Immobilization stress-induced changes in brain acetylcholinesterase activity and cognitive function in mice

Nanowired delivery of dl-3-n-butylphthalide with antibodies to alpha synuclein potentiated neuroprotection in Parkinson's disease with emotional stress

Stress is one of the most serious consequences of life leading to several chronic diseases and neurodegeneration. Recent studies show that emotional stress and other kinds of anxiety and depression adversely affects Parkinson's disease symptoms. However, the details of how stress affects Parkinson's disease is still not well known. Traumatic brain injury, stroke, diabetes, post-traumatic stress disorders are well known to modify the disease precipitation, progression and persistence. However, show stress could influence Parkinson's disease is still not well known. The present investigation we examine the role of immobilization stress influencing Parkinson's disease brain pathology in model experiments. In ore previous report we found that mild traumatic brain injury exacerbate Parkinson's disease brain pathology and nanodelivery of dl-3-n-butylphthalide either alone or together with mesenchymal stem cells significantly attenuated Parkinson's disease brain pathology. In this chapter we discuss the role of stress in exacerbating Parkinson's disease pathology and nanowired delivery of dl-3-n-butylphthalide together with monoclonal antibodies to alpha synuclein (ASNC) is able to induce significant neuroprotection. The possible mechanisms of dl-3-n-butylphthalide and ASNC induced neuroprotection and suitable clinical therapeutic strategy is discussed.

Translation of Preclinical PET Imaging Findings: Challenges and Motion Correction to Overcome the Confounding Effect of Anesthetics

Preclinical brain positron emission tomography (PET) in animals is performed using anesthesia to avoid movement during the PET scan. In contrast, brain PET scans in humans are typically performed in the awake subject. Anesthesia is therefore one of the principal limitations in the translation of preclinical brain PET to the clinic. This review summarizes the available literature supporting the confounding effect of anesthesia on several PET tracers for neuroscience in preclinical small animal scans. In a second part, we present the state-of-the-art methodologies to circumvent this limitation to increase the translational significance of preclinical research, with an emphasis on motion correction methods. Several motion tracking systems compatible with preclinical scanners have been developed, each one with its advantages and limitations. These systems and the novel experimental setups they can bring to preclinical brain PET research are reviewed here. While technical advances have been made in this field, and practical implementations have been demonstrated, the technique should become more readily available to research centers to allow for a wider adoption of the motion correction technique for brain research.

Acetylcholinesterase Inhibitors in the Treatment of Neurodegenerative Diseases and the Role of Acetylcholinesterase in their Pathogenesis

Acetylcholinesterase (AChE) plays an important role in the pathogenesis of neurodegenerative diseases by influencing the inflammatory response, apoptosis, oxidative stress and aggregation of pathological proteins. There is a search for new compounds that can prevent the occurrence of neurodegenerative diseases and slow down their course. The aim of this review is to present the role of AChE in the pathomechanism of neurodegenerative diseases. In addition, this review aims to reveal the benefits of using AChE inhibitors to treat these diseases. The selected new AChE inhibitors were also assessed in terms of their potential use in the described disease entities. Designing and searching for new drugs targeting AChE may in the future allow the discovery of therapies that will be effective in the treatment of neurodegenerative diseases.

Does the application of acetylcholinesterase inhibitors in the treatment of Alzheimer's disease lead to depression?

Introduction: Alzheimer's disease and depression are health conditions affecting millions of people around the world. Both are strongly related to the level of the neurotransmitter acetylcholine. Since cholinergic deficit is characteristic of Alzheimer's disease, acetylcholinesterase inhibitors are applied as relevant drugs for the treatment of this disease, elevating the level of acetylcholine. On the other hand, a high level of acetylcholine is found to be associated with the symptoms of clinical depression.Areas covered: This article aims to discuss if acetylcholinesterase inhibitors used as anti-Alzheimer's drugs could be the cause of the symptoms of clinical depression often linked to this neurological disorder. Emphasis will be put on drugs currently in use and on newly investigated natural products, which can inhibit AChE activity.Expert opinion: Currently, it is not proven that the patient treated for Alzheimer's disease is prone to increased risk for depression due to the acetylcholinesterase inhibition, but there are strong indications. The level of acetylcholine is not the only factor in highly complicated diseases like AD and depression. Still, it needs to be considered isolated, keeping in mind the nature of presently available therapy, especially during a rational drug design process.

Protective effects of duloxetine against chronic immobilisation stress-induced anxiety, depression, cognitive impairment and neurodegeneration in mice

OBJECTIVES

This study aimed to evaluate the effect of duloxetine (10 and 20 mg/kg) against chronic immobilisation stress (CIS)-induced anxiety, depression, cognitive impairment and neurodegeneration in mice.

METHODS

CIS, 2 h/10 days (11:00 AM-1:00 PM) was applied after 30 min of pretreatment with saline, duloxetine 10 mg/kg and 20 mg/kg to the respective groups of animals, except the control group. Animals were examined for physiological (body weight, locomotion and grip strength), psychological (memory impairment, anxiety and depression), neurochemical (GABA and glutamate), biochemical (MDA, catalase, glutathione, superoxide dismutase) and histopathological changes.

KEY FINDINGS

CIS exposure revealed anxiety-like behaviour, depression-like behaviour, motor in-coordination and learning and memory impairment in mice. Besides, CIS induction decreased the antioxidant enzymes (GSH, SOD and catalase), GABA and the viable neuronal cell count, whereas CIS exposure significantly elevated the MDA, AChE activity and glutamate content in the cortex and hippocampus. Pretreatment with duloxetine10 and 20 mg/kg showed dose-dependent ameliorated effect against the CIS-induced alterations in mice.

CONCLUSION

In conclusion, the results of this study demonstrated the protective effect of duloxetine against neuropsychiatric symptoms, memory impairment caused by CIS-induction through inhibition of oxidative stress, AChE activity and glutamate release.

Vaccinium bracteatum Improves Spatial Learning and Memory by Regulating N-methyl-D-aspartate Receptors and Tau Phosphorylation in Chronic Restraint Stress-Induced Memory Impaired Mice

Vaccinium bracteatum Thunb. Leaves (VBL) are a component of traditional herbal medicines. However, molecular mechanisms of VBL in stress-related memory impairment are still unclear. This study aimed to investigate the spatial memory improvement effects of VBL in an animal model of chronic restraint stress (CRS) by using Y maze test and identified possible protective mechanisms against oxidative stress inducers (e.g., corticosterone and hydrogen peroxide [H2O2]) in SH-SY5Y neuronal cells. VBL showed neuroprotective effects via reduced release of lactate dehydrogenase (LDH) in corticosterone or H2O2-induced cell death that was mediated through the regulation of cleaved caspase-3 and Nrf2 pathways. Furthermore, CRS-exposed mice were orally administered VBL (10, 50, 100, and 200 mg/kg) daily for 21 days. CRS-exposed mice treated with VBL showed significantly increased spontaneous alternation in short-term memory (STM) and long-term memory (LTM) trials, and number of total arm entries in LTM trials as measured by the Y maze test. Moreover, VBL (50, 100, and 200 mg/kg) decreased acetylcholinesterase (AChE) activity in the hippocampus (HC, [Formula: see text] ¡ 0.01 and [Formula: see text] ¡ 0.001, respectively) and prefrontal cortex (PFC). CRS-exposed mice treated with VBL had dramatically decreased total Tau and Tau phosphorylation in the synapse of the HC and PFC which might be mediated by the regulation of CaMKII and GSK3[Formula: see text] phosphorylation. Additionally, VBL reduced CRS-induced upregulation of N-methyl-D-aspartate (NMDA) receptor subunits (NMDAR1, 2A, and 2B). Thus, VBL exerts spatial memory improvement by regulating CRS-induced NMDA receptor neurotoxicity and Tau hyperphosphorylation.

Evaluation of Insulin Resistance Induced Brain Tissue Dysfunction in Obese Dams and their Neonates: Role of Ipriflavone Amelioration

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is associated with activation of liver fibrogenesis and predisposes to cirrhosis and associated morbi-mortality. A high fat high cholesterol diet (HFD) was provided to female albino rats to establish a NASH model. It is well known that the offspring of obese mothers have an increased risk of obesity and diabetes. The present study aimed at evaluating the ameliorative effects of ipriflavone (IP) as a natural food supplement on lipid metabolism, improving insulin sensitivity, reducing oxidative stress and inflammation, modifying metabolic risk factors and/or reduce brain damage, in both neonates and their dams.

MATERIALS AND METHODS

The present aim was achieved by evaluating the oxidative stress and antioxidant defense system biomarkers, as thiobarbituric acid reactive substances (TBARS) and reduced glutathione (GSH), catalase, and superoxide dismutase (SOD) activities. In addition, the neurotransmitter acetylcholine (Ach) and acetylcholine esterase (AchE) activities, as well as levels of the apolipoprotein E4 (APOE4); β-secretase, hyper phosphor-tau and β-amyloid 42; 3-hydroxy- 3-methyl glutaryl coenzyme A reductase (HMG CoA R)" and COX-II by immunoblotting assays in the brain tissue of neonates and their dams in all the studied groups.

RESULTS

A very significant amelioration in acetylcholine and acetylcholine esterase neurotransmitters, Alzheimer's makers (β-amyloid), antioxidants (reduced glutathione (GSH) contents, catalase (CAT) and superoxide dismutase (SOD); and inflammatory cytokines in NASH model is observed upon administrating ipriflavone (IP) as a natural food supplement. The multifunctional activities of ipriflavone as an antioxidant, anti-inflammatory and anti-insulin resistance drug were discussed and correlated with other investigations.

CONCLUSION

Regarding steatohepatitis, the present study confirmed the anti-inflammatory effects of the ipriflavone (IP). Therefore, future studies should focus on hepatic fatty acid uptake, hepatic lipogenesis, and fatty acid oxidation and the role of IP in regulating hepatic fat metabolism. In addition, natural products like IP could be combined with the highly used pharmaceutical drugs to reduce the side effects of nonalcoholic steatohepatitis, and minimize progression of dementia. Moreover, the present study supports further attempts to heal the neural dysfunction via antioxidant and anti-inflammatory cascade activities using ipriflavone (IP).

Protective Effects of Citicoline and Benfotiamine Each Alone and in Combination on Streptozotocin-induced Memory Impairment in Mice

Objective

Diabetes mellitus is associated with cognitive disorders such as Alzheimer’s disease. Studies have shown that citicoline and benfotiamine can improve memory and learning through different mechanism of actions. The aim of this study was to compare the individual effects of benfotiamine (100, 200, 300 mg/kg) and citicoline (50, 100, 250, 500 mg/kg, gavage) and their co-administration on memory impairments in diabetic mice.

Methods

Diabetes was induced by a single dose of streptozotocin (STZ, 140 mg/kg, intraperitoneal) and benfotiamine and/or citicoline were administered for three weeks. Memory was evaluated using the object recognition task (ORT) and passive avoidance test (PAT).

Results

Results from ORT shows that citicoline at 50, 100, 250, and 500 mg/kg and benfotiamine at 100, 200, and 300 mg/kg and their combination (benfotiamine at 100 mg/kg added to citicoline at 50, 100, and 250 mg/kg) are equally effective in reversing the memory loss induced by STZ (p < 0.001). PAT results demonstrate that citicoline at 100, 250, and 500 mg/kg and benfotiamine at above doses did not improve the latency time when administered separately, but benfotiamine at a fixed dose of 100 mg/kg in the presence of citicoline at 50, 100, and 250 mg/kg increased the latency time and improved memory significantly.

Conclusion

In conclusion, in PAT, co-administration of benfotiamine and citicoline was more effective than either alone in improving memory. Regarding ORT, although benfotiamine added to citicoline improved memory notably, the difference between combination therapy and single-drug therapy was not considerable.

Impact of space allowance on performance traits, brain neurotransmitters and blood antioxidant activity of New Zealand White rabbits

The objective of this trial was to investigate the effect of space allowance on performance, welfare-related parameters and the levels of brain neurotransmitters in growing male rabbits. In a cage housing system, a total of 96 weaned rabbits were accommodated on three space allowance conditions (S₁ = 1425 cm²/rabbit; S₂ = 850 cm²/rabbit; S₃ = 625 cm²/rabbit), with 8 replicate cages per each group. Rabbits in the S₁ and S₂ groups showed better daily feed intake and feed conversion ratio compared with the high stocking density group (p = 0.004 and 0.018, respectively). Compared to the highest stocking density group (S₃), rabbits in the S₁ and S₂ groups showed significantly lower serum cortisol, MDA and GSSH level (p = 0.026, 0.018 and 0.009, respectively). The concentration of dopamine in brain tissues was significantly decreased in the S₃ group compared with other experimental groups (P = 0.001). However, there was no significant effect of space allowance on the brain AChE level (P = 0.277). Brain serotonin and GABA levels showed a significant decrease in rabbits reared with a limited space allowance (S₃) compared with S₁ and S₂ groups (P = 0.001 and 0.038, respectively). The level of brain MDA was significantly increased in the S₃ group compared with the S₁ group (P = 0.006). However, there were no detectable differences in the brain ATP level in rabbits reared with different space allowance (P = 0.693). In conclusion, the current study indicates that the 850 cm²/rabbit stocking density has resulted in a better feed intake, and welfare-related conditions compared with the 625 cm²/rabbit. Furthermore, the limited space allowance may impair the most important brain neurotransmitters in male rabbits.

Near-infrared photobiomodulation combined with coenzyme Q10 for depression in a mouse model of restraint stress: reduction in oxidative stress, neuroinflammation, and apoptosis

This study was aimed to evaluate the effects of near-infrared (NIR) photobiomodulation (PBM) combined with coenzyme Q₁₀ (CoQ₁₀) on depressive-like behavior, cerebral oxidative stress, inflammation, and apoptosis markers in mice. To induce a depressive-like model, mice were subjected to sub-chronic restraint stress for 5 consecutive days. NIR PBM (810 nm laser, 33.3 J/cm²) and/or CoQ₁₀ (500 mg/kg/day, gavage) were administered for five days concomitantly with immobilization. Behavior was evaluated by the forced swim test (FST), tail suspension test (TST), and open field test (OFT). Mitochondrial membrane potential as well as oxidative stress, neuroinflammatory, and markers of apoptosis were evaluated in the prefrontal cortex (PFC) and hippocampus (HIP). The serum levels of pro-inflammatory cytokines, cortisol, and corticosterone were also measured. PBM or CoQ₁₀, or the combination, ameliorated depressive-like behaviors induced by restraint stress as indicated by decreased immobility time in both the FST and TST. PBM and/or CoQ₁₀ treatments decreased lipid peroxidation and enhanced total antioxidant capacity (TAC), GSH levels, GPx and SOD activities in both brain areas. The neuroinflammatory response in the HIP and PFC was suppressed, as indicated by decreased NF-kB, p38, and JNK levels in PBM and/or CoQ₁₀ groups. Intrinsic apoptosis biomarkers, BAX, Bcl-2, cytochrome c release, and caspase-3 and -9, were also significantly down-regulated by both treatments. Furthermore, both treatments decreased the elevated serum levels of cortisol, corticosterone, TNF-α, and IL-6 induced by restraint stress. Transcranial NIR PBM and CoQ₁₀ therapies may be effective antidepressant strategies for the prevention of psychopathological and behavioral symptoms induced by stress.

Quercetin protects against stress-induced anxiety- and depression-like behavior and improves memory in male mice

The present study evaluates the protective role of Quercetin (Quer), against immobilization stress- induced anxiety, depression and cognition alteration in mice using behavioral and biochemical parameters. 24 adult Albino mice were distributed into 2 groups vehicle (n=12; 1 ml/kg) and Quer injected (n=12; 20 mg/kg/ml). The animals received their respective treatment for 14 days. On day 15, after the drug administration, animals were sub-divided into 4 groups (n=6); (i) unstressed + vehicle; (ii) stressed + vehicle; (iii) unstressed + Quer; (iv) stressed + Quer. On day 16, 24 h after the immobilization stress behavioral activities (light-dark activity, elevated plus maze, Morris water maze, and forced swim test) monitored and then animals were decapitated 1 h after the drug administration. Brain samples were collected for biochemical (antioxidant enzymes, AChE, ACh, 5-HT and its metabolite) analysis. The present study indicates the Quer reversed the stress-induced anxiety and depression, in addition, memory performance was more enhanced in stressed group. Following the treatment of Quer, stress-induced elevation of lipid peroxidation and suppression of antioxidant enzymes were also reversed. Administration of Quer decreased AChE in unstressed, while levels of acetylcholine were increased in vehicle and Quer treated stressed animals. The metabolism of 5-HT was increased in Quer treated stressed than unstressed animals. In conclusion, the present finding showed that Quer could prevent the impairment of antioxidant enzymes and also regulate the serotonergic and cholinergic neurotransmission and produce antianxiety, antidepressant effect and enhance memory following 2 h immobilization stress in mice.

Administration of Allium cepa L. bulb attenuates stress-produced anxiety and depression and improves memory in male mice

In view of anxiolytic, antidepressant and memory strengthen properties of Allium cepa (AC; onion) bulb in various investigations; we aimed to evaluate the useful effects of onion on single immobilization stress -induced biochemical and behavioral changes. Mice in test group were treated with AC powder (200 mg/kg/day), dissolved in water, while the control group were received drinking water for 14 days. After 14 days control and AC treated mice were further divided into unstressed and stressed groups. Animals in the stressed group were subjected to immobilization stress for 2 h. 24-h after the immobilization stress, behavioral activities were monitored. Immobilization stress-induced an anxiogenic behavior in mice subjected to elevated plus maze test (EPM) and light dark activity test (LDA). 2-h immobilization stress-induced depressive behavior in animals measured by forced swim test (FST). Administration of AC attenuated the immobilization stress-induced behavioral deficits. Highest memory performance was observed in stressed mice that were pre-treated with AC in Morris water maze (MWM). Brain lipid peroxidation, antioxidant enzymes (SOD, CAT, GPx) and acetylcholinesterase (AChE) activities were also estimated. Present study suggests a role of antioxidant enzymes in the attenuation of 2-h stress induced anxiety and depression, and enhanced cognitive function as well by AC. The findings therefore suggest that supplementation of AC may be beneficial in the treatment of anxiety, depression and enhancement of memory function.

Brain region-specific effects of immobilization stress on cholinesterases in mice

Brain acetylcholinesterase (AChE) variant AChE_R expression increases with acute stress, and this persists for an extended period, although the timing, strain and laterality differences, have not been explored previously. Acute stress transiently increases acetylcholine release, which in turn may increase activity of cholinesterases. Also the AChE gene contains a glucocorticoid response element (GRE), and stress-inducible AChE transcription and activity changes are linked to increased glucocorticoid levels. Corticotropin-releasing hormone knockout (CRH-KO) mice have basal glucocorticoid levels similar to wild type (WT) mice, but much lower levels during stress. Hence we hypothesized that CRH is important for the cholinesterase stress responses, including butyrylcholinesterase (BChE). We used immobilization stress, acute (30 or 120 min) and repeated (120 min daily × 7) in 48 male mice (24 WT and 24 CRH-KO) and determined AChE_R, AChE and BChE mRNA expression and AChE and BChE activities in left and right brain areas (as cholinergic signaling shows laterality). Immobilization decreased BChE mRNA expression (right amygdala, to 0.5, 0.3 and 0.4, × control respectively) and AChE_R mRNA expression (to 0.5, 0.4 and 0.4, × control respectively). AChE mRNA expression increased (1.3, 1.4 and 1.8-fold, respectively) in the left striatum (Str). The AChE activity increased in left Str (after 30 min, 1.2-fold), decreased in right parietal cortex with repeated stress (to 0.5 × control). BChE activity decreased after 30 min in the right CA3 region (to 0.4 × control) but increased (3.8-fold) after 120 min in the left CA3 region. The pattern of changes in CRH-KO differed from that in WT mice.

Attenuation of stress induced memory deficits by nonsteroidal anti-inflammatory drugs (NSAIDs) in rats: Role of antioxidant enzymes

BACKGROUND

Repeated stress paradigms have been shown to cause devastating alterations on memory functions. Stress is linked with inflammation. Psychological and certain physical stressors could lead to neuroinflammation. Inflammatory process may occur by release of mediators and stimulate the production of prostaglandins through cyclooxygenase (COX). Treatment with COX inhibitors, which restrain prostaglandin production, has enhanced memory in a number of neuroinflammatory states showing a potential function for raised prostaglandins in these memory shortfalls. In the present study, potential therapeutic effects of indomethacin and diclofenac sodium on memory in both unrestraint and restraint rats were observed.

METHODS AND RESULTS

Two components, long term memory and short term memory were examined by Morris water maze (MWM) and elevated plus maze (EPM) respectively. The present study also demonstrated the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) on lipid peroxidation (LPO) and activities of antioxidant enzymes along with the activity of acetylcholinesterase (AChE). Results of MWM and EPM showed significant effects of drugs in both unrestraint and restraint rats as escape latency and transfer latency, in respective behavioral models were decreased as compared to that of control. This study also showed NSAIDs administration decreased LPO and increased antioxidant enzymes activity and decreased AChE activity in rats exposed to repeated stress.

CONCLUSION

In conclusion this study suggests a therapeutic potential of indomethacin and diclofenac against repeated stress-induced memory deficits.

Acute administration of fenproporex increased acetylcholinesterase activity in brain of young rats

Fenproporex is the second most commonly amphetamine-based anorectic consumed worldwide; this drug is rapidly converted into amphetamine, in vivo, and acts by increasing dopamine levels in the synaptic cleft. Considering that fenproporex effects on the central nervous system are still poorly known and that acetylcholinesterase is a regulatory enzyme which is involved in cholinergic synapses and may indirectly modulate the release of dopamine, the present study investigated the effects of acute administration of fenproporex on acetylcholinesterase activity in brain of young rats. Young male Wistar rats received a single injection of fenproporex (6.25, 12.5 or 25mg/kg i.p.) or vehicle (2% Tween 80). Two hours after the injection, the rats were killed by decapitation and the brain was removed for evaluation of acetylcholinesterase activity. Results showed that fenproporex administration increased acetylcholinesterase activity in the hippocampus and posterior cortex, whereas in the prefrontal cortex, striatum and cerebellum the enzyme activity was not altered. In conclusion, in the present study we demonstrated that acute administration of fenproporex exerts an effect in the cholinergic system causing an increase in the activity of acetylcholinesterase in a dose-dependent manner in the hippocampus and posterior cortex. Thus, we suggest that the imbalance in cholinergic homeostasis could be considered as an important pathophysiological mechanism underlying the brain damage observed in patients who use amphetamines such as fenproporex.

Bone status of acetylcholinesterase-knockout mice

Acetylcholinesterase (AChE) hydrolyzes acetylcholine (ACh) to acetate and choline and thereby terminates nerve impulse transmission. ACh is also expressed in bone tissue and enhances here proliferation and differentiation of osteoblasts, which makes it interesting to investigate effects of AChE deficiency on bone. To our knowledge, this is the first study that analyzed bone of heterozygous acetylcholinesterase-knockout (AChE-KO) mice. Tibia, femur, thoracic and lumbar vertebrae of 16-week-old female heterozygous AChE-KO mice and their corresponding wildtypes (WT) were analyzed using real-time RT-PCR, dual-energy X-ray absorptiometry, biomechanics, micro-computed tomography, histology and histomorphometry. Our data revealed that heterozygous AChE-KO did not cause negative effects upon bone parameters analyzed. In contrast, the number of osteoclasts per perimeter was significantly reduced in lumbar vertebrae. In addition, we found a significant decrease in trabecular perimeter of lumbar vertebrae and cortical area fraction (Ct.Ar/Tt.Ar) in the mid-diaphysis of femurs of AChE-KO mice compared to their WT. Therefore, presumably a local homozygous knockout of AChE or AChE-inhibitor administration might be beneficial for bone formation due to ACh accumulation. However, many other bone parameters analyzed did not differ statistically significantly between AChE-KO and WT mice. That might be reasoned by the compensating effect of butyrylcholinesterase (BChE).

Chronic stress impacts the cardiovascular system: animal models and clinical outcomes

Psychological stresses are associated with cardiovascular diseases to the extent that cardiovascular diseases are among the most important group of psychosomatic diseases. The longstanding association between stress and cardiovascular disease exists despite a large ambiguity about the underlying mechanisms. An array of possibilities have been proposed including overactivity of the autonomic nervous system and humoral changes, which then converge on endothelial dysfunction that initiates unwanted cardiovascular consequences. We review some of the features of the two most important stress-activated systems, i.e., the humoral and nervous systems, and focus on alterations in endothelial function that could ensue as a result of these changes. Cardiac and hematologic consequences of stress are also addressed briefly. It is likely that activation of the inflammatory cascade in association with oxidative imbalance represents key pathophysiological components of stress-induced cardiovascular changes. We also review some of the commonly used animal models of stress and discuss the cardiovascular outcomes reported in these models of stress. The unique ability of animals for adaptation under stressful conditions lessens the extrapolation of laboratory findings to conditions of human stress. An animal model of unpredictable chronic stress, which applies various stress modules in a random fashion, might be a useful solution to this predicament. The use of stress markers as indicators of stress intensity is also discussed in various models of animal stress and in clinical studies.

Strain dependent effects of conditioned fear in adult C57Bl/6 and Balb/C mice following postnatal exposure to chlorpyrifos: relation to expression of brain acetylcholinesterase mRNA

Following reports of emotional psychopathology in children and adults exposed to organophosphates, the effects of postnatal chlorpyrifos (CPF) on fear-conditioning and depression-like behaviors were tested in adult mice. Concomitant changes in expression of mRNA for synaptic and soluble splice variants of acetylcholinesterase (AChE) were examined in mouse pups and adults of the Balb/C and C57Bl/6 (B6) strains, which differ in their behavioral and hormonal stress response. Mice were injected subcutaneously with 1 mg/kg CPF on postnatal days 4–10 and tested as adults for conditioned fear, sucrose preference, and forced swim. Acetylcholinesterase activity was assessed in the brains of pups on the first and last day of treatment. Expression of soluble and synaptic AChE mRNA was assessed in brains of treated pups and fear-conditioned adults using real-time PCR. Adult Balb/C mice exposed postnatally to CPF showed exacerbated fear-conditioning and impaired active avoidance. Adult B6 mice exposed postnatally to CPF showed a more specific fear response to tones and less freezing in the inter-tone intervals, in contrast to the vehicle-pretreated mice. Chlorpyrifos also attenuated sweet preference and enhanced climbing in the forced swim test. Chlorpyrifos-treated mice had increased expression of both synaptic and readthrough AChE transcripts in the hippocampus of Balb/C mice and decreased expression in the amygdala following fear-conditioning. In conclusion, postnatal CPF had long-term effects on fear and depression, as well as on expression of AChE mRNA. These changes may be related to alteration in the interaction between hippocampus and amygdala in regulating negative emotions.

Acute stress in adulthood impoverishes social choices and triggers aggressiveness in preclinical models

Adult C57BL/6J mice are known to exhibit high level of social flexibility while mice lacking the β2 subunit of nicotinic receptors (β2(-/-) mice) present social rigidity. We asked ourselves what would be the consequences of a restraint acute stress (45 min) on social interactions in adult mice of both genotypes, hence the contribution of neuronal nicotinic receptors in this process. We therefore dissected social interaction complexity of stressed and not stressed dyads of mice in a social interaction task. We also measured plasma corticosterone levels in our experimental conditions. We showed that a single stress exposure occurring in adulthood reduced and disorganized social interaction complexity in both C57BL/6J and β2(-/-) mice. These stress-induced maladaptive social interactions involved alteration of distinct social categories and strategies in both genotypes, suggesting a dissociable impact of stress depending on the functioning of the cholinergic nicotinic system. In both genotypes, social behaviors under stress were coupled to aggressive reactions with no plasma corticosterone changes. Thus, aggressiveness appeared a general response independent of nicotinic function. We demonstrate here that a single stress exposure occurring in adulthood is sufficient to impoverish social interactions: stress impaired social flexibility in C57BL/6J mice whereas it reinforced β2(-/-) mice behavioral rigidity.

Preclinical experimental stress studies: protocols, assessment and comparison

Stress is a state of threatened homeostasis during which a variety of adaptive processes are activated to produce physiological and behavioral changes. Preclinical models are pivotal for understanding these physiological or pathophysiological changes in the body in response to stress. Furthermore, these models are also important for the development of novel pharmacological agents for stress management. The well described preclinical stress models include immobilization, restraint, electric foot shock and social isolation stress. Stress assessment in animals is done at the behavioral level using open field, social interaction, hole board test; at the biochemical level by measuring plasma corticosterone and ACTH; at the physiological level by measuring food intake, body weight, adrenal gland weight and gastric ulceration. Furthermore the comparison between different stressors including electric foot shock, immobilization and cold stressor is described in terms of intensity, hormonal release, protein changes in brain, adaptation and sleep pattern. This present review describes these preclinical stress protocols, and stress assessment at different levels.

Resveratrol exerts anti-inflammatory and neuroprotective effects to prevent memory deficits in rats exposed to chronic unpredictable mild stress

A number of studies have recently focused on the neuroprotective and anti-inflammatory effects of resveratrol. In prior studies, we described its beneficial effects on scopolamine-induced learning deficits in rats. The aim of this study was to investigate the effects of resveratrol on emotional and spatial cognitive functions, neurotropic factor expression, and plasma levels of proinflammatory cytokines in rats exposed to chronic unpredictable mild stress (CUMS), which is known to induce cognitive deficits. Resveratrol (5 or 20mg/kg) was administered intraperitoneally for 35 days. Rats in the CUMS group and in the 5mg/kg resveratrol+CUMS group performed poorly in tasks designed to assess emotional and spatial learning and memory. The 20mg/kg resveratrol+CUMS group showed improved performance compared to the CUMS group. In addition, the CUMS procedure induced lower expression of brain-derived neurotrophic factor and c-Fos in hippocampal CA1 and CA3 and in the amygdala of stressed rats. These effects were reversed by chronic administration of resveratrol (20mg/kg). In addition, plasma levels of tumor necrosis factor-alpha and interleukin-1 beta were increased by CUMS, but were restored to normal by resveratrol. These results indicate that resveratrol significantly attenuates the deficits in emotional learning and spatial memory seen in chronically stressed rats. These effects may be related to resveratrol-mediated changes in neurotrophin factor expression in hippocampus and in levels of proinflammatory cytokines in circulation.

The catecholaminergic-cholinergic balance hypothesis of bipolar disorder revisited

Bipolar disorder is a unique illness characterized by fluctuations between mood states of depression and mania. Originally, an adrenergic-cholinergic balance hypothesis was postulated to underlie these different affective states. In this review, we update this hypothesis with recent findings from human and animal studies, suggesting that a catecholaminergic-cholinergic hypothesis may be more relevant. Evidence from neuroimaging studies, neuropharmacological interventions, and genetic associations support the notion that increased cholinergic functioning underlies depression, whereas increased activations of the catecholamines (dopamine and norepinephrine) underlie mania. Elevated functional acetylcholine during depression may affect both muscarinic and nicotinic acetylcholine receptors in a compensatory fashion. Increased functional dopamine and norepinephrine during mania on the other hand may affect receptor expression and functioning of dopamine reuptake transporters. Despite increasing evidence supporting this hypothesis, a relationship between these two neurotransmitter systems that could explain cycling between states of depression and mania is missing. Future studies should focus on the influence of environmental stimuli and genetic susceptibilities that may affect the catecholaminergic-cholinergic balance underlying cycling between the affective states. Overall, observations from recent studies add important data to this revised balance theory of bipolar disorder, renewing interest in this field of research.

Anti-oxidative effects of Rooibos tea (Aspalathus linearis) on immobilization-induced oxidative stress in rat brain

Exposure to chronic psychological stress may be related to increased reactive oxygen species (ROS) or free radicals, and thus, long-term exposure to high levels of oxidative stress may cause the accumulation of oxidative damage and eventually lead to many neurodegenerative diseases. Compared with other organs, the brain appears especially susceptible to excessive oxidative stress due to its high demand for oxygen. In the case of excessive ROS production, endogenous defense mechanisms against ROS may not be sufficient to suppress ROS-associated oxidative damage. Dietary antioxidants have been shown to protect neurons against a variety of experimental neurodegenerative conditions. In particular, Rooibos tea might be a good source of antioxidants due to its larger proportion of polyphenolic compounds. An optimal animal model for stress should show the features of a stress response and should be able to mimic natural stress progression. However, most animal models of stress, such as cold-restraint, electric foot shock, and burn shock, usually involve physical abuse in addition to the psychological aspects of stress. Animals subjected to chronic restraint or immobilization are widely believed to be a convenient and reliable model to mimic psychological stress. Therefore, in the present study, we propose that immobilization-induced oxidative stress was significantly attenuated by treatment with Rooibos tea. This conclusion is demonstrated by Rooibos tea's ability to (i) reverse the increase in stress-related metabolites (5-HIAA and FFA), (ii) prevent lipid peroxidation (LPO), (iii) restore stress-induced protein degradation (PD), (iv) regulate glutathione metabolism (GSH and GSH/GSSG ratio), and (v) modulate changes in the activities of antioxidant enzymes (SOD and CAT).

Design, synthesis and evaluation of tacrine-flurbiprofen-nitrate trihybrids as novel anti-Alzheimer's disease agents

To search for multifunctional anti-Alzheimer's disease (AD) agents with good safety, the previously synthesized tacrine-flurbiprofen hybrids 1a and 1b were modified into tacrine-flurbiprofen-nitrate trihybrids 3a-h. These compounds displayed comparable or higher cholinesterase inhibitory activity relative to the bivalent hybrids. Compound 3a was the most potent, which released moderate NO, exerted blood vessel relaxative activity, and showed significant Aβ inhibitory effects whereas tacrine and flurbiprofen did not exhibit any Aβ inhibitory activity at the same dose. In addition, 3a was active in improving memory impairment in vivo. More importantly, the hepatotoxicity study showed that 3a was much safer than tacrine, suggesting it might be a promising anti-AD agent for further investigation.

Increased resistance of immobilized-stressed mice to infection: correlation with behavioral alterations

Immobilization is an easy and convenient method to induce both psychological and physical stress resulting in restricted motility and aggression and is believed to be the most severe type of stress in rodent models. Although it has been generally accepted that chronic stress often results in immunosuppression while acute stress has been shown to enhance immune responses, the effects of IS on the host resistance to Escherichia coli (E. coli) infection and associated behavioral changes are still not clear. In a series of experiments aimed at determining the level of hypothalamic COX-2, HSP-90, HSP-70, SOD-1 and plasma level of corticosterone, cytokine, antibody titer and their association with behavioral activities, mice were infected with viable E. coli during acute and chronic IS by taping their paws. In this study we show that acute and chronic IS enhances the resistance of mice to E. coli infection via inhibiting the production of pro-inflammatory cytokines, free radicals, and by improving the exploratory behavior. Altogether, our findings support the notion that cytokines released during immune activation and under the influence of corticosterone can modulate the open field behavior both in terms of locomotor activity as well as exploration. One of the features observed with chronic stressor was a lower ability to resist bacterial infection, although in case of acute stress, a better clearance of bacterial infection was observed in vivo with improvement of exploratory behavior and cognitive functions.

Enhanced brain performance in mice following postnatal stress

The double postnatal stress model (brief maternal separation plus sham injection daily applied from birth to weaning) induces metabolic alterations similar to type 2 diabetes in young-adult male mice. We verify whether 1) the stress also induces brain metabolic-functional alterations connected to diabetes and 2) different alterations are modulated selectively by two stress-damaged endogenous systems (opioid- and/or ACTH-corticosteroid-linked). Here, diabetes-like metabolic plus neurophysiologic-neurometabolic parameters are studied in adult mice following postnatal stress and drug treatment. Surprisingly, together with 'classic' diabetes-like alterations, the stress model induces in young-adult mice significantly enhanced brain neurometabolic-neurophysiologic performances, consisting of decreased latency to flash-visual evoked potentials (- ~8%); increased level (+ ~40%) and reduced latency (- ~30%) of NAD(P)H autofluorescence postsynaptic signals following electric stimuli; enhanced passive avoidance learning (+ ~135% latency); and enhanced brain-derived neurotrophic factor level (+ ~70%). Postnatal treatment with the opioid receptor antagonist naloxone prevents some alterations, moreover the treatment with antisense (AS; AS vs proopiomelanocortin mRNA) draws all parameters to control levels, thus showing that some alterations are bound to endogenous opioid-system hyper-functioning, while others depend on ACTH-corticosterone system hyper-functioning. Our stress model induces diabetes-like metabolic alterations coupled to enhanced brain neurometabolic-neurophysiologic performances. Taken all together, these findings are compatible with an 'enduring acute-stress' reaction, which puts mice in favorable survival situations vs controls. However, prolonged hormonal-metabolic imbalances are expected to also produce diabetes-like complications at later ages in stressed mice.

Inhibition of acetylcholinesterase activity in brain and behavioral analysis in adult rats after chronic administration of fenproporex

Fenproporex is an amphetamine-based anorectic and it is rapidly converted in vivo into amphetamine. It elevates the levels of extracellular dopamine in the brain. Acetylcholinesterase is a regulatory enzyme which is involved in cholinergic synapses and may indirectly modulate the release of dopamine. Thus, we investigated whether the effects of chronic administration of fenproporex in adult rats alters acquisition and retention of avoidance memory and acetylcholinesterase activity. Adult male Wistar rats received repeated (14 days) intraperitoneal injection of vehicle or fenproporex (6.25, 12.5 or 25 mg/kg i.p.). For behavioral assessment, animals were submitted to inhibitory avoidance (IA) tasks and continuous multiple trials step-down inhibitory avoidance (CMIA). Acetylcholinesterase activity was measured in the prefrontal cortex, hippocampus, hypothalamus and striatum. The administration of fenproporex (6.25, 12.5 and 25 mg/kg) did not induce impairment in short and long-term IA or CMIA retention memory in rats. In addition, longer periods of exposure to fenproporex administration decreased acetylcholinesterase activity in prefrontal cortex and striatum of rats, but no alteration was verified in the hippocampus and hypothalamus. In conclusion, the present study showed that chronic fenproporex administration decreased acetylcholinesterase activity in the rat brain. However, longer periods of exposure to fenproporex did not produce impairment in short and long-term IA or CMIA retention memory in rats.

A review on animal models for screening potential anti-stress agents

Stress is a state of threatened homeostasis that produces different physiological as well as pathological changes depending on severity, type and duration of stress. The animal models are pivotal for understanding the pathophysiology of stress-induced behavioral alterations and development of effective therapy for its optimal management. A battery of models has been developed to simulate the clinical pain conditions with diverse etiology. An ideal animal model should be able to reproduce each of the aspects of stress response and should be able to mimic the natural progression of the disease. The present review describes the different types of acute and chronic stress models including immersion in cold water with no escape, cold environment isolation, immobilization/restraint-induced stress, cold-water restraint stress, electric foot shock-induced stress, forced swimming-induced stress, food-deprived activity stress, neonatal isolation-induced stress, predatory stress, day-night light change-induced stress, noise-induced stress, model of post-traumatic stress disorder and chronic unpredictable stress models.

Cholinergic influence on memory stages: A study on scopolamine amnesic mice

Objectives:

The study was planned to determine cholinergic influence on different stages of memory - acquisition, consolidation and recall in scopolamine-induced amnesia (memory impairment) in mice.

Materials and Methods:

To study acquision, consolidation and recall stages of memory, we administered scopolamine (0.75, 1.5 and 3 mg/kg ip) 30 minutes and five minutes prior to first trial acquisition and consolidation and 30 minutes prior to second trial recall of passive avoidance (PA) test, respectively, in separate groups. Tacrine (5 mg/kg po) and rivastigmine (5 mg/kg po) were administered one hour prior to first trial in separate groups which received scopolamine (3 mg/kg ip) 30 minutes and five minutes prior to first trial where as the control group received vehicle only.

Results:

In the control group, there was a significant (P < 0.01) increase in transfer latency time (TLT) in the second trial compared to first indicating successful learning. In scopolamine treated groups, administering scopolamine 30 minutes or five minutes prior to first trial did not show any significant (P > 0.05) change in TLT whereas mice treated with scopolamine 30 minutes prior to second trial showed significant (P < 0.01) increase in TLT in second trial as compared to the first. Both tacrine and rivastigmine administration in scopolamine treated mice showed significant (P < 0.05-0.01) increase in TLT in second trial as compared to first trial while the rivastigmine treated group showed greater percentage retention compared to tacrine treated group.

Conclusion:

Results show that acquisition and consolidation are more susceptible to the scopolamine effects than recall. Thus, it may be concluded that cholinergic influence is more on acquisition and consolidation as compared to recall.

Krill phosphatidylserine improves learning and memory in Morris water maze in aged rats

The ameliorating effect of phosphatidylserine (PS) isolated from krill (KR-PS) on the learning and memory deficits associated with normal aging in rats was investigated, as compared with soybean PS (SOY-PS). Rats were orally administered with KR-PS (20, 50 mg kg-1) and SOY-PS (50 mg kg-1) daily, for 7 days, 30 min before behavioral assessment using the Morris water maze (MWM). Changes in the cholinergic system were examined by measuring choline acetyltransferase (ChAT) and acetylcholinesterase (AchE) immunoreactivity in the hippocampus. The daily administration of KR-PS produced a significant improvement in the escape latency for finding the platform in the MWM, as compared with SOY-PS. Consistent with the behavioral results, KR-PS treatments significantly alleviated age-associated losses of cholinergic immunoreactivity, and muscarinic acetylcholine receptor type 1 (mAChR-M1) and choline transporter (CHT) mRNA expression in the hippocampus. These findings demonstrate that KR-PS showed significant neuroprotective activity against the neuronal and cognitive impairments that occur with normal aging in rats; comparable results were obtained with SOY-PS. These data indicate that oral administration of PS derived from marine life could substitute for bovine cerebral cortex PS (BC-PS) as therapy for the improvement of diminished memory function in elderly people.

Effect of wild ginseng on scopolamine-induced acetylcholine depletion in the rat hippocampus

Objectives

The ameliorating effects of wild ginseng on learning and memory deficits were investigated in rats.

Methods

Rats were treated daily with wild ginseng or cultivated ginseng for 7 days at 30 min before scopolamine injection (2 mg/kg, i.p.). After inducing cognitive impairment by the administration of scopolamine, behavioural assessment using the Morris water maze was performed. Changes in cholinergic system reactivity were also examined by measuring the immunoreactive neurons of choline acetyltransferase and the reactivity of acetylcholinesterase in the hippocampus.

Key findings

Scopolamine injection induced impaired performance in the water maze test and severe cell losses in hippocampal cholinergic neurons, as indicated by decreased choline acetyltransferase immunoreactivity and increased acetylcholinesterase reactivity. Daily administration of wild ginseng produced a significant improvement in the escape latency for finding the platform in the Morris water maze and reduced the loss of cholinergic immunoreactivity in the hippocampus. The reduced expression of brain-derived neurotrophic factor mRNA due to the scopolamine injection was recovered to normal levels by the administration of wild ginseng.

Conclusions

Wild ginseng demonstrates a significant neuroprotective effect against scopolamine-induced neuronal and cognitive impairment.

Effect of Bupleurum falcatum on the stress-induced impairment of spatial working memory in rats

Many studies have shown that Bupleurum falcatum (BF), which is widely used in the treatment of various psychosomatic diseases in traditional Oriental medicine, is an effective therapeutic intervention for memory impairment. The purpose of this study was to examine the effect of BF on stress-induced alterations in learning and memory in rats using the Morris water maze (MWM) and elevated plus maze (EPM) behavioral tests. In addition, we examined the effects of BF treatment on the cholinergic system, as indicated by changes in neuronal choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) immunoreactivity in the hippocampus. BF (150, 300, or 600 mg/kg) was administered orally 30 min before exposure to repeated immobilization (IMO) stress (4 h/d for 14 d). The BF treatment produced a significant improvement in escape latency (time required to find the platform) in the MWM, and it also produced an anxiolytic-like effect in the EPM. Consistent with the behavioral data, BF treatment significantly attenuated the IMO stress-induced loss of cholinergic immunoreactivity in the hippocampus. These findings indicate that BF has a protective effect against repeated IMO stress-induced neuronal and cognitive impairments, and they suggest that BF may be useful in the treatment of stress-induced memory impairment.

THE EFFECT OF CHRONIC RESTRAINT STRESS ON SPATIAL LEARNING AND MEMORY: RELATION TO OXIDANT STRESS

The aim of this study was to investigate the effect of chronic restraint stress (RS) on spatial learning and memory. Fifty healthy male Wistar rats, aged three months were used. They were equally divided into five groups--C: Control, W: Water Maze, CS-1: Restrained for 21 days (1 h/day) + water maze protocol following stress period, CS-2: Restrained for 28 days (1 h/day) + water maze protocol during last 7 days of stress period, CS-3: Restrained for 21 days and allowed to recovery for 7 days (1 h/day). Corticosterone levels were higher in all stress groups than in C and W groups. Nitrite levels of frontal cortex and hippocampus were found to be elevated in chronic stress groups with respect to C and W groups. Thiobarbituric acid reactive substances (TBARS) of both tissues were increased significantly in CS1 and CS2 groups compared with C, W, and CS3 groups. Escape latencies of CS1 and CS2 groups were longer than those of the W group on each day of acquisition. In transfer test, CS1 and CS2 groups stayed significantly shorter in target quadrant according to the W group. Significant correlations between corticosterone and either nitrite or TBARS of hippocampus and frontal cortex were found. Both acquisition and memory performances were negatively correlated with plasma corticosterone level, nitrite, and TBARS levels of hippocampus and frontal cortex. The results of this study suggest that stress-induced lipid peroxidation may affect the acquisition and memory performances.

Delayed behavioral and endocrine effects of sarin and stress exposure in mice

The organophosphorus agent sarin is a potent inhibitor of acetylcholinesterase. Experiments tested the influence of exposure to low doses of sarin along with psychological stress on delayed behavioral and endocrine changes in mice. Motor activity, acoustic startle response (ASR), pre-pulse inhibition (PPI) of ASR, activity of cholinesterase in blood and catecholamine levels in adrenals were evaluated after low dose sarin exposure (3 x 0.4 LD50 subcutaneously) combined with chronic intermittent stress in C57BL/6J mice. While sarin alone produced depression of motor activity, no interaction of the stress with sarin exposure was observed. Cholinesterase activity was significantly reduced 24 h after exposure to sarin; however, the basal activity was re-established 3 weeks later. The combination of low dose sarin exposure and stress produced delayed behavioral change manifested as excessive grooming together with endocrine alterations in adrenals 7 weeks after exposure. The size of the adrenals in the combined exposure group was increased and the concentration of catecholamines was significantly decreased. In conclusion, these findings indicate that sarin in low doses is more dangerous when combined with shaker stress inducing delayed behavioral and endocrine changes.

Brain leptin and nerve growth factor are differently affected by stress in male and female mice: possible neuroendocrine and cardio-metabolic implications

The aim of the present study was to investigate the variations in leptin and nerve growth factor (NGF) expression induced by immobilization stress in the brain of male and female adult CD1 mice. We found that 10 days of repeated immobilization stress induced an increase of hypothalamus and thalamus NGF that was more pronounced in female than in male mice. We also found that this type of stress induced an increase of leptin expression in the hypothalamus of female mice, and a decrease in the thalamus of both male and female mice, associated with enhanced expression of leptin receptors in the hypothalamus and thalamus, both in male and female mice. The observation that the brain leptin and NGF receptors were altered by stress suggests a functional role for these molecules in neuroendocrine and cardiovascular response to stress events.

Gugulipid, an extract of Commiphora whighitii with lipid-lowering properties, has protective effects against streptozotocin-induced memory deficits in mice

Gugulipid, an ethyl acetate extract of the resin of plant Commiphora whighitii is an established hypolipidemic agent in clinical practice. The major constituent of gugulipid is guggulsterone [4, 17 (20)-pregnadiene-3, 16-dione]. It has been observed recently that patients receiving lipid-lowering drugs like statins have a reduced risk of dementia. Therefore, the present study was planned to explore the potential of gugulipid as cognitive enhancer. Gugulipid (12.5, 25 and 50 mg/kg, p.o.) showed dose dependent improvement in scopolamine-induced deficits in passive avoidance test. The maximal effective dose of gugulipid i.e. 50 mg/kg, p.o. was used for further studies on streptozotocin (STZ) model of dementia in mice. Gugulipid was investigated for its effect on learning and memory, parameters of oxidative stress (GSH and MDA) and acetylcholinesterase (AChE) activity in the STZ (ic)-treated mice. Intracerebral (ic) injections of STZ (0.5 mg/kg) on 1st and 3rd day caused significant deficit in memory in passive avoidance and Morris water maze test after the 14th day of first dose. In passive avoidance, transfer latency time (TLT) was not increased on retention trials in STZ (ic) group while gugulipid treatment resulted in significant increase in TLT on retention trials in STZ (ic)-treated mice. In Morris water maze test the latency time to reach platform in STZ (ic)-treated mice was significantly higher than control and vehicle (artificial CSF). Pre-treatment of gugulipid (50 mg/kg, p.o.) daily for 14 days started with the first dose of STZ (ic), significantly prevented STZ (ic)-induced memory deficit. Post-treatment i.e. after 14 days of first dose of STZ (ic) of gugulipid (50 mg/kg, p.o.) significantly decreased the latency time indicating anti-dementia activity. Effect of gugulipid and STZ in visible platform test was similar to those seen with hidden platform. Gugulipid and STZ-treated mice did not cause significant change in locomotor activity. Furthermore, STZ (ic) resulted into increase in AChE activity, low level of GSH and high concentration of MDA in brain on 21st day as compared to control. Gugulipid treatment caused significant decrease in AChE activity, low level of MDA and high concentration of GSH in brain following STZ (ic) as compared to vehicle administration in STZ (ic)-treated mice. The study demonstrated that gugulipid has significant protective affect against streptozotocin-induced memory deficits model of dementia that can be attributed to anti-oxidant and anti-AChE activity of gugulipid. These observations suggest gugulipid as a potential anti-dementia drug (CDRI, Lucknow has obtained US patent No. 6896901 for use of gugulipid as cognitive enhancer).

Effect of hormone replacement therapy in normalizing age related neuronal markers in different age groups of naturally menopausal rats

Aging of the normal brain is accompanied by changes in its structure, function, and metabolism. There are significant gender differences in aging brain. Most of these changes increase during menopausal condition in females when the level of estradiol and progesterone are decreased. The objective of this study was to determine the effect of estradiol and progesterone (separate as well as combined) hormones in neuronal tissues from naturally menopausal rats of different age groups. Results show decreased activity of Acetylcholine esterase (AChE) whereas the level of lipid peroxidation increased with age, and after the hormone treatments both AChE activity and level of lipid peroxidation returned to control values. The deposition of lipofuscin, a pigment that accumulated intraneuronally in brain and other tissues and is considered a marker of aging, was increased with aging and the hormone treatment decreased this deposition. The present study clearly shows reduction in risk factors associated with aging in the murine model system by hormone treatments, namely estrogen and progesterone by increasing the activity of acetylcholine esterase and decreasing the levels of lipid peroxidation and lipofuscin deposition in different parts of aging brain. This study suggests that hormone replacement therapy may either reduce or delay the onset of age related diseases like Alzheimer's, Parkinson's and other neurological disorders.

Nature of stress: differential effects on brain acetylcholinesterase activity and memory in rats

Effect of acute, chronic-predictable and chronic-unpredictable stress on memory and acetylcholinesterase (AChE) was investigated in rats. The animals were subjected to 3 type of stressors--(1) acute immobilization stress, (2) chronic-predictable stress i.e., immobilization daily for 5 consecutive days and (3) chronic-unpredictable stress that included reversal of light/dark cycle, over-night fasting, forced-swimming, immobilization and forced exercise in random unpredictable manner daily for 5 consecutive days. Learning and memory function was studied by single trial Passive avoidance test. AChE activity was assayed spectrophotometrically in the detergent (DS) and salt (SS) soluble fractions in different brain regions. Learning was obtained in acute and chronic-predictable stress groups but not in chronic-unpredictable group. Acute, chronic-predictable and chronic-unpredictable stress caused significant decrease in AChE activity in the DS fraction of cortex, hippocampus and hypothalamus as compared to control. Results indicate that AChE in DS fraction is predominantly affected in stressed and stressed-trained group but cognition is affected only by chronic-unpredictable stress. In acute and chronic-predictable groups the decreased AChE activity in the hippocampal DS fraction during learning may be responsible to maintain cognitive function by enhancing the cholinergic activity.

Anti-stress effects of Ginkgo biloba and Panax ginseng: a comparative study

Stress is a global menace fortified by the advancement of industrialization. Failure of stress management is due to lack of proper evaluation of anti-stress products. We explored the anti-stress potential of the Ginkgo biloba (G. biloba, 30 mg/kg, p.o.) and compared it with that of Panax ginseng (P. ginseng, 100 mg/kg, p.o.) against acute stress (AS) and chronic stress (CS) models in rats. Immediately after AS and CS, the rats were sacrificed, and adrenal glands and stomach were dissected out for weight determination and scoring of the ulcer index (UI), respectively, as well as changes in biochemical parameters like plasma glucose (GL), triglycerides (TG), cholesterol (CL), creatine kinase (CK), and serum corticosterone (CORT) were also estimated. AS significantly increased UI, adrenal gland weight (AGW), GL, CK activity, and CORT, whereas G. biloba significantly reduced them. P. ginseng significantly reverted GL and CK activity. In CS, a significant increase was found in the UI, AGW, CK activity, and CORT with a decrease in the level of CL and TG. G. biloba did not produce any significant effect on CS-induced alterations. P. ginseng reduced the UI, AGW, plasma GL, TG, CK activity, and CORT level significantly. From the above study, G. biloba is more effective in AS, whereas for CS, P. ginseng will be a better option. Hence these extracts possess significant anti-stress properties and can be used for the treatment of stress-induced disorders.

The serotonin transporter is required for stress-evoked increases in adrenal catecholamine synthesis and angiotensin II AT(2) receptor expression

High numbers of serotonin transporter (SERT) binding sites and high serotonin (5-HT) content are expressed in the adrenal medulla of wild-type (SERT+/+) mice. Acute restraint stress increases adrenomedullary 5-HT, norepinephrine (NE) and epinephrine (E) release, adrenomedullary tyrosine hydroxylase (TH) mRNA, and angiotensin II AT(2) receptor expression. There are no alterations in adrenal catecholamine content during restraint. In littermate SERT-/- mice, which do not express SERT binding sites, the basal adrenomedullary 5-HT content is significantly reduced and does not increase after stress. The stress-induced increase in plasma E is higher in SERT-/- than in SERT+/+ animals. In SERT-/- mice, the stress-induced increase in expression of TH mRNA does not occur, and as a consequence, adrenal E content decreases, and adrenal E and NE content are lower than that of SERT+/+ mice during restraint. In addition, instead of increased expression, stress induces a profound decrease in the number of adrenomedullary AT(2) receptors in SERT-/- mice. Our results indicate that SERT is necessary for the stress-induced increase in adrenomedullary catecholamine synthesis and AT(2) receptor expression. These data further indicate a close relationship between the adrenomedullary 5-HT and angiotensin II systems, and an important role of adrenomedullary AT(2) receptors in catecholamine synthesis and release during stress.

Exaggerated adrenomedullary response to immobilization in mice with targeted disruption of the serotonin transporter gene

This study examined whether serotonin transporter (5-HTT) gene knockout influences adrenomedullary, sympathoneural, or hypothalamo-pituitary-adrenal responses to acute immobilization. In conscious, cannulated mice, arterial plasma concentrations of catecholamines, ACTH, and corticosterone were measured at baseline and after 15 min of immobilization. Tissue levels of serotonin (5-HT), catecholamines, and hormones were also measured in pituitary and adrenal glands. At baseline, adrenal and pituitary 5-HT concentrations in knockout (5-HTT(-/-)) mice were markedly lower than those in littermate control (5-HTT(+/+)) mice, whereas the groups did not differ in levels of catecholamines or hormones in plasma or tissue. Immobilization increased plasma levels of catecholamines, ACTH, and corticosterone in all genotypes. 5-HTT(-/-) mice had exaggerated responses of plasma epinephrine to immobilization and significant reductions in adrenal epinephrine, norepinephrine, and 5-HT contents compared with values in littermate controls. Pituitary ACTH was significantly reduced after immobilization in 5-HTT(-/-) mice only, but increases in plasma ACTH and corticosterone levels did not differ between genotypes. The results suggest that one 5-HTT function is to restrain adrenomedullary activation in response to immobilization. Exaggerated adrenomedullary responses seem to be an autonomic correlate of the anxiety-like behaviors in 5-HTT knockout mice.