Repeated exposure to novelty promotes resilience against the amyloid-beta effect through dopaminergic stimulation.

RATIONALE: The accumulation of beta-amyloid peptide (Aß) in the forebrain leads to cognitive dysfunction and neurodegeneration in Alzheimer's disease. Studies have shown that individuals with a consistently cognitively active lifestyle are less vulnerable to Aß toxicity. Recent research has demonstrated that intrahippocampal Aß can impact catecholaminergic release and spatial memory. Interestingly, exposure to novelty stimuli has been found to stimulate the release of catecholamines in the hippocampus. However, it remains uncertain whether repeated enhancing catecholamine activity can effectively alleviate cognitive impairment in individuals with Alzheimer's disease. OBJECTIVES: Our primary aim was to investigate whether repeated exposure to novelty could enable cognitive resilience against Aß. This protection could be achieved by modulating catecholaminergic activity within the hippocampus. METHODS: To investigate this hypothesis, we subjected mice to three different conditions-standard housing (SH), repeated novelty (Nov), or daily social interaction (Soc) for one month. We then infused saline solution (SS) or Aß (Aß1-42) oligomers intrahippocampally and measured spatial memory retrieval in a Morris Water Maze (MWM). Stereological analysis and extracellular baseline dopamine levels using in vivo microdialysis were assessed in independent groups of mice. RESULTS: The mice that received Aß1-42 intrahippocampal infusions and remained in SH or Soc conditions showed impaired spatial memory retrieval. In contrast, animals subjected to the Nov protocol demonstrated remarkable resilience, showing strong spatial memory expression even after Aß1-42 intrahippocampal infusion. The stereological analysis indicated that the Aß1-42 infusion reduced the tyrosine hydroxylase axonal length in SH or Soc mice compared to the Nov group. Accordingly, the hippocampal extracellular dopamine levels increased significantly in the Nov groups. CONCLUSIONS: These compelling results demonstrate the potential for repeated novelty exposure to strengthen the dopaminergic system and mitigate the toxic effects of Aß1-42. They also highlight new and promising therapeutic avenues for treating and preventing AD, especially in its early stages.

Effects of association between resveratrol and ketamine on behavioral and biochemical analysis in mice.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a phenol commonly found in grapes and wine, has been associated as protective in experimental models involving alterations in different neurotransmitter systems. However, studies are reporting that resveratrol could have adverse effects. This study evaluated if the association of a low dose of ketamine and resveratrol could induce behavioral manifestations associated with biochemical alterations. Moreover, the effects of treatment with resveratrol and/or ketamine on monoamine oxidase (MAO) activity, oxidative stress markers, and IL-6 levels in the brain were also investigated. Male Swiss mice received a low dose of ketamine (20 mg/kg) for 14 consecutive days, and resveratrol (10, 30, or 100 mg/kg) from day 8 up to day 14 of the experimental period, intraperitoneally. Locomotor, stereotyped behavior, Y-maze, novel recognition object test (NORT), and social interaction were quantified as well as ex vivo analysis of MAO activity, IL-6 levels, and oxidative stress markers (TBARS and total thiol levels) in brain tissues. Ketamine per se reduced the number of bouts of stereotyped behavior on day 8 of the experimental period. Resveratrol per se reduced the locomotor and exploratory activity in the open field, the time of exploration of new objects in the NORT, MAO-A activity in the striatum and increased the IL-6 levels in the cortex. These effects were attenuated when the mice were co-treated with ketamine and resveratrol. There was a decrease in MAO-A activity in the cortex of mice treated with ketamine + resveratrol 100 mg/kg. No significant alterations were found in oxidative stress markers. Resveratrol does not appear to cause summative effects with ketamine on behavioral alterations. However, the effect of resveratrol per se, mainly on locomotor and exploratory activity, should be better investigated.

Stress effects on spatial memory retrieval and brain c-Fos expression pattern in adults are modulated by early nicotine exposure.

The cognitive effects of nicotine are linked to persistent modifications in extended neural systems that regulate cognitive and emotional processes, and these changes occur during development. Additionally, acute stress has modulatory effects on cognition that involve broad neural systems and can be influenced by prior environmental challenges. The effects of nicotine and stress may be interconnected, leading to modifications in a network of shared brain substrates. Here, we explored the interaction between nicotine and stress by evaluating the effects of acute stress exposure in spatial memory retrieval for animals pretreated with nicotine during adolescence or adulthood. Adolescent (35 days old) and adult (70 days old) male Wistar rats were treated for 21 days with one daily subcutaneous injection of nicotine 0.14 mg/ml (free base). 30 days after the last injection, rats were trained in the Barnes maze and tested 24 h later, half the rats were tested under regular conditions, and half of them were exposed to 1 h of restraining stress before the retrieval test, and brain samples were collected and c-Fos immunopositive cells were stained. Prolonged nicotine withdrawal or acute stress improved spatial memory retrieval. Acute stress in nicotine pretreated adults impaired spatial memory retrieval. Nicotine exposure during early adulthood resulted in long-lasting brain adaptations that amplified emotional responses to acute stress after prolonged drug withdrawal.

Long-term potentiation and spatial memory training stimulate the hippocampal expression of RyR2 calcium release channels.

Introduction: Neuronal Ca2+ signals generated through the activation of Ca2+-induced Ca2+ release in response to activity-generated Ca2+ influx play a significant role in hippocampal synaptic plasticity, spatial learning, and memory. We and others have previously reported that diverse stimulation protocols, or different memory-inducing procedures, enhance the expression of endoplasmic reticulum-resident Ca2+ release channels in rat primary hippocampal neuronal cells or hippocampal tissue. Methods and Results: Here, we report that induction of long-term potentiation (LTP) by Theta burst stimulation protocols of the CA3-CA1 hippocampal synapse increased the mRNA and protein levels of type-2 Ryanodine Receptor (RyR2) Ca2+ release channels in rat hippocampal slices. Suppression of RyR channel activity (1 h preincubation with 20 µM ryanodine) abolished both LTP induction and the enhanced expression of these channels; it also promoted an increase in the surface expression of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluR1 and GluR2 and caused a moderate but significant reduction of dendritic spine density. In addition, training rats in the Morris water maze induced memory consolidation, which lasted for several days after the end of the training period, accompanied by an increase in the mRNA levels and the protein content of the RyR2 channel isoform. Discussion: We confirm in this work that LTP induction by TBS protocols requires functional RyR channels. We propose that the increments in the protein content of RyR2 Ca2+ release channels, induced by LTP or spatial memory training, play a significant role in hippocampal synaptic plasticity and spatial memory consolidation.

Can anxiety-like behavior and spatial memory predict the extremes of skilled walking performance in mice? An exploratory, preliminary study.

Introduction: Skilled walking is influenced by memory, stress, and anxiety. While this is evident in cases of neurological disorders, memory, and anxiety traits may predict skilled walking performance even in normal functioning. Here, we address whether spatial memory and anxiety-like behavior can predict skilled walking performance in mice. Methods: A cohort of 60 adult mice underwent a behavioral assessment including general exploration (open field), anxiety-like behavior (elevated plus maze), working and spatial memory (Y-maze and Barnes maze), and skilled walking performance (ladder walking test). Three groups were established based on their skilled walking performance: superior (SP, percentiles ≥75), regular (RP, percentiles 74-26), and inferior (IP, percentiles ≤25) performers. Results: Animals from the SP and IP groups spent more time in the elevated plus maze closed arms compared to the RP group. With every second spent in the elevated plus maze closed arms, the probability of the animal exhibiting extreme percentiles in the ladder walking test increased by 1.4%. Moreover, animals that spent 219 s (73% of the total time of the test) or more in those arms were 4.67 times more likely to exhibit either higher or lower percentiles of skilled walking performance. Discussion: We discuss and conclude anxiety traits may influence skilled walking performance in facility-reared mice.

Efecto del estímulo masticatorio y estrés agudo sobre la interleuquina 6, la memoria y el aprendizaje espacial en ratones Balb/c

Introducción. El estrés agudo altera la memoria y aprendizaje espacial y la expresión de la interleuquina 6 (IL-6), mientras que el estímulo masticatorio evitaría dichos efectos. Objetivo. Determinar el efecto del estímulo masticatorio y el estrés agudo sobre la expresión de interleuquina 6, la memoria y el aprendizaje espacial en ratones. Métodos. Experimento con 70 ratones albinos machos de 2 meses de edad de la cepa Balb/c que fueron distribuidos aleatoriamente en grupo A1: estrés agudo 1 hora; grupo A2: estrés agudo 1 hora + estímulo masticatorio 1 hora; grupo B1: estrés agudo 2 horas; grupo B2: estrés agudo 2 horas + estímulo masticatorio 2 horas; grupo C1: estrés agudo 3 horas; grupo C2: estrés agudo 3 horas + estímulo masticatorio 3 horas; y grupo D: sin intervención. Durante 3 días, se evaluó la memoria y el aprendizaje espacial en el laberinto acuático de Morris. La IL-6 fue determinada mediante ELISA. Resultados. La IL-6 fue mayor en el grupo B2 vs los demás grupos (p < 0,001). Además, en el primer día de evaluación, la adquisición de memoria y aprendizaje espacial fue menor en el grupo A1 vs A2 (p = 0,042). Conclusión. Solo en el primer día de evaluación encontramos que el estímulo masticatorio previno la disminución de la adquisición de memoria y aprendizaje espacial en ratones sometidos a estrés agudo de baja intensidad. Los resultados en general no fueron concluyentes sobre el efecto del estímulo masticatorio. Además, la IL-6 fue mayor en el estrés + el estímulo masticatorio (grupo B2) sobre el resto.

Introduction. Acute stress alters memory and spatial learning and the expression of interleukin 6, the chewing stimulus would prevent these effects. Objective. To determine the effect of chewing stimulation and acute stress on the expression of interleukin 6 and memory and spatial learning in mice. Methods. Experiment where 70 male albino mice of the Balb/c of age 2 month were randomly distributed into: Group A1: acute stress 1 hour; Group A2: acute stress 1 hour + chewing stimulus 1 hour; Group B1: acute stress 2 hours; Group B2: acute stress 2 hours + chewing stimulus 2 hours; Group C1: acute stress 3 hours; C2: acute stress 3 hours + chewing stimulus 3 hours; Group D: without intervention. For 3 days, spatial memory and learning were tested in the Morris water maze. Interleukin 6 (IL-6) was analyzed by ELISA test. Results. IL-6 was higher in the B2 group vs the other groups (p<0.0001). In addition, on the first day of evaluation, the acquisition of spatial memory and spatial was lower in the A1 vs. A2 group (p=0.042). Conclusión. Only on the first day of evaluation, we found that the masticatory stimulus prevented the decrease in memory acquisition and spatial learning in mice subjected to low-intensity acute stress. The results were generally inconclusive on the effect of masticatory stimulation. In addition, IL-6 was higher in the stress + masticatory stimulus (group B2) over the rest.

Visual-spatial processing impairment in the occipital-frontal connectivity network at early stages of Alzheimer's disease.

Introduction: Alzheimer's disease (AD) is the leading cause of dementia worldwide, but its pathophysiological phenomena are not fully elucidated. Many neurophysiological markers have been suggested to identify early cognitive impairments of AD. However, the diagnosis of this disease remains a challenge for specialists. In the present cross-sectional study, our objective was to evaluate the manifestations and mechanisms underlying visual-spatial deficits at the early stages of AD. Methods: We combined behavioral, electroencephalography (EEG), and eye movement recordings during the performance of a spatial navigation task (a virtual version of the Morris Water Maze adapted to humans). Participants (69-88 years old) with amnesic mild cognitive impairment-Clinical Dementia Rating scale (aMCI-CDR 0.5) were selected as probable early AD (eAD) by a neurologist specialized in dementia. All patients included in this study were evaluated at the CDR 0.5 stage but progressed to probable AD during clinical follow-up. An equal number of matching healthy controls (HCs) were evaluated while performing the navigation task. Data were collected at the Department of Neurology of the Clinical Hospital of the Universidad de Chile and the Department of Neuroscience of the Faculty of Universidad de Chile. Results: Participants with aMCI preceding AD (eAD) showed impaired spatial learning and their visual exploration differed from the control group. eAD group did not clearly prefer regions of interest that could guide solving the task, while controls did. The eAD group showed decreased visual occipital evoked potentials associated with eye fixations, recorded at occipital electrodes. They also showed an alteration of the spatial spread of activity to parietal and frontal regions at the end of the task. The control group presented marked occipital activity in the beta band (15-20 Hz) at early visual processing time. The eAD group showed a reduction in beta band functional connectivity in the prefrontal cortices reflecting poor planning of navigation strategies. Discussion: We found that EEG signals combined with visual-spatial navigation analysis, yielded early and specific features that may underlie the basis for understanding the loss of functional connectivity in AD. Still, our results are clinically promising for early diagnosis required to improve quality of life and decrease healthcare costs.

Vitamin D3 improves spatial memory and modulates cytokine levels in aged rats.

Vitamin D3 deficiency is associated with an increased risk of dementia. An association between vitamin D3 deficiency and subjective cognitive complaints in geriatric patients has been previously reported. This study aimed to evaluate the effects of two doses of vitamin D3 on spatial memory (using the Radial Maze) and cytokine levels [tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and interleukin-10 (IL-10)] on 2-, 6-, 13-, 22-, and 31-month-old male Wistar rats. Animals were supplemented with vitamin D3 at doses of 42 IU/kg and 420 IU/kg for 21 days. A radial maze test was performed to evaluate spatial memory. After the behavioral test, the frontal cortex and hippocampus were dissected for enzyme immunoassay analyses to measure the cytokine levels (TNFα, IL-1ß, IL-6, and IL-10). Our results showed that vitamin D3 supplementation reversed spatial memory impairment at the supplemented doses (42 and 420 IU/kg) in 6-, 13-, and 22-month-old animals and at a dose of 420 IU/kg in 31-month-old animals. The lower dose (42 IU/kg) regulates both pro- and anti-inflammatory cytokines mainly in the frontal cortex. Our results suggest that vitamin D3 has a modulatory action on pro- and anti-inflammatory cytokines, since older animals showed increased cytokine levels compared to 2-month-old animals, and that vitamin D3 may exert an immunomodulatory effect on aging.

Pre-clinical evidence that methylphenidate increases motivation and/or reward preference to search for high value rewards.

Methylphenidate is a stimulant used to treat attention deficit and hyperactivity disorder (ADHD). In the last decade, illicit use of methylphenidate has increased among healthy young adults, who consume the drug under the assumption that it will improve cognitive performance. However, the studies that aimed to assess the methylphenidate effects on memory are not consistent. Here, we tested whether the effect of methylphenidate on a spatial memory task can be explained as a motivational and/or a reward effect. We tested the effects of acute and chronic i.p. administration of 0.3, 1 or 3 mg/kg of methylphenidate on motivation, learning and memory by using the 8-arm radial maze task. Adult male Wistar rats learned that 3 of the 8 arms of the maze were consistently baited with 1, 3, or 6 sucrose pellets, and the number of entries and reentries into reinforced and non-reinforced arms of the maze were scored. Neither acute nor chronic (20 days) methylphenidate treatment affected the number of entries in the non-baited arms. However, chronic, but not acute, 1-3 mg/kg methylphenidate increased the number of reentries in the higher reward arms, which suggests a motivational/rewarding effect rather than a working memory deficit. In agreement with this hypothesis, the methylphenidate treatment also decreased the approach latency to the higher reward arms, increased the approach latency to the low reward arm, and increased the time spent in the high, but not low, reward arm. These findings suggest that methylphenidate may act more as a motivational enhancer rather than a cognitive enhancer in healthy people.

Effects of working memory training on cognition in healthy older adults: A systematic review / Efeitos do treino de memória operacional na cognição de idosos saudáveis: um estudo de revisão sistemática

ABSTRACT. The working memory (WM) training in older adults can benefit their cognition. However, there is a dearth of literature reviews on the subject. Objective: This study aimed to investigate and evaluate the effects of WM training on the cognition of healthy older adults, in individual and group interventions reported in the literature. Methods: This is a systematic review involving a qualitative analysis of publications on the SciELO, LILACS, and MEDLINE databases carried out between March and June 2021. Results: A total of 47 studies were identified and analyzed, comprising 40 in older adults only and 7 comparing older and younger adults, investigating individual or group WM training or other types of intervention focused on WM effects. Conclusions: Both individual and group intervention contributed to the maintenance and/or improvement of cognition in older adults exploiting brain plasticity to promote mental health and prevent cognitive problems that can negatively impact quality of life of this group.

RESUMO. O treino da memória operacional (WM) com idosos pode gerar benefícios em sua cognição. Entretanto, há escassez de revisões da literatura sobre o tema. Objetivo: Investigar e avaliar, na literatura, os efeitos do treino da WM na cognição de idosos saudáveis, em intervenções individuais e grupais. Métodos: Estudo de revisão sistemática realizado entre março e junho de 2021, utilizando-se as bases Scientific Electronic Library Online (SciELO), Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS) e Medical Literature Analysis and Retrieval System Online (MEDLINE). Resultados: Foram identificados e analisados 47 estudos, 40 apenas com idosos, e sete comparativos entre idosos e adultos mais jovens, que realizaram treino individual ou em grupo com foco nos efeitos na WM. Conclusões: Os trabalhos analisados mostraram que ambos os tipos de intervenções podem contribuir para a manutenção e/ou melhoria da cognição de pessoas idosas, aproveitando sua plasticidade cerebral e, portanto, para a promoção de sua saúde mental e para a prevenção de problemas cognitivos que podem interferir em sua qualidade de vida.

Maternal enrichment increases infantile spatial amnesia mediated by postnatal neurogenesis modulation.

Infantile amnesia, the inability to form long-lasting episodic memories, is a phenomenon extensively known but with no clear understanding of its origins. However, a recent study showed that high rates of hippocampal postnatal neurogenesis degrade episodic-like memories in infants a few days after memory acquisition. Additionally, new studies indicate that exposure to an enriched environment in mice leads to high hippocampal neurogenesis in their offspring. Nevertheless, it is still unclear how this intergenerational trait affects the persistence of hippocampal memories. Therefore, we evaluated spatial memory retention in the offspring of enriched female mice after weaning to address this question. Ten days after spatial learning, we tested memory retention, observing that the offspring of enriched dams increased spatial memory failure; this finding correlates with high proliferation rates in the hippocampus. Furthermore, we evaluated the causal relationship between postnatal hippocampal neurogenesis and memory failure using the antiproliferative drug Temozolomide (TMZ), which rescued spatial memory retrieval. Finally, we evaluated neuronal activity in the hippocampus quantifying the cells expressing the immediate early gene c-Fos. This evaluation showed engram modifications between groups. This neural activity pattern indicates that the high neurogenesis rates can modify memory engrams and cognitive performance. In conclusion, the inherited increase of hippocampal neurogenesis by enriched dams leads to plastic changes that exacerbate infantile amnesia in a spatial task.

Memory improvement in senile rats after prebiotic and probiotic supplementation is not induced by GLP-1.

INTRODUCTION: The mechanism underlying the memory improvement induced by prebiotic and probiotic supplementation remains unclear. Glucagon-like peptide type 1 (GLP-1) could play an important role since it is induced by prebiotics and enhances memory and learning. AIMS: We correlated the levels of GLP-1 with spatial memory in senile animals to determine its role in memory improvement after prebiotic and probiotic supplementation. METHODS: Senile rats were randomly assigned to four groups: (1) water (control); (2) Enterococcus faecium (probiotic); (3) agave inulin (prebiotic); and (4) E. faecium + agave inulin (symbiotic). Each supplement was administered by an orogastric cannula for 5 weeks. In the fifth week, spatial memory was assessed using the Morris Water Maze test (MWM). We extracted the hippocampus, intestine, and serum. GLP-1 levels were quantified by enzyme-linked immunosorbent assay. RESULTS: A significant decrease in escape latency time in the MWM was observed in all groups treated with supplements. The symbiotic group achieved the highest reduction (15.13 s ± 6.40) (p < 0.01). We did not find a significant increase in GLP-1 levels nor a direct correlation of its levels with spatial memory improvement (p > 0.05). CONCLUSION: Prebiotic and probiotic supplementation improved spatial memory in senile animals. However, this beneficial effect did not correlate with GLP-1 levels.

Object recognition tasks in rats: Does sex matter?

Novelty recognition tasks based on object exploration are frequently used for the evaluation of cognitive abilities and investigation of neurobiological and molecular aspects of memory in rodents. This is an interesting approach because variations of the object recognition tasks focus on different aspects of the memory events such as novelty, location, context, and combinations of these elements. Nevertheless, as in most animal neuroscience research, female subjects are underrepresented in object recognition studies. When studies include females, the particularities of this sex are not always considered. For example, appropriate controls for manipulations conducted exclusively in females (such as estrous cycle verification) are not included. In addition, interpretation of data is often based on standardizations conducted with male subjects. Despite that, females are frequently reported as deficient and unable to adequately perform some memory tests. Thus, our study aims to review studies that describe similarities and differences between male and female performances in the different variations of object recognition tasks. In summary, although females are commonly described with deficits and the articles emphasize sex differences, most published data reveal similar performances when sexes are compared.

Hippocampal DNA Methylation, Epigenetic Age, and Spatial Memory Performance in Young and Old Rats.

In humans and rats, aging is associated with a progressive deterioration of spatial learning and memory. These functional alterations are correlated with morphological and molecular changes in the hippocampus. Here, we assessed age-related changes in DNA methylation (DNAm) landscape in the rat hippocampus and the correlation of spatial memory with hippocampal DNAm age in 2.6- and 26.6-month-old rats. Spatial memory performance was assessed with the Barnes maze test. To evaluate learning ability and spatial memory retention, we assessed the time spent by animals in goal sector 1 (GS1) and 3 (GS3) when the escape box was removed. The rat pan-tissue clock was applied to DNAm data from hippocampal tissue. An enrichment pathway analysis revealed that neuron fate commitment, brain development, and central nervous system development were processes whose underlying genes were enriched in hypermethylated CpGs in the old rats. In the old rat hippocampi, the methylation levels of CpG proximal to transcription factors associated with genes Pax5, Lbx1, Nr2f2, Hnf1b, Zic1, Zic4, Hoxd9; Hoxd10, Gli3, Gsx1 and Lmx1b, and Nipbl showed a significant regression with spatial memory performance. Regression analysis of different memory performance indices with hippocampal DNAm age was significant. These results suggest that age-related hypermethylation of transcription factors related to certain gene families, such as Zic and Gli, may play a causal role in the decline in spatial memory in old rats. Hippocampal DNAm age seems to be a reliable index of spatial memory performance in young and old rats.

Voluntary physical activity improves spatial and recognition memory deficits induced by post-weaning chronic exposure to a high-fat diet.

Childhood and adolescent exposure to obesogenic environments has contributed to the development of several health disorders, including neurocognitive impairment. Adolescence is a critical neurodevelopmental window highly influenced by environmental factors that affect brain function until adulthood. Post-weaning chronic exposure to a high-fat diet (HFD) adversely affects memory performance; physical activity is one approach to coping with these dysfunctions. Previous studies indicate that voluntary exercise prevents HFD's detrimental effects on memory; however, it remains to evaluate whether it has a remedial/therapeutical effect when introduced after a long-term HFD exposure. This study was conducted on a diet-induced obesity mice model over six months. After three months of HFD exposure (without interrupting the diet) access to voluntary physical activity was provided. HFD produced weight gain, increased adiposity, and impaired glucose tolerance. Voluntary physical exercise ameliorated glucose tolerance and halted weight gain and fat accumulation. Additionally, physical activity mitigated HFD-induced spatial and recognition memory impairments. Our data indicate that voluntary physical exercise starting after several months of periadolescent HFD exposure reverses metabolic and cognitive alterations demonstrating that voluntary exercise, in addition to its known preventive effect, also has a restorative impact on metabolism and cognition dysfunctions associated with obesity.

Effect of providing purple sweet potato water extract on tumor necrosis factor-α levels, protein 53 expression, glial fibrillary acidic protein expression, brain-derived neurotrophic factor levels, and spatial working memory in rats with d-galactose induction.

Alzheimer's dementia (AD) is a neurodegenerative disease. The mechanism of oxidative stress in AD is due to amyloid beta (Aß) protein that aggregates to form plaques, which further triggers chronic inflammation and neuronal apoptosis. Purple sweet potato extract with the main content of anthocyanins is a potential antioxidant with a direct target on the amyloid cascade hypothesis. Objective: The research objective was to determine the role of purple sweet potato water extract as an antioxidant and anti-inflammatory in preventing apoptosis in order to provide a neuroprotective effect in d-galactose-induced rats. Methods: A total of 100 male Wistar rats with randomized posttest-only control group design that met the eligibility criteria were included in this study. The treatment group was given 200 mg/kg BW/day of purple sweet potato water extract on days 1-70. d-galactose induction was administered in the treatment and control groups on days 15-70. Results: The independent t-test showed that the mean tumor necrosis factor-α (TNF-α) levels in the treatment group (735.36±139.74) was significantly lower than that in the control group (896.77±152.52). The p53 and glial fibrillary acidic protein (GFAP) expressions of astrocyte cells in the treatment group were significantly lower than that in the control group. The brain-derived neurotrophic factor (BDNF) levels in the treatment group (498.13±121.47) were higher than that in the control (391.93±140.28), and there was a significant increase in spatial working memory in the treatment group (72.01±10.22) than the control (59.77±11.87). Conclusions: The neuroprotective effect of purple sweet potato extract is due to d-galactose induction resulting from decrease in TNF-α levels, p53 expression, and GFAP expression and increase in BDNF levels and spatial working memory.

A doença de Alzheimer (DA) é uma doença neurodegenerativa. O mecanismo de estresse oxidativo na DA ocorre devido à proteína beta amilóide que se agrega para formar placas que desencadeiam inflamação crônica e apoptose neuronal. O extrato de batata-doce roxa composto principalmente por antocianinas é um potencial antioxidante com efeito direto sobre a hipótese da cascata amilóide. Objetivo: O objetivo da pesquisa foi determinar o papel do extrato aquoso de batata-doce roxa como antioxidante e anti-inflamatório na prevenção da apoptose, para proporcionar um efeito neuroprotetor em ratos induzidos por D-galactose. Métodos: Grupo controle randomizado pós-teste com 100 ratos Wistar machos que preencheram os critérios de elegibilidade. O grupo de tratamento recebeu 200mg/kg de peso corporal/dia de extrato aquoso de batata-doce roxa nos dias 1-70. A indução de D-galactose foi testada nos grupos de tratamento e controle nos dias 15-70. Resultados: O teste t independente mostrou que a média dos níveis de TNF-α no grupo de tratamento (735,36±139,74) foi significativamente menor do que no grupo controle (896,77±152,52). A expressão de p53 e a expressão de GFAP de células de astrócitos foram significativamente menores no grupo de tratamento do que no grupo controle. Os níveis de BDNF no grupo de tratamento (498,13±121,47) foram maiores que no grupo controle (391,93±140,28) e houve um aumento significativo da memória de trabalho espacial no grupo de tratamento (72,01±10,22) em relação ao controle (59,77±11,87). Conclusões: O efeito neuroprotetor do extrato de batata-doce roxa é devido à indução de D-galactose pela diminuição dos níveis de TNF-α, expressão de p53 e expressão de GFAP, aumentando assim os níveis de BDNF e memória espacial.

Spatial navigation in older adults with mild cognitive impairment and dementia: A systematic review and meta-analysis.

In this systematic review and meta-analysis, we compared the spatial navigation performance of older adults with mild cognitive impairment (MCI), Alzheimer's Disease (AD), and other dementias, using healthy older adults as controls. In addition, we evaluated the possible influence of the environment type (virtual and real), protocol (object- or environment-based), and the navigation mode (active and passive navigation) on spatial navigation task performance. In total, 1372 articles were identified and 24 studies were included in the meta-analysis. We found a large effect size on the spatial navigation performance of patients with cognitive decline (standardized mean difference (SMD) = 0.87, confidence interval (CI95%) = 0.62-1.09, p < 0.001), especially amnestic MCI (SMD = 1.10, CI95% = 0.71-1.49, p < 0.001) and patients with AD (SMD = 1.60, CI95% = 1.25-1.95, p < 0.001). However, the tasks did not identify mixed and vascular dementia (SMD = 0.92, CI95% = -0.33-2.18, p = 0.15 and SMD = 0.65, CI95% = -0.67-1.97, p = 0.33, respectively). Spatial navigation ability assessed using the Floor Maze Test showed the largest effect size in differentiating healthy older adults and patients with cognitive decline (SMD = 1.98,CI95% = 1.00-2.97, p < 0.001). In addition, tasks that require walking showed the greatest differences between the two groups. These results suggest that spatial navigation impairment is important, but disease-specific behavioral biomarker of the dementia pathology process that can be identified even in the early stages.

Effect of providing purple sweet potato water extract on tumor necrosis factor-α levels, protein 53 expression, glial fibrillary acidic protein expression, brain-derived neurotrophic factor levels, and spatial working memory in rats with d-galactose induction / Efeito do extrato de água de batata doce roxo no fator de necrose tumoral níveis alfa, na expressão da proteína 53, na expressão de proteína ácida fibrilar glial, nos níveis de fator neurotrófico cerebral e na memória espacial em ratos com indução de d-galactose

ABSTRACT. Alzheimer's dementia (AD) is a neurodegenerative disease. The mechanism of oxidative stress in AD is due to amyloid beta (Aβ) protein that aggregates to form plaques, which further triggers chronic inflammation and neuronal apoptosis. Purple sweet potato extract with the main content of anthocyanins is a potential antioxidant with a direct target on the amyloid cascade hypothesis. Objective: The research objective was to determine the role of purple sweet potato water extract as an antioxidant and anti-inflammatory in preventing apoptosis in order to provide a neuroprotective effect in d-galactose-induced rats. Methods: A total of 100 male Wistar rats with randomized posttest-only control group design that met the eligibility criteria were included in this study. The treatment group was given 200 mg/kg BW/day of purple sweet potato water extract on days 1-70. d-galactose induction was administered in the treatment and control groups on days 15-70. Results: The independent t-test showed that the mean tumor necrosis factor-α (TNF-α) levels in the treatment group (735.36±139.74) was significantly lower than that in the control group (896.77±152.52). The p53 and glial fibrillary acidic protein (GFAP) expressions of astrocyte cells in the treatment group were significantly lower than that in the control group. The brain-derived neurotrophic factor (BDNF) levels in the treatment group (498.13±121.47) were higher than that in the control (391.93±140.28), and there was a significant increase in spatial working memory in the treatment group (72.01±10.22) than the control (59.77±11.87). Conclusions: The neuroprotective effect of purple sweet potato extract is due to d-galactose induction resulting from decrease in TNF-α levels, p53 expression, and GFAP expression and increase in BDNF levels and spatial working memory.

RESUMO. A doença de Alzheimer (DA) é uma doença neurodegenerativa. O mecanismo de estresse oxidativo na DA ocorre devido à proteína beta amilóide que se agrega para formar placas que desencadeiam inflamação crônica e apoptose neuronal. O extrato de batata-doce roxa composto principalmente por antocianinas é um potencial antioxidante com efeito direto sobre a hipótese da cascata amilóide. Objetivo: O objetivo da pesquisa foi determinar o papel do extrato aquoso de batata-doce roxa como antioxidante e anti-inflamatório na prevenção da apoptose, para proporcionar um efeito neuroprotetor em ratos induzidos por D-galactose. Métodos: Grupo controle randomizado pós-teste com 100 ratos Wistar machos que preencheram os critérios de elegibilidade. O grupo de tratamento recebeu 200mg/kg de peso corporal/dia de extrato aquoso de batata-doce roxa nos dias 1-70. A indução de D-galactose foi testada nos grupos de tratamento e controle nos dias 15-70. Resultados: O teste t independente mostrou que a média dos níveis de TNF-α no grupo de tratamento (735,36±139,74) foi significativamente menor do que no grupo controle (896,77±152,52). A expressão de p53 e a expressão de GFAP de células de astrócitos foram significativamente menores no grupo de tratamento do que no grupo controle. Os níveis de BDNF no grupo de tratamento (498,13±121,47) foram maiores que no grupo controle (391,93±140,28) e houve um aumento significativo da memória de trabalho espacial no grupo de tratamento (72,01±10,22) em relação ao controle (59,77±11,87). Conclusões: O efeito neuroprotetor do extrato de batata-doce roxa é devido à indução de D-galactose pela diminuição dos níveis de TNF-α, expressão de p53 e expressão de GFAP, aumentando assim os níveis de BDNF e memória espacial.

Male rats are more vulnerable to pentylenetetrazole-kindling model but females have more spatial memory-related deficits.

Epilepsy is the most common neurological condition worldwide and is largely associated with memory impairment, both in human as well as animal models. Furthermore, differences in seizure onset and severity have already been observed between the sexes. The induction of epilepsy through multiple systemic injections of pentylenetetrazole (PTZ), a protocol known as chemical kindling, is a well-established tool for studies regarding epileptogenesis, as well as the efficacy of antiseizure medication. The aim of this study was to compare possible sex-related differences in seizure severity, memory, neuronal damage as well as the effects of the estrous cycle on seizure severity. Male (n = 10) and Female (n = 11) animals received 30 mg/kg i.p. injections three days a week for 6 weeks and, after the last application, were tested for short and long-term memory. Control, Male (n = 8) and Female (n = 5) groups did not receive PTZ injections. Although PTZ did not promote important changes into the estrous cycle phases throughout the entire experiment, female animals presented lower seizure scores but had both short and long-term memory impairments associated with cell loss in the hippocampus and anterior cingulate area. Male rats presented higher seizure scores associated with pronounced cell loss, but only long-term memory deficits. Our results demonstrate that the PTZ kindling protocol results in higher seizure scores with increased vulnerability in male rats, but female rats displayed more intense memory deficits.

Efecto de Spirulina maxima sobre la memoria espacial en Rattus norvegicus var. albinus / Effect of Spirulina maxima on spatial memory in Rattus norvegicus var. albinus

RESUMEN Introducción: La memoria es un proceso fisiológico que se activa por estímulos externos, es necesaria para modificar la conducta, adaptación al medio y la diferenciación del modelo animal. Este proceso complejo que involucra no sólo a las redes sinápticas sino otros mecanismos neurofisiológicos, suele ser estimulado por algunos nutraceúticos. Objetivo: Evaluar el efecto de Spirulina maxima sobre la memoria espacial en Rattus norvegicus var. albinus Material y Métodos: Se desarrolló un diseño de estímulo creciente donde se ordenaron cuatro grupos con 5 ratas cada uno, se agruparon en grupos Tratamiento I, II y III; a los que se les dio por vía oral Spirulina maxima a diferentes concentraciones y el grupo testigo sin tratamiento, se valoró la memoria espacial en el laberinto acuático de Morris. Resultados: Las ratas presentaron un tiempo de latencia equivalente para desarrollar la fase de adquisición y de retención, se registraron tiempos promedio; al aplicar la dosis 200 y 400 mg/kg no varían los índices de aprendizaje entre sí; y ante la dosis de concentración más alta 800 mg/kg se observó una disminución leve del tiempo de latencia de la fase de adquisición. De acuerdo con la prueba ANOVA hubo poca diferencia. Conclusiones: Hubo efecto de la Spirulina maxima en la memoria espacial del sujeto experimental, evidenciable en la duración de la conducta motora en el laberinto acuático de Morris, a través de índices de aprendizaje los cuales presentaron modificación favorable.

ABSTRACT Introduction: Memory is a physiological process that is activated by external stimuli. It is necessary for behavior modification, adaptation to the environment, and differentiation in the animal model. This complex process that involves not only synaptic networks but other neurophysiological mechanisms, is usually stimulated by some nutraceuticals. Objective: To evaluate the effect of Spirulina maxima on spatial memory in Rattus norvegicus var. albinus. Material and Methods: An increasing stimulus design was developed. Four similar groups of 5 rats were arranged and grouped into treatment I, II and III groups which were given Spirulina maxima orally at different concentrations; the control group did not received treatment. Spatial memory was assessed using the Morris water maze. Results: The rats presented an equal latency time to develop the acquisition and the retention phases; average times were recorded; the learning rates did not differ from each other at doses of 200 and 400 mg / kg; at the highest concentration dose of 800 mg / kg, there was a slight decrease in the latency time during the acquisition phase. There was a slight difference according to the ANOVA test. Conclusions: There was an effect of Spirulina maxima on the spatial memory of the experimental subject, which was evident in the duration of the motor behavior in the Morris water maze through learning rates which presented a favorable modification.