Modulating Oxidative Stress Relieves Stress-Induced Behavioral and Cognitive Impairments in Rats.

Background: Persistent psychological stress often leads to anxiety disorders and depression. Benzodiazepines and selective serotonin reuptake inhibitors are popular treatment options but have limited efficacy, supporting the need for alternative treatment. Based on our recent preclinical work suggesting a causal link between neurobehavioral deficits and elevated oxidative stress, we hypothesized that interventions that mitigate oxidative stress can attenuate/overcome neurobehavioral deficits. Methods: Here, we employed the rat social defeat model of psychological stress to determine whether increasing antioxidant levels using grape powder would prevent and/or reverse social defeat-induced behavioral and cognitive deficits. Furthermore, a hippocampal-derived HT22 cell culture model of oxidative stress was employed to identify the individual beneficial constituent(s) of grape powder and the underlying mechanism(s) of action. Results: Grape powder treatment prevented and reversed social defeat-induced behavioral and cognitive deficits and also decreased social defeat-induced increase in plasma corticosterone and 8-isoprostane (systemic and oxidative stress markers, respectively). And grape powder treatment replenished social defeat-induced depleted pool of key antioxidant enzymes glyoxalase-1, glutathione reducatse-1, and superoxide dismutase. Grape powder constituents, quercetin and resveratrol, were most effective in preventing oxidative stress-induced decreased cellular antioxidant capacity. Grape powder protected oxidative stress-induced cell death by preventing calcium influx, mitochondrial dysfunction, and release of cytochrome c. Conclusions: Grape powder treatment by increasing antioxidant pool and preventing cell damage and death prevented and reversed social defeat-induced behavioral and cognitive deficits in rats. Quercetin and resveratrol are the major contributors towards beneficial effects of grape powder.

Conserved amino acid residues of the NuoD segment important for structure and function of Escherichia coli NDH-1 (complex I).

The NuoD segment (homologue of mitochondrial 49 kDa subunit) of the proton-translocating NADH:quinone oxidoreductase (complex I/NDH-1) from Escherichia coli is in the hydrophilic domain and bears many highly conserved amino acid residues. The three-dimensional structural model of NDH-1 suggests that the NuoD segment, together with the neighboring subunits, constitutes a putative quinone binding cavity. We used the homologous DNA recombination technique to clarify the role of selected key amino acid residues of the NuoD segment. Among them, residues Tyr273 and His224 were considered candidates for having important interactions with the quinone headgroup. Mutant Y273F retained partial activity but lost sensitivity to capsaicin-40. Mutant H224R scarcely affected the activity, suggesting that this residue may not be essential. His224 is located in a loop near the N-terminus of the NuoD segment (Gly217-Phe227) which is considered to form part of the quinone binding cavity. In contrast to the His224 mutation, mutants G217V, P218A, and G225V almost completely lost the activity. One region of this loop is positioned close to a cytosolic loop of the NuoA subunit in the membrane domain, and together they seem to be important in keeping the quinone binding cavity intact. The structural role of the longest helix in the NuoD segment located behind the quinone binding cavity was also investigated. Possible roles of other highly conserved residues of the NuoD segment are discussed.

Witnessing traumatic events causes severe behavioral impairments in rats.

Witnessing a traumatic event but not directly experiencing it can be psychologically quite damaging. In North America alone, ∼30% of individuals who witness a traumatic event develop post-traumatic stress disorder (PTSD). While effects of direct trauma are evident, consequences of indirect or secondary trauma are often ignored. Also unclear is the role of social support in the consequences of these experiences. The social defeat paradigm, which involves aggressive encounters by a large Long-Evans male rat (resident) towards a smaller Sprague-Dawley male rat (intruder), is considered a rodent model of PTSD. We have modified this model to create a trauma witness model (TWM) and have used our TWM model to also evaluate social support effects. Basically, when an intruder rat is placed into the home cage of a resident rat, it encounters an agonistic behavior resulting in intruder subordination. The socially defeated intruder is designated the SD rat. A second rat, the cage mate of the SD, is positioned to witness the event and is the trauma witnessing (TW) rat. Experiments were performed in two different experimental conditions. In one, the SD and TW rats were cagemates and acclimatized together. Then, one SD rat was subjected to three sessions of social defeat for 7 d. TW rat witnessed these events. After each social defeat exposure, the TW and SD rats were housed together. In the second, the TW and SD rats were housed separately starting after the first defeat. At the end of each protocol, depression-anxiety-like behavior and memory tests were conducted on the SD and TW rats, blood withdrawn and specific organs collected. Witnessing traumatic events led to depression- and anxiety-like behavior and produced memory deficits in TW rats associated with elevated corticosterone levels.

Roles of subunit NuoK (ND4L) in the energy-transducing mechanism of Escherichia coli NDH-1 (NADH:quinone oxidoreductase).

The bacterial H(+)-translocating NADH:quinone oxidoreductase (NDH-1) catalyzes electron transfer from NADH to quinone coupled with proton pumping across the cytoplasmic membrane. The NuoK subunit (counterpart of the mitochondrial ND4L subunit) is one of the seven hydrophobic subunits in the membrane domain and bears three transmembrane segments (TM1-3). Two glutamic residues located in the adjacent transmembrane helices of NuoK are important for the energy coupled activity of NDH-1. In particular, mutation of the highly conserved carboxyl residue ((K)Glu-36 in TM2) to Ala led to a complete loss of the NDH-1 activities. Mutation of the second conserved carboxyl residue ((K)Glu-72 in TM3) moderately reduced the activities. To clarify the contribution of NuoK to the mechanism of proton translocation, we relocated these two conserved residues. When we shifted (K)Glu-36 along TM2 to positions 32, 38, 39, and 40, the mutants largely retained energy transducing NDH-1 activities. According to the recent structural information, these positions are located in the vicinity of (K)Glu-36, present in the same helix phase, in an immediately before and after helix turn. In an earlier study, a double mutation of two arginine residues located in a short cytoplasmic loop between TM1 and TM2 (loop-1) showed a drastic effect on energy transducing activities. Therefore, the importance of this cytosolic loop of NuoK ((K)Arg-25, (K)Arg-26, and (K)Asn-27) for the energy transducing activities was extensively studied. The probable roles of subunit NuoK in the energy transducing mechanism of NDH-1 are discussed.

Complex I inhibition in the visual pathway induces disorganization of the node of Ranvier.

Mitochondrial defects can have significant consequences on many aspects of neuronal physiology. In particular, deficiencies in the first enzyme complex of the mitochondrial respiratory chain (complex I) are considered to be involved in a number of human neurodegenerative diseases. The current work highlights a tight correlation between the inhibition of complex I and the state of axonal myelination of the optic nerve. Exposing the visual pathway of rats to rotenone, a complex I inhibitor, resulted in disorganization of the node of Ranvier. The structure and function of the node depend on specific cell adhesion molecules, among others, CASPR (contactin associated protein) and contactin. CASPR and contactin are both on the axonal surfaces and need to be associated to be able to anchor their myelin counterpart. Here we show that inhibition of mitochondrial complex I by rotenone in rats induces reactive oxygen species, disrupts the interaction of CASPR and contactin couple, and thus damages the organization and function of the node of Ranvier. Demyelination of the optic nerve occurs as a consequence which is accompanied by a loss of vision. The physiological impairment could be reversed by introducing an alternative NADH dehydrogenase to the mitochondria of the visual system. The restoration of the nodal structure was specifically correlated with visual recovery in the treated animal.

Grape powder supplementation prevents oxidative stress-induced anxiety-like behavior, memory impairment, and high blood pressure in rats.

We examined whether or not grape powder treatment ameliorates oxidative stress-induced anxiety-like behavior, memory impairment, and hypertension in rats. Oxidative stress in Sprague-Dawley rats was produced by using L-buthionine-(S,R)-sulfoximine (BSO). Four groups of rats were used: 1) control (C; injected with vehicle and provided with tap water), 2) grape powder-treated (GP; injected with vehicle and provided for 3 wk with 15 g/L grape powder dissolved in tap water), 3) BSO-treated [injected with BSO (300 mg/kg body weight), i.p. for 7 d and provided with tap water], and 4) BSO plus grape powder-treated (GP+BSO; injected with BSO and provided with grape powder-treated tap water). Anxiety-like behavior was significantly greater in BSO rats compared with C or GP rats (P < 0.05). Grape powder attenuated BSO-induced anxiety-like behavior in GP+BSO rats. BSO rats made significantly more errors in both short- and long-term memory tests compared with C or GP rats (P < 0.05), which was prevented in GP+BSO rats. Systolic and diastolic blood pressure was significantly greater in BSO rats compared with C or GP rats (P < 0.05), whereas grape powder prevented high blood pressure in GP+BSO rats. Furthermore, brain extracellular signal-regulated kinase-1/2 (ERK-1/2) was activated (P < 0.05), whereas levels of glyoxalase-1 (GLO-1), glutathione reductase-1 (GSR-1), calcium/calmodulin-dependent protein kinase type IV (CAMK-IV), cAMP response element-binding protein (CREB), and brain-derived neurotrophic factor (BDNF) were significantly less (P < 0.05) in BSO but not in GP+BSO rats compared with C or GP rats. We suggest that by regulating brain ERK-1/2, GLO-1, GSR-1, CAMK-IV, CREB, and BDNF levels, grape powder prevents oxidative stress-induced anxiety, memory impairment, and hypertension in rats.

A high-salt diet further impairs age-associated declines in cognitive, behavioral, and cardiovascular functions in male Fischer brown Norway rats.

Aging-associated declines in cognitive, emotional, and cardiovascular function are well known. Environmental stress triggers critical changes in the brain, further compromising cardiovascular and behavioral health during aging. Excessive dietary salt intake is one such stressor. Here, we tested the effect of high salt (HS) on anxiety, learning-memory function, and blood pressure (BP) in male Fischer brown Norway (FBN) rats. Adult (A; 2 mo) and old (O; 20 mo) male rats were fed normal-salt (NS; 0.4% NaCl) or HS (8% NaCl) diets for 4 wk after being implanted with telemeter probes for conscious BP measurement. Thereafter, tests to assess anxiety-like behavior and learning-memory were conducted. The rats were then killed, and samples of plasma, urine, and brain tissue were collected. We found that systolic BP was higher in O-NS (117 ± 1.2 mm Hg) than in A-NS (105 ± 0.8 mm Hg) rats (P < 0.05). Furthermore, BP was higher in O-HS (124 ± 1.4 mm Hg) than in O-NS (117 ± 1.2 mm Hg) rats (P < 0.05). Moreover, anxiety-like behavior (light-dark and open-field tests) was not different between A-NS and O-NS rats but was greater in O-HS rats than in A-NS, O-NS, or A-HS rats (P < 0.05). Short-term memory (radial arm water maze test) was similar in A-NS and O-NS rats but was significantly impaired in O-HS rats compared with A-NS, O-NS, or A-HS rats (P < 0.05). Furthermore, oxidative stress variables (in plasma, urine, and brain) as well as corticosterone (plasma) were greater in O-HS rats when compared with A-NS, O-NS, or A-HS rats (P < 0.05). The antioxidant enzyme glyoxalase-1 expression was selectively reduced in the hippocampus and amygdala of O-HS rats compared with A-NS, O-NS, or A-HS rats (P < 0.05), whereas other antioxidant enzymes, glutathione reductase 1, manganese superoxide dismutase (SOD), and Cu/Zn SOD remained unchanged. We suggest that salt-sensitive hypertension and behavioral derangement are associated with a redox imbalance in the brain of aged FBN rats.

Neuroprotective effects and mechanisms of exercise in a chronic mouse model of Parkinson's disease with moderate neurodegeneration.

The protective impact of exercise on neurodegenerative processes has not been confirmed, and the mechanisms underlying the benefit of exercise have not been determined in human Parkinson's disease or in chronic animal disease models. This research examined the long-term neurological, behavioral, and mechanistic consequences of endurance exercise in experimental chronic parkinsonism. We used a chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse model of Parkinson's disease with moderate neurodegeneration and examined the effects of treadmill exercise on movement and balance coordination, changes in dopamine neuron biomarkers, mitochondrial functions, and neurotrophic factor activities in the nigrostriatal system. The exercise results were compared with those of the control and sedentary chronic parkinsonian animals. After 18 weeks of exercise training in the chronic parkinsonian mice, we observed a significant deterrence in the loss of neuronal dopamine-producing cells and other functional indicators. The impaired movement and balance incoordination in the chronic parkinsonian mice were also markedly reduced following exercise. Mechanistic investigations revealed that the neuronal and behavioral recovery produced by exercise in the chronic parkinsonian mice was associated with an improved mitochondrial function and an increase in the brain region-specific levels of brain-derived and glial cell line-derived neurotrophic factors. Our findings indicate that exercise not only produces neuronal and mitochondrial protection, it also boosts nigrostriatal neurotrophic factor levels in the chronic parkinsonian mice with moderate neurodegeneration. Therefore, modifying lifestyle with increased exercise activity would be a non-pharmacological neuroprotective approach for averting neurodegenerative processes, as demonstrated in experimental chronic parkinsonism.

Behavioral effects of early life maternal trauma witness in rats.

BACKGROUND: Earlier, we have reported that post-traumatic stress disorder (PTSD)-like behaviors developed in rats that witnessed their cage mates undergo repeated traumatic stress. More recently, we published that early life physical traumatic stress leads to later life depression-like behaviors in rats. Whether early life trauma witness causes later life PTSD-like behaviors is not known. Also unclear are sex-specific stress-induced behavioral variations in later life. The early life witness component of stress is an important aspect of stress-induced psychopathologies and must be investigated. OBJECTIVE: Here, we have examined the impact of early life repeated witnessing of traumatic events by pups from post-natal day (PND) 21-PND27, on later life behaviors at PND60, and the behavioral impact of postpartum traumatic stress in female rats. METHODS: We used a modified version of rodent social defeat model to induce postpartum stress in female rats and trauma witness stress in pups. One female Sprague-Dawley rat (intruder) was introduced into the cage of an aggressive Long-Evans male rat (resident). The encounter between the two resulted in attacks between the female rat and the Long-Evans male rat. Three exposures of social defeat (attacks) were given for 7 consecutive days. The social defeat traumatic events were witnessed by 6 pups (offspring of the intruder female rat, PND21-27), placed in six separate enclosures surrounding the cage. The objective of this experiment was three-fold: 1) to test later life behavioral effects in pups from witnessing maternal defeat, 2) to examine gender susceptibility of pups in maternal defeat witness-induced behaviors, 3) to test behavioral effect in female rats 24h after receiving the last social defeat exposure. RESULTS: We observed that while anxiety-like behavior assessed in open-field and elevated plus-maze tests, was not affected in male or female rats upon witnessing repeated maternal traumatic stress, depression-like behavior in forced-swim test was observed at PND60 in both male and female rats, with greater effect in male rats. No change was observed in learning and memory functions using radial arm water maze test in both male and female rats. Interestingly, socially defeated female rats (dams: mother of the pups) developed both anxiety and depression-like behavior with no change in learning-memory function when compared to control female rats. CONCLUSIONS: Our findings suggest that early life maternal stress witness history leads to depression-like behavior in both male and female adult rats, and dams developed both anxiety and depression-like behaviors.

Psychological Impact of Vehicle Exhaust Exposure: Insights from an Animal Model.

Air pollution resulting from exhaust emissions of vehicles has risen in the recent years, reportedly causing major adverse effects on the heart, lungs and the brain. Though respiratory and cardiovascular effects of these emissions are well identified, psychological and neurobiological complications of prolonged exposure to vehicle emissions remain unknown. Pro-oxidants are considered as major constituents of vehicle emissions. This is important considering causal link between oxidative stress and behavioral and cognitive impairments. We hypothesized that prolonged exposure to pro-oxidants in vehicle emissions result in behavioral and cognitive deficits. We developed a simulated vehicle exhaust exposure model in rats. The model used a simulated mixture of vehicle exhaust that comprised of pro-oxidant constituents of exhaust, namely, carbon dioxide (13%), carbon monoxide (0.68%) and nitrogen dioxide (1000 ppm) in air. Rats were exposed either to a high (1:10 dilution) or low (~1:1000 dilution) physiologically relevant dose of simulated mixture in air for two weeks in separate experiments followed by a comprehensive behavioral and cognitive analysis. We observed that prolonged exposure to pro-oxidants in vehicle exhaust increased anxiety-and depression-like behavior as well as led to impaired memory in rats. This is important preclinical evidence, particularly relevant to human population exposed to high vehicular traffic.

Protective Effect of Tempol on Buthionine Sulfoximine-Induced Mitochondrial Impairment in Hippocampal Derived HT22 Cells.

Using a simulated oxidative stress model of hippocampus-derived immortalized cell line (HT22), we report that prooxidant buthionine sulfoximine (BSO, 1 mM, 14 h), without adversely affecting cell viability or morphology, induced oxidative stress by inhibiting glutathione synthesis. BSO treatment also significantly reduced superoxide dismutase (SOD) activity (p < 0.05) and significantly lowered total antioxidant capacity (p < 0.001) in HT22 cells when compared to vehicle treated control cells. Antioxidant tempol, a piperidine nitroxide considered a SOD mimetic, reversed BSO-induced decline in SOD activity (p < 0.01) and also increased BSO-induced decline in total antioxidant capacity (p < 0.05). Interestingly, BSO treatment significantly reduced mitochondrial oxygen consumption (p < 0.05), decreased mitochondrial membrane potential (p < 0.05), and lowered ATP production (p < 0.05) when compared to vehicle treated control cells, collectively indicative of mitochondrial impairment. Antioxidant tempol treatment mitigated all three indicators of mitochondrial impairment. We postulate that BSO-induced oxidative stress in HT22 cells caused mitochondrial impairment, and tempol by increasing SOD activity and improving antioxidant capacity presumably protected the cells from BSO-induced mitochondrial impairment. In conclusion, present study provides an interesting simulation of oxidative stress in hippocampal cells, which will serve as an excellent model to study mitochondrial functions.

Witnessing traumatic events and post-traumatic stress disorder: Insights from an animal model.

It is becoming increasingly recognized that post-traumatic stress disorder (PTSD) can be acquired vicariously from witnessing traumatic events. Recently, we published an animal model called the "Trauma witness model" (TWM) which mimics PTSD-like symptoms in rats from witnessing daily traumatic events (social defeat of cage mate) [14]. Our TWM does not result in any physical injury. This is a major procedural advantage over the typical intruder paradigm in which it is difficult to delineate the inflammatory response of tissue injury and the response elicited from emotional distress. Using TWM paradigm, we examined behavioral and cognitive effects in rats [14] however, the long-term persistence of PTSD-like symptoms or a time-course of these events (anxiety and depression-like behaviors and cognitive deficits) and the contribution of olfactory and auditory stress vs visual reinforcement were not examined. This study demonstrates that some of the features of PTSD-like symptoms in rats are reversible after a significant time lapse of the witnessing of traumatic events. We also have established that witnessing is critical to the PTSD-like phenotype and cannot be acquired solely due to auditory or olfactory stresses.

High aggression in rats is associated with elevated stress, anxiety-like behavior, and altered catecholamine content in the brain.

The social defeat paradigm involves aggressive encounters between Long-Evans (L-E) (resident) and Sprague-Dawley (S-D) (intruder) rats. Successful application of chronic social defeat stress in S-D rats is dependent upon selection of highly aggressive L-E rats. Half of the L-E rats screened for aggression did not meet the criterion for aggression (L-E rats performing a defeat, characterized by the intruder surrendering or acquiring a supine position for at least 3s). The observation of the differences in the level of aggression between age and weight matched L-E rats was quite compelling which led us to the present study. Herein, we measured behavioral differences between aggressor and non-aggressor L-E rats. We analyzed their anxiety-like behavior using open-field and elevated plus maze tests. We also measured aggression/violence-like behavior using two tests. In one, time taken to defeat the intruder S-D rat was recorded. In the second test, time taken to attack a novel object was compared between the two groups. We observed a significant increase in anxiety-like behavior in aggressor rats when compared to the non-aggressive group. Furthermore, time taken to defeat the intruder rat and to attack a novel object was significantly lower in aggressive L-E rats. Biochemical data suggests that heightened anxiety-like behavior and aggression is associated with increased plasma levels of corticosterones and elevated oxidative stress. Significant alterations in dopamine (DA), norepinephrine (NE) and epinephrine (EPI) were observed within the hippocampus, amygdala, and the prefrontal cortex, suggesting potential involvement of dopaminergic and noradrenergic systems in regulation of aggressive behaviors.

Grape powder treatment prevents anxiety-like behavior in a rat model of aging.

Earlier, we have reported that grape powder (GP) treatment prevented pharmacologic and psychological stress-induced anxiety-like behavior and memory impairment in rats. Protective effects of GP were attributed to its antioxidant effects. In this study, we tested the hypothesis that age-associated behavioral and cognitive deficits such as anxiety and memory impairment will be ameliorated with GP treatment. Using a National Institute of Aging recommended rodent model of aging, we examined a potentially protective role of antioxidant-rich GP in age-associated anxiety-like behavior and memory impairment. Male Fischer 344 rats were randomly assigned into 4 groups: young rats (3 months old) provided with tap water or with 15 g/L GP dissolved in tap water for 3 weeks, aged rats (21 months old) provided with tap water or with GP-treated tap water for 3 weeks (AG-GP). Anxiety-like behavior was significantly greater in aged rats compared with young rats, GP-treated young rats, or aged control rats (P < .05). Also, GP treatment prevented age-induced anxiety-like behavior in AG-GP rats (P < .05). Neither short-term nor long-term age-associated memory deficits improved with GP treatment in AG-GP rats. Furthermore, aged rats showed increased level of physiological stress (corticosterone) and increased oxidative stress in the plasma (8-isoprostane) as well as in selected brain areas (protein carbonylation). Grape powder treatment prevented age-induced increase in corticosterone levels and plasma 8-isoprostane levels in aged rats (P < .05), whereas protein carbonylation was recovered in the amygdala region only (P < .05). Grape powder by regulating oxidative stress ameliorates age-induced anxiety-like behavior in rats, whereas age-associated memory deficits seem unaffected with GP treatment.

Grape powder prevents cognitive, behavioral, and biochemical impairments in a rat model of posttraumatic stress disorder.

Previously, using the single-prolonged stress (SPS) rat model of posttraumatic stress disorder, we reported that moderate treadmill exercise, via modulation of oxidative stress-related mechanisms, rescued anxiety- and depression-like behaviors and reversed SPS-induced memory impairment. In this study using the SPS model (2-hour restrain, 20-minute forced swimming, 15-minute rest, and 1-2-minute diethyl ether exposure), we hypothesized that antioxidant rich grape powder (GP) prevents SPS-induced behavioral and memory impairment in rats. Male Sprague Dawley rats were randomly assigned into control (CON) (provided tap water), SPS (provided tap water), GP-SPS (provided 15 g/L GP in tap water for 3 weeks followed by SPS), or GP-CON (3 weeks of GP followed by CON exposure). Anxiety- and depression-like behaviors were significantly greater in SPS rats, when compared with CON- or GP-treated rats, and GP reversed these behavioral deficits. Single-prolonged stress rats made significantly more errors in both short- and long-term memory tests compared with CON- or GP-treated rats, which were prevented in GP-SPS rats. Grape powder prevented SPS-induced increase in plasma corticosterone level. Furthermore, brain-derived neurotrophic factor levels were significantly decreased in amygdala of SPS rats but not in GP-SPS rats compared with CON or (GP-CON) rats. In addition, GP significantly increased acetylated histone 3 and histone deacetylase 5 in hippocampus and amygdala of SPS rats as compared with CON or GP-CON rats. In conclusion, we suggest protective role of GP in SPS-induced behavioral, cognitive, and biochemical impairments in rats. Perhaps, epigenetic regulation of brain-derived neurotrophic factor enables GP-mediated prevention of SPS-induced deficits in rats.

Tempol treatment reduces anxiety-like behaviors induced by multiple anxiogenic drugs in rats.

We have published that pharmacological induction of oxidative stress (OS) causes anxiety-like behavior in rats. Using animal models, we also have established that psychological stress induces OS and leads to anxiety-like behaviors. All evidence points towards the causal role of OS in anxiety-like behaviors. To fully ascertain the role of OS in anxiety-like behaviors, it is reasonable to test whether the pro-anxiety effects of anxiogenic drugs caffeine or N-methyl-beta-carboline-3-carboxamide (FG-7142) can be mitigated using agents that minimize OS. In this study, osmotic pumps were either filled with antioxidant tempol or saline. The pumps were attached to the catheter leading to the brain cannula and inserted into the subcutaneous pocket in the back pocket of the rat. Continuous i.c.v. infusion of saline or tempol in the lateral ventricle of the brain (4.3 mmol/day) was maintained for 1 week. Rats were intraperitoneally injected either with saline or an anxiogenic drug one at a time. Two hours later all groups were subjected to behavioral assessments. Anxiety-like behavior tests (open-field, light-dark and elevated plus maze) suggested that tempol prevented anxiogenic drug-induced anxiety-like behavior in rats. Furthermore, anxiogenic drug-induced increase in stress examined via plasma corticosterone and increased oxidative stress levels assessed via plasma 8-isoprostane were prevented with tempol treatment. Protein carbonylation assay also suggested preventive effect of tempol in the prefrontal cortex brain region of rats. Antioxidant protein expression and pro-inflammatory cytokine levels indicate compromised antioxidant defense as well as an imbalance of inflammatory response.

Long-term evaluation of Leber's hereditary optic neuropathy-like symptoms in rotenone administered rats.

Leber's hereditary optic neuropathy (LHON) is an inherited disorder affecting the retinal ganglion cells (RGCs) and their axons that lead to the loss of central vision. This study is aimed at evaluating the LHON symptoms in rats administered with rotenone microspheres into the superior colliculus (SC). Optical coherence tomography (OCT) analysis showed substantial loss of retinal nerve fiber layer (RNFL) thickness in rotenone injected rats. Optokinetic testing in rotenone treated rats showed decrease in head-tracking response. Electrophysiological mapping of the SC surface demonstrated attenuation of visually evoked responses; however, no changes were observed in the ERG data. The progressive pattern of disease manifestation in rotenone administered rats demonstrated several similarities with human disease symptoms. These rats with LHON-like symptoms can serve as a model for future investigators to design and implement reliable tests to assess the beneficial effects of therapeutic interventions for LHON disease.

Moderate treadmill exercise rescues anxiety and depression-like behavior as well as memory impairment in a rat model of posttraumatic stress disorder.

Post-traumatic stress disorder (PTSD) is a condition which can develop from exposure to a severe traumatic event such as those occurring during wars or natural disasters. Benzodiazepines and selective serotonin reuptake inhibitors (SSRIs) are considered the gold standard for PTSD treatment, but their side effects pose a serious problem. While regular physical exercise is regarded as a mood elevator and known to enhance cognitive function, its direct role in rescuing core symptoms of PTSD including anxiety and depression-like behaviors and cognitive impairment is unclear. In the present study using the single-prolonged stress (SPS) rat model of PTSD (2h restrain, 20 min forced swimming, 15 min rest, and 1-2 min diethyl ether exposure), we examined the beneficial effect of moderate treadmill exercise on SPS-induced behavioral deficits including anxiety and depression-like behaviors and memory impairment. Male Wistar rats were randomly assigned into four groups: control (sedentary), exercised, SPS (no exercise), or SPS-exercised. Rats were exercised on a rodent treadmill for 14 consecutive days. Rats in all groups were tested for anxiety-like behaviors using open field (OF), light-dark and elevated-plus maze tests. All rats were tested for short-term and long-term memory in the radial arm water maze test. Rats were then sacrificed, blood was collected (for corticosterone levels), and individual organs (spleen, adrenals, and thymus) harvested. Results suggest that moderate physical exercise ameliorates SPS-induced behavioral deficits in rats.

Novel mechanistic insights into treadmill exercise based rescue of social defeat-induced anxiety-like behavior and memory impairment in rats.

Social defeat (SD) induced stress causes physiological and behavioral deficits in rodents, including depression and anxiety-like behaviors, as well as memory impairment. Anxiolytic and mood elevating effects of physical exercise are also known. However, rescue effect of physical exercise in social defeat-induced anxiety, depression or memory impairment has not been addressed. The role of epigenetic mechanisms that potentially contribute to these rescue or protective effects is also not known. The present study investigated the effect of moderate treadmill exercise on anxiety-like behavior and memory function in rats subjected to SD using a modified version of the resident-intruder model for social stress (defeat). Changes in histone acetylation and histone-modifying enzymes were examined in hippocampus, amygdala and frontal cortex which are considered critical for anxiety, depression and cognition. Sprague Dawley rats were randomly assigned in four groups; control, exercised, social defeat, social defeat and exercise. At the end of the SD or control exposure lasting 30 min daily for 7 days, one group of SD rats was subjected to treadmill exercise for 2 weeks, whereas the other SD group was handled without exercise. Anxiety-like behavior tests and radial arm water maze test suggested that moderate treadmill exercise rescued social defeat induced anxiety-like behavior and memory impairment. Moreover, exercise normalized SD-induced increase in oxidative stress, most likely by adjusting antioxidant response. Our data suggests involvement of epigenetic mechanisms including histone acetylation of H3 and modulation of methyl-CpG-binding in the hippocampus that might contribute to the rescue effects of exercise in SD-induced behavioral deficits in rats.

Depression, anxiety-like behavior and memory impairment are associated with increased oxidative stress and inflammation in a rat model of social stress.

In the present study, we have examined the behavioral and biochemical effect of induction of psychological stress using a modified version of the resident-intruder model for social stress (social defeat). At the end of the social defeat protocol, body weights, food and water intake were recorded, depression and anxiety-like behaviors as well as memory function was examined. Biochemical analysis including oxidative stress measurement, inflammatory markers and other molecular parameters, critical to behavioral effects were examined. We observed a significant decrease in the body weight in the socially defeated rats as compared to the controls. Furthermore, social defeat increased anxiety-like behavior and caused memory impairment in rats (P<0.05). Socially defeated rats made significantly more errors in long term memory tests (P<0.05) as compared to control rats. Furthermore, brain extracellular signal-regulated kinase-1/2 (ERK1/2), and an inflammatory marker, interleukin (IL)-6 were activated (P<0.05), while the protein levels of glyoxalase (GLO)-1, glutathione reductase (GSR)-1, calcium/calmodulin-dependent protein kinase type (CAMK)-IV, cAMP-response-element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) were significantly less (P<0.05) in the hippocampus, but not in the prefrontal cortex and amygdala of socially defeated rats, when compared to control rats. We suggest that social defeat stress alters ERK1/2, IL-6, GLO1, GSR1, CAMKIV, CREB, and BDNF levels in specific brain areas, leading to oxidative stress-induced anxiety-depression-like behaviors and as well as memory impairment in rats.