Spatial Learning Test Research Articles

Low-dose intranasal deferoxamine modulates memory, neuroinflammation, and the neuronal transcriptome in the streptozotocin rodent model of Alzheimer’s disease

IntroductionIntranasal (IN) deferoxamine (DFO) has emerged over the past decade as a promising therapeutic in preclinical experiments across neurodegenerative and neurovascular diseases. As an antioxidant iron chelator, its mechanisms are multimodal, involving the binding of brain iron and the consequent engagement of several pathways to counter pathogenesis across multiple diseases. We and other research groups have shown that IN DFO rescues cognitive impairment in several rodent models of Alzheimer Disease (AD).MethodsThis study was designed to probe dosing regimens to inform future clinical trials, while exploring mechanisms within the intracerebroventricular (ICV) streptozotocin (STZ) model.ResultsFive weeks of daily IN dosing of Long Evans rats with 15 μL of a 1% (0.3 mg), but not 0.1% (0.03 mg), solution of DFO rescued cognitive impairment caused by ICV STZ administration as assessed with the Morris Water Maze (MWM) test of spatial memory and learning. Furthermore, IN DFO modulated several aspects of the neuroinflammatory milieu of the ICV STZ model, which was assessed through a novel panel of brain cytokines and immunohistochemistry. Using RNA-sequencing and pathway analysis, STZ was shown to induce several pathways of cell death and neuroinflammation, and IN DFO engaged multiple transcriptomic pathways involved in hippocampal neuronal survival.DiscussionTo our knowledge this study is the first to assess the transcriptomic pathways and mechanisms associated with either the ICV STZ model or DFO treatment, and the first to demonstrate efficacy at this low dose.

Sex Affects Cognitive Outcomes in HIV-1 Tat Transgenic Mice: Role of CCR5.

People living with HIV (PLWH) experience HIV-associated neurocognitive disorders (HAND), even though combination antiretroviral therapy (cART) suppresses HIV replication. HIV-1 transactivator of transcription (HIV-1 Tat) contributes to the development of HAND through neuroinflammatory and neurotoxic mechanisms. C-C chemokine 5 receptor (CCR5) is important in immune cell targeting and is a co-receptor for HIV viral entry into CD4+ cells. Notably, CCR5 has been implicated in cognition unrelated to HIV infection. Inhibition of CCR5 has been shown to improve learning and memory. To test whether CCR5 is involved in cognitive changes in HAND, we used a non-infectious, transgenic model in which HIV-1 Tat is inducibly expressed. Well-powered cohorts of male and female mice were placed on a diet containing doxycycline to induce Tat expression for 8-wks. Males showed Tat-mediated deficits in the Barnes maze test of spatial learning and memory; females showed no impairments. Deficits in the males were fully reversed by the CCR5 antagonist, maraviroc (MVC). Tat-mediated deficits were not found in novel object recognition or contextual fear conditioning in either sex. Based on earlier work, we hypothesized that MVC might increase brain-derived neurotrophic factor (BDNF), which is essential in maintaining synaptodendritic function. MVC did increase the mBDNF to proBDNF ratio in males, perhaps contributing to improved cognition.

Beneficial effects of fenoprofen on cognitive impairment induced by the kindling model of epilepsy: interaction of oxidative stress and inflammation

Hippocampal-dependent cognitive impairments are consequences of temporal lobe epilepsy. This study aimed to assess the modulatory effects of fenoprofen on Pentylenetetrazol (PTZ)-induced cognitive dysfunction in the rat model of epilepsy. Male Wistar rats were randomly divided into five groups. Except for the control group, the kindling model was induced by intraperitoneal (IP) injection of PTZ (35mg/kg) every other day for a month. Three groups received fenoprofen (10, 20, and 40mg/kg) before each PTZ injection. One week after kindling development, rats were challenged with PTZ (70mg/kg). The Morris Water Maze, Shuttle Box, and Elevated Plus Maze tests were applied to assess cognitive functions. Rats’ serum and brain samples were prepared for biochemical, histological, and gene expression studies. Fenoprofen pretreatment effectively reduced the mean seizure score, and treated rats had better cognitive performance than the PTZ group in passive avoidance and spatial memory and learning tests; they also showed less anxiety-like behaviors. Its administration also showed anti-oxidative properties. So the serum level of Nitric oxide was significantly reduced while Glutathione and Catalase increased significantly. It also diminished the expression of inflammatory genes (Tumor Necrosis Factor alpha (TNF-α) and Nuclear Factor Kappa B (NF-kB)) in the hippocampus, these results were confirmed by histological observation from Hematoxylin & Eosin staining. These results show the ability of fenoprofen to reduce cognitive impairments caused by epilepsy induction. These effects seem to be through the modulation of inflammatory mediators and oxidative stress.

Traceable teleportation: Improving spatial learning in virtual locomotion

In virtual reality, point-and-teleport (P&T) is a locomotion technique that is popular for its user-friendliness, lowering workload and mitigating cybersickness. However, most P&T schemes use instantaneous transitions, which has been known to hinder spatial learning. While replacing instantaneous transitions with animated interpolations can address this issue, they may inadvertently induce cybersickness. To counter these deficiencies, we propose Traceable Teleportation (TTP), an enhanced locomotion technique grounded in a theoretical framework that was designed to improve spatial learning. TTP incorporates two novel features: an Undo-Redo mechanism that facilitates rapid back-and-forth movements, and a Visualized Path that offers additional visual cues. We have conducted a user study via a set of spatial learning tests within a virtual labyrinth to assess the effect of these enhancements on the P&T technique. Our findings indicate that the TTP Undo-Redo design generally facilitates the learning of orientational spatial knowledge without incurring additional cybersickness or diminishing sense of presence.

Long-term effects of Preweaning environmental impoverishment on neurobehavioral and neurocognitive outcomes in Sprague Dawley rats: An early environmental stress model

Developmental stress, including low socioeconomic status (SES), can induce dysregulation of the hypothalamic-pituitary-adrenal axis and result in long-term changes in stress reactivity. Children in lower SES conditions often experience more stress than those in other SES groups. There are multiple model systems of early environmental stress (EES), one of which is reduced cage bedding. Here we tested the effects of both prenatal and lactational EES in rats on a range of long-term behavioral and cognitive outcomes. There were persistent reductions in body weight in the EES rats in both sexes. The behavioral results showed no effects on learning and memory using tests of spatial learning or cognitive flexibility in the Morris water maze, egocentric learning in the Cincinnati water maze, or working memory in the radial-arm maze. There were no effects on basic open-field activity, elevated zero-maze, or forced swim test, but EES rats had reduced time in the dark side of the light/dark test. When rats were drug challenged in the open-field with d-amphetamine or MK-801, there were no differential responses to d-amphetamine, but the EES group under responded compared with the drug-induced hyperactivity in the control group in both males and females. The objective was to establish a developmental stress model that induced cognitive deficits and to the extent that this method did not cause such effects it was not the model we sought. However, the data showed several long-term effects of EES, including the reduced response to the irreversible NMDA antagonist MK-801. This effect merits further investigation.

Changes in Paraoxonase, β-Glucosidase, and Carbonic Anhydrase Enzymes Related to Age and Scopolamine-Induced Memory Impairment in Rats

This study aimed to investigate the changes in Paraoxonase (PON), Carbonic Anhydrase (CA), and β-glucosidase levels of different aged rats and scopolamine-induced memory impairment rats. This study used young, adult, and middle-aged male Wistar Albino rats. Scopolamine was administered as a single dose/multiple doses and a Morris water maze (MWM) was used for spatial learning testing in rats. Enzyme-linked immunosorbent assays (ELISAs) were used to determine serum and liver PON and β-glucosidase levels. The CA enzyme activity was assayed following the hydration of CO2. As a result of the comparison of age-related and scopolamine-related changes in PON and β-glucosidase levels in liver and serum samples, no significant age-related and scopolamine-effective changes were observed in serum, while liver PON and liver β-glucosidase levels were found to change significantly. CA activity studies, on the other hand, showed that adults have the lowest CA activity compared to young and middle-aged groups and scopolamine inhibited CA activity in vivo. We found that adult rats modeled with memory impairment had statistically lower levels of liver PON and liver β-glucosidase. CA activity was also found to be significantly reduced. β-glucosidase and CA should be further investigated in terms of neurodegenerative disease risk factors, just like PON, whose importance has been determined by numerous studies in the literature.

Air bubble curtain improves the welfare of captive rainbow trout fry and fingerlings

Fish welfare is becoming a priority for the fish farming industry. The search for practical, easy-to-implement methods to promote farmed fish welfare is therefore essential. Environmental enrichment aims to improve the psychological and physiological needs of a captive animal by increasing the complexity of its environment. During previous studies, we observed that fish seemed to be positively affected by short diffusions of air bubbles. In this study, we evaluated the effects of an innovative enrichment strategy consisting of introducing into the tank at the earliest stages of life, a pipe generating a curtain of air bubbles. Using rainbow trout (Oncorhynchus mykiss) as a captive fish model, we compared the short- (∼7 weeks) and long-term (∼21 weeks) effects of this bubble curtain diffused for one hour four times a day (Bubble condition) to a standard condition without bubbles (Control) on fish growth, aggressive and abnormal behaviors, as well as on fish motivation to access a bubble curtain, their emotional responses and their learning abilities. We found that bubble diffusion decreased aggressive and abnormal behaviors during diffusions in both the short-term and the long-term experiments. In the long-term experiment, this decrease was also observed during feedings and neutral periods when no bubble was diffused. Bubbles were found to be attractive for young Control fish (bubble-naive fish) subjected to a motivation test in the short-term experiment. When subjected to the emotional reactivity test, Bubble fish seemed less fearful, exhibiting a lower maximum velocity than Control fish in the long-term experiment only. However, the other behavioral parameters measured during this test, appetite and plasma cortisol levels were similar between treatments, irrespective of the experimental period. The latency to consume the reward observed in the spatial learning test in the long-term experiment was decreased in Bubble fish compared with Control fish, showing enhanced learning abilities in fish that experienced bubbles for 21 weeks. Growth parameters and fin erosion index did not differ between treatments. We conclude that repeated bubble diffusions act as an environmental enrichment for fish, combining physical, occupational, and sensory enrichment via the tactile stimulations provided by the air bubbles. This type of enrichment had a positive impact on the behavior of farmed rainbow trout in the long term, and would make it possible to integrate the notion of “positive welfare” into fish farms, while guaranteeing easy technical maintenance.

Sevoflurane anesthesia reduces the expression of inflammatory response genes and β-site amyloid precursor protein-cleaving enzyme in hippocampi of diabetic mice.

Diabetes and inhaled anesthesia are associated with an increased likelihood of developing postoperative cognitive dysfunction in humans and animal models, but the mechanisms are unclear. This study aimed to investigate the effect and mechanism of sevoflurane anesthesia on cognitive function in diabetic (DM) mice. Spontaneously diabetic db/db and control db/m mice were subject to sevoflurane anesthesia or allowed to breathe air, respectively. The Morris water maze test as spatial learning and novel object recognition test as recognition memory were performed. The expression of inflammatory cytokines and neurotoxicity-related genes in the hippocampus of four groups was measured using real-time PCR. The expression level of neurotoxicity and neuroprotection-related proteins in DM mice hippocampus were estimated using Western blot assay. It is found that DM mice developed cognitive impairment; however, the cognitive impairment was not exacerbated in sevoflurane-exposed mice. Sevoflurane anesthesia led to a decrease in mRNA levels of inflammatory cytokines in DM mice hippocampi, including interleukin 17 (IL-17), C-C motif chemokine (CCL20), CCL7 as well as high mobility group box 1 and beta-site amyloid-β cleaving enzyme 1; and no effect was observed on the expression of neurotoxicity genes, including amyloid precursor protein, choline O-acetyltransferase, tumor necrosis factor, alpha-induced protein 1, B-cell lymphoma 2 and estrogen receptor 2. In addition, we observed elevated phosphorylation of cAMP response element-binding protein in DM mice exposed to sevoflurane anesthesia. In conclusion, sevoflurane did not exacerbate DM-associated cognitive impairment.

Learning induces EPO/EPOr expression in memory relevant brain areas, whereas exogenously applied EPO promotes remote memory consolidation.

Memory and learning allow animals to appropriate certain properties of nature with which they can navigate in it successfully. Memory is acquired slowly and consists of two major phases, a fragile early phase (short-term memory, <4h) and a more robust and long-lasting late one (long-term memory, >4h). Erythropoietin (EPO) prolongs memory from 24 to 72h when animals are trained for 5min in a place recognition task but not when training lasted 3min (short-term memory). It is not known whether it promotes the formation of remote memory (≥21 days). We address whether the systemic administration of EPO can convert a short-term memory into a long-term remote memory, and the neural plasticity mechanisms involved. We evaluated the effect of training duration (3 or 5min) on the expression of endogenous EPO and its receptor to shed light on the role of EPO in coordinating mechanisms of neural plasticity using a single-trial spatial learning test. We administered EPO 10min post-training and evaluated memory after 24h, 96h, 15 days, or 21 days. We also determined the effect of EPO administered 10min after training on the expression of arc and bdnf during retrieval at 24h and 21 days. Data show that learning induces EPO/EPOr expression increase linked to memory extent, exogenous EPO prolongs memory up to 21 days; and prefrontal cortex bdnf expression at 24h and in the hippocampus at 21 days, whereas arc expression increases at 21 days in the hippocampus and prefrontal cortex.

Correlation of HIV-Induced Neuroinflammation and Synaptopathy with Impairment of Learning and Memory in Mice with HAND.

Over 38 million people worldwide are living with HIV/AIDS, and more than half of them are affected by HIV-associated neurocognitive disorders (HAND). Such disorders are characterized by chronic neuroinflammation, neurotoxicity, and central nervous system deterioration, which lead to short- or long-term memory loss, cognitive impairment, and motor skill deficits that may show gender disparities. However, the underlying mechanisms remain unclear. Our previous study suggested that HIV-1 infection and viral protein R (Vpr) upregulate the SUR1-TRPM4 channel associated with neuroinflammation, which may contribute to HAND. The present study aimed to explore this relationship in a mouse model of HAND. This study employed the HIV transgenic Tg26 mouse model, comparing Tg26 mice with wildtype mice in various cognitive behavioral and memory tests, including locomotor activity tests, recognition memory tests, and spatial learning and memory tests. The study found that Tg26 mice exhibited impaired cognitive skills and reduced learning abilities compared to wildtype mice, particularly in spatial memory. Interestingly, male Tg26 mice displayed significant differences in spatial memory losses (p < 0.001), while no significant differences were identified in female mice. Consistent with our early results, SUR1-TRPM4 channels were upregulated in Tg26 mice along with glial fibrillary acidic protein (GFAP) and aquaporin 4 (AQP4), consistent with reactive astrocytosis and neuroinflammation. Corresponding reductions in neurosynaptic responses, as indicated by downregulation of Synapsin-1 (SYN1) and Synaptophysin (SYP), suggested synaptopathy as a possible mechanism underlying cognitive and motor skill deficits. In conclusion, our study suggests a possible relationship between SUR1-TRPM4-mediated neuroinflammation and synaptopathy with impairments of learning and memory in mice with HAND. These findings could help to develop new therapeutic strategies for individuals living with HAND.

ICA69 regulates activity-dependent synaptic strengthening and learning and memory.

Long-term potentiation (LTP) is one of the major cellular mechanisms for learning and memory. Activity-dependent increases in surface AMPA receptors (AMPARs) are important for enhanced synaptic efficacy during LTP. Here, we report a novel function of a secretory trafficking protein, ICA69, in AMPAR trafficking, synaptic plasticity, and animal cognition. ICA69 is first identified as a diabetes-associated protein well characterized for its function in the biogenesis of secretory vesicles and trafficking of insulin from ER, Golgi to post-Golgi in pancreatic beta cells. In the brain, ICA69 is found in the AMPAR protein complex through its interaction with PICK1, which binds directly to GluA2 or GluA3 AMPAR subunits. Here, we showed that ICA69 regulates PICK1's distribution in neurons and stability in the mouse hippocampus, which in turn can impact AMPAR function in the brain. Biochemical analysis of postsynaptic density (PSD) proteins from hippocampi of mice lacking ICA69 (Ica1 knockout) and their wild-type littermates revealed comparable AMPAR protein levels. Electrophysiological recording and morphological analysis of CA1 pyramidal neurons from Ica1 knockout also showed normal AMPAR-mediated currents and dendrite architecture, indicating that ICA69 does not regulate synaptic AMPAR function and neuron morphology at the basal state. However, genetic deletion of ICA69 in mice selectively impairs NMDA receptor (NMDAR)-dependent LTP but not LTD at Schaffer collateral to CA1 synapses, which correlates with behavioral deficits in tests of spatial and associative learning and memory. Together, we identified a critical and selective role of ICA69 in LTP, linking ICA69-mediated synaptic strengthening to hippocampus-dependent learning and memory.

Rescue of Long-Term Spatial Memory by 7,8-Dihydroxyflavone in Mice with Reduced Oligodendrogenesis.

Oligodendrogenesis is the process by which new oligodendrocytes are produced in the CNS. Oligodendrocytes form myelin, which has a vital role in neural signal transmission and integration. Here we tested mice with reduced adult oligodendrogenesis in the Morris water maze, a test of spatial learning. These mice were found to have impaired long-term (28 d) spatial memory. However, when 7,8-dihydroxyflavone (7,8-DHF) was administered immediately after each training session, their long-term spatial memory impairment was rescued. An increase in the number of newly formed oligodendrocytes in the corpus callosum was also observed. 7,8-DHF has previously been shown to improve spatial memory in animal models of Alzheimer's disease, post-traumatic stress disorder, Wolfram syndrome and Down syndrome, as well as in normal aging. Understanding the underlying mechanisms of the effect of this drug on spatial memory is therefore helpful in assessing it for clinical relevance and development.

A Comparative Study of the Impact of NO-Related Agents on MK-801- or Scopolamine-Induced Cognitive Impairments in the Morris Water Maze

Learning and memory deficits accompany numerous brain dysfunctions, including schizophrenia and Alzheimer's disease (AD), and many studies point to the role of nitric oxide (NO) in these processes. The present investigations constitute the follow-up of our previous research, in which we investigated the activity of NO releasers and a selective inhibitor of neuronal NO synthase (nNOS) to prevent short-term memory deficits in novel object recognition and T-maze. Here, the ability of the compounds to prevent the induction of long-term memory deficits by MK-801 or scopolamine administration was investigated. The Morris Water Maze test, a reliable and valid test of spatial learning and memory, was used, in which escape latency in the acquisition phase and nine different parameters in the retention phase were measured. A fast NO releaser (spermine NONOate), a slow NO releaser (DETA NONOate), and a nNOS inhibitor, N(ω)-propyl-L-arginine (NPLA), were used. The compounds were administered i.p. at a dose range of 0.05-0.5 mg/kg. All compounds prevented learning deficits in the acquisition phase and reversed reference memory deficits in the retention phase of the scopolamine-treated mice. Spermine NONOate was the least effective. In contrast, the drugs poorly antagonised MK-801-induced deficits, and only the administration of DETA NONOate induced some improvements in the retention trial.

Effect of fearfulness and cortisol reactivity to stress on the spatial learning performance in mountain primitive horses

This study aimed to determine whether the level of fearfulness and cortisol reactivity influenced spatial learning performance in primitive mountain Hucul horses. The Huculs had to overcome particularly difficult, sometimes dangerous conditions to survive over centuries. We hypothesized that they were familiar with danger and should learn easily. The study involved 22 mares. They were divided into groups of different fearfulness levels according to behavioral score and cortisol concentration increase in the saliva, both of which were determined in a test of a novel object. In the next step, the mares were subjected to a spatial learning test in a maze with food reward at the end, conducted in two trials, on consecutive days. Their spatial learning performance was assessed with an error score and time taken to complete the maze. The study found that both the level of fearfulness and cortisol concentration increase varied in the mares. The spatial learning performance of mares that had low, medium and high levels of fearfulness and cortisol increase was similar within a trial, although animals displaying a medium fearfulness level or moderate cortisol change achieved better results in the second trial than in the first trial. These results indicate a weak influence of the fearfulness and cortisol reactivity on spatial learning performance in Huculs which may suggest an effect of the origin and historical environment of the breed.

Continuous high-frequency deep brain stimulation of the anterior insula modulates autism-like behavior in a valproic acid-induced rat model

BackgroundUntil now, the treatment of patients with autism spectrum disorder (ASD) remain a difficult problem. The insula is involved in empathy and sensorimotor integration, which are often impaired in individuals with ASD. Deep brain stimulation, modulating neuronal activity in specific brain circuits, has recently been considered as a promising intervention for neuropsychiatric disorders. Valproic acid (VPA) is a potential teratogenic agent, and prenatal exposure can cause autism-like symptoms including repetitive behaviors and defective sociability. Herein, we investigated the effects of continuous high-frequency deep brain stimulation in the anterior insula of rats exposed to VPA and explored cognitive functions, behavior, and molecular proteins connected to autism spectrum disorder.MethodsVPA-exposed offspring were bilaterally implanted with electrodes in the anterior insula (Day 0) with a recovery period of 1 week. (Day 0–7). High-frequency deep brain stimulation was applied from days 11 to 29. Three behavioral tests, including three-chamber social interaction test, were performed on days 7, 13, 18, 25 and 36, and several rats were used for analysis of immediate early genes and proteomic after deep brain stimulation intervention. Meanwhile, animals were subjected to a 20 day spatial learning and cognitive rigidity test using IntelliCage on day 11.ResultsDeep brain stimulation improved the sociability and social novelty preference at day 18 prior to those at day 13, and the improvement has reached the upper limit compared to day 25. As for repetitive/stereotypic-like behavior, self- grooming time were reduced at day 18 and reached the upper limit, and the numbers of burried marbles were reduced at day 13 prior to those at day 18 and day 25. The improvements of sociability and social novelty preference were persistent after the stimulation had ceased. Spatial learning ability and cognitive rigidity were unaffected. We identified 35 proteins in the anterior insula, some of which were intimately linked to autism, and their expression levels were reversed upon administration of deep brain stimulation.ConclusionsAutism-like behavior was ameliorated and autism-related proteins were reversed in the insula by deep brain stimulation intervention, these findings reveal that the insula may be a potential target for DBS in the treatment of autism, which provide a theoretical basis for its clinical application., although future studies are still warranted.

Understanding the Neuronal Requirement for Glycolysis

AbstractBackgroundThe brain has a high energy demand and consumes large amounts of glucose. In Alzheimer’s disease (AD), glucose uptake is reduced, but the significance of this change for neurodegeneration is unclear. Furthermore, whether or not neurons directly take up glucose has been debated in the field. Indeed, the lactate‐shuttle hypothesis predicts that glucose is primarily metabolized by glia or astrocytes into lactate, which is subsequently delivered to neurons and utilized continuously under aerobic conditions. However, studies utilizing glucose analogs challenge that model, and support direct glucose uptake by neurons. Here, we sought to understand the essential role of the neuronal glucose metabolism, to provide a starting point for new approaches to understand and target metabolic changes in AD.MethodTo interrogate the role of neuronal glucose metabolism, we generated mice with targeted deletion of the dominant glucose transporter (GLUT3), or the enzyme that catalyzes the final step in glycolysis (PKM1), specifically in CA1 and other forebrain neurons from postnatal day 19. Mice were assessed with spatial learning and memory behavioral tests, and glucose metabolism and ATP production were monitored in individual neurons and synapses using a FRET‐based live imaging approach.ResultMale and female GLUT3 KO mice showed age‐dependent memory deficits beginning at 7 months of age, and PKM1 KO mice showed impaired memory at 12 months of age, although this defect was only present in female mice. GLUT3KO neurons had decreased basal glucose levels and uptake. GLUT3KO synapses also showed significantly reduced basal ATP levels, and their ATP levels were unresponsive to electrical stimulation, which increases neuronal energy demand. In hippocampal neurons, blocking the last step of glycolysis by PKM1 knockout decreased the basal level of ATP production at synapses in cultures prepared from female pups, and resulted in unresponsiveness to electrical stimulation in both female and male cultures.ConclusionOur results indicate that to function properly and maintain ATP levels at synapses, neurons require glucose that can be taken up directly and metabolized through glycolysis. Therefore, decreased glucose uptake in AD may contribute to neuronal dysfunction and degeneration.

Resting behavior of broilers reared with or without artificial brooders.

Rest and sleep are important for the welfare of mammals and birds. A large part of the daily time budget of broiler chickens is taken up by resting behavior and the quality of resting is important. However, in intensive broiler production systems, disruptions of resting behaviors are common. These disruptions of resting behavior could be negative for the health and growth of the birds. This study investigated if artificial brooders that provide a delimited and darker resting place, away from active birds, reduce disruptions of resting behavior compared to a control situation without artificial brooders. Six pens of each treatment were used in the same building, keeping 60 chickens (Ross 308) per pen. The artificial brooders were removed at 21 days of age. Data on disturbances and duration of resting bouts and activity between resting bouts were collected on 20 and 34 days of age. Also, as an indicator of the quality of rest, the animals' cognitive performance was evaluated in a spatial learning test that was performed at 11 days of age. The results showed that birds housed in pens with access to brooders have longer resting bouts (260.7 ± 5.2 vs. 132.8 ± 5.3s, p < 0.001) and are less likely to be disturbed during resting by other individuals (0.15 vs. 0.48, p < 0.001). The effect of the artificial brooders on both the duration of resting bouts and the proportion of disturbances remained after the removal of the brooders at 21 days of age. The duration of activity between resting bouts was shorter if the resting bout was ended by a disturbance (9.98 ± 1.0 vs. 61.0 ± 2.4s, p < 0.001). Birds reared with brooders were more likely to solve the spatial learning task (0.5 vs. 0.27, p < 0.01), but those succeeding were not faster at solving it. Broilers may be exposed to disrupted rest due to the lack of a dedicated resting place separated from areas with high activity. Using artificial brooders reduces disturbances but does not eliminate them. Therefore, additional changes to the housing conditions or management will be needed to prevent disturbances.

All-trans Retinoic Acid has Limited Therapeutic Effects on Cognition and Hippocampal Protein Expression After Controlled Cortical Impact

Traumatic brain injury (TBI) is known to impair synaptic function, and subsequently contribute to observed cognitive deficits. Retinoic Acid (RA) signaling modulates expression of synaptic plasticity proteins and is involved in hippocampal learning and memory. All trans-retinoic acid (ATRA), a metabolite of Vitamin A, has been identified as a potential pharmacotherapeutic for other neurological disorders due to this role. This study conducted an ATRA dose response to determine its therapeutic effects on cognitive behaviors and expression of hippocampal markers of synaptic plasticity and RA signaling proteins after experimental TBI. Under isoflurane anesthesia, adult male Sprague Dawley rats received either controlled cortical impact (CCI, 2.5 mm deformation, 4 m/s) or control surgery. Animals received daily intraperitoneal injection of 0.5, 1, 5, or 10 mg/kg of ATRA or vehicle for 2 weeks. Animals underwent motor and spatial learning and memory testing. Hippocampal expression of synaptic plasticity proteins neurogranin (Ng), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluA1 sub-unit, as well as RA signaling proteins STRA6, ADLH1a1, CYP26A1 and CYP26B1 were evaluated by western blot at 2-weeks post-injury. ATRA treatment significantly recovered Ng synaptic protein expression, while having no effect on motor performance, spatial learning, and memory, and GluA1 expression after TBI. RA signaling protein expression is unchanged 2 weeks after TBI.Overall, ATRA administration after TBI showed limited therapeutic benefits compared to the vehicle.

Small Extracellular Vesicles in Milk Cross the Blood-Brain Barrier in Murine Cerebral Cortex Endothelial Cells and Promote Dendritic Complexity in the Hippocampus and Brain Function in C57BL/6J Mice.

Human milk contains large amounts of small extracellular vesicles (sEVs) and their microRNA cargos, whereas infant formulas contain only trace amounts of sEVs and microRNAs. We assessed the transport of sEVs across the blood-brain barrier (BBB) and sEV accumulation in distinct regions of the brain in brain endothelial cells and suckling mice. We further assessed sEV-dependent gene expression profiles and effects on the dendritic complexity of hippocampal granule cells and phenotypes of EV depletion in neonate, juvenile and adult mice. The transfer of sEVs across the BBB was assessed by using fluorophore-labeled bovine sEVs in brain endothelial bEnd.3 monolayers and dual chamber systems, and in wild-type newborn pups fostered to sEV and cargo tracking (ECT) dams that express sEVs labeled with a CD63-eGFP fusion protein for subsequent analysis by serial two-photon tomography and staining with anti-eGFP antibodies. Effects of EVs on gene expression and dendritic architecture of granule cells was analyzed in hippocampi from juvenile mice fed sEV and RNA-depleted (ERD) and sEV and RNA-sufficient (ERS) diets by using RNA-sequencing analysis and Golgi-Cox staining followed by integrated neuronal tracing and morphological analysis of neuronal dendrites, respectively. Spatial learning and severity of kainic acid-induced seizures were assessed in mice fed ERD and ERS diets. bEnd.3 cells internalized sEVs by using a saturable transport mechanism and secreted miR-34a across the basal membrane. sEVs penetrated the entire brain in fostering experiments; major regions of accumulation included the hippocampus, cortex and cerebellum. Two hundred ninety-five genes were differentially expressed in hippocampi from mice fed ERD and ERS diets; high-confidence gene networks included pathways implicated in axon guidance and calcium signaling. Juvenile pups fed the ERD diet had reduced dendritic complexity of dentate granule cells in the hippocampus, scored nine-fold lower in the Barnes maze test of spatial learning and memory, and the severity of seizures was 5-fold higher following kainic acid administration in adult mice fed the ERD diet compared to mice fed the ERS diet. We conclude that sEVs cross the BBB and contribute toward optimal neuronal development, spatial learning and memory, and resistance to kainic acid-induced seizures in mice.

Effect of disrupted episodic memory on food consumption: no impact of neuronal loss of endophilin A1 on food intake and energy balance

Food intake is generally assumed to reflect a regulatory tension between homeostatic and hedonic drivers. Information from individuals with memory dysfunction suggests that episodic memory may also play a significant role. We reasoned that if memory influences food intake, then disrupting a genetic factor that is important in episodic memory formation should affect food intake and energy balance. We performed spatial learning tests on neuronal specific endophilin A1 (EENA1) KO mice using the four-arm baited version of the radial arms maze (RAM). Energy regulation has also been evaluated. As anticipated neuronal EENA1 KO mice had impaired spatial memory. However, loss of endophilin A1 did not result in greater food intake, or altered energy absorption efficiency, relative to wild-type (WT) mice, when fed either low or high fat diets. Moreover, loss of EENA1 did not significantly affect other features of energy balance—physical activity and energy expenditure. No statistically significant changes were observed in the expression of hypothalamic neuropeptides related to food intake regulation, or circulating levels of leptin. We conclude that food intake and energy balance are largely governed by homeostatic and hedonic processes, and when these processes are intact memory probably plays a relatively minor role in food intake regulation.