Vitamins E and C pretreatment prevents ovariectomy-induced memory deficits in water maze

Search Strategy Analysis of 5xFAD Alzheimer Mice in the Morris Water Maze Reveals Sex- and Age-Specific Spatial Navigation Deficits

Spatial disorientation and navigational impairments are not only some of the first memory deficits in Alzheimer's disease, but are also very disease-specific. In rodents, the Morris Water Maze is used to investigate spatial navigation and memory. Here, we examined the spatial memory in the commonly used 5xFAD Alzheimer mouse model in a sex- and age-dependent manner. Our findings show first spatial learning deficits in 7-month-old female 5xFAD and 12-month-old male 5xFAD mice, respectively. While the assessment of spatial working memory using escape latencies provides a global picture of memory performance, it does not explain how an animal solves a spatial task. Therefore, a detailed analysis of swimming strategies was performed to better understand the behavioral differences between 5xFAD and WT mice. 5xFAD mice used a qualitatively and quantitatively different search strategy pattern than wildtype animals that used more non-spatial strategies and showed allocentric-specific memory deficits. Furthermore, a detailed analysis of swimming strategies revealed allocentric memory deficits in the probe trial in female 3-month-old and male 7-month-old 5xFAD animals before the onset of severe reference memory deficits. Overall, we could demonstrate that spatial navigation deficits in 5xFAD mice are age- and sex-dependent, with female mice being more severely affected. In addition, the implementation of a search strategy classification system allowed an earlier detection of behavioral differences and therefore could be a powerful tool for preclinical drug testing in the 5xFAD model.

Effect of rosuvastatin on spatial learning, memory, and anxiety-like behaviour in ovariectomized rats

The effect of rosuvastatin (Ros) on cognitive function and anxiety-like behaviour in ovariectomized rats were evaluated. Eighteen female Wistar rats (218-310 g, 6-8 months old) were allocated into sham (n = 6), ovariectomy (Ovx, n = 6) or Ovx + Ros (up to eighth week n = 6, then n = 4) groups. Ros was administered at 20 mg/kg/day by oral gavage for 12 weeks. Behavioural tests were performed at 4, 8 and 12 weeks following Ovx. At 12 weeks, Ovx group had significantly longer escape latency than the sham group at the first day of the four-day training period of the Morris Water Maze test (p < .01). In the Elevated Plus Maze test, Ovx group spent significantly more time in the closed arms than the sham group (p < .01), and this anxiety-like behavioural effect of Ovx was prevented by 12-weeks Ros treatment (p < .05). In conclusion, Ros prevents memory deficit and anxiety-like behaviour in the ovariectomized rats, a model for human surgical menopause. Impact StatementWhat is already known on this subject? Reduced levels of oestrogen in surgical postmenopausal period has been linked to an increased risk of cognitive dysfunction. Although statins have been shown to improve cognitive function in experimental and clinical studies, there are limited studies evaluating the effect of statins on the cognitive decline and anxiety-like behaviour associated with surgical menopause.What do the results of this study add? Rosuvastatin, a long-acting statin, prevents learning and memory deficit and anxiety-like behaviour in the ovariectomized rat model.What are the implications of these findings for future clinical practice and/or future clinical research? These findings will form the basis for further experimental and clinical research on the effects of statins on cognitive functions and anxiety-like behaviour in the surgical menopause.

The protective effect of vitamin supplementation (E and E + C) on passive avoidance learning and memory during exposure to 900 MHz RFW emitted from BTS

Deleterious effects of exposure to electromagnetic radiation on public health have been widely studied. This study was conducted to evaluate the protective effect of vitamin supplementation (E or E + C) on passive avoidance learning (PAL) and memory in rats subjected to 900 MHz radiofrequency waves (RFW). Thirty adult male Sprague-Dawley rats (190 ± 20 g) were randomly divided into six groups as: control I (vehicle), control II (vitamin E 250 mg/kg), control III (vitamin E 100 mg/kg + l-ascorbic acid 200 mg/kg), and three exposed groups to RFW as: sham-exposed, treatment I (vitamin E), and treatment II (vitamin E + C). The duration of exposure was 30 continuous days (4 h/day). The PAL was evaluated on the last day by the shuttle box. Learning and memory of animals demonstrated as the duration of remaining within the light area, which is called the light time (LT). The sham-exposed group showed a significant decrease in LT on the learning, consolidation, and retention days compared to other groups (p < 0.05). Pretreatment with vitamins (E and E + C) could protect PAL against adverse effects of RFW, and the administration of vitamin E + C improved PAL performance in control III compared to control I and treatment II groups (p < 0.05). Administration of vitamin E + C to exposed group (treatment II) caused a significant increase in LT on the learning (p = 0.013), consolidation, and retention (p = 0.009) sessions compared to the treatment group I (vitamin E). Long-term exposure to 900 MHz RFW impaired PAL and memory, and pretreatment of vitamin (E or E + C) prevented these effects, which may be a new potential mechanism against side effects of RFW.

Voluntary exercise and estradiol reverse ovariectomy-induced spatial learning and memory deficits and reduction in hippocampal brain-derived neurotrophic factor in rats

Ample evidences have demonstrated the beneficial effects of physical exercise on cognitive functions such as learning and memory. It is well established that female sex hormones have an important role in regulating learning and memory. This study was designed to investigate the effects of voluntary exercise and estrogen replacement on learning and memory deficits and reduction in hippocampal brain derived neurotrophic factor (BDNF) levels induced by ovariectomy. Ovariectomized rats were given daily vehicle or 17 β-estradiol (20 μg/kg) and allowed to freely exercise in a running wheel over the course of 2 weeks. After this period, they were trained and tested on a water-maze spatial task for 5 consecutive days, followed by a probe test one day later. At the end of the behavioral tests, all animals were decapitated and their hippocampal levels of BDNF were measured. Ovariectomy impaired spatial learning and memory and reduced hippocampal BDNF levels. Exercise significantly improved performance during both training and the retention of the water-maze task and increased hippocampal BDNF. Exercise, 17 β-estradiol and their combination recovered the impairing effects of ovariectomy on learning and memory performance. The combined treatment did not produce stronger effect than either exercise or 17 β-estradiol alone. Our findings provide an important evidence about positive influences of regular exercise and estrogen treatment against cognitive and BDNF deficits induced in ovariectomized rats, an experimental model of menopause.

Pharmacological Effects of Melatonin as Neuroprotectant in Rodent Model: A Review on the Current Biological Evidence

The progressive loss of structure and functions of neurons, including neuronal death, is one of the main factors leading to poor quality of life. Promotion of functional recovery of neuron after injury is a great challenge in neuroregenerative studies. Melatonin, a hormone is secreted by pineal gland and has antioxidative, anti-inflammatory, and anti-apoptotic properties. Besides that, melatonin has high cell permeability and is able to cross the blood-brain barrier. Apart from that, there are no reported side effects associated with long-term usage of melatonin at both physiological and pharmacological doses. Thus, in this review article, we summarize the pharmacological effects of melatonin as neuroprotectant in central nervous system injury, ischemic-reperfusion injury, optic nerve injury, peripheral nerve injury, neurotmesis, axonotmesis, scar formation, cell degeneration, and apoptosis in rodent models.

Effect of a Strawberry and Spinach Dietary Supplement on Spatial Learning in Early and Late Middle-Aged Female Rats

The present experiment sought to determine the effect of an eight-week, high antioxidant, whole-foods dietary supplement on Morris Water Maze performance in early and late middle-aged female rats. To improve ecological validity over past experimental studies, rats in the current study received antioxidants by consuming freeze-dried organic strawberries and spinach rather than by being given food extracts or antioxidant injections. Latency and path length measures both indicated that late middle-aged rats fed the high antioxidant diet performed on a par with the younger animals earlier in training than their standard diet counterparts (p < 0.05). Superior performance was not due to improved fitness in the antioxidant-supplemented rats. Thus, our model showed that a high antioxidant diet of relatively short duration mitigated the mild cognitive decline that was seen in control animals during the developmental period of late middle-age. The current results offer support for the promising role of dietary antioxidants in maintaining cognitive health in normal aging and extend past findings to females, who have been relatively neglected in experimental investigations. Moreover, the current model suggests that the period of transition from early to late middle age is a promising target for dietary intervention in healthy adults.

Hippocampus-dependent Task Improves the Cognitive Function after Ovariectomy in Rats

Objectives

Estrogen is an important hormone for cell growth, development, and differentiation by transcriptional regulation and modulation of intracellular signaling via second messengers. The reduction in the estrogen level after ovariectomy may lead to cognitive impairments associated with morphological changes in areas of the brain mediate memory. The aim of the present study was to find out the effect of tasks on the cognitive function after ovariectomy in rats.

Methods

The animals used in the experiment were 50 Sprague-Dawley female rats. This study applied a hippocampus-independent task (wheel running) and a hippocampus-dependent task (Morris water maze) after ovariectomy in rats and measured the cognitive performance (object-recognition and object-location test) and growth-associated protein 43 (GAP-43) and neurotrophin 3 (NT-3) expression in the hippocampus, which is an important center for memory and learning.

Results

There were meaningful differences between the hippocampus-independent and hippocampus-dependent task groups for the object-location test and GAP-43 and NT-3 expression in the hippocampus, but not the object-recognition test. However, the hippocampus-independent task group showed a significant improvement in the object-recognition test, compared to the control group.

Conclusion

These results suggest that hippocampus-dependent task training after ovariectomy enhances the hippocampus-related memory and cognitive function that are associated with morphological and functional changes in the cells of the hippocampus.

Vitamin D3 Reverses the Hippocampal Cytoskeleton Imbalance But Not Memory Deficits Caused by Ovariectomy in Adult Wistar Rats

The objective of study was to investigate changes caused by ovariectomy (OVX) on aversive and non-aversive memories, as well as on cytoskeleton phosphorylating system and on vitamin D receptor (VDR) immunocontent in hippocampus. The neuroprotective role of vitamin D was also investigated. Ninety-day-old female Wistar rats were divided into four groups: SHAM, OVX, VITAMIN D and OVX + VITAMIN D; 30 days after the OVX, vitamin D supplementation (500 IU/kg), by gavage, for 30 days was started. Results showed that OVX impaired short-term and long-term recognition, and long-term aversive memories. OVX altered hippocampal cytoskeleton phosphorylating system, evidenced by the hyperphosphorylation of glial fibrillary acidic protein (GFAP), low molecular weight neurofilament subunit (NFL), medium molecular weight neurofilament subunit (NFM) and high molecular weight neurofilament subunit (NFH), and increased the immunocontent of c-Jun N-terminal protein kinases (JNK), Ca²⁺/calmodulin-dependent protein kinase II (PKCaMII) and of the sites phosphorylated lysine-serine-proline (KSP) repeats, Ser55 and Ser57. Vitamin D reversed the effects caused by OVX on cytoskeleton in hippocampus, but it was not able to reverse the effects on memory.

Establishment and identification of a hypoxia-ischemia brain damage model in neonatal rats

The present study was designed to set up a reliable model of severe hypoxia-ischemia brain damage (HIBD) in neonatal rats and several methods were used to identify whether the model was successful. A total of 40 healthy 7-day-old Sprague-Dawley rats were randomly divided into 2 groups: The sham-surgery group (n=18) and the HIBD model group (n=22). The HIBD model was produced according to the traditional Rice method. The rats were anesthetized with ethyl ether. The left common carotid artery (CCA) was exposed, ligated and cut. Following this, the rats were exposed to hypoxia in a normobaric chamber filled with 8% oxygen and 92% nitrogen for 2 h. In the sham-surgery group, the left CCA was exposed but was not ligated, cut or exposed to hypoxia. The neurobehavioral changes of the rats were observed in the 24 h after HIBD. The brains were collected after 72 h to observe the pathological morphological changes of the brain tissue. The behavioral ability and neurobehavioral changes were studied in each group. The water maze test was used for evaluating the learning-memory ability when the rats were 28 days old. Compared with the sham-surgery group, all the HIBD model rats had a lag of motor development. The rats had evident changes in anatomy and Nissl staining, and cognitive impairment was shown through the result of the water maze. Therefore, the model of HIBD in neonatal rats is feasible and provides a reliable model for subsequent studies.

Effects of edible bird's nest on hippocampal and cortical neurodegeneration in ovariectomized rats

The aim of this research is to investigate whether edible bird's nest (EBN) attenuates cortical and hippocampal neurodegeneration in ovariectomized rats. Ovariectomized rats were randomly divided into seven experimental groups (n = 6): the ovariectomy (OVX) group had their ovaries surgically removed; the sham group underwent surgical procedure similar to OVX group, but ovaries were left intact; estrogen group had OVX and received estrogen therapy (0.2 mg kg(-1) per day); EBN treatment groups received 6%, 3%, and 1.5% EBN, respectively. Control group was not ovariectomized. After 12 weeks of intervention, biochemical assays were performed for markers of neurodegeneration, and messenger ribonucleic acid (mRNA) levels of oxidative stress-related genes in the hippocampus and frontal cortex of the brain were analysed. Caspase 3 (cysteine-aspartic proteases 3) protein levels in the hippocampus and frontal cortex were also determined using western blotting. The results show that EBNs significantly decreased estrogen deficiency-associated serum elevation of advanced glycation end-products (AGEs), and they changed redox status as evidenced by oxidative damage (malondialdehyde content) and enzymatic antioxidant defense (superoxide dismutase and catalase) markers. Furthermore, genes associated with neurodegeneration and apoptosis were downregulated in the hippocampus and frontal cortex by EBN supplementation. Taken together, the results suggest that EBN has potential for neuroprotection against estrogen deficiency-associated senescence, at least in part via modification of the redox system and attenuation of AGEs.

Luteinizing hormone: Evidence for direct action in the CNS

This article is part of a Special Issue "SBN 2014". Hormonal dysfunction due to aging, especially during menopause, plays a substantial role in cognitive decline as well as the progression and development of neurodegenerative diseases. The hypothalamic-pituitary-gonadal (HPG) axis has long been implicated in changes in behavior and neuronal morphology. Most notably, estrogens have proven beneficial in the healthy brain through a host of different mechanisms. Recently, luteinizing hormone (LH) has emerged as a candidate for further investigation for its role in the CNS. The basis of this is that both LH and the LH receptor are expressed in the brain, and serum levels of LH correlate with cognitive deficits and Alzheimer's disease (AD) incidence. The study of LH in cognition and AD primarily focuses on evaluating the effects of downregulation of this peptide. This literature has shown that decreasing peripheral LH, through a variety of pharmacological interventions, reduces cognitive deficits in ovariectomy and AD models. However, few studies have researched the direct actions of LH on neurons and glial cells. Here we summarize the role of luteinizing hormone in modulating cognition, and we propose a mechanism that underlies a role for brain LH in this process.

Does vitamin C deficiency affect cognitive development and function?

Vitamin C is a pivotal antioxidant in the brain and has been reported to have numerous functions, including reactive oxygen species scavenging, neuromodulation, and involvement in angiogenesis. Absence of vitamin C in the brain has been shown to be detrimental to survival in newborn SVCT2(−/−) mice and perinatal deficiency have shown to reduce hippocampal volume and neuron number and cause decreased spatial cognition in guinea pigs, suggesting that maternal vitamin C deficiency could have severe consequences for the offspring. Furthermore, vitamin C deficiency has been proposed to play a role in age-related cognitive decline and in stroke risk and severity. The present review discusses the available literature on effects of vitamin C deficiency on the developing and aging brain with particular focus on in vivo experimentation and clinical studies.

Protective role of endogenous ovarian hormones against learning and memory impairments and brain tissues oxidative damage induced by lipopolysaccharide

BACKGROUND

The contribution of neuroinflammation in Alzheimer's disease (AD) has been widely reported. The effects of female gonadal hormones in both neuroinflammation and brain cognitive functions have also been well considered.

OBJECTIVES

In the present study, the possible protective role for endogenous ovarian hormones against learning and memory impairment as well as brain tissues oxidative damage induced by lipopolysachride (LPS) was investigated in rats.

MATERIALS AND METHODS

THE RATS WERE DIVIDED INTO FOUR GROUPS: Sham-LPS, Ovariectomized (OVX)-LPS, Sham, and OVX. The animals of sham group were in proestrous phase in which the serum concentration of estradiol is high. The Sham-LPS and OVX-LPS groups were treated with LPS (250 µg/kg) before acquisition. The animals were examined using passive avoidance (PA) test. The brains were then removed and malondialdehyde (MDA) and total thiol groups concentrations were measured.

RESULTS

The time latency to enter the dark compartment by OVX-LPS group was shorter than that of OVX at both first and 24th hours after the shock (P < 0.05 - P < 0.001). In Sham-LPS and OVX-LPS groups, total thiol concentration in hippocampal and cortical tissues were significantly lower while MDA concentrations were higher than that of Sham and OVX groups (P < 0.05 - P < 0.001). ). The hippocampal MDA concentration in OVX-LPS group was higher than Sham- LPS group (P < 0.01).

CONCLUSIONS

Brain tissue oxidative damage contributed in deleterious effects of LPS on learning and memory. Some protective effects for the endogenous ovarian hormones against damaging effects of LPS on learning and memory function, as well as brain tissues oxidative damage could be postulated; however, it needs more investigation.

Effect of tempol on the passive avoidance and novel object recognition task in diabetic rats

Diabetes mellitus (DM) has several effects, including cognitive impairment. Oxidative stress is associated with complications from diabetes. It seems that antioxidants can reduce some complications of the diabetes induced by oxidative stress. The objective of this study was to evaluate the effect of synthetic antioxidant, tempol on the passive avoidance (PA) memory and novel object recognition (NOR) tests in the diabetic rats. Forty male Wistar rats randomly divided into the control, diabetic, diabetic receiving tempol and healthy receiving tempol groups. Diabetes was induced by injection of streptozotocin (STZ) (60 mg/kg, i.p.). Then, the rats received saline or tempol (30 mg/kg) orally by gavages for 60 days. After that, they were assessed using the PA memory and NOR tests. The results of NOR test showed that the discrimination index (DI) in the healthy receiving tempol group and diabetic control group was significantly lower than control group. Also the amount of this index in diabetic receiving tempol group was significantly higher than diabetic group. The results of PA test indicated that the number of trials to acquisition in the diabetic rats is significantly more than control and diabetic tempol treated groups. Also, the time spent in the dark compartment (TDC) in the control and diabetic receiving tempol groups was less than diabetic group. TDC in the healthy receiving tempol group was more than control group. It can be concluded that although use of tempol is restricted as a cognitive enhancer in non-diabetic subjects but long-term administration of synthetic antioxidant, tempol, is able to dramatically improve diabetes-induced learning and memory deficit in both PA and NOR tests.

Effects of SuperUlam on Supporting Concentration and Mood: A Randomized, Double-Blind, Placebo-Controlled Crossover Study

Background. SuperUlam is a proprietary blend of natural ingredients aimed at supporting brain health. We aimed to evaluate the effect of SuperUlam on attention and mood in healthy adults. Methods. Twenty healthy individuals aged 35–65 were enrolled in this randomized, double-blind, placebo-controlled, crossover study. Study duration was 3 weeks and consisted of 3 visits. Measurement of cognitive function included computer-based testing of reaction time, complex attention, working memory, sustained attention, and executive functioning. Mood testing was performed via the profile of mood states (POMS) survey and the Chalder fatigue scale. Results. Cognitive function testing demonstrated a significant improvement from baseline in executive functioning, cognitive flexibility, reaction time, and working memory in the product group only (P < 0.05). When comparing the study product to placebo, the data demonstrated a significant decrease in tension, depression, and anger (P < 0.05). There was no significant difference between the product and placebo in the other measures of mood, including vigor, fatigue, confusion, and total mood disturbance. No adverse events were reported. Conclusions. Supplementation with SuperUlam is safe to consume with potential benefits to cognitive function and mood.

Brain tissue oxidative damage as a possible mechanism for the deleterious effect of a chronic high dose of estradiol on learning and memory in ovariectomized rats

In addition to antioxidative effects, estrogens also exert pro-oxidative actions. The effect of chronic administration of a high dose of estradiol valerate on Morris water maze tasks and brain tissues oxidative damage was investigated. The Sham-Est and OVX-Est groups were treated with estradiol valerate (4 mg/kg) for 12 weeks. Escape latency and traveled path in the Sham-Est and OVX-Est groups were significantly higher than in the Sham and OVX groups (p≪0.01 and p≪0.001). In the probe trial, the animals of the Sham-Est and OVX-Est groups spent lower time in Q1 compared to Sham and OVX groups (p≪0.05 and p≪0.001). In Sham-Est and OVX-Est groups, the brain tissue total thiol concentration was significantly lower, and malondialdehyde (MDA) concentrations were higher than in the Sham and OVX groups (p≪0.05 and p≪0.001). It is concluded that administration of high exogenous levels of estradiol impairs performance and enhances oxidative stress.

Effect of sesamol on the pathophysiological changes induced by surgical menopause in rodents

OBJECTIVE

Estrogen deprivation after menopause is associated with increased oxidative stress. The present study was designed to study the role of sesamol (3,4-methylenedioxyphenol), a phenolic antioxidant and anti-inflammatory molecule, in oxidative stress-induced changes in three major affected organ systems, the central nervous system, the cardiovascular system and the skeletal system in ovariectomized rats, a widely used animal model of menopause.

DESIGN

Animals were divided into eight different groups (n = 6-8). Five groups underwent ovariectomy; starting from the 2nd day of ovariectomy, three of these groups received sesamol (2, 4, 8 mg/kg) and the fourth group was administered α-tocopherol (100 mg/kg) orally for 7 weeks. The fifth ovariectomized group did not receive any drug treatment. Rats in the naïve (non-operated) and sham-operated groups did not receive any drug treatment, while the eighth group consisted of naïve animals which were treated for 7 weeks with only sesamol 8 mg/kg orally daily. After 7 weeks, animals were subjected to testing of behavioral paradigms (elevated plus maze and Morris water maze for assessment of anxiety and memory, respectively) 24 h after the last dose. After behavioral studies, animals were sacrificed for various biochemical estimations.

RESULT

Administration of sesamol (2, 4, 8 mg/kg orally) to ovariectomized rats for 7 weeks significantly and dose-dependently improved memory, attenuated anxiety, decreased oxidative stress in brain, improved the serum lipid profile and reduced serum tumor necrosis factor-α levels when compared with ovariectomized control rats. Similar protective effects were observed in the case of the skeletal system studies. Sesamol increased the bone ash content and the mechanical stress parameters in treated groups.

CONCLUSION

The results emphasize the involvement of oxidative stress and inflammation in the development of ovariectomy-induced pathophysiological changes and point towards the therapeutic potential of sesamol in menopausal pathologies.

Nutrition, adult hippocampal neurogenesis and mental health

INTRODUCTION

Over the last 8 years, emerging studies bridging the gap between nutrition and mental health have resolutely established that learning and memory abilities as well as mood can be influenced by diet. However, the mechanisms by which diet modulates mental health are still not well understood. Sources of data In this article, a review of the literature was conducted using PubMed to identify studies that provide functional implications of adult hippocampal neurogenesis (AHN) and its modulation by diet.

AREAS OF AGREEMENT

One of the brain structures associated with learning and memory as well as mood is the hippocampus. Importantly, the hippocampus is one of the two structures in the adult brain where the formation of newborn neurons, or neurogenesis, persists.

AREAS OF CONTROVERSY

The exact roles of these newborn neurons in learning, memory formation and mood regulation remain elusive.

GROWING POINTS

Nevertheless, there has been accumulating evidence linking cognition and mood to neurogenesis occurring in the adult hippocampus. Therefore, modulation of AHN by diet emerges as a possible mechanism by which nutrition impacts on mental health.

AREAS TIMELY FOR DEVELOPING RESEARCH

This area of investigation is new and needs attention because a better understanding of the neurological mechanisms by which nutrition affect mental health may lead to novel dietary approaches for disease prevention, healthier ageing and discovery of new therapeutic targets for mental illnesses.

Zingiber officinale Improves Cognitive Function of the Middle-Aged Healthy Women

The development of cognitive enhancers from plants possessing antioxidants has gained much attention due to the role of oxidative stress-induced cognitive impairment. Thus, this study aimed to determine the effect of ginger extract, or Zingiber officinale, on the cognitive function of middle-aged, healthy women. Sixty participants were randomly assigned to receive a placebo or standardized plant extract at doses of 400 and 800 mg once daily for 2 months. They were evaluated for working memory and cognitive function using computerized battery tests and the auditory oddball paradigm of event-related potentials at three different time periods: before receiving the intervention, one month, and two months. We found that the ginger-treated groups had significantly decreased P300 latencies, increased N100 and P300 amplitudes, and exhibited enhanced working memory. Therefore, ginger is a potential cognitive enhancer for middle-aged women.

Behavioral and neurochemical effects of proline

Proline is an amino acid with an essential role for primary metabolism and physiologic functions. Hyperprolinemia results from the deficiency of specific enzymes for proline catabolism, leading to tissue accumulation of this amino acid. Hyperprolinemic patients can present neurological symptoms and brain abnormalities, whose aetiopathogenesis is poorly understood. This review addresses some of the findings obtained, mainly from animal studies, indicating that high proline levels may be associated to neuropathophysiology of some disorders. In this context, it has been suggested that energy metabolism deficit, Na(+),K(+)-ATPase, kinase creatine, oxidative stress, excitotoxicity, lipid content, as well as purinergic and cholinergic systems are involved in the effect of proline on brain damage and spatial memory deficit. The discussion focuses on the relatively low antioxidant defenses of the brain and the vulnerability of neural tissue to reactive species. This offers new perspectives for potential therapeutic strategies for this condition, which may include the early use of appropriate antioxidants as a novel adjuvant therapy, besides the usual treatment based on special diets poor in proline.

Antioxidants prevent memory deficits provoked by chronic variable stress in rats

Learning and memory deficits occur in depression and other stress related disorders. Although the pathogenesis of cognitive impairment after stress has not been fully elucidated, factors such as oxidative stress and neurotrophins are thought to play possible roles. Here we investigated the effect of treatment with vitamin E (40 mg/kg) and vitamin C (100 mg/kg) on the effects elicited by chronic variable stress on rat performance in Morris water maze. Brain-derived neurotrophic factor (BDNF) immunocontent was also evaluated in hippocampus of rats. Sixty-day old Wistar rats were submitted to different stressors for 40 days (stressed group). Half of stressed group received administration of vitamins once a day, during the period of stress. Chronically stressed rats presented a marked decrease in reference memory in the water maze task as well as a reduced efficiency to find the platform in the working memory task. Rats treated with vitamins E and C had part of the above effects prevented, suggesting the participation of oxidative stress in such effects. The BDNF levels were not altered in hippocampus of stressed group when compared to controls. Our findings lend support to a novel therapeutic strategy, associated with these vitamins, to the cognitive dysfunction observed in depression and other stress related diseases.

Ovariectomy alters energy metabolism in rat striatum: effect of supplementation with soy diet rich in isoflavones

In the present study we investigated the effect of ovariectomy on some parameters of energy metabolism, namely Na(+),K(+)-ATPase and pyruvate kinase activities, as well as the mitochondrial respiratory chain enzymes activities succinate dehydrogenase, complex II and cytochrome c oxidase in rat striatum. The influence of soy diet rich in isoflavones on the effects elicited by ovariectomy on enzyme activities was also evaluated. Female adult Wistar rats were assigned to one of the following groups: sham (submitted to surgery without removal of the ovaries) and ovariectomized. Seven days after surgery animals were fed for 30 days on a special diet with soy protein or a standard diet with casein (control). Rats were sacrificed after treatment and the striatum was dissected. Results showed that rats subjected to ovariectomy presented a significant increase in Na(+),K(+)-ATPase, succinate dehydrogenase and complex II activities. Treatment with isoflavones-rich soy diet was able to reverse the increase of Na(+),K(+)-ATPase activity, but was not effective in reversing the changes caused by ovariectomy on succinate dehydrogenase and complex II activities. Since ovariectomy mimics postmenopausal changes, our findings suggest that dysfunction of brain energy metabolism may be related to neurological symptoms observed in some postmenopausal women.

Aqueous Extract of Black Maca (Lepidium meyenii) on Memory Impairment Induced by Ovariectomy in Mice

The present study aims to test two different doses of aqueous extract of black maca on learning and memory in ovariectomized (OVX) mice and their relation with malonalehyde (MDA), acetylcholinesterase (Ache) and monoamine oxidase (MAO) brain levels. Female mice were divided into five groups: (i) naive (control), (ii) sham, (iii) OVX mice and OVX mice treated with (iv) 0.50 g kg⁻¹ and (v) 2.00 g kg⁻¹ black maca. Mice were orally treated with distilled water or black maca during 35 days starting 7 days after surgery. Memory and learning were assessed using the water Morris maze (from day 23–27) and the step-down avoidance test (days 34 and 35). At the end of each treatment, mice were sacrificed by decapitation and brains were dissected out for MDA, Ache and MAO determinations. Black maca (0.5 and 2.0 g/kg) increased step-down latency when compared to OVX control mice. Black maca decreased MDA and Ache levels in OVX mice; whereas, no differences were observed in MAO levels. Finally, black maca improved experimental memory impairment induced by ovariectomy, due in part, by its antioxidant and Ache inhibitory activities.

Chronic treatment with the nitric oxide synthase inhibitor, L-NAME, attenuates estradiol-mediated improvement of learning and memory in ovariectomized rats

INTRODUCTION

The role of ovarian hormones and nitric oxide in learning and memory has been widely investigated.

OBJECTIVE

The present study was carried out to evaluate the effect of the nitric oxide synthase (NOS) inhibitor, N (G)-nitro-L-arginine methyl ester (L-NAME), on the ability of estradiol to improve learning in OVX rats using the Morris water maze.

METHODS

Forty rats were divided into five groups: (1) ovariectomized (OVX), (2) ovariectomized-estradiol (OVX-Est), (3) ovariectomized-L-NAME 10 (OVX-LN 10), (4) ovariectomized-L-NAME 50 (OVX-LN 50) and (5) ovariectomized-estradiol-L-NAME 50 (OVX-Est-LN 50). The animals in the OVX-Est group were treated with a weekly injection of estradiol valerate (2 mg/kg; i.m.). The OVX-LN 10 and OVX-LN 50 groups were treated with daily injections of 10 and 50 mg/kg L-NAME (i.p.), respectively. The animals in the OVX-Est-LN 50 group received a weekly injection of estradiol valerate and a daily injection of 50 mg/kg L-NAME. After 8 weeks, all animals were tested in the Morris water maze.

RESULTS

The animals in the OVX-Est group had a significantly lower latency in the maze than the OVX group (p<0.001). There was no significant difference in latency between the OVX-LN 10 and OVX-LN 50 groups in comparison with the OVX group. The latency in the OVX-Est-LN 50 group was significantly higher than that in the OVX-Est group (p<0.001).

CONCLUSION

These results show that L-NAME treatment attenuated estradiol-mediated enhancement of spatial learning and memory in OVX rats, but it had no significant effect in OVX rats without estrogen, suggesting an interaction of nitric oxide and estradiol in these specific brain functions.

Running exercise effects on spatial and avoidance tasks in ovariectomized rats

Since previous studies have shown that ovariectomy impairs memory and cognition, we investigated whether physical exercise would affect ovariectomy-induced memory deficits in inhibitory avoidance and Morris water maze tasks. Female adult Wistar rats were assigned to one of the following groups: sham (submitted to surgery without removal of the ovaries), exercise, ovariectomy (Ovx) and Ovx plus exercise. Thirty days after ovariectomy or sham surgery, animals were submitted to 1 month of treadmill exercise training for 20 min, three times per week. Rats were than tested in inhibitory avoidance and Morris water maze tasks in order to verify ovariectomy effects on aversive and spatial memory performance. Results show that ovariectomized rats were impaired in aversive memory and spatial navigation, both in reference and working memory protocols. Confirming the working hypothesis, ovariectomized rats submitted to exercise had those impairments prevented. These findings support that physical exercise might constitute an important strategy to minimize cognitive deficits found in post-menopausal women.

The effect of chronic administration of L-arginine on the learning and memory of estradiol-treated ovariectomized rats tested in the morris water maze

OBJECTIVE

The present study was carried out to evaluate the effect of L-arginine on the learning and memory of estradiol-treated ovariectomized (OVX) rats.

METHODS

Forty-eight rats were divided into six groups: (1) sham, (2) OVX, (3) sham-Est, (4) OVX-Est, (5) sham-Est-LA, and (6) OVX-Est-LA. The animals of the sham-Est and OVX-Est groups were treated by weekly injection of estradiol valerate (2mg/kg). The sham-Est-LA and OVX-Est-LA groups were treated in the same manner but with an additional daily injection of L-arginine (200mg/kg). After eight weeks, animals of all groups were tested in the Morris water maze. The escape latency and path traveled to reach the platform were compared between groups.

RESULTS

Time latency and path length in the OVX group were significantly higher than in the sham group (P<0.05). The OVX-Est group had a significantly shorter traveled path length and time latency compared to the OVX group (P<0.001). Time latency and path length in the sham-Est group was significantly higher than in the sham group (P<0.001). Time latency and path length in the OVX-Est-LA group were significantly higher than in the OVX-Est group.

CONCLUSIONS

These results allow us to propose that chronic treatment with estradiol enhances the spatial learning and memory of OVX rats, and that long term L-arginine treatment attenuates the effects of improvement produced by estradiol in OVX rats.

The beneficial effects of olibanum on memory deficit induced by hypothyroidism in adult rats tested in Morris water maze

Functional consequences of hypothyroidism include impaired learning and memory and inability to produce long-term potentiation (LTP) in hippocampus. Olibanum has been used for variety of therapeutic purposes. In traditional medicine, oilbanum is used to enhance learning and memory. In the present study the effect of olibanum on memory deficit in hypothyroid rats was investigated. Male wistar rats were divided into four groups and treated for 180 days. Group 1 received tap drinking water while in group 2, 0.03% methimazol was added to drinking water. Group 3 and 4 were treated with 0.03% methimazole as well as 100 and 500 mg/kg olibanum respectively. The animals were tested in Morris water maze. The swimming speed was significantly lower and the distance and time latency were higher in group 2 compared with group 1. In groups 3 and 4 the swimming speed was significantly higher while, the length of the swim path and time latency were significantly lower in comparison with group 2. It is concluded that methimazole-induced hypothyroidism impairs learning and memory in adult rats which could be prevented by using olibanum.

Effects of combined treatment with vitamins C and E on passive avoidance learning and memory in diabetic rats

Learning and memory deficits occur in diabetes mellitus. Although the pathogenesis of cognitive impairment in diabetes has not been fully elucidated, factors such as metabolic impairments, vascular complications and oxidative stress are thought to play possible roles. Here we investigated the effect of chronic treatment with vitamin C (50mg/kg, p.o), vitamin E (100mg/kg, p.o) and both together on passive avoidance learning (PAL) and memory in male Wistar control and diabetic rats. Treatments were begun at the onset of hyperglycemia. Passive avoidance learning was assessed 30 days later. Retention was tested 24h after training. At the end, animals were weighed and blood samples were drawn for plasma glucose measurement. Diabetes caused impairment in acquisition and retrieval processes of PAL and memory. The combination of vitamin C and E improved learning and memory in controls and reversed learning and memory deficits in diabetic rats. Combined treatment also affected the body weight and plasma glucose level of diabetic treated animals compared to untreated diabetic animals. Hypoglycemic effects and antioxidant properties of the vitamins may be involved in the nootropic effect of such treatment. These results show that combined treatment with vitamins C and E improved PAL and memory of control rats. In addition, combined vitamins administration to rats for 30 days from onset of diabetes alleviated the negative influence of diabetes on learning and memory. Therefore, combined vitamins treatment may provide a new potential alternative for prevention of impaired cognitive functions associated with diabetes and may warrant further clinical study.

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

INTRODUCTION

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

METHODS

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

DISCUSSION

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

CONCLUSION

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

Exercise effects on activities of Na(+),K(+)-ATPase, acetylcholinesterase and adenine nucleotides hydrolysis in ovariectomized rats

Hormone deficiency following ovariectomy causes activation of Na(+),K(+)-ATPase and acetylcholinesterase (AChE) that has been related to cognitive deficits in experimental animals. Considering that physical exercise presents neuroprotector effects, we decide to investigate whether exercise training would affect enzyme activation in hippocampus and cerebral cortex, as well as adenosine nucleotide hydrolysis in synaptosomes from cerebral cortex of ovariectomized rats. Female adult Wistar rats were assigned to one of the following groups: sham (submitted to surgery without removal of the ovaries), exercise, ovariectomized (Ovx) and Ovx plus exercise. Thirty days after surgery, animals were submitted to one month of exercise training, three times per week. After, rats were euthanized, blood serum was collected and hippocampus and cerebral cortex were dissected. Data demonstrated that exercise reversed the activation of Na(+),K(+)-ATPase and AChE activities both in hippocampus and cerebral cortex of ovariectomized rats. Ovariectomy decreased AMP hydrolysis in cerebral cortex and did not alter adenine nucleotides hydrolysis in blood serum. Exercise per se decreased ADP and AMP hydrolysis in cerebral cortex. On the other hand, AMP hydrolysis in blood serum was increased by exercise in ovariectomized adult rats. Present data support that physical exercise might have beneficial effects and constitute a therapeutic alternative to hormone replacement therapy for estrogen deprivation.

Ovariectomy impairs spatial memory: prevention and reversal by a soy isoflavone diet

Since a previous study has shown that ovariectomy impairs spatial memory, we, herein, investigate the influence of pre- and post-treatment with a soy diet on the effects elicited by ovariectomy on spatial memory. In the pre-treatment, 20-day-old female Wistar rats were first fed for 60 days on a standard diet with casein (control) or a soy diet. At 80 days of age, the animals were assigned to one of the following groups: sham (submitted to surgery without removal of ovaries) and ovariectomized. One week after surgery, the rats were submitted to behavioral testing. In the post-treatment, 80-day-old female rats were assigned to one of the following groups: sham and ovariectomized. One week after surgery, animals were fed for 30 days with the same diet described above. Then, rats were submitted to water maze testing. Pre-treatment for two months before ovariectomy with the soy diet effectively prevented the increase in latency in finding the platform on the fifth day of training in the ovariectomized group. Ovariectomized rats subjected to soy diet post-treatment reversed the increase in latency to find the platform in the ovariectomized group on the fifth day of training and, the decrease in the time spent in target quadrant, the increase in the time spent in opposite quadrant and the latency to cross the platform location. Results show that both pre- and post-treatment protected against the impairment of memory, caused by ovariectomy. Post-treatment reversed various parameters of memory reference, indicating that post-treatment was more efficient than pre-treatment. Based on these findings, we suggest that soy diet (rich in isoflavones) may represent a novel therapeutic strategy to prevent or to treat cognitive symptoms found in some menopausal women.

Effects of phytoestrogen on mitochondrial structure and function of hippocampal CA1 region of ovariectomized rats

The present study was undertaken to evaluate whether estrogen deprivation might lead to mitochondrial alteration of hippocampal neurons of ovariectomized (OVX) rats, and to evaluate the protective effect of estrogen and phytoestrogen on the mitochondrial alteration. First, OVX rats were used to mimic the pathologic changes of neurodegeneration of postmenopausal female, and we looked into the alteration of the mitochondrial ultrastructure and ATP content of hippocampal CA1 region after ovariectomy on different phase by transmission electron microscope (TEM) and reversed-phase high-performance liquid chromatography (HPLC), and found the best phase points of the alteration of the mitochondrial ultrastructure and ATP content. Next, estrogen and phytoestrogen were administered to the OVX rats for the protective effects on the mitochondrial ultrastructure and ATP content. Meanwhile, the density, size, shape, and distribution parameters of mitochondrial ultrastructure were analyzed according to the morphometry principle. The experimental results presented that (1) The alteration of mitochondrial ultrastructure elicited by ovariectomy worsened with the days going on, and the changes were the most noteworthy in volume density (Vv), average surface area (S), specific surface area (delta), and particle dispersity (Clambdaz) on 12th day (P < 0.05 or P < 0.01). Moreover, there was no statistical significance of the numerical density (Nv) among the five groups in the first step experiment. (2) The treatment with estrogen, genistein (Gs), and ipriflavone (Ip) significantly reversed the effect elicited by ovariectomy on Vv, S, delta, Clambdaz, Nv, and particle average diameter (D) of mitochondria of hippocampal CA1 region (P < 0.05). (3) Furthermore, ATP content of hippocampal CA1 region after ovariectomy declined significantly on 7th day (P < 0.05), and estrogen and phytoestrogen could reverse the alteration (P < 0.05). Taken together, these results revealed that phytoestrogen may have a protective role against the neurodegeneration after menopause via protecting mitochondrial structure and functions. Phytoestrogen may be a good alternative as a novel therapeutic strategy for menopausal syndrome.

Aqueous and hydroalcoholic extracts of Black Maca (Lepidium meyenii) improve scopolamine-induced memory impairment in mice

Lepidium meyenii Walp. (Brassicaceae), known as Maca, is a Peruvian hypocotyl growing exclusively between 4,000 and 4,500 m altitude in the central Peruvian Andes, particularly in Junin plateau. Previously, Black variety of Maca showed to be more beneficial than other varieties of Maca on learning and memory in ovariectomized mice on the water finding test. The present study aimed to test two different doses of aqueous (0.50 and 2.00 g/kg) and hydroalcoholic (0.25 and 1.00 g/kg) extracts of Black Maca administered for 35 days on memory impairment induced by scopolamine (1mg/kg body weight i.p.) in male mice. Memory and learning were evaluated using the water Morris maze and the step-down avoidance test. Brain acetylcholinesterase (AChE) and monoamine oxidase (MAO) activities in brain were also determined. Both extracts of Black Maca significantly ameliorated the scopolamine-induced memory impairment as measured in both the water Morris maze and the step-down avoidance tests. Black Maca extracts inhibited AChE activity, whereas MAO activity was not affected. These results indicate that Black Maca improves scopolamine-induced memory deficits.

Anti-dementia drugs and hippocampal-dependent memory in rodents

Abnormalities in hippocampal structure and function are characteristics of early Alzheimer's disease (AD). Behavioral tests measuring hippocampal-dependent memory in rodents are often used to evaluate novel treatments for AD and other dementias. In this study, we review the effects of drugs marketed for the treatment of AD, such as the acetylcholinesterase inhibitors, donepezil, rivastigmine, galantamine and the N-methyl-D-aspartic acid antagonist, memantine, in rodent models of memory impairment. We also briefly describe the effects of novel treatments for cognitive impairment in rodent models of memory impairment, and discuss issues concerning the selection of the animal model and behavioral tests. Suggestions for future research are offered.

Supplementation with vitamins E plus C or soy isoflavones in ovariectomized rats: effect on the activities of Na(+), K (+)-ATPase and cholinesterases

Since a previous study demonstrated that ovariectomized rats present an activation of Na(+), K(+)-ATPase and acetylcholinesterase (AChE) activities, in the present study we investigated the influence of vitamins E plus C or soy isoflavones on the effects elicited by ovariectomy on the activities of these enzyme in hippocampus of ovariectomized rats. We also determined the effect of the same compounds on the reduction of serum butyrylcholinesterase (BuChE) activity caused by ovariectomy. Female adult Wistar rats were assigned to one of the following groups: sham (submitted to surgery without removal of the ovaries) and ovariectomized. Seven days after surgery, animals were treated for 30 days with a single daily intraperitoneous injection of vitamins E (40 mg/kg) plus C (100 mg/kg) or saline (control). In another set of experiments, the rats were fed for 30 days on a special diet with soy protein or a standard diet with casein (control). Rats were sacrificed after treatments and the hippocampus was dissected and serum was separated. Data demonstrate that vitamins E plus C reversed the activation of Na(+), K(+)-ATPase and AChE in hippocampus of ovariectomized rats. Conversely, soy protein supplementation reversed the increase of AChE activity, but not of Na(+), K(+)-ATPase activity, caused by ovariectomized group. Neither treatment was able to reverse the reduction of serum BuChE activity. Furthermore, treatments with vitamins E plus C or soy were unable to reverse the decrease in estradiol levels caused by ovariectomy. Our findings show that the treatment with vitamins E plus C significantly reversed the effect of ovariectomy on hippocampal Na(+), K(+)-ATPase and AChE activities. However, a soy diet that was rich in isoflavones was able to reverse just the increase of AChE. Neither treatment altered the reduction in serum BuChE activity. Taken together, these vitamins and soy may have a protective role against the possible brain dysfunction observed in some menopause women. Vitamins E plus C and soy isoflavones may be a good alternative as a novel therapeutic strategy.

alpha7 Nicotinic receptor gene delivery into mouse hippocampal neurons leads to functional receptor expression, improved spatial memory-related performance, and tau hyperphosphorylation

Brain alpha7 nicotinic receptors have become therapeutic targets for Alzheimer's disease (AD) based on their memory-enhancing and neuroprotective actions. This study investigated the feasibility of increasing neuronal alpha7 receptor functions using a gene delivery approach based on neuron-selective recombinant adeno-associated virus (rAAV)-derived vectors. In order to determine whether alpha7 receptor-mediated cytotoxicity was dependent on receptor density, rat alpha7 nicotinic receptors were expressed at high concentrations in GH4C1 cells as measured with nicotine-displaceable [3H]methyllycaconitine (MLA) binding. The potency of GTS-21 (an alpha7 receptor agonist) to induce cell loss was similar in these cells to that seen in pheochromocytoma (PC12) cells expressing nine-times-lower receptor levels, suggesting that cytotoxicity was more dependent on agonist concentration than receptor density. Hippocampal transduction with rat alpha7 nicotinic receptors increased [3H]MLA binding in this region in wild type and alpha7 receptor-knockout (KO) mice without apparent cytotoxicity. No difference was observed in Kd values for MLA binding between endogenous and transgenic receptors. Single cell recordings demonstrated that dentate granule cells that normally have no alpha7 receptor response did so following alpha7 receptor gene delivery in wild type mice. Recovery of alpha7 function was also observed in stratum oriens and stratum radiatum neurons of KO mice following gene delivery. Wild type mice exhibited improved acquisition performance in the Morris water task 1 month after bilateral hippocampal transductions with the rat alpha7 receptor gene compared with green fluorescent protein-transduced controls. However, both groups reached similar training levels and there was no difference in subsequent probe performance. Finally, this gene delivery approach was used to test whether alpha7 receptors affect tau-phosphorylation. Chronic (i.e. 2 month but not 2 week) expression of high levels of alpha7 receptors in hippocampus increased AT8 staining characteristic of hyperphosphorylated tau in that region, indicating that endogenous agonist-mediated receptor activation may be able to modulate this process.