Effects of treadmill exercise on memory and c-Fos expression in the hippocampus of the rats with intracerebroventricular injection of streptozotocin

Exercise induction at expression immediate early gene (c-Fos, ARC, EGR-1) in the hippocampus: a systematic review

The immediate early gene exhibits activation markers in the nervous system consisting of ARC, EGR-1, and c-Fos and is related to synaptic plasticity, especially in the hippocampus. Immediate early gene expression is affected by physical exercise, which induces direct ARC, EGR-1, and c-Fos expression.

Objective

To assess the impact of exercise, we conducted a literature study to determine the expression levels of immediate early genes (ARC, c-Fos, and EGR-1).

Methods

The databases accessed for online literature included PubMed-Medline, Scopus, and ScienceDirect. The original English articles were selected using the following keywords in the title: (Exercise OR physical activity) AND (c-Fos) AND (Hippocampus), (Exercise OR physical activity) AND (ARC) AND (Hippocampus), (Exercise OR physical activity) AND (EGR-1 OR zif268) AND (Hippocampus).

Results

Physical exercise can affect the expression of EGR-1, c-Fos, and ARC in the hippocampus, an important part of the brain involved in learning and memory. High-intensity physical exercise can increase c-Fos expression, indicating neural activation. Furthermore, the expression of the ARC gene also increases due to physical exercise. ARC is a gene that plays a role in synaptic plasticity and regulation of learning and memory, changes in synaptic structure and increased synaptic connections, while EGR-1 also plays a role in synaptic plasticity, a genetic change that affects learning and memory. Overall, exercise or regular physical exercise can increase the expression of ARC, c-Fos, and EGR-1 in the hippocampus. This reflects the changes in neuroplasticity and synaptic plasticity that occur in response to physical activity. These changes can improve cognitive function, learning, and memory.

Conclusion

c-Fos, EGR-1, and ARC expression increases in hippocampal neurons after exercise, enhancing synaptic plasticity and neurogenesis associated with learning and memory.

Audiogenic Seizures in the Streptozotocin-Induced Rat Alzheimer's Disease Model

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative and progressive disorder with no cure and constant failures in clinical trials. The main AD hallmarks are amyloid-β (Aβ) plaques, neurofibrillary tangles, and neurodegeneration. However, many other events have been implicated in AD pathogenesis. Epilepsy is a common comorbidity of AD and there is important evidence indicating a bidirectional link between these two disorders. Some studies suggest that disturbed insulin signaling might play an important role in this connection.

OBJECTIVE

To understand the effects of neuronal insulin resistance in the AD-epilepsy link.

METHODS

We submitted the streptozotocin (STZ) induced rat AD Model (icv-STZ AD) to an acute acoustic stimulus (AS), a known trigger of seizures. We also assessed animals' performance in the memory test, the Morris water maze and the neuronal activity (c-Fos protein) induced by a single audiogenic seizure in regions that express high levels of insulin receptors.

RESULTS

We identified significant memory impairment and seizures in 71.43% of all icv-STZ/AS rats, in contrast to 22.22% of the vehicle group. After seizures, icv-STZ/AS rats presented higher number of c-Fos immunopositive cells in hippocampal, cortical, and hypothalamic regions.

CONCLUSION

STZ may facilitate seizure generation and propagation by impairment of neuronal function, especially in regions that express high levels of insulin receptors. The data presented here indicate that the icv-STZ AD model might have implications not only for AD, but also for epilepsy. Finally, impaired insulin signaling might be one of the mechanisms by which AD presents a bidirectional connection to epilepsy.

Neurobiological effects of gallic acid: current perspectives

Gallic acid (GA) is a phenolic molecule found naturally in a wide range of fruits as well as in medicinal plants. It has many health benefits due to its antioxidant properties. This study focused on finding out the neurobiological effects and mechanisms of GA using published data from reputed databases. For this, data were collected from various sources, such as PubMed/Medline, Science Direct, Scopus, Google Scholar, SpringerLink, and Web of Science. The findings suggest that GA can be used to manage several neurological diseases and disorders, such as Alzheimer's disease, Parkinson's disease, strokes, sedation, depression, psychosis, neuropathic pain, anxiety, and memory loss, as well as neuroinflammation. According to database reports and this current literature-based study, GA may be considered one of the potential lead compounds to treat neurological diseases and disorders. More preclinical and clinical studies are required to establish GA as a neuroprotective drug.

Performance of the intracerebroventricularly injected streptozotocin Alzheimer's disease model in a translationally relevant, aged and experienced rat population

The intracerebroventricularly (icv) injected streptozotocin (STZ) induced brain state is a widely used model of sporadic Alzheimer-disease (AD). However, data have been generated in young, naive albino rats. We postulate that the translationally most relevant animal population of an AD model should be that of aged rats with substantial learning history. The objective of the study was thus to probe the model in old rats with knowledge in various cognitive domains. Long-Evans rats of 23 and 10 months age with acquired knowledge in five-choice serial reaction time task (5-CSRTT), a cooperation task, Morris water-maze (MWM) and "pot-jumping" exercise were treated with 3 × 1.5 mg/kg icv. STZ and their performance were followed for 3 months in the above and additional behavioral assays. Both STZ-treated age groups showed significant impairment in the MWM (spatial learning) and novel object recognition test (recognition memory) but not in passive avoidance and fear conditioning paradigms (fear memory). In young STZ treated rats, significant differences were also found in the 5CSRTT (attention) and pot jumping test (procedural learning) while in old rats a significant increase in hippocampal phospho-tau/tau protein ratio was observed. No significant difference was found in the cooperation (social cognition) and pairwise discrimination (visual memory) assays and hippocampal β-amyloid levels. STZ treated old animals showed impulsivity-like behavior in several tests. Our results partly coincide with partly deviate from those published on young, albino, unexperienced rats. Beside the age, strain and experience level of the animals differences can also be attributed to the increased dose of STZ, and the applied food restriction regime. The observed cognitive and non-cognitive activity pattern of icv. STZ in aged experienced rats call for more extensive studies with the STZ model to further strengthen and specify its translational validity.

Treadmill exercise sex-dependently alters susceptibility to depression-like behaviour, cytokines and BDNF in the hippocampus and prefrontal cortex of rats with sporadic Alzheimer-like disease

Alzheimer's disease (AD) is associated with increased depression-related behaviours. Previous studies have reported a greater risk of AD and depression in women. In recent years, we and others have provided evidence that exercise during life could be used as a therapeutic strategy for stress-related disorders such as depression. The main goal of the current study was to determine whether treadmill exercise during life can reduce depression-related behaviours in male and female Wistar rats with sporadic Alzheimer-like disease (ALD). Animals were subjected to treadmill exercise eight weeks before and four weeks after ALD induction by streptozocin (STZ). We measured body weight, food intake, and depression-related symptoms in rats using five behavioural tests. We measured brain-derived-neurotrophic factor (BDNF), tumour-necrosis factor (TNF)-α, and interleukin (IL)-10 levels in the hippocampus and prefrontal cortex of animals. Our findings showed that exercise but not ALD induction decreased body weight and food intake in male and female rats. ALD induction increased depression-related symptoms and hippocampal TNF-α in male and female rats. Besides, treadmill exercise alone decreased depression-related behaviours and increased hippocampal BDNF in females but not males. We also found that treadmill exercise decreased depression-related behaviours and TNF-α in the hippocampus and prefrontal cortex, and increased IL-10 in the prefrontal cortex and BDNF in the hippocampus of female ALD-induced rats. However, treadmill exercise only reduced anhedonia-like behaviour and hippocampal TNF-α in male ALD-induced rats. Overall, the evidence from this study suggests that treadmill exercise alters depression-related behaviours, brain BDNF and cytokines in a sex-dependant manner in rats with sporadic Alzheimer-like disease.

Endurance exercise improves avoidance learning and spatial memory, through changes in genes of GABA and relaxin-3, in rats

Different exercise patterns, neurotransmitters, and some genes have numerous effects on learning and memory. This research aims to investigate the long-term effects of submaximal aerobic exercise on spatial memory (SM), passive avoidance learning (PAL), levels of serum relaxin-3, gamma-aminobutyric acid (GABA), RLN3 gene, and glutamic acid decarboxylase (GAD65/67 genes) in the brainstem of adult male Wistar rats. Fifty male Wistar rats were randomly divided into five groups: aerobic exercise groups, performed on a treadmill running (TR), for 5 weeks (Ex_5, n = 10), 10 weeks (Ex_10, n = 10), involuntary running wheel group for 5 weeks (IRW₅, n = 10), sham (Sh, n = 10) and control (Co, n = 10). Consequently, SM, PAL, serum relaxin-3, GABA, and GAD65/67 and RLN3 genes were measured by ELISA and PCR. Ex_5, Ex₁₀ and IRW₅ improved significantly SM (p ≤ 0.05), PAL (p ≤ 0.001) and decreased significantly relaxin-3 (p ≤ 0.001). RLN3 in the brain also decreased. However, it was not significant. GABA and GAD65/GAD67 increased significantly (p ≤ 0.05) in Ex₅, Ex₁₀ compared to Sh and Co. Aerobic exercise enhanced SM and PAL in Ex compared to Co and Sh. However, duration and type of exercise affected the level of enhancement. The serum relaxin-3 and RLN3 gene displayed reverse functions compared to GABA and GAD65/67 genes in Ex. Therefore, the changes of neurotransmitters in serum relaxin-3, GABA, and their genes: RLN3 and GAD65/67 respectively, influenced learning and memory meaningfully.

Intracerebroventricularly Injected Streptozotocin Exerts Subtle Effects on the Cognitive Performance of Long-Evans Rats

Intracerebroventricularly injected streptozotocin (STZ)-induced learning impairment has been an increasingly used rat model of Alzheimer disease. The evoked pathological changes involve many symptoms of the human disease (cognitive decline, increase in β-amyloid and phospho-tau level, amyloid plaque-like deposits). However, the model has predominantly been used with Wistar rats in the literature. The objective of the current study was to transfer it to Long-Evans rats with the ulterior aim to integrate it in a complex cognitive test battery where we use this strain because of its superior cognitive capabilities. We performed two experiments (EXP1, EXP2) with three months old male animals. At EXP1, rats were treated with 2 × 1.5 mg/kg STZ (based on the literature) or citrate buffer vehicle injected bilaterally into the lateral ventricles on days 1 and 3. At EXP2 animals were treated with 3 × 1.5 mg/kg STZ or citrate buffer vehicle injected in the same way as in EXP1 at days 1, 3, and 5. Learning and memory capabilities of the rats were then tested in the following paradigms: five choice serial reaction time test (daily training, started from week 2 or 8 post surgery in Exp1 or Exp2, respectively, and lasting until the end of the experiment); novel object recognition (NOR) test (at week 8 or 14), passive avoidance (at week 11 or 6) and Morris water-maze (at week 14 or 6). 15 or 14 weeks after the STZ treatment animals were sacrificed and brain phospho-tau/tau protein ratio and β -amyloid level were determined by western blot technique. In EXP1 we could not find any significant difference between the treated and the control groups in any of the assays. In EXP2 we found significant impairment in the NOR test and elevated β-amyloid level in the STZ treated group in addition to slower learning of the five-choice paradigm and a trend for increased phospho-tau/tau ratio. Altogether our findings suggest that the Long-Evans strain may be less sensitive to the STZ treatment than the Wistar rats and higher doses may be needed to trigger pathological changes in these animals. The results also highlight the importance of strain diversity in modelling human diseases.

The Role of Natural Antioxidants in the Prevention of Dementia-Where Do We Stand and Future Perspectives

Dementia, and especially Alzheimer's disease (AD), puts significant burden on global healthcare expenditure through its increasing prevalence. Research has convincingly demonstrated the implication of oxidative stress in the pathogenesis of dementia as well as of the conditions which increase the risk of developing dementia. However, drugs which target single pathways have so far failed in providing significant neuroprotection. Natural antioxidants, due to their effects in multiple pathways through which oxidative stress leads to neurodegeneration and triggers neuroinflammation, could prove valuable weapons in our fight against dementia. Although efficient in vitro and in animal models of AD, natural antioxidants in human trials have many drawbacks related to the limited bioavailability, unknown optimal dose, or proper timing of the treatment. Nonetheless, trials evaluating several of these natural compounds are ongoing, as are attempts to modify these compounds to achieve improved bioavailability.

Intracerebroventricular streptozotocin administration impairs mitochondrial calcium homeostasis and bioenergetics in memory-sensitive rat brain regions

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with cardinal manifestation of cognitive dysfunction. The limitation to avail a successful drug candidate encourages researchers to establish an appropriate animal model in the novel anti-AD drug discovery process. In this context, the mechanism of mitochondrial dysfunction in cognitive deficit animals is yet to be established for intracerebroventricular injection of streptozotocin (ICV-STZ). Experimental dementia was induced in male rats by ICV-STZ on day-1 (D-1) of the experimental protocol at a sub-diabetogenic dose (3 mg/kg) twice at an interval of 48 h into both rat lateral ventricles. ICV-STZ caused cognitive decline in terms of increase in the escape latency on D-14 to D-17 and, decrease in the time spent and percentage of distance travelled in the target quadrant during Morris water maze and decrease in the spontaneous alteration behavior during Y-maze tests in rats. Further, ICV-STZ decreased the level of acetylcholine and activity of choline acetyltransferase and increased the activity of acetylcholinesterase in rat hippocampus, pre-frontal cortex and amygdala. Interestingly, ICV-STZ increased the mitochondrial calcium in addition to decrease in the mitochondrial function, integrity and bioenergetics in all rat brain regions. Further, ICV-STZ enhanced the levels of expression of NR1 subunit of N-methyl-D-aspartate receptor, mitochondrial calcium uniporter and sodium-calcium exchanger in these rat brain regions. Thus, NR1-dependent mitochondrial calcium accumulation could be considered as a major attribute to the animal model of ICV-STZ-induced AD-like manifestations. Further, drugs targeting to manage mitochondrial calcium homeostasis could best be studied in this animal model.

Does calorie restriction improve cognition?

Calorie restriction (CR) has been considered the most effective non-pharmacological intervention to counteract aging-related diseases and improve longevity. This intervention has shown beneficial effects in the prevention and treatment of several chronic diseases and functional declines related to aging, such as Parkinson's, Alzheimer's, and neuroendocrine disorders. However, the effects of CR on cognition show controversial results since its effects vary according to intensity, duration, and the period of CR. This review focuses on the main studies published in the last ten years regarding the consequences of CR on cognition in different neurological diseases and conditions of experimental animals. Also, possible CR mimetics are discussed. These findings highlight the potential beneficial effects of CR of up to 40 % on cognition when started early in life in non human animals.

Effects of environmental enrichment on forebrain neural plasticity and survival success of stocked Atlantic salmon

Fish reared for stocking programmes are severely stimulus deprived compared with their wild conspecifics raised under natural conditions. This leads to reduced behavioural plasticity and low post-release survival of stocked fish. Environmental enrichment can have positive effects on important life skills, such as predator avoidance and foraging behaviour, but the neural mechanisms underpinning these behavioural changes are still largely unknown. In this study, juvenile Atlantic salmon (Salmo salar) were reared in an enriched hatchery environment for 7 weeks, after which neurobiological characteristics and post-release survival were compared with those of fish reared under normal hatchery conditions. Using in situ hybridization and qPCR, we quantified the expression of brain-derived neurotrophic factor (bdnf) and the neural activity marker cfos in telencephalic subregions associated with relational memory, emotional learning and stress reactivity. Aside from lower expression of bdnf in the Dlv (a region associated with relational memory) of enriched salmon, we observed no other significant effects of enrichment in the studied regions. Exposure to an enriched environment increased post-release survival during a 5 month residence in a natural river by 51%. Thus, we demonstrate that environmental enrichment can improve stocking success of Atlantic salmon parr and that environmental enrichment is associated with changes in bdnf expression in the fish's hippocampus-equivalent structure.

Neuregulin1β improves both spatial and associative learning and memory in Alzheimer model of rats possibly through signaling pathways other than Erk1/2

BACKGROUND

Neuregulin-1β (NRG1 β) is associated with various neurological disorders such as schizophrenia, depression and Parkinson's disease. However, its role in Alzheimer's (AD) has not been understood yet. Here, we have studied the effect of NRG1 β and extracellular-signal-regulated kinase (ERK) signaling on special and associative memories and emotional stress in AD model of rats.

METHODS

Fifty six male Wistar rats were divided into eight groups of: Saline + Saline, Aβ + Saline, Aβ + NRG1β (5 μg/5 ul), Aβ + PBS, Aβ + NRG1β + PD98059 (PD, 5 μg/2 μl), Aβ + NRG1β + Saline and Saline + PD. AD model was induced by intracerebroventricular (ICV) injection of beta-amyloid protein (Aβ1-42, 4 μg/2 μl). The cognitive performances of rats were evaluated using Morris Water Maze (MWM) and Step through passive avoidance. Also locomotors activity and emotionality of animals were considered in an Open field test. Data were analyzed by one way Anova one way, repeated measure and T-test.

RESULTS

Significant improvement was found in spatial learning and memory assessed by total time spent in target quadrant [F (4, 32) = 12.4, p = 0.001], escape latency [F (4, 32) = 15.767, p = 0.001] and distance moved [F (4, 32) = 5.55, p = 0.002], in Aβ + NRG1β compared with Aβ + Saline in MWM. Also Aβ + NRG1β showed long latencies to enter into the dark compartment [F (4, 32) = 6.43, p = 0.001], but short time spent [F (4, 32) =6.93, p = 0.001] compared with control. Administration of an ERK inhibitor (PD98059, 5 μg, 15 min before NRG1β) didn't completely block learning memory restored by NRG1β in AD model (p = 0.7). No significant between groups differences was found in emotional stress characteristics in open field, except the grooming numbers which were higher in Saline + PD compared with Saline + Saline (p = 0.02).

CONCLUSION

Our findings indicate that NRG1β restores cognitive dysfunctions induced by amyloid β through signaling pathways possibly other than Erk1/2, with no significant change in anxiety, locomotion and vegetative activities.

Co-treatment of vitamin D supplementation and aerobic training improves memory deficit in ovariectomized rat

Objective: Metabolic syndrome (MetS) and insufficient vitamin D levels are globally increasing phenomena which are correlated with cognitive impairment. This study investigated the interactive effect of aerobic training with vitamin D supplementation on memory deficit in rats with metabolic syndrome induced by ovariectomy.Methods: A total of forty Wistar rats weighing 240-255 gr were randomly matched on their body weight and divided into ovariectomy (OVX, n = 32) and sham-operated (SHAM; n = 8) groups. OV group was then divided into vitamin D supplementation (OVX + Vit D; 10000 IU/kg/week, for 8 weeks, n = 8), aerobic training (OVX + AT; n = 8), aerobic training and vitamin D supplementation (OVX + AT + Vit D; 10000 IU/kg/week, for 8 weeks, n = 8), and vehicle control group receiving sesame oil (OVX + Ses Oil; n = 8). After the end of intervention, passive avoidance learning and memory were assessed in step through passive avoidance paradigm. Obtained data were analyzed by ANOVA and post hoc Tukey test.Results: After 8 weeks of aerobic training and vitamin D supplementation, step through dark compartment latency (STL) was significantly higher and total time spent in that compartment (TSD) was lower in OVX + AT + Vit D compared to the other counterpart groups.Conclusion: Vitamin D supplementation combined with 8-week aerobic training alleviates cognitive impairment metabolic syndrome induced by ovariectomy.

Corticolimbic analysis of microRNAs and protein expressions in scopolamine-induced memory loss under stress

The aim of the present study was to assess thealterations of corticolimbic microRNAs and protein expressions in the effect of scopolamine with or without stress on passive-avoidance memory in male Wistar rats. The expressions of miR-1, miR-10 and miR-26 and also the levels of p-CREB, CREB, C-FOS and BDNF in the prefrontal cortex (PFC), the hippocampus and the amygdala were evaluated using RT-qPCR and Western blotting techniques. The data showed that the administration of a muscarinic receptor antagonist, scopolamine or the exposure to 30 min stress significantly induced memory loss. Interestingly, the injection of an ineffective dose of scopolamine (0.5 mg/kg) alongside with exposure to an ineffective time of stress (10 min) impaired memory formation, suggesting a potentiative effect of stress on scopolamine response. Our results showed that memory formation was associated with the down-regulated expression of miR-1, miR-10 and miR-26 in the PFC and the hippocampus, but not the amygdala. The relative expression increase of miR-1 and miR-10 in the PFC and the hippocampus was shown in memory loss induced by scopolamine administration or 30-min stress. The PFC level of miR-10 and also hippocampal level of miR-1 and miR-10 were significantly up-regulated, while amygdala miR-1 and miR-26 were down-regulated in scopolamine-induced memory loss under stress. Memory formation increased BDNF, C-FOS and p-CREB/CREB in the PFC, the hippocampus and the amygdala. In contrast, the PFC, hippocampal and amygdala protein expressions were significantly decreased in memory loss induced by scopolamine administration (2 mg/kg), stress exposure (for 30 min) or scopolamine (0.5 mg/kg) plus stress (10 min). One of the most significant findings to emerge from this study is that the stress exposure potentiated the amnesic effect of scopolamine may via affecting the expressions of miRs and proteins in the PFC, the hippocampus and the amygdala. It is possible to hypothesis that corticolimbic signaling pathways play a critical role in relationship between stress and Alzheimer's disease.

Acute and long-term treadmill running differentially induce c-Fos expression in region- and time-dependent manners in mouse brain

Acute and long-term exercise differentially affect brain functions. It has been suggested that neuronal activation is one of the mechanisms for exercise-induced enhancement of brain functions. However, the differential effects of acute and long-term exercise on the spatial and temporal profiles of neuronal activation in the brain have been scarcely explored. In this study, we profiled the expression of c-Fos, a marker of neuronal activation, in selected 26 brain regions of 2-month-old male C57/B6 mice that received either a single bout of treadmill running (acute exercise) or a 4-week treadmill training (long-term exercise) at the same duration (1 h/day) and intensity (10 m/min). The c-Fos expression was determined before, immediately after, and 2 h after the run. The results showed that acute exercise increased the densities of c-Fos⁺ cells in the ventral hippocampal CA1 region, followed by (in a high to low order) the primary somatosensory cortex, other hippocampal subregions, and striatum immediately after the run; significant changes remained evident in the hippocampal subregions after a 2-h rest. Long-term exercise increased the densities of c-Fos⁺ cells in the striatum, followed by the primary somatosensory, primary and secondary motor cortices, hippocampal subregions, hypothalamic nuclei, and lateral periaqueductal gray; significant changes remained evident in the striatum, hippocampal subregions, hypothalamic nuclei, and lateral periaqueductal gray after a 2-h rest. Interestingly, the densities of c-Fos⁺ cells in the substantia nigra and ventral tegmental area only increased after a 2-h rest after the run in the long-term exercise group. The densities of c-Fos⁺ cells were positively correlated with the expression of brain-derived neurotrophic factor in the selected brain regions. In conclusion, both acute and long-term treadmill running at mild intensity induce c-Fos expression in the limbic system and movement-associated cortical and subcortical regions, with long-term exercise involving more brain regions (i.e., hypothalamus and periaqueductal gray) and longer lasting effects.

G, Calderon O, Moreno-Gonzalez I. Modifiable Risk Factors for Alzheimer's Disease

Since first described in the early 1900s, Alzheimer's disease (AD) has risen exponentially in prevalence and concern. Research still drives to understand the etiology and pathogenesis of this disease and what risk factors can attribute to AD. With a majority of AD cases being of sporadic origin, the increasing exponential growth of an aged population and a lack of treatment, it is imperative to discover an easy accessible preventative method for AD. Some risk factors can increase the propensity of AD such as aging, sex, and genetics. Moreover, there are also modifiable risk factors-in terms of treatable medical conditions and lifestyle choices-that play a role in developing AD. These risk factors have their own biological mechanisms that may contribute to AD etiology and pathological consequences. In this review article, we will discuss modifiable risk factors and discuss the current literature of how each of these factors interplay into AD development and progression and if strategically analyzed and treated, could aid in protection against this neurodegenerative disease.

Neuroprotective effects of exercise in rodent models of memory deficit and Alzheimer's

Alzheimer's disease (AD) is a fastest growing neurodegenerative condition with no standard treatment. There are growing evidence about the beneficial effects of exercise in brain health promotion and slowing the cognitive decline. The aim of this study was to review the protective mechanisms of treadmill exercise in different models of rodent memory deficits. Online literature database, including PubMed-Medline, Scopus, Google scholar were searched from 2003 till 2017. Original article with English language were chosen according to following key words in the title: (exercise OR physical activity) AND (memory OR learning). Ninety studies were finally included in the qualitative synthesis. The results of these studies showed the protective effects of exercise on AD induced neurodegerative and neuroinflammatory process. Neuroperotective effects of exercise on the hippocampus seem to be increasing in immediate-early gene c-Fos expression in dentate gyrus; enhancing the Wnt3 expression and inhibiting glycogen synthase kinase-3β expression; increasing the 5-bro-mo-2'-deoxyridine-positive and doublecortin-positive cells (dentate gyrus); increasing the level of astrocytes glial fibrillary acidic protein and decrease in S100B protein, increasing in blood brain barrier integrity; prevention of oxidative stress injury, inducing morphological changes in astrocytes in the stratum radiatum of cornu ammonis 1(CA1) area; increase in cell proliferation and suppress apoptosis in dentate gyrus; increase in brain-derived neurotrophic factor and tropomyosin receptor kinase B expressions; enhancing the glycogen levels and normalizing the monocarboxylate transporter 2 expression.

Genome-wide identification of brain miRNAs in response to high-intensity intermittent swimming training in Rattus norvegicus by deep sequencing

Background

Physical exercise can improve brain function by altering brain gene expression. The expression mechanisms underlying the brain’s response to exercise still remain unknown. miRNAs as vital regulators of gene expression may be involved in regulation of brain genes in response to exercise. However, as yet, very little is known about exercise-responsive miRNAs in brain.

Results

We constructed two comparative small RNA libraries of rat brain from a high-intensity intermittent swimming training (HIST) group and a normal control (NC) group. Using deep sequencing and bioinformatics analysis, we identified 2109 (1700 from HIST, 1691 from NC) known and 55 (50 from HIST, 28 from NC) novel candidate miRNAs. Among them, 34 miRNAs were identified as significantly differentially expressed in response to HIST, 16 were up-regulated and 18 were down-regulated. The results showed that all members of mir-200 family were strongly up-regulated, implying mir-200 family may play very important roles in HIST response mechanisms of rat brain. A total of 955 potential target genes of these 34 exercise-responsive miRNAs were identified from rat genes. Most of them are directly involved in the development and regulatory function of brain or nerve. Many acknowledged exercise-responsive brain genes such as Bdnf, Igf-1, Vgf, Ngf c-Fos, and Ntf3 etc. could be targeted by exercise-responsive miRNAs. Moreover, qRT-PCR and SABC immunohistochemical analysis further confirm the reliability of the expression of miRNAs and their targets.

Conclusions

This study demonstrated that physical exercise could induce differential expression of rat brain miRNAs and 34 exercise-responsive miRNAs were identified in rat brain. Our results suggested that exercise-responsive miRNAs could play important roles in regulating gene expression of rat brain in response to exercise.

Electronic supplementary material

The online version of this article (10.1186/s12867-019-0120-4) contains supplementary material, which is available to authorized users.

Impaired chemoreflex correlates with decreased c-Fos in respiratory brainstem centers of the streptozotocin-induced Alzheimer's disease rat model

Besides impairment in cognition and memory, patients with Alzheimer's disease (AD) often exhibit marked dysfunction in respiratory control. Sleep-disordered breathing (SDB) is commonly found in cases of AD, resulting in periods of hypoxia during sleep. Early structural changes in brainstem areas controlling respiratory function may account for SDB in the course of AD. However, to date the underlying mechanisms for these complications are not known. The streptozotocin (STZ)-induced rat model of AD exhibits abnormal responses to hypoxia and increased astrogliosis in a key region for respiratory control. In this study we further defined the pathophysiological respiratory response of STZ-AD rats to 10% O₂. In addition, we analyzed hypoxia-induced neuronal activation in respiratory and cardiovascular nuclei of the dorsal and ventral brainstem. Two hours of hypoxia induced a transient increase in tidal volume that was followed by a prolonged increase in respiratory rate. Only respiratory rate was significantly blunted in the STZ-AD model, which continued over the entire duration of the hypoxic episode. Analysis of c-Fos expression as a marker for neuronal activation showed abundant labeling throughout the nTS, nuclei of the ventral respiratory column, and A1/C1 cells of cardiovascular centers in the ventral brainstem. STZ-AD rats showed a significant decrease of c-Fos labeling in the caudal/medial nTS, rostral ventral respiratory group, and Bötzinger complex. c-Fos in other respiratory centers and A1/C1 cells was unaltered when compared to control. The results of this study document a region-specific impact of STZ-induced AD in respiratory brainstem nuclei. This decrease in c-Fos expression correlates with the observed blunting of respiration to hypoxia in the STZ-AD rat model.

Memorcise and Alzheimer's disease

Alzheimer's disease (AD) is a debilitating disease influencing a multitude of outcomes, including memory function. Recent work suggests that memory may be influenced by exercise ('memorcise'), even among those with AD. The present narrative review details (1) the underlying mechanisms of AD; (2) whether exercise has a protective effect in preventing AD; (3) the mechanisms through which exercise may help to prevent AD; (4) the mechanisms through which exercise may help attenuate the progression of AD severity among those with existing AD; (5) the effects and mechanisms through which exercise is associated with memory among those with existing AD; and (6) exercise recommendations for those with existing AD. Such an understanding will aid clinicians in their ability to use exercise as a potential behavioral strategy to help prevent and treat AD.

Effects of exercise on sexual function and central mechanism in the streptozotocin-induced diabetic rats

Diabetes mellitus is associated with the impairment of sexual function including desire and orgasmic dysfunction. Sexual dysfunction in the diabetes mellitus is due to a selective defect of the nitric oxide synthase (NOS) within paraventricular nucleus (PVN). c-Fos is an immediate early gene and c-Fos expression represents neuronal activity in response to various stimuli. In the present study, we investigated the effects of treadmill exercise on sexual behaviors and the expressions of NOS and c-Fos in the PVN were evaluated using streptozotocin (STZ)-induced diabetic rats. Diabetes mellitus was induced by intraperitoneal injection of STZ. The rats in the treadmill exercise groups were made to run on a treadmill for 30 min once a day during 4 weeks. Male sexual behaviors were evaluated by recording the number of mounting, intromission, and ejaculation frequency. The present results revealed that treadmill exercise ameliorated sexual dysfunction in the STZ-induced diabetic rats. Treadmill exercise restored the contents of NOS and c-Fos in the PVN. The improving effect of treadmill exercise on sexual function can be considered as the neuronal activating effect of exercise through increasing expressions of NO and c-Fos.

Sex Differences in the Cognitive and Hippocampal Effects of Streptozotocin in an Animal Model of Sporadic AD

More than 95% of Alzheimer's disease (AD) belongs to sporadic AD (sAD), and related animal models are the important research tools for investigating the pathogenesis and developing new drugs for sAD. An intracerebroventricular infusion of streptozotocin (ICV-STZ) is commonly employed to generate sporadic AD animal model. Moreover, the potential impact of sex on brain function is now emphasized in the field of AD. However, whether sex differences exist in AD animal models remains unknown. Here we reported that ICV-STZ remarkably resulted in learning and memory impairment in the Sprague-Dawley male rats, but not in the female rats. We also found tau hyperphosphorylation, an increase of Aβ40/42 as well as increase in both GSK-3β and BACE1 activities, while a loss of dendritic and synaptic plasticity was observed in the male STZ rats. However, STZ did not induce above alterations in the female rats. Furthermore, estradiol levels of serum and hippocampus of female rats were much higher than that of male rats. In conclusion, sex differences exist in this sporadic AD animal model (Sprague-Dawley rats induced by STZ), and this should be considered in future AD research.

Treadmill exercise ameliorates symptoms of Alzheimer disease through suppressing microglial activation-induced apoptosis in rats

Alzheimer disease (AD) is a most common form of dementia and eventually causes impairments of learning ability and memory function. In the present study, we investigated the effects of treadmill exercise on the symptoms of AD focusing on the microglial activation-induced apoptosis. AD was made by bilateral intracerebroventricular injection of streptozotocin. The rats in the exercise groups were made to run on a treadmill once a day for 30 min during 4 weeks. The distance and latency in the Morris water maze task and the latency in the step-down avoidance task were increased in the AD rats, in contrast, treadmill exercise shortened these parameters. The numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive and caspase-3-positive cells in the hippocampal dentate gyrus were decreased in the AD rats, in contrast, treadmill exercise suppressed these numbers. Expressions of glial fibrillary acidic protein (GFAP) and cluster of differentiation molecule 11B (CD11b) in the hippocampal dentate gyrus were increased in the AD rats, in contrast, treadmill exercise suppressed GFAP and CD11b expressions. Bax expression was increased and Bcl-2 expression was decreased in the hippocampus of AD rats, in contrast, treadmill exercise decreased Bax expression and increased Bcl-2 expression. The present results demonstrated that treadmill exercise ameliorated AD-induced impairments of spatial learning ability and short-term memory through suppressing apoptosis. The antiapoptotic effect of treadmill exercise might be ascribed to the inhibitory effect of treadmill exercise on microglial activation.

Neuroprotective Effects of Endurance Exercise Against High-Fat Diet-Induced Hippocampal Neuroinflammation

Obesity contributes to systemic inflammation, which is associated with the varied pathogenesis of neurodegenerative diseases. Growing evidence has demonstrated that endurance exercise (EE) mitigates obesity-induced brain inflammation. However, exercise-mediated anti-inflammatory mechanisms remain largely unknown. We investigated how treadmill exercise (TE) reverses obesity-induced brain inflammation, mainly focusing on toll-like receptor-4 (TLR-4)-dependent neuroinflammation in the obese rat brain after 20 weeks of a high-fat diet (HFD). TE in HFD-fed rats resulted in a significant lowering in the homeostasis model assessment of insulin resistance index, the area under the curve for glucose and abdominal visceral fat, and also improved working memory ability in a passive avoidance task relative to sedentary behaviour in HFD-fed rats, with the exception of body weight. More importantly, TE revoked the increase in HFD-induced proinflammatory cytokines (tumour necrosis factor α and interleukin-1β) and cyclooxygenase-2, which is in parallel with a reduction in TLR-4 and its downstream proteins, myeloid differentiation 88 and tumour necrosis factor receptor associated factor 6, and phosphorylation of transforming growth factor β-activated kinase 1, IkBα and nuclear factor-κB. Moreover, TE reduced an indicator of microglia activation, ionised calcium-binding adapter molecule-1, and also decreased glial fibrillary acidic protein, an indicator of gliosis formed by activated astrocytes in the cerebral cortex and the hippocampal dentate gyrus, compared to HFD-fed sedentary rats. Finally, EE up-regulated the expression of anti-apoptotic protein, Bcl-2, and suppressed the expression of pro-apoptotic protein, Bax, in the hippocampus compared to HFD-fed sedentary rats. Taken together, these data suggest that TE may exert neuroprotective effects as a result of mitigating the production of proinflammatory cytokines by inhibiting the TLR4 signalling pathways. The results of the present study suggest that the unique combination of the beneficial effects of TE on the restoration of the blood profile and the anti-inflammatory and anti-apoptotic effects on cognitive function should inspire further investigations into its therapeutic potential for metabolic disorders and neurodegenerative diseases.

Noisy galvanic vestibular stimulation enhances spatial memory in cognitive impairment-induced by intracerebroventricular-streptozotocin administration

There are several anatomical connections between vestibular system and brain areas construct spatial memory. Since subliminal noisy galvanic vestibular stimulation (GVS) has been demonstrated to enhance some types of memory, we speculated that application of noisy GVS may improve spatial memory in a rat model of intracerebroventricular streptozotocin (ICV-STZ)-induced cognitive impairment. Moreover, we attempted to determine the effect of repeated exposure to GVS on spatial memory performance. The spatial memory was assessed using Morris water maze test. The groups received 1 (ICV-STZ/GVS-I) or 5 (ICV-STZ/GVS-II) sessions, each lasting 30 min, of low amplitude noisy GVS, or no GVS at all (Control, ICV-saline, ICV-STZ/noGVS). Hippocampal morphological changes investigated with cresyl violet staining and the immediate early gene product c-Fos, as a neuronal activity marker, was measured. Hippocampal c-Fos positive cells increased in both GVS stimulated groups. We observed significantly improved spatial performance only in ICV-STZ/GVS-II group. Histological evaluation showed normal density in ICV-STZ/GVS-II group whereas degeneration observed in ICV-STZ/GVS-I group similar to ICV-STZ/noGVS. The results showed the improvement of memory impairment after repeated exposure to GVS. This effect may be due in part to frequent activation of the vestibular neurons and the hippocampal regions connected to them. Our current study suggests the potential role of GVS as a practical method to combat cognitive decline induced by sporadic Alzheimer disease.

Streptozotocin Intracerebroventricular-Induced Neurotoxicity and Brain Insulin Resistance: a Therapeutic Intervention for Treatment of Sporadic Alzheimer's Disease (sAD)-Like Pathology

Alzheimer's disease (AD) is a neurodegenerative disorder that is remarkably characterized by pathological hallmarks which include amyloid plaques, neurofibrillary tangles, neuronal loss, and progressive cognitive loss. Several well-known genetic mutations which are being used for the development of a transgenic model of AD lead to an early onset familial AD (fAD)-like condition. However, these settings are only reasons for a small percentage of the total AD cases. The large majorities of AD cases are considered as a sporadic in origin and are less influenced by a single mutation of a gene. The etiology of sporadic Alzheimer's disease (sAD) remains unclear, but numerous risk factors have been identified that increase the chance of developing AD. Among these risk factors are insulin desensitization/resistance state, oxidative stress, neuroinflammation, synapse dysfunction, tau hyperphosphorylation, and deposition of Aβ in the brain. Subsequently, these risk factors lead to development of sAD. However, the underlying molecular mechanism is not so clear. Streptozotocin (STZ) produces similar characteristic pathology of sAD such as altered glucose metabolism, insulin signaling, synaptic dysfunction, protein kinases such as protein kinase B/C, glycogen synthase-3β (GSK-3β) activation, tau hyperphosphorylation, Aβ deposition, and neuronal apoptosis. Further, STZ also leads to inhibition of Akt/PKB, insulin receptor (IR) signaling molecule, and insulin resistance in brain. These alterations mediated by STZ can be used to explore the underlying molecular and pathophysiological mechanism of AD (especially sAD) and their therapeutic intervention for drug development against AD pathology.

Betaine inhibits vascularization via suppression of Akt in the retinas of streptozotocin-induced hyperglycemic rats

Diabetic retinopathy is a severe microvascular complication amongst patients with diabetes, and is the primary cause of visual loss through neovascularization. Betaine is one of the components of Fructus Lycii. In the present study, the effects of betaine on the expression levels of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF)-1α in association with the Akt pathway were investigated in the retinas of streptozotocin (STZ)-induced diabetic rats using western blot and immunohistochemical analyses. The results of the present study revealed that the expression levels of VEGF, HIF-1α, and Akt were increased in the retinas of the STZ-induced diabetic rats. Betaine treatment attenuated this increase in VEGF and HIF-1α expression via suppression of diabetes-induced Akt activation in the retinas of the diabetic rats. The results suggested that betaine may potentially be used to delay the onset of complications associated with diabetic retinopathy via inhibition of retinal neovascularization in patients with diabetes.

Bacopa monniera ameliorates cognitive impairment and neurodegeneration induced by intracerebroventricular-streptozotocin in rat: behavioral, biochemical, immunohistochemical and histopathological evidences

The standardized extract of Bacopa monniera (BM) is a complex mixture of ingredients with a uniquely wide spectrum of neuropharmacological influences upon the central nervous system including enhanced learning and memory with known antioxidant potential and protection of the brain from oxidative damage. The present study demonstrates the therapeutic efficacy of BM on cognitive impairment and oxidative damage, induced by intracerebroventricular injection of streptozotocin (ICV-STZ) in rat models. Male Wistar rats were pre-treated with BM at a selected dose (30 mg/Kg) given orally for 2 weeks and then were injected bilaterally with ICV-STZ (3 mg/Kg), while sham operated rats were received the same volume of vehicle. Behavioral parameters were subsequently monitored 2 weeks after the surgery using the Morris water maze (MWM) navigation task then were sacrificed for biochemical, immunohistochemical (Cu/Zn-SOD) and histopathological assays. ICV-STZ-infused rats showed significant loss in learning and memory ability, which were significantly improved by BM supplementation. A significant increase in thiobarbituric acid reactive species and a significant decrease in reduced glutathione, antioxidant enzymes in the hippocampus were observed in ICV-STZ rats. Moreover, decrease in Cu/Zn-SOD expression positive cells were observed in the hippocampus of ICV-STZ rats. BM supplementation significantly ameliorated all alterations induced by ICV-STZ in rats. The data suggest that ICV-STZ might cause its neurotoxic effects via the production of free radicals. Our study demonstrates that BM is a powerful antioxidant which prevents cognitive impairment, oxidative damage, and morphological changes in the ICV-STZ-infused rats. Thus, BM may have therapeutic value for the treatment of cognitive impairment.

Effect of treadmill exercise on social interaction and tyrosine hydroxylase expression in the attention-deficit/ hyperactivity disorder rats

Attention-deficit/hyperactivity disorder (ADHD) involves clinically heterogeneous dysfunctions of sustained attention, with behavioral hyper-activity and impulsivity. The exact underlying mechanisms of ADHD are not known, however, impairment of dopaminergic system in the nigrostriatal pathway was suggested as the one of the possible mechanisms of ADHD. Tyrosine hydroxylase (TH) is the rate-limiting enzyme that is involved in the synthesis of dopamine. Spontaneous hypertensive rats have been used as the animal model for ADHD. Physical exercise is known to restore the brain functions disrupted by several neurode-generative and psychiatric disorders. In the present study, we investigated whether treadmill exercise exerts therapeutic effect on ADHD. Social interaction test for the evaluation of impulsivity was performed using spontaneous hypertensive rats. TH expressions in the substantia nigra and striatum were evaluated by immunohistochemistry. In the present results, the rats of ADHD model showed hyper-social behaviors. TH expressions in the substantia nigra and striatum were decreased in the rats of ADHD model. Treadmill exercise alleviated hyper-social behaviors in the ADHD rats. TH expressions of ADHD rats were also enhanced by treadmill exercise. Here in this study, we showed that treadmill exercise effectively alleviates the ADHD-induced symptoms through enhancing of TH expression in the brain.

Treadmill exercise improves spatial learning ability by enhancing brain-derived neurotrophic factor expression in the attention-deficit/hyperactivity disorder rats

Attention-deficit/hyperactivity disorder (ADHD) patients show learning difficulty and impulsiveness. Exercise is known to improve learning ability and memory function. In the present study, we investigated the duration-dependence of the effect of treadmill exercise on spatial learning ability in relation with brain-derived neurotrophic factor (BDNF) expression in ADHD rats. For this study, radial 8-arm maze test and western blot for BDNF and tyrosine kinase B (TrkB) were performed. Spontaneous hypertensive rats were used as the ADHD rats and Wistar-Kyoto rats were used as the control rats. The rats in the exercise groups were forced to run on a treadmill for 10 min, 30 min, and 60 min once a day for 28 consecutive days. ADHD rats displayed impairment of spatial learning ability, in contrast treadmill exercise ameliorated impairment of spatial learning ability. Treadmill exercise for 30 min per day showed most potent ameliorating effect on impairment of spatial learning ability. BDNF and TrkB expressions in the hippocampus were decreased in the ADHD rats, in contrast treadmill exercise enhanced BDNF and TrkB expressions. Treadmill exercise for 30 min and for 60 min per day showed enhancing effects on BDNF and TrkB expressions. Treadmill exercise alleviated deficits in the spatial learning ability through enhancing BDNF and TrkB expressions in the ADHD rats. Treadmill exercise for 30 min per day can be considered as the most effective therapeutic modality for the ADHD symptoms.

Duration-dependence of the effect of treadmill exercise on hyperactivity in attention deficit hyperactivity disorder rats

Attention-deficit hyperactivity disorder (ADHD) is a common neurobehavioral disorder, and its symptoms are hyperactivity and deficits in learning and memory. Physical exercise increases dopamine synthesis and neuronal activity in various brain regions. In the present study, we investigate the duration-dependence of the treadmill exercise on hyperactivity in relation with dopamine expression in ADHD. Spontaneously hypertensive rats were used for the ADHD rats and Wistar-Kyoto rats were used for the control rats. The rats in the exercise groups were forced to run on a treadmill for 10 min, 30 min, and 60 min once daily for 28 consecutive days. For this experiment, open field test and immunohistochemistry for tyrosine hydroxylase were conducted. The present results revealed that ADHD rats showed hyperactivity, and tyrosine hydroxylase expression in the striatum and substantia nigra were decreased in ADHD rats. Treadmill exercise alleviated hyperactivity and also increased TH expression in ADHD rats. Treadmill exercise for 30 min per day showed most potent suppressing effect on hyperactivity, and this dose of treadmill exercise also most potently inhibited tyrosine hydroxylase expression. The present study suggests that treadmill exercise for 30 min once a day is the most effective therapeutic intervention for ADHD patients.

Treadmill exercise alleviates impairment of spatial learning ability through enhancing cell proliferation in the streptozotocin-induced Alzheimer's disease rats

Alzheimer’s disease is the most common cause of dementia. This disease is a progressive and irreversible brain disorder accompanied with severe learning and memory impairment. Exercise increases cognitive ability, attenuates motor deficits, increases new neuron formation, and ameliorates neurological impairments in several neurodegenerative diseases. This study investigated the effects of treadmill exercise on spatial learning ability in relation with cell proliferation in the hippocampus. The rat model of Alzheimer’s disease was induced by intracerebroventricular (ICV) injection of streptozotocin (STZ) using a stereotaxic instrument. The rats in the exercise groups were forced to run on a treadmill for once 30 min daily for 28 consecutive days starting at 3 days after the ICV injection of STZ. Radial 8-arm maze test was conducted for the spatial learning ability. New neuron formation in the hippocampus was detected by 5-bromo-2’-deoxyuridine (BrdU) immunohistochemistry. Brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB) expressions were examined by western blot analysis. The present results show that ICV injection of STZ impaired spatial learning ability. Decreased cell proliferation with decrement of BDNF and TrkB expressions in the hippocampus were observed in the STZ-induced Alzheimer’s disease rats. However, treadmill exercise alleviated deficits of spatial learning ability. Treadmill exercise enhanced cell proliferation and increased BDNF and TrkB expressions in the rats with ICV injection of STZ. The present study suggests that treadmill exercise can be a useful strategy for treating memory impairment induced by several neurodegenerative diseases.

Treadmill exercise improves short-term memory by enhancing neurogenesis in amyloid beta-induced Alzheimer disease rats

Alzheimer's disease is one of the most devastating neurodegenerative disorders, and this disease is characterized by severe memory impairment and decline of cognition. Hippocampal neurons are vulnerable to injury induced by Alzheimer's disease. Physical exercise is known to promote cell survival and functional recovery after brain injuries. In the present study, we investigated the effects of treadmill exercise on short-term memory in relation with neurogenesis in the rats with amyloid β25-35 (Aβ25-35)-induced Alzheimer's disease. The rat model of Alzheimer's disease was induced by the intracerebroventricular (ICV) injection of Aβ25-35, using a stereotaxic instrument. The rats in the exercise group were forced to run on a treadmill for 30 min once daily for 4 consecutive weeks, starting 2 days after Aβ25-35 injection. Presently, short-term memory was deteriorated and apical dendritic length in the hippocampus was shortened in the hippocampus by Aβ25-35 injection. In contrast, treadmill exercise alleviated memory impairment and increased apical dendritic length in the Aβ25-35-injected rats. Neurogenesis and brain-derived neurotorphic factor (BDNF) and tyrosine kinase B (trkB) in the hippocampal dentate gyrus were decreased by Aβ25-35 injection. Treadmill exercise increased neurogenesis and expressions of BDNF and trkB expressions. The present study shows that treadmill exercise may provide therapeutic value for the alleviating symptoms of Alzheimer's disease.

Treadmill exercise enhances NMDA receptor expression in schizophrenia mice

Schizophrenia is a serious psychiatric disorder with several symptoms including cognitive dysfunction. Although the causes of schizophrenia are still unclear, there is a strong suspicion that the abnormality in N-methyl-D-aspartate (NMDA) receptor may contribute to schizophrenia symptoms. In the present study, the effect of treadmill exercise on the NMDA receptor expression was evaluated using MK-801-induced schizophrenia mice. Immunohistochemistry for expressions of NMDA receptor tyrosine hydroxylase (TH) was conducted. Western blot for brain-derived neurotrophic factor (BDNF) was also performed. In the present results, the mice in the MK-801-treated group displayed reduced NMDA receptor expression. Enhanced TH expression and suppressed BDNF expression were also observed in the MK-801-treated mice. Treadmill exercise improved NMDA receptor expression in the MK-801-induced schizophrenia mice. Treadmill exercise also suppressed TH expression and enhanced BDNF expression in the MK-801-induced schizophrenia mice. The present study showed that down-regulation of NMDA receptor demonstrated schizophrenia-like parameters, meanwhile treadmill running improved schizophrenia-related parameters through enhancing NMDA receptor expression.

Effects of treadmill exercise on brain insulin signaling and β-amyloid in intracerebroventricular streptozotocin induced-memory impairment in rats

[Purpose]

The purpose of the study is to explore effect of 6 weeks treadmill exercise on brain insulin signaling and β-amyloid(Aβ).

[Methods]

The rat model of Alzheimer’s disease(AD) used in the present study was induced by the intracerebroventricular(ICV) streptozotocin(STZ). To produce the model of animal with AD, STZ(1.5mg/kg) was injected to a cerebral ventricle of both cerebrums of Sprague-Dawley rat(20 weeks). The experimental animals were divided into ICV-Sham(n=7), ICV-STZ CON(n=7), ICV-STZ EXE(n=7). Treadmill exercise was done for 30 min a day, 5 days a week for 6 weeks. Passive avoidance task was carried out before and after treadmill exercise.

[Results]

The results of this study show that treadmill exercise activated Protein kinase B(AKT)/ Glycogen synthase kinase 3α (GSK3α), possibly via activation of insulin receptor(IR) and insulin receptor substrate(IRS) and reduced Aβ in the brain of ICV-STZ rats. More interestingly, treadmill exercise improved cognitive function of ICV-STZ rats. Finally, physical exercise or physical activity gave positive influences on brain insulin signaling pathway.

[Conclusion]

Therefore, treadmill exercise can be applied to improve AD as preventive and therapeutic method.

Swimming exercise alleviates the symptoms of attention-deficit hyperactivity disorder in spontaneous hypertensive rats

Attention-deficit hyperactivity disorder (ADHD) is a neurobehavioral disorder characterized by inattention, hyperactivity and impulsivity. In the present study, we investigated the effects of swimming exercise on the symptoms of ADHD in correlation with the expression levels of dopamine and the dopamine D2 receptor. Adult male spontaneous hypertensive rats (SHRs) were used as animal models of ADHD and Wistar-Kyoto rats were used as controls. The activity, impulsivity and levels of non-aggressive and aggressive behaviors in rats were measured. The short-term memory in the animal models of ADHD was assessed using an open-field test. The social interaction test, elevated plus maze test and step-through avoidance test were additionally performed. The expression levels of tyrosine hydroxylase (TH), which catalyzes the rate‑limiting step of dopamine synthesis, and the dopamine D2 receptor in the prefrontal cortex, substantia nigra and striatum were evaluated. The expression levels of TH and the dopamine D2 receptor were detected using immunohistochemistry and western blotting, respectively. In ADHD rats, the activity, impulsivity and levels of non-aggressive and aggressive behaviors were higher than that in control rats. By contrast, short-term memory in ADHD rats deteriorated. Swimming exercise suppressed hyperactivity, impulsivity and non-aggressive and aggressive behaviors, and alleviated the short-term memory impairment observed in ADHD rats. The expression levels of TH and the dopamine D2 receptor were decreased and increased in ADHD rats, respectively, when compared with control rats. Swimming exercise enhanced the expression of TH and suppressed the expression of the dopamine D2 receptor in ADHD rats. In the present study, swimming exercise improved the symptoms of ADHD by upregulating the expression of dopamine and downregulating the expression of the dopamine D2 receptor.

Taurine ameliorates neurobehavioral, neurochemical and immunohistochemical changes in sporadic dementia of Alzheimer's type (SDAT) caused by intracerebroventricular streptozotocin in rats

Oxidative loads in the brain are involved in age related impairments like learning and memory as well as neurodegeneration. Taurine, the most abundant free amino acid in humans has many potential health benefits through its anti-oxidant and anti-inflammatory properties. Therefore, we investigated the neuroprotective potential of taurine on oxidative stress, neuronal loss and memory impairments in streptozotocin model of cognitive impairments in rats. The cognitive impairment was developed by giving single intracerebroventricular (ICV) injection of streptozotocin (STZ) 3 mg/kg body weight bilaterally. An increased latency and path length was observed in ICV-STZ group animals as compared to sham group animals and these were inhibited significantly in STZ group pre-treated with taurine (50 mg/kg body weight orally once daily for 15 days). Moreover, the significantly depleted content of GSH and elevated level of thiobarbituric acid reactive substances (TBARS) in ICV-STZ group animals were protected significantly with pre-treatment of taurine. The activity of antioxidant enzymes, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, catalase, and superoxide dismutase was decreased in STZ group as compared to sham group and pre-treatment of STZ group with taurine has protected their activities significantly. Furthermore, the increased activity of acetylcholine esterase and decreased expression of choline acetyl transferase were attenuated by the pre-treatment of taurine. Taurine also protected the morphology of the hippocampal pyramidal neurons. This study concludes that the prophylactic intervention of taurine may be used to prevent the deterioration of cognitive functions and neurobehavioral activities, often associated with the generation of free radicals.

Changes in spatial memory and BDNF expression to simultaneous dietary restriction and forced exercise

Previous literature suggests that learning and memory formation can be influenced by diet and exercise. In the current study, we investigated the combined effects of forced swimming exercise (FSE) and every other day fasting (EODF) on spatial memory formation and on the levels of brain-derived neurotrophic factor (BDNF) in the hippocampus of Wistar male rats. The radial arm water maze (RAWM) paradigm was used to assess changes in learning and memory formation, whereas ELISA assay was used to measure BDNF protein levels. The FSE and/or EODF were simultaneously instituted for 6 weeks. Results show that FSE improved learning, short-term as well as long-term memory formation, and significantly increased BDNF protein in the hippocampus (p<0.05). However, EODF had no effect on either spatial learning and memory formation or the levels of hippocamapal BDNF protein (p>0.05). In addition, EODF did not modulate beneficial effect of swimming exercise on cognitive function (p>0.05). Thus exercise enhanced, while EODF did not affect spatial learning and memory formation.

Brain activation patterns at exhaustion in rats that differ in inherent exercise capacity

In order to further understand the genetic basis for variation in inherent (untrained) exercise capacity, we examined the brains of 32 male rats selectively bred for high or low running capacity (HCR and LCR, respectively). The aim was to characterize the activation patterns of brain regions potentially involved in differences in inherent running capacity between HCR and LCR. Using quantitative in situ hybridization techniques, we measured messenger ribonuclease (mRNA) levels of c-Fos, a marker of neuronal activation, in the brains of HCR and LCR rats after a single bout of acute treadmill running (7.5-15 minutes, 15° slope, 10 m/min) or after treadmill running to exhaustion (15-51 minutes, 15° slope, initial velocity 10 m/min). During verification of trait differences, HCR rats ran six times farther and three times longer prior to exhaustion than LCR rats. Running to exhaustion significantly increased c-Fos mRNA activation of several brain areas in HCR, but LCR failed to show significant elevations of c-Fos mRNA at exhaustion in the majority of areas examined compared to acutely run controls. Results from these studies suggest that there are differences in central c-Fos mRNA expression, and potential brain activation patterns, between HCR and LCR rats during treadmill running to exhaustion and these differences could be involved in the variation in inherent running capacity between lines.

The effect of red grape juice on Alzheimer's disease in rats

Background:

Alzheimer's disease is a neurodegenerative disease appearing as a result of free radicals and oxidative stress. Antioxidants agents boost memory and control Alzheimer's disease. Since red grape juice contains antioxidant agents, its effects on speed of learning and improvement of memory was studied in Alzheimer's rats.

Materials and Methods:

Alzheimer's model was induced by bilateral infusion of streptozocine into lateral ventricles of brain of male rats. Rats drank 10% red grape juice for 21 days. Passive avoidance learning test was used for measuring memory and learning in rats.

Results:

Our results showed that learning and memory in STZ-group decreased significantly compared to Sham group. However, intake of red grape juice increased speed of learning and improvement of memory in Alzheimer's rats.

Conclusions:

Our results suggest that there are active ingredients in red grape juice, which probably have therapeutic and preventive effects on cognitive impairments in Alzheimer's disease.

Naringenin ameliorates Alzheimer's disease (AD)-type neurodegeneration with cognitive impairment (AD-TNDCI) caused by the intracerebroventricular-streptozotocin in rat model

Oxidative stress is involved in Alzheimer's disease (AD)-type neurodegeneration with cognitive impairment (AD-TNDCI) as well as age related cognitive deficit. The present study was designed to investigate the pre-treatment effects of naringenin (NAR), a polyphenolic compound on cognitive dysfunction, oxidative stress in the hippocampus, and hippocampal neuron injury in a rat model of AD-TNDCI. The rats were pre-treated with NAR at a selective dose (50mg/kg, orally) for 2 weeks followed by intracerebroventricular-streptozotocin (ICV-STZ) (3mg/kg; 5μl per site) injection bilaterally. Behavioral alterations were monitored after 2 weeks from the lesion using passive avoidance test and Morris water maze paradigm. Three weeks after the lesion, the rats were sacrificed for measuring non-enzymatic [4-hydroxynonenal (4-HNE), malonaldehyde (MDA), thiobarbituric reactive substances (TBARS), hydrogen peroxide (H(2)O(2)), protein carbonyl (PC), reduced glutathione (GSH)] content and enzymatic [glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and Na(+)/K(+)-ATPase] activity in the hippocampus, and expression of choline acetyltransferase (ChAT) positive neuron, and histopathology of hippocampal neurons. The non-enzymatic level and enzymatic activity was significantly increased and decreased, respectively, with striking impairments in spatial learning and memory, loss of ChAT positive neuron and severe damage to hippocampal neurons in the rat induced by ICV-STZ. These abnormalities were significantly improved by NAR pre-treatment. The study suggests that NAR can protect against cognitive deficits, neuronal injury and oxidative stress induced by ICV-STZ, and may be used as a potential agent in treatment of neurodegenerative diseases such as AD-TNDCI.

Physical exercise alleviates debilities of normal aging and Alzheimer's disease

Both healthy aging and the pathologic incidence of disorders associated with aging involve an array of debilities. Physical exercise harnesses implicit and inherent biologic characteristics amenable to the putative interventional influences under clinical, institutional or laboratory conditions. The neurodegenerative and pathophysiologic progressions that constitute Alzheimer's disease (AD), amnestic mild cognitive impairment (aMCI), normal aging, and different animal models of AD have shown the existence of several putative mechanisms. A large variety of moderating factors have demonstrated that the ever-proliferating plethora of neurotrophic factors, neurogenesis as observed through generality of expression and neuronal arborization. The insistent efficacy of brain vascular angiogenesis may delay also the comorbid incidence of depressive disorders with dementia pathology. The pathogenesis of aging may be contained by selective treatments: these diverse conditions, linked to the basis of the aging concept, have been shown, to greater or lesser extents, to respond to a variety of scheduled applications of physical exercise. The range of reports that provide accounts of the mechanisms mediating the positive progressive response to exercise intervention is far-ranging; these studies indicate that subtle changes at molecular, neuronal, vascular and epigenetic levels may exert notable consequence at functional expression and, perhaps most essentially, offer convincing expectancy of significant benefits.