Non-stressed Rats Research Articles

Maternal stress programs a demasculinization of glutamatergic transmission in stress-related brain regions of aged rats

Brain aging may be programmed by early-life stress. Aging affects males and females differently, but how perinatal stress (PRS) affects brain aging between sexes is unknown. We showed behavioral and neurobiological sex differences in non-stressed control rats that were strongly reduced or inverted in PRS rats. In particular, PRS decreased risk-taking behavior, spatial memory, exploratory behavior, and fine motor behavior in male aged rats. In contrast, female aged PRS rats displayed only increased risk-taking behavior and reduced exploratory behavior. PRS induced large reductions in the expression of glutamate receptors in the ventral and dorsal hippocampus and prefrontal cortex only in male rats. PRS also reduced the expression of synaptic vesicle-associated proteins, glucocorticoid receptors (GR), and mineralocorticoid receptors (MR) in the ventral hippocampus of aged male rats. In contrast, in female aged rats, PRS enhanced the expression of MRs and brain-derived neurotrophic factor (BDNF) in the ventral hippocampus and the expression of glial fibrillary acidic protein (GFAP) and BDNF in the prefrontal cortex. A common PRS effect in both sexes was a reduction in exploratory behavior and metabotropic glutamate (mGlu2/3) receptors in the ventral hippocampus and prefrontal cortex. A multidimensional analysis revealed that PRS induced a demasculinization profile in glutamate-related proteins in the ventral and dorsal hippocampus and prefrontal cortex, as well as a demasculinization profile of stress markers only in the dorsal hippocampus. In contrast, defeminization was observed only in the ventral hippocampus. Measurements of testosterone and 17-β-estradiol in the plasma and aromatase in the dorsal hippocampus were consistent with a demasculinizing action of PRS. These findings confirm that the brains of males and females differentially respond to PRS and aging suggesting that females might be more protected against early stress and age-related inflammation and neurodegeneration. Taken together, these results may contribute to understanding how early environmental factors shape vulnerability to brain aging in both sexes and may lay the groundwork for future studies aimed at identifying new treatment strategies to improve the quality of life of older individuals, which is of particular interest given that there is a high growth of aging in populations around the world.

Therapeutic Effects of Nano-Phytosome of Curcumin on Anxiety-like Behaviors, Neuroinflammation and Biochemical Parameters in Rats Exposed to Stress

Curcumin and its nano-phytosome have anti-inflammation and antioxidant properties that may decrease the concentration of metabolic factors, inflammatory parameters and anxiety in stressed rats. However, the effects of administration of of curcumin on inflammation and anxiety have not still been investigated. This study was conducted to scrutinize the metabolic factors, anxiety-like behavior and inflammatory factors in rats exposed to stress and treated with nano-phytosome of curcumin. Eighty femalerats were divided into four groups (n=20), including 1 and 2) non-stressed rats treated with saline (negative control) and nanophytosome (N-nano), 3 and 4) stressed rats treated with saline (Positive control) and nanophytosome (P-Nano). The rats in stressed groups were exposed to stress for 13 days and then treated for 21 days. Anxiety‑like behavior and inflammatory factors of IL-6, IL-1β, TNF-α and COX-2 and the concentration of glucose and triglycerides were assessed following the treatment with nano-phytosome. The results showed that the induction of stress increased anxiety symptoms (p <0.05), the inflammation (p <0.05) and blood parameters (p <0.05), but the treatment with nano-phytosome of curcumin reduced anxiety symptoms (p <0.05), the inflammation (p <0.05) and blood parameters (p <0.05). Overall, the induction of stress caused the inflammation and anxiety and increased the concentration of glucose and triglycerides. However, the treatment of the rats with nanophytosome of curcumin reduced adverse effects of the stress on inflammation and anxiety paramters. This study showed positive effects of curcumin for decreasing the inflammation and anxiety in the stressed rats, but clinical studies are required for its confirmation on human.

Stress-induced differential gene expression in cardiac tissue

The stress response is adaptive and aims to guarantee survival. However, the persistence of a stressor can culminate in pathology. Catecholamines released as part of the stress response over activate beta adrenoceptors (β-AR) in the heart. Whether and how stress affects the expression of components of the intracellular environment in the heart is still, however, unknown. This paper used microarray to analyze the gene expression in the left ventricle wall of rats submitted to foot shock stress, treated or not treated with the selective β2-AR antagonist ICI118,551 (ICI), compared to those of non-stressed rats also treated or not with ICI, respectively. The main findings were that stress induces changes in gene expression in the heart and that β2-AR plays a role in this process. The vast majority of genes disregulated by stress were exclusive for only one of the comparisons, indicating that, in the same stressful situation, the profile of gene expression in the heart is substantially different when the β2-AR is active or when it is blocked. Stress induced alterations in the expression of such a large number of genes seems to be part of stress-induced adaptive mechanism.

Stress Alters the Effect of Alcohol on Catecholamine Dynamics in the Basolateral Amygdala.

The current rodent study applied in vivo fast-scan cyclic voltammetry (FSCV), paired with a pharmacological approach, to measure the release of the catecholamines (CA) dopamine (DA) and norepinephrine (NE) in the basolateral amygdala (BLA) following locus coeruleus (LC) stimulation. The primary goal was to determine if exposure to either social (social defeat) or non-social (forced swim) stress altered LC-evoked catecholamine release dynamics in the BLA. We used idazoxan (α2 adrenergic receptor antagonist) and raclopride (D2 dopamine receptor antagonist) to confirm the presence of NE and DA, respectively, in the measured CA signal. In non-stressed rats, injection of idazoxan, but not raclopride, resulted in a significant increase in the detected CA signal, indicating the presence of NE but not DA. Following exposure to either stress paradigm, the measured CA release was significantly greater after injection of either drug, suggesting the presence of both NE and DA in the LC-induced CA signal after social or non-social stress. Furthermore, acute administration of alcohol significantly decreased the CA signal in stressed rats, while it did not have an effect in naïve animals. Together, these data reveal that, while LC stimulation primarily elicits NE release in the BLA of control animals, both social and non-social stress unmask a novel dopaminergic component of LC catecholamine signaling. Future studies will be needed to identify the specific neural mechanism(s) responsible for these plastic changes in LC-BLA catecholamine signaling and to assess the possible contribution of these changes to the maladaptive behavioral phenotypes that develop following exposure to these stressors.

Selective H3 Antagonist (ABT-239) Differentially Modifies Cognitive Function Under the Impact of Restraint Stress.

Background: A considerable number of competitive antagonists/inverse agonists of histamine H3 receptor (H3R) have progressed to clinical assessment, with pitolisant approved for the treatment of narcolepsy. H3R, highly expressed in the CNS, is regarded as a relevant target in CNS disorders. At the same time, new compounds including ABT-239 H3R antagonist (ABT; benzonitrile, 4-[2-[2-[(2R)-2-methyl-1-pyrrolidinyl]ethyl]-5-benzofuranyl]-) are continually being tested. The study aimed to test ABT-239 as a prophylactic agent in stress-induced memory impairments.Methods: Stressed and non-stressed rats were pre-treated with ABT-239 and subsequently subjected to several behavioral tests aimed at assessing the animals’ working and spatial reference memory [Morris water maze (MWM), Barnes maze (BM)], assessing the locomotor function and anxiety-like behavior [Open field (OF), elevated “plus” maze—EPM].Results: Chronically stressed rats displayed a significant decline in spatial (working and reference) memory. In the MWM test, we observed an improvement in spatial reference memory in stressed animals and a positive after ABT-239 pre-treatment. In the BM test, the effect of ABT-239 administration on spatial memory changed in successive attempts, from negative initially to favorable in subsequent attempts, and negative in the last trial of the test in the control group of rats. However, a beneficial effect is noted in the group of stressed animals, which remained throughout the entire testing period.Conclusions: Presented findings demonstrate that ABT-239 shows the potential to abolish or prevent restraint stress-induced spatial memory impairments and cognitive deficits. However, in conditions of appetitive modulation, it could increase damage to memory (unstressed animals).

Optogenetically-induced long term depression in the rat orbitofrontal cortex ameliorates stress-induced reversal learning impairment

Cognitive flexibility is a higher-order executive function that requires plasticity in neuronal circuits of the prefrontal cortex. Deficits in cognitive flexibility are prominent in a variety of psychiatric disorders, such as major depression, obsessive-compulsive disorder, and posttraumatic stress disorder. Chronic stress induces deficits in cognitive flexibility, perhaps through effects on plasticity, but the mechanism is not well understood. Previous work has demonstrated that stress reduces activity and dendritic elaboration in the medial prefrontal cortex (mPFC). In contrast, stress appears to increase dendritic elaboration in the orbitofrontal cortex (OFC). This suggests that there may be a differential effect of stress on plasticity in different prefrontal cortical areas. To test this hypothesis, we examined the effects of inducing plasticity optogenetically in the OFC on reversal learning, an OFC-mediated form of cognitive flexibility, in stressed and non-stressed rats. Inducing opto-LTD in the projection from mediodorsal thalamus to OFC ameliorated reversal learning deficits in rats exposed to chronic intermittent cold (CIC) stress. Additionally, we found that inducing opto-LTP in non-stressed rats produced deficits in reversal learning similar to those seen in rats after CIC stress. Finally, CIC stress produced complex subregion-specific changes in dendritic material and spine subtype composition in the OFC. These results indicate that the effects of stress on plasticity in the OFC are distinct from those in the mPFC, and that the PFC should therefore not be treated as a homogenous region in studying either stress effects or potential treatments for stress-related psychiatric disorders.

Participation of the intestinal microbiota in the mechanism of beneficial effect of treatment with synbiotic Syngut on experimental colitis under stress conditions.

Gut-brain axis plays a central role in the regulation of stress related diseases such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD). It is increasingly recognized that stress modulates gut microbiota community structure and activity and represents an important causal factor in dysbiosis. This study was designed to determine the effect of daily treatment with synbiotic (Syngut) containing inulin, Lactobacillus acidophilus, Bifidobacterium lactis W51, Lactobacillus plantarum W21 and Lactococcus lactis applied i.g. at a dose of 50 mg/kg i.g. on the colonic damage and colonic mucosal blood flow in rats with experimentally induced TNBS-colitis that were additionally exposed or not to acute stress (episodes of cold restraint stress every other day before colitis induction). Control rats received daily treatment with vehicle (saline, i.g.) or mesalazine (50 mg/kg-d i.g.), the standard drug recommended in therapy of IBD. At the termination of TNBS colitis, the histologic evaluation of colonic mucosa, mucosal malonyldialdehyde (MDA) level and plasma concentrations of proinflammatory cytokines (TNF-α, IL-1β) and adipokine adiponectin were assessed. the samples of colonic mucosa not involving colonic lesions and surrounding the flared mucosa were excised for the determination of mRNA expression for proinflammatory biomarkers TNF-α, IL-1β, IL-10 and COX-2 as well as antioxidazing factors SOD-1 and SOD-2. Finally, the gut microbial profiles were analyzed by 16S rRNA sequencing at phylum, family and genus level. Episodes of cold stress significantly aggravated the course of TNBS colitis, and significantly increased the release of proinflammatory cytokines as well as the significant increase in the MDA concentration has been observed as compared with non-stressed TNBS rats. These changes were followed by the significant fall in the CBF and plasma adiponectin levels and by the overexpression of mRNA of proinflammatory biomarkers. Synbiotic treatment with Syngut significantly reduced the area of colonic lesions observed macroscopically and microscopically in rats with TNBS colitis with or without exposure to cold stress, significantly increased the CBF, normalized plasma adiponectin levels and significantly attenuated the release and colonic expression of proinflammatory cytokines and biomarkers. the analysis of the gut microbiota showed a significant reduction of microbial diversity (Shannon index) in rats with TNBS colitis with or without exposure to stress. The therapy with Syngut failed to significantly affect the alpha diversity. At the phylum level, the significant rise in Proteobacteria has been observed in stressed rats with TNBS colitis and this effects was attenuated by treatment with Syngut. At family level, TNBS colitis alone or in combination with stress led to a significant decrease of SCFA producing bacterial taxa such as Ruminococaceae and Lachnospiraceae and Syngut counteracted this effect. We conclude that: 1) cold stress exacerbates the gastrointestinal inflammation in experimental colitis; 2) the synbiotic therapy with Syngut ameliorates the gut inflammation in rats with TNBS colitis combined with cold stress; 3) the beneficial effect of Syngut is accompanied by increase of anti-inflammatory taxa such as Ruminococaceae and Lachnospiraceae, and 4) the modulation of gut microbiota with Syngut alleviates stress-related intestinal inflammation suggesting a potential usefulness of synbiotic therapy in intestinal disorders accompanied by stress in patients with IBD.

The Effect of Swimming on Anxiety-Like Behaviors and Corticosterone in Stressed and Unstressed Rats.

This study assessed the effect of swimming training on anxiety-like behaviors and corticosterone. Thirty adult male Wistar rats were randomly assigned to five study conditions: swimming training (ST); exposure to chronic mild stress (CS); exposure to chronic mild stress followed by swimming training (CS + ST); exposure to chronic mild stress followed by a recovery period (CS + recovery); control. The exercise training consisted of 60 min of swimming exercise per day, for five days a week, and four consecutive weeks. A chronic mild stress program (CMS) was applied for a period of four weeks. Anxiety-like behaviors were measured by open field test (OFT). The number of excrements and blood corticosterone were used as physiological parameters of anxiety. To assess corticosterone, blood samples were taken 48 h after the last session of experiments. Compared to other study conditions, the lowest anxiety-like behaviors and corticosterone concentrations were observed in the ST condition in unstressed rats. In stressed rats, as in the ST + CS group, swimming training probably reduced some anxiety behaviors, but the results showed increased corticosterone compared to control and CS + Recovery. Anxiety parameters and corticosterone concentrations were greatest in the CS condition. In the ST group, anxiety parameters were less than for the ST + CS group. In the CS + Recovery group, anxiety parameters were less than for the CS group. In summary, self-paced swimming training could attenuate some anxiety parameters in both stressed and non-stressed rats. The effect of swimming training in unstressed rats was more prominent than in stressed rats. In stressed rats, a period of recovery was more effective than swimming training in reducing corticosterone. Mechanisms of anxiety reduction other than cortisol should be investigated in future research.

Repeated unpredictable stress blunts alcohol-induced memory deficit in adolescent rat.

There exists a complex interaction between alcohol and stress on brain and behavior. Alcohol and stress are both known to affect memory. Whether stress and alcohol together can modulate memory functions in adolescent rats is not known. In the present study, effects of repeated unpredictable stress (RUPS) on contextual fear conditioning, a hippocampus-related memory function, were investigated in alcohol-treated adolescent rats. Rats were divided into four experimental groups: group i - saline-treated non-stressed rats (sal no stress), group ii - alcohol-treated non-stressed rats (alc no stress), group iii - saline-treated rats subjected to stress (sal + RUPS), group iv - alcohol-treated rats subjected to stress (alc + RUPS). All rats were trained in the fear conditioning paradigm, and 24 h later were tested for contextual fear conditioning in the conditioning chamber, and nonspecific fear memory in a modified chamber. Stress, in the presence or absence of alcohol, did not alter nonspecific fear. RUPS exposure did not affect contextual freezing in vehicle-treated adolescent rats. Compared to vehicle-treated non-stressed rats, alcohol-treated non-stressed rats showed significant impairments in contextual freezing. Alcohol-treated RUPS rats performed better in the contextual freezing task than alcohol-treated non-stressed rats. RUPS exposure did not alter contextual fear conditioning in adolescent rats. Alcohol significantly reduced contextual fear memory in non-stressed rats. Alcohol-treated RUPS rats showed significantly better memory than alcohol-treated non-stressed rats. Together, these data suggest resiliency to stress-induced memory impairment in adolescent rats, and RUPS exposure causes blunting of alcohol's negative effects on contextual fear conditioning.

Both CRF1 and CRF2 receptors in the bed nucleus of stria terminalis are involved in baroreflex impairment evoked by chronic stress in rats

Chronic exposure to adverse events has been proposed as a prominent factor involved in etiology and progression of cardiovascular dysfunctions in humans and animals. However, the neurobiological mechanisms involved are still poorly understood. In this sense, chronic stress has been reported to evoke neuroplasticity in corticotropin-releasing factor (CRF) neurotransmission in several limbic structures, including the bed nucleus of the stria terminalis. However, a possible involvement of BNST CRF neurotransmission in cardiovascular dysfunctions evoked by chronic stress has never been reported. Thus, this study investigated the involvement of CRF1 and CRF2 receptors within the BNST in cardiovascular changes evoked by chronic stress in rats. We identified that exposure to a 10-day chronic variable stress (CVS) protocol decreased expression of both CRF1 and CRF2 receptors within the BNST. These effects were followed by increased arterial pressure and impairment of baroreflex function, but without changes on heart rate. Bilateral microinjection of either the selective CRF1 receptor antagonist CP376395 or the selective CRF2 receptor antagonist antisauvagine-30 into the BNST did not affect CVS-evoked arterial pressure increase. Nevertheless, BNST treatment with CP376395 decreased both tachycardic and bradycardic responses of the baroreflex in non-stressed rats; but these effects were not identified in chronically stressed animals. BNST pharmacological treatment with antisauvagine-30 decreased the reflex tachycardia in control animals, whereas reflex bradycardic response was increased in CVS animals. Altogether, the results reported in the present study indicate that down regulation of both CRF1 and CRF2 receptors within the BNST is involved in baroreflex impairment evoked by chronic stress.

Effects of Chrysin on Serum Corticosterone Levels and Brain Oxidative Damages Induced by Immobilization in Rat.

Chrysin (CH) is one of the main flavonoids of vegetables, fruits, and plants, the neuroprotective effect of which has been demonstrated in this study. The aim of the current investigation is the evaluation of the impact of chrysin (CH) on serum corticosterone level. Additionally, depression due to chronic stress was studied in animal models. The rats were restrained for 1 hour daily for 3 weeks. During these weeks, all animals were daily injected with either vehicle or CH (10, 20, 30 µg/kg). Present data indicated that the serum corticosterone levels markedly elevated in the stressed group versus the non-stressed group (p<0.001). The serum corticosterone levels were significantly lower in the stress-exposed rats administered with CH versus the stress-exposed non- CH-treated rats (p<0.05). In addition, immobility time significantly increased in the rats submitted to restraint stress versus the non-stressed group (p<0.001). Also, the number of crossing significantly decreased in the rats submitted to restraint stress versus non-stressed rats (p<0.001). The immobility time and the number of crossing were also reduced in the CH-administrated stressed rats (30 mg/kg) versus non-treated stressed group (p<0.001, p<0.05, respectively). CH also ameliorated the MDA and GSH content as well as antioxidant enzymes activities in stressed rats (p<0.05). The present study suggested that CH might be useful for the management of depressant-like effects induced by chronic stress via decreasing oxidative damage in the brain.

Effects of stress preconditioning on vulnerability of gastric and small intestinal mucosa to ulcerogenic action of indomethacin in rats.

The preconditioning effect of a mild stressor can reduce the ulcerogenic effect of a severe stressor on the gastric mucosa. The aim of the study was to investigate the effect of preconditioning stress on the gastric and the small intestinal injury caused by a single injection of indomethacin (IM) in conscious rats. Preliminary fasting (24 hours) rats were subjected IM administration (35 mg/kg, subcutaneously) with preconditioning stress (30 min cold-restraint at 10°C and further 1 hour keeping in cages at room temperature) or without stress. Plasma corticosterone level, heart rate (HR), blood pressure (BP) and somatic pain sensitivity (tail flick latency) were measured under circumstances of the gastrointestinal IM-induced injury in preliminary stressed and non-stressed rats. IM administration induced formation of gastric erosions well visible 4 hours after its injection. The healing of gastric erosions for 48 hours was accompanied by the development of a small intestinal injury. Corticosterone levels were elevated under formation of gastric erosions (4 hours after IM injection) but decreased following their healing (24 and 48 hours IM injection). Cold-restraint stress caused corticosterone rise 30 min after its onset. IM-induced gastrointestinal injury resulted in an increase of tail flick latencies (somatic hypoalgesia) and gradual decrease of systolic BP and increase of the HR. Stress preconditioning attenuated IM-induced gastric erosions as well as small intestinal injury 4 and 24 hours after its injection, respectively. The preconditioning also resulted in elimination of somatic hypoalgesia 4 hours after IM, but didn't influence an appearance of somatic hypoalgesia 24 and 48 hours after IM. Preconditioning stress recovered the HR and systolic BP (48 hours after IM). Elevated corticosterone level could be observed only in the 4th hour, but not in the 24th and 48th hours after IM administration. Thus, the data suggest that preconditioning stress reduces the vulnerability of the gastric and the small intestinal mucosa to ulcerogenic action of IM, stabilizes the hemodynamic parameters and normalizes somatic pain sensitivity.

Valproic acid administration exerts protective effects against stress-related anhedonia in rats

Anhedonia or inability to experience pleasure is the sign of various neuropsychiatric conditions. Current treatment options do not provide adequate control of anhedonia. The present study was conducted to evaluate the protective effects of valproic acid (VPA) as a nonspecific histone deacetylase (HDAC) inhibitor to reverse the effects of stress on induction of anhedonia and explore possible mechanisms.To induce anhedonia, a rat model of chronic unpredictable mild stress (CUMS) was established. Animals were assigned into no stress, stress (6 weeks of CUMS) and two treatment groups. VPA treatment was carried out for 4 continuous weeks (200 mg/kg/day). Behavioral assessments were performed using sucrose consumption (SCT) and new object recognition (NOR) tests. The expression of genes was evaluated using qRT-PCR. The cell density was determined using Nissl staining.Rats with CUMS showed depressive-like behaviors and impaired memory performance compared with the non-stressed group (p < 0.01). Moreover, they had significantly higher levels of HDAC3 and MC4R expression in the nucleus accumbens (NAc) compared to the non-stressed group (p < 0.01). The NAc cell density was significantly higher in the non-stressed rats (p < 0.05). Corticosterone plasma level was increased in the CUMS compared to the non-stressed group (p < 0.05). In the CUMS + VPA subgroup, the corticosterone (CORT) plasma level was lower compared with the CUMS + Saline and/or the CUMS groups (p < 0.05).These findings suggest that VPA can improve anhedonia and stress. Although the protective effect of VPA might link to decreasing HDAC3 and MC4R genes expression in NAc.

Effect of lurasidone treatment on chronic mild stress-induced behavioural deficits in male rats: The potential role for glucocorticoid receptor signalling

Stress represents one of the main precipitating factors for psychiatric diseases, characterised by an altered function of glucocorticoid receptors (GR), known to play a role in mood and cognitive function. We investigated the ability of the antipsychotic lurasidone to modulate the involvement of genomic and non-genomic GR signalling in the behavioural alterations due to chronic stress exposure. Male Wistar rats were exposed to seven weeks of chronic mild stress (CMS) and treated with lurasidone (3 mg/kg/day) starting from the second week of stress for more five weeks. Gene expression and protein analyses were conducted in dorsal hippocampus. Seven weeks of CMS induced anhedonia and cognitive impairment, which were normalised by lurasidone. At molecular level, CMS rats showed an increase of GR protein levels by 60% (p<0.001 vs. CTRL/VEH) in the membrane compartment, which was paralleled by an up-regulation of phosphoSINAPSYN Ia/b by 88% (p<0.01 vs. CTRL/VEH) and of the mitochondrial marker Cox3 by 21% (p<0.05 vs. CTRL/VEH). Moreover, while exposure to the novel object recognition test increased the nuclear translocation of GRs by 96% (p<0.01 vs. CTRL/VEH/Naïve) and their transcriptional activity in non-stressed rats, such mechanisms were impaired in CMS rats. Interestingly, the genomic and non-genomic alterations of GR, induced by CMS, were normalised by lurasidone. Our results further support the role of glucocorticoid signalling in the dysfunction associated with stress exposure. We provide novel insights on the mechanism of lurasidone, suggesting its effectiveness on different domains associated with psychiatric disorders.

Effects of l-theanine on glutamine metabolism in enterotoxigenic Escherichia coli (E44813)-stressed and non-stressed rats

Abstract l -theanine, a non-protein-derived amino acid, is widely used as a functional ingredient in foods. Here, we evaluated the in vivo effects of l -theanine on glutamine metabolism in healthy rats and in a stressed rat model, which was established by infecting rats with enterotoxigenic Escherichia coli (E44813). The results showed that l -theanine significantly enhanced the synthesis of glutamine and stabilized the intestinal tract in healthy rats. In E44813-stressed rats, l -theanine could replace l -glutamine, thereby alleviating intestinal stress by reducing the expression of inflammatory factors, enhancing the activities of antioxidant enzymes, and regulating glutamine metabolism by modulating its synthesis. Treatment with a combination of l -theanine and l -glutamine was superior to treatment with l -glutamine alone in enhancing the activity of antioxidant enzymes, reducing the expression of inflammatory factors, and increasing the intestinal villi height and crypt depth.

MgO and ZnO nanoparticles anti-nociceptive effect modulated by glutamate level and NMDA receptor expression in the hippocampus of stressed and non-stressed rats

The anti-nociceptive mechanisms of MgO and ZnO nanoparticles have not been thoroughly investigated; in this study, we evaluated the effects of anti-nociceptive dose of MgO and ZnO NPs on glutamate level and NMDA receptor subunits expression (NR1, NR2 and NR2B) in the rat whole hippocampus with and without acute restraint stress. Adult rats were divided into control, MgO and ZnO NPs 5 mg/kg, the stress of 90 min alone and with MgO or ZnO NPs 5 mg/kg groups. All components injected intraperitoneally and the nociceptive response was measured with hot plate apparatus 90 min after injections or stress induction. Magnesium, zinc, glutamate levels and NMDA receptor subunits expression were measured in the animal hippocampus. MgO NPs, ZnO NPs and acute stress induced anti-nociceptive effect. MgO NPs observably decreased glutamate and increased magnesium levels and NR2B subunit expression. ZnO NPs decreased glutamate level. Stress elevated endogenous magnesium and zinc levels and also the NR2B expression, but did not change glutamate level. MgO and ZnO NPs in the presence of stress increased the glutamate level and ZnO NPs increased the zinc and the NR2A expression. Stress decreased endogenous magnesium in the hippocampus. MgO and ZnO NPs could affect pain perception by changing glutamate level in the whole hippocampus tissue, while ion level changes followed by injection could probably affect the gene expression in the presence and the absence of stress. It seems that stress indirectly could adverse nanoparticles effects on glutamate level and increase zinc ion releasing from ZnO NPs by activating the gene expression without affecting pain perception.

Cannabinoid receptor type 1 modulates the effects of polyunsaturated fatty acids on memory of stressed rats

ABSTRACT Memory and GABAergic activity in the hippocampus of stressed rats improve after n-3 polyunsaturated fatty acid (PUFA) supplementation. On the other hand, cannabinoid receptor type 1 (CB1) strongly regulates inhibitory neurotransmission in the hippocampus. Speculation about a possible relation between stress, endocannabinoids, and PUFAs. Here, we examined whether the effects of PUFAs on memory of chronically stressed rats depends on pharmacological manipulation of CB1 receptors. Male Sprague-Dawley rats were orally supplemented with n-3 (fish oil) or n-6 (primrose oil) PUFAs during chronic restraint stress (CRS) protocol (6 h/day; 21 days). First, we studied if the expression of CB1 receptors in the hippocampus may be affected by CRS and PUFAs supplementation by real-time PCR and immunofluorescence. CRS up-regulated the CB1 expression compared with the non-stressed rats, while only n-3 PUFAs countered this effect. Memory was evaluated in the Morris water maze. Stressed rats were co-treated with PUFAs and/or modulators of CB1 receptor (AM251, antagonist, 0.3 mg/kg/day; WIN55,212-2, agonist, 0.5 mg/kg/day) by intraperitoneal injections. Memory improved in the stressed rats that were treated with AM251 and/or n-3 PUFAs. Supplementation with n-6 PUFAs did not affect memory of stressed rats, but co-treatment with AM251 improved it, while co-treatment with WIN55,212-2 did not affect memory. Our results demonstrate that activity of the CB1 receptors may modulate the effects of PUFAs on memory of stressed rats. This study suggests that endocannabinoids and PUFAs can both become a singular system by being self-regulated in limbic areas, so they control the effects of stress on the brain.

EVALUATION OF ANTISTRESS ACTIVITY OF ETHANOLIC EXTRACT OF CHROMOLAENA ODORATA LEAVES IN ALBINO WISTAR RATS

Objective: The objective of this study was to study the effect of ethanolic extract of Chromolaena odorata (EECO) Linn. on acute restraint stress (ARS)-induced stress-like behavior and biochemical alterations in albino Wistar rats.&#x0D; Methods: The ARS was induced by immobilizing the rats for a period of 12 h using rodent restraint device preventing them from any physical movement. Immediately, after 12 h rats were released and doses were given to each rat. 40 min post-release various behavioral parameters such as immobility time in force swim test and tail suspension test (TST), locomotor activity in open field test (OFT), and oxidative stress parameters and biochemical alterations in rat brain tissue were also performed.&#x0D; Statistical Analysis: Expression of data was done as mean±standard error of mean. The normally distributed data were subjected to one-way ANOVA followed by Dunnett’s test. p&lt;0.05 was considered statistically significant.&#x0D; Results: Experimental findings revealed that rats subjected to ARS exhibited significant increase in immobility time in forced swim test and TST models, decrease in locomotor activity in OFT model, and increase in malondialdehyde formation and impaired superoxide dismutase, and catalase activities in hippocampus and cerebral cortex as compared to non-stressed rats. EECO treatment (250 mg/kg and 500 mg/kg) significantly attenuated immobility time, locomotion, and restored the antioxidant enzymes after ARS.&#x0D; Conclusion: EECO significantly alleviated ARS-induced stress-like behavior.

Cortical 5-hydroxytryptamine 1A receptor biased agonist, NLX-101, displays rapid-acting antidepressant-like properties in the rat chronic mild stress model.

NLX-101 (also known as F15599) is a highly selective and efficacious 'biased' agonist at cortical 5-hydroxytryptamine 1A (5-HT1A) heteroreceptors. In rodents, it possesses marked antidepressant-like activity, potently and completely abolishing immobility in the forced swim test (FST) with extended duration of action. We investigated the antidepressant-like activity of NLX-101 using the rat chronic mild stress (CMS) model of depression, considered to have a higher translational potential than the FST, as it possesses construct, face and predictive validity. The effects of CMS and repeated NLX-101 treatment were tested using sucrose consumption (a measure of anhedonia), novel object recognition (NOR; a measure of working memory) and elevated plus maze (EPM; a measure of anxiety) tests. NLX-101 reversed the CMS-induced decrease of sucrose intake on day 1 of testing, with full reversal observed at the dose of 0.16 mg/kg and a less pronounced but still significant effect at 0.04 mg/kg, both given twice a day intraperitoneally. The effects of NLX-101 were maintained over the 2 week treatment period and persisted for four weeks following cessation of treatment. In the NOR test, both doses of NLX-101 rescued the deficit in discrimination index caused by CMS, without any effect on locomotor activity. However, NLX-101 had no effect on the reduction of open-arms entries produced by CMS in the EPM model. In control, non-stressed rats, NLX-101 produced non-significant effects in all three models. NLX-101 displayed efficacious activity in the CMS test, with more rapid (1 day) antidepressant-like effects than pharmacological compounds tested previously under the same experimental conditions. These observations suggest that biased agonist targeting of cortical 5-HT1A receptors constitutes a promising strategy to achieve rapid-acting and sustained antidepressant effects.

Impact of Stress on Gamma Oscillations in the Rat Nucleus Accumbens During Spontaneous Social Interaction.

Alteration in social behavior is one of the most debilitating symptoms of major depression, a stress related mental illness. Social behavior is modulated by the reward system, and gamma oscillations in the nucleus accumbens (NAc) seem to be associated with reward processing. In this scenario, the role of gamma oscillations in depression remains unknown. We hypothesized that gamma oscillations in the rat NAc are sensitive to the effects of social distress. One group of male Sprague-Dawley rats were exposed to chronic social defeat stress (CSDS) while the other group was left undisturbed (control group). Afterward, a microelectrode array was implanted in the NAc of all animals. Local field potential (LFP) activity was acquired using a wireless recording system. Each implanted rat was placed in an open field chamber for a non-social interaction condition, followed by introducing another unfamiliar rat, creating a social interaction condition, where the implanted rat interacted freely and continuously with the unfamiliar conspecific in a natural-like manner (see Supplementary Videos). We found that the high-gamma band power in the NAc of non-stressed rats was higher during the social interaction compared to a non-social interaction condition. Conversely, we did not find significant differences at this level in the stressed rats when comparing the social interaction- and non-social interaction condition. These findings suggest that high-gamma oscillations in the NAc are involved in social behavior. Furthermore, alterations at this level could be an electrophysiological signature of the effect of chronic social stress on reward processing.