurotoxic effects of MA is unknown. We assessed the effects of MA (4 × 10 mg/kg at 2 h intervals) in combination with prior barren-cage housing in adult male Sprague-Dawley rats on monoamines and glial fibrillary acid protein (GFAP) in one cohort and spatial learning and memory in the Morris water maze in another cohort. MA reduced dopamine (DA) and serotonin (5-HT) in the neostriatum and nucleus accumbens, 5-HT in the hippocampus, and increased GFAP in neostriatum and nucleus accumbens compared with saline controls. In neostriatum, barren-cage housing protected against MA-induced increases in GFAP, but it did not prevent DA and 5-HT reductions, although it did increase hippocampal norepinephrine. MA impaired spatial learning during acquisition, reversal, and shift phases and impaired reference memory on reversal and shift probe trials. Barren-cage housing enhanced performance during acquisition but not during reversal or shift or on probe trials. The data indicate that prior barren-cage housing moderates MA-induced neostriatal astrogliosis and initial spatial learning, but has no protective effect when the platform is smaller and relocated and therefore requires cognitive flexibility in relearning.

Dynamic Changes in the Renin-Angiotensin-Aldosterone System and the Beneficial Effects of Renin-Angiotensin-Aldosterone Inhibitors on Spatial Learning and Memory in a Rat Model of Chronic Cerebral Ischemia

Renin-angiotensin-aldosterone system (RAAS) plays an important role in the regulation of blood pressure and brain function. Therefore, we studied the dynamic changes in the RAAS in the blood, cerebral cortex, and hippocampus and the effects of RAAS inhibitors on spatial learning and memory and hippocampal apoptosis in a rat model of chronic cerebral ischemia (CCI) established by bilateral ligation of the common carotid arteries of rats. The levels of renin, angiotensin II (Ang II), and aldosterone (ALD) in the plasma, and the homogenates of the left side of cerebral cortex and whole hippocampus of rats were detected on day 1, 3, 7, 14, 21, and 30 by radioimmunoassay. Spatial learning and memory and hippocampal apoptosis were evaluated on day 30 by Morris water maze test (navigation and space exploration tests) and terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay, respectively, after rats were orally administered with distilled water (DW), renin inhibitor aliskiren (30 mg/kg), Ang converting enzyme inhibitor enalapril (4 mg/kg), or Ang II receptor antagonist candesartan (2 mg/kg) daily for 30 days. The results showed that the levels of renin and Ang II were significantly higher but ALD fluctuated in the blood, cerebral cortex, and hippocampus in CCI rats compared to normal rats. However, aliskiren and enalapril could significantly decrease (p < 0.05) the levels of renin, Ang II and ALD in the blood, cerebral cortex, and hippocampus compared to DW treatment; while candesartan had similar effect on renin and ALD but no effect on Ang II in CCI rats. Furthermore, spatial learning and memory were significantly decreased but apoptosis in the hippocampus was obviously increased in CCI rats compared to normal rats (p < 0.05). However, aliskiren, enalapril, and candesartan were equally effective to improve spatial learning and memory and decrease apoptosis in the hippocampus. Therefore, RAAS plays an important role in the development of cerebral ischemia and RAAS inhibitors aliskiren, enalapril, and candesartan improve spatial learning and memory and protect brain injury by inhibiting hippocampal apoptosis in CCI rats.

Endogenous nitric oxide regulates blood vessel growth factors, capillaries in the cortex, and memory retention in Sprague-Dawley rats

The effects of nitric oxide (NO) on cerebral capillary angiogenesis and the regulation of pro- and anti-angiogenic factors that affect cerebral capillary angiogenesis, spatial learning, and memory ability are unclear. We assessed the effects of the NO precursor L-arginine (L-ARG) and the NO synthesis inhibitor Nω-nitro-L-arginine methylester (L-NAME) on cortical capillaries and spatial learning and memory abilities. We administered intracerebroventricular injections of L-ARG or L-NAME to rats before they were evaluated in the Morris water maze. We measured the levels of NO synthase activity, pro-angiogenic factors, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (FGF-2), and the expression of the anti-angiogenic factors angiostatin and endostatin. We also quantitatively investigated parameters of the cortical capillaries using immunohistochemistry and stereological methods. The L-ARG treatment significantly improved rats' spatial learning abilities and increased NOS activity in the cortex. L-NAME disrupted spatial learning. Following the L-ARG treatment, the expression of the pro-angiogenic factors (VEGF and FGF-2) was higher and the expression of anti-angiogenic factors (endostatin) was lower than the vehicle-treated animals. In contrast, the L-NAME treatment reduced the expression of VEGF and increased the expression of endostatin. Based on these results, modulation of the NO content in the brain regulates VEGF, FGF-2, and endostatin expression, as well as capillary parameters in the cortex, which in turn influence spatial learning and memory performance.

T3D-959: A Multi-Faceted Disease Remedial Drug Candidate for the Treatment of Alzheimer's Disease

BACKGROUND

T3D-959, a dual PPAR-δ/PPAR γ nuclear receptor agonist and former diabetes drug candidate, has been repositioned as an Alzheimer's disease (AD)-modifying therapy.

OBJECTIVE

This study examines the effectiveness and mechanisms of T3D-959's therapeutic effects using in vivo and ex vivo rat models of sporadic AD.

METHODS

A sporadic AD model was generated by intracerebral (i.c.) administration of streptozotocin (STZ). Control and i.c. STZ treated rats were gavaged with saline or T3D-959 (0.3 to 3.0 mg/kg/day) for 28 days. Spatial learning and memory were evaluated using the Morris water maze test. Frontal lobe slice cultures generated 24 hours after i.c. STZ or vehicle were used to study early effects of T3D-959 (0.5-1.0 μM) on viability and molecular markers of AD.

RESULTS

T3D-959 significantly improved spatial learning and memory in i.c STZ-treated rats. Mechanistically, T3D-959 significantly improved culture viability and brain morphology, reduced levels of oxidative stress and Aβ, and normalized expression of phospho-tau, choline acetyltransferase, and myelin-associated glycoprotein. Protective effects occurred even at the lowest tested dose of T3D-959.

CONCLUSIONS

Pre-clinical proof of concept has been demonstrated that T3D-959 can improve multiple pathologies of AD resulting in significant improvements in cognitive function and molecular and biochemical indices of neurodegeneration. These results support the theses that (1) effective disease modification in AD can be achieved by targeting relevant nuclear receptors, and (2) treating AD as a metabolic disease has the potential to be disease remedial. A Phase 2a trial of T3D-959 in mild-to-moderate AD patients has been initiated (ClinicalTrials.gov identifier NCT02560753).