Open Arms Of Elevated Plus-maze Research Articles

Unmoving and uninflamed: Characterizing neuroinflammatory dysfunction in the Wistar-Kyoto rat model of depression.

Reductionistic research on depressive disorders has been hampered by the limitations of animal models. Recently, it has been hypothesized that neuroinflammation is a key player in depressive disorders. The Wistar-Kyoto (WKY) rat is an often-used animal model of depression, but no information so far exists on its neuroinflammatory profile. As such, we compared male young adult WKY rats to Wistar (WS) controls, with regard to both behavioral performance and brain levels of key neuroinflammatory markers. We first assessed anxiety- and depression-like behaviors in a battery consisting of the Elevated Plus Maze (EPM), the Novelty Suppressed Feeding (NSFT), Open Field (OFT), Social Interaction (SIT), Forced Swim (FST), Sucrose Preference (SPT), and Splash tests (ST). We found that WKY rats displayed increased NSFT feeding latency, decreased OFT center zone permanence, decreased EPM open arm permanence, decreased SIT interaction time, and increased immobility in the FST. However, WKY rats also evidenced marked hypolocomotion, which is likely to confound performance in such tests. Interestingly, WKY rats performed similarly, or even above, to WS levels in the SPT and ST, in which altered locomotion is not a significant confound. In a separate cohort, we assessed prefrontal cortex (PFC), hippocampus and amygdala levels of markers of astrocytic (GFAP, S100A10) and microglial (Iba1, CD86, Ym1) activation status, as well as of three key proinflammatory cytokines (IL-1β, IL-6, TNF-α). There were no significant differences between strains in any of these markers, in any of the regions assessed. Overall, results highlight that behavioral data obtained with WKY rats as a model of depression must be carefully interpreted, considering the marked locomotor activity deficits displayed. Furthermore, our data suggest that, despite WKY rats replicating many depression-associated neurobiological alterations, as shown by others, this is not the case for neuroinflammation-related alterations, thus representing a novel limitation of this model.

Anti-anxiety and Hypnotic Effects of Lawsonia inermis Hydroalcoholic Extract

Background: Sleep is a vital biological feature, and insomnia causes maladaptive physical and psychological functions. The main flaws of current insomnia medications are significant side effects. A suitable substitute can be herbal products. We aimed to evaluate the anti-anxiety, sleep-inducing, and - prolonging effects of Lawsonia inermis extract and fractions in mice. Methods: Male albino mice were pretreated intraperitoneally (i.p.) with either three doses (40, 80, and 160 mg/kg) of L. inermis extract or n-butanol fraction (NBF), ethyl acetate fraction (EAF), and water fraction (WF), 30 minutes before i.p. injection of 30 mg/kg pentobarbital. Sleep latency and duration of sleep were recorded. For anxiolytic activity, elevated plus-maze (EPM) tests were used. Moreover, the toxicity of the extract was determined in both in vivo and in vitro experiments. Results: L. inermis extract (160 mg/kg) significantly reduced sleep latency and increased sleep duration. EAF at 160 mg/kg decreased sleep latency and increased sleep duration. Flumazenil reversed the hypnotic effect of L. inermis extract (160 mg/kg). L. inermis extract (80, 160 mg/kg) increased the time spent and the number of entries in the open arms of EPM. The tested extracts and fractions administration found no adverse effects on PC12 cell viability. The LD50 was 2.4 g/kg. Conclusion: L. inermis extracts exhibit anxiolytic and hypnotic effects, probably modulating the GABAergic system.

Pharmacological Manipulation of Corticotropin-Releasing Factor Receptors in the Anterior and Posterior Subregions of the Insular Cortex Differently Affects Anxiety-Like Behaviors in the Elevated Plus Maze in Rats.

Neuroimaging data in humans and neurobiological studies in rodents have suggested an involvement of the insular cortex (IC) in anxiety manifestations. However, the local neurochemical mechanisms involved are still poorly understood. Corticotropin-releasing factor (CRF) neurotransmission has been described as a prominent neurochemical mechanism involved in the expression of anxiety-like behaviors, but the brain sites related are poorly understood. Additionally, several findings indicate that control of physiological and behavioral responses by the IC occurs in a site-specific manner along its rostrocaudal axis. Thus, this study is aimed at evaluating the effect of CRF receptor agonism and antagonism within the anterior and posterior subregions of the IC in controlling anxiety-related behaviors in the elevated plus maze (EPM). For this, independent groups (six groups) of animals received bilateral microinjections of vehicle, the selective CRF1 receptor antagonist CP376395, or CRF into either the anterior or posterior subregions of the IC. Ten minutes later, the behavior in the EPM was evaluated for five minutes. Treatment of the anterior IC with CP376395, but not with CRF, increased the time and number of entries into the open arms of the EPM. CRF, but not the CRF1 receptor antagonist, microinjected into the posterior IC also increased exploration of the EPM open arms. Taken together, these data indicate that CRFergic neurotransmission in the anterior IC is involved in the expression of anxiety-related behaviors in the EPM. This neurochemical mechanism does not seem to be activated within the posterior IC during exposure to the EPM, but the effects caused by CRF microinjection indicate that activation of CRF receptors in this IC subregion might evoke anxiolytic-like effects.

Treadmill Exercise Reverses the Adverse Effects of Intermittent Fasting on Behavior and Cortical Spreading Depression in Young Rats.

Intermittent fasting (IF) and physical exercise (PE) have beneficial psychological and physiological effects, improving memory and anxiety-like behavior. However, the impact of this combination on brain electrophysiological patterns is unknown. We aimed to evaluate the behavior and parameters of a brain excitability-related phenomenon named cortical spreading depression (CSD) in young rats (31-87 days of life) submitted to IF and treadmill PE for eight weeks. Sixty-four male and female Wistar rats aged 24 days were randomized into control, IF, PE, and IF+PE groups. Behavioral tests (open field (OF), object recognition, and elevated plus maze (EPM)) were performed, and the CSD propagation features were recorded. IF caused behavioral responses indicative of anxiety (lower number of entries and time spent in the OF center and EPM open arms). IF also reduced the discrimination index for object recognition memory tests and increased the propagation velocity of CSD. PE rats displayed more entries into the OF center and lowered CSD propagation speed. Data suggest that IF worsens anxiety-like behavior and memory and accelerates CSD in young rats. In contrast, PE reverted the unfavorable effects of IF. The brain effects of IF and PE at younger ages are recommended for study.

Chronic kidney disease is associated with cognitive dysfunction and cardiovascular remodeling in aged male and female Sprague‐Dawley rats

AbstractBackgroundCardiovascular diseases (CVD), including increased central arterial stiffness (CAS), accompany chronic kidney disease (CKD) development. An increase in pulse wave velocity (PWV), an index for CAS, is implicated in age‐associated changes in the brain and potentiates the development of CI in CVD and CKD in humans and animal models. The aim of this study was to determine whether inducing CKD accelerates the development of CI and CAS in aged male and female rats.MethodTen months‐old male and female Sprague‐Dawley rats were fed with 0.25% adenine diet to accelerate CKD (n = 10‐12; CKD‐male, CKD‐female) or regular diet (n = 8‐10; CNT‐male, CNT‐female) for 8weeks. Body weight (BW), blood pressure (BP), heart rate (HR), aortic‐PWV (aPWV), behavioral tests, blood urea nitrogen (BUN), creatinine and hematocrit were assessed at the endpoint. The anxiety‐like behavior was tested in open field test (OFT) and elevated plus maze (EPM). Morris water maze (MWM) and cross maze (CM) were used to test spatial memory. The data were analyzed using two‐way ANOVA.ResultCKD development in both sexes was accompanied by kidneys enlargement, increase in BUN and creatinine, and reduction in hematocrit. In CKD‐male the kidney function was more compromised with higher levels of BUN and creatinine vs. CKD‐female (Table 1). CKD‐male had lower BW and SBP vs. CNT‐male (Table 1). CKD induced a reduction in HR, increase in aPWV and aortic weight in both sexes vs. respective CNT‐groups (Figure 1). Both CKD‐male and CKD‐female demonstrated a tendency of increase in path length to find the hidden platform in MWM, e.g., both sexes had numerically impaired spatial memory. CKD‐male spent less time in the center of OFT, a measure of anxiety, and loss of spatial memory, with a reduction of spontaneous alternation task assessed by CM. CKD‐female exhibited higher level of anxiety spending less time in open arm of EPM vs. CNT‐female (Figure 2).ConclusionCKD development in old male and female Sprague‐Dawley rats was accompanied by an increase in CAS, cardiovascular remodeling, and cognitive dysfunction. In CKD, CI affected different cognitive domains in the old males than in the age‐matched females.Supported by NIA/NIH/IRP

Chronic Exposure of 5‐Alpha Reductase Inhibitor in Young Male Rats Induces Not Only Metabolic Disturbance, But Also Depressive‐Like Behaviors as Similar with Obese Condition

AbstractBackgroundFinasteride (FIN), a 5‐alpha reductase inhibitor (5‐ARIs), is one of the drugs approved for the treatment of androgenetic alopecia (AGA) and benign prostatic hyperplasia (BPH). AGA has been found to be associated with obesity. Obesity and AGA themselves often co‐occurs with anxiety and depression. Nevertheless, several studies reported adverse effects of FIN on anxiety and depression, especially in young men. A previous study also reported that FIN caused anxiety and depression in male rats; however, the effects of chronic FIN exposure in young obese condition has not been investigated.MethodTwenty male Wistar rats (8‐week‐old) were divided into two groups (N = 10/group) to feed with either normal diet (ND) or high‐fat diet (HFD) for 18 weeks. At week 13, rats in each dietary group were subdivided into two subgroups to treat with either vehicle as control or FIN (5 mg/kg/day) via oral gavage. At the end of the experimental protocol, the anxiety/depression‐like behaviors were measured using the Elevated‐Plus Maze (EPM) and the Splash Test (ST), while the Open‐Field Test (OFT) was examined for locomotor activity. In addition, blood in each rat was collected for determining the metabolic profiles.ResultHFD‐fed rats developed obesity and hypercholesterolemia, with an increase in systemic oxidative stress (Figure 1A‐C). Anxiety and depressive‐like behaviors were observed in vehicle‐treated HFD‐fed rats, as indicated by decreasing % preference index in the open arm of EPM and grooming time in ST (Figure 1D‐E). FIN treated ND‐fed rats also showed depression‐like behaviors, similar to those in vehicle‐treated HFD‐fed rats (Figure 1E). Although FIN increased plasma cholesterol levels in HFD‐fed rats, it did not aggravate anxiety and depression‐like behaviors in HFD‐fed rats. Regarding the locomotor activity, no significant difference was found among all groups. (Figure 1F).ConclusionAll of these findings suggest that FIN exposure induced metabolic disturbance, and depression‐like behaviors as similar to obesity without the aggravating effects of FIN and obesity on depressive‐like behaviors.

Chronic Exposure with 5‐Alpha Reductase Inhibitor Ameliorates Anxiety and Depression‐like Behaviors By Reducing Systemic Oxidative Stress in D‐galactose‐Induced Aging Male Rats

AbstractBackgroundThe most common geriatric psychiatric disorders are anxiety and depression. The 5‐alpha reductase inhibitor (5‐ARIs), finasteride (Fin), is a standard medication used to treat benign prostatic hyperplasia (BPH), that often occurs in the elderly. However, the effects of Fin on mental health in aged population are still unclear. D‐galactose (D‐gal)‐induced aging has been recognized worldwide, as a model to mimic natural aging in rodents. Therefore, we investigated the effect of Fin on anxiety and depression‐like behaviors in D‐gal‐induced aging male rats.MethodTwenty‐male Wistar rats (8‐week‐old) were randomly divided into two groups (n = 10/group) to receive either vehicle as control or D‐gal (150 mg/kg/day via subcutaneous injection) for 18 weeks. At week 13, rats in each group were divided into two subgroups (n = 5/subgroup) in order to receive either vehicle (drinking water) or Fin (5 mg/kg/day) via oral gavage. At the end of the treatment, elevated‐plus maze (EPM), and splash test (ST) were performed for quantifying anxiety and depression‐like behaviors, while open‐field test (OFT) to determine locomotor activity. In addition, blood in each rat was collected for determining the metabolic profiles.ResultD‐gal‐treated rat showed no effect on metabolic disturbance, but increased systemic oxidative stress (Figure 1A‐C). Anxiety and depression‐like behavior were observed in D‐gal‐treated rats, as indicated by a decrease % preference index in the open arm of EPM and grooming time in ST (Figure 1D‐E). Fin‐treated control rats demonstrated hypercholesterolemia (Figure 1A‐B), and depression‐like behavior was observed (Figure 1E). Anxiety and depression‐like behaviors were attenuated in Fin‐treated D‐gal rats (Figure 1D‐E). Regarding the locomotor activity, no significant difference was found among all groups. (Figure 1F).ConclusionFIN exposure induced metabolic disturbance, and depression‐like behaviors in male rats. In contrast, Fin ameliorated anxiety and depression‐like behaviors in D‐gal‐induced aging rat, which may due to a reducing systemic oxidative stress. The findings in this study provide information for future clinical applications such as the use of Fin for therapeutic approach for anxiety/depression‐like behaviors in the elderly. However, caution is advised when using Fin in young men since it may induce depressive‐like behaviors.

Experimental evaluation of anxiolytic and antidepressant activities of methanolic extract of Triticum aestivum (wheatgrass) in albino mice

Background: Anxiety and depression are common psychiatric conditions. The present study was carried out to find antianxiety and antidepressant activity of methanolic extract of Triticum aestivum (wheat grass) in mice. Materials and methods: The methanolic extract of Triticum aestivum (META) was screened for antianxiety activity by elevated plus maze (EPM) and light and dark box (LDB) and for antidepressant activity by forced swim test (FST) and tail suspension test (TST) in mice. Animals were divided into four groups having six animals in each group. Group I served as control and received gum acacia aqueous suspension 10 ml/kg, Groups II and III served as test groups and received META 200 and 400 mg/kg, respectively, Group IV served as standard group and received diazepam 1 mg/kg for antianxiety activity and fluoxetine (20 mg/kg) for antidepressant activity once daily for thirty days. Result: META 200 and 400 mg/kg showed significant (P < 0.01) dose-dependent increase in entries and stay in the open arms in EPM and entries and stay in the light compartment in LDB as compared to control. Antianxiety effect of META at dose of 400 mg/kg was comparable (P > 0.05) with diazepam 1mg/kg. META 200 and 400 mg/kg also produced dose-dependent significant (P < 0.01) antidepressant effect, indicated by reduction in the immobility time as compared to control in both FST and TST. The antidepressant activity of META at dose of 400 mg/kg was comparable (P > 0.05) with fluoxetine 20 mg/kg. Conclusion: Results of our study suggested that META possess dose-dependent significant antianxiety and antidepressant activities.

Investigation of effects of transferrin-conjugated gold nanoparticles on hippocampal neuronal activity and anxiety behavior in mice.

Gold nanoparticles (GNPs) have been widely used in medicine such as imaging, drug delivery and therapeutics due to their multifunctional properties. Alterations in neuronal function may contribute to various neurological diseases. Transferrin plays a primary role in iron transportation and delivery and has recently been utilized for drug delivery to the brain. We have investigated effects of transferrin-conjugated GNPs (Tf-GNPs) on anxiety and locomotor behavior in vivo and also hippocampal neuronal activity ex vivo. Electrophysiological effects of Tf-GNP on hippocampal neurons were determined by patch clamp method. Fifteen male young adult C57BL/6 mice were randomly divided into three groups as control (200 µL PBS), GNP (bare GNP; 2.2μg/g in PBS) and Tf-GNPs (2.2μg/g Tf-GNP). Animals intraperitoneally received the respective treatments for seven consecutive days and were subjected to elevated plus maze (EPM) and open field tests (OFT). Ex vivo, firing frequency of the neurons significantly increased by GNP treatment (p < 0.001). In vivo, animals in Tf-GNP group showed significantly longer distance in open arms but significantly lower number of entries to the open arms in EPM (p < 0.05). Mice received bare GNPs had significantly higher locomotor activity in OFT (p < 0.05), while Tf-GNP did not alter the locomotor activity significantly (p = 0.051). Animals in Tf-GNP group spent significantly longer time in the peripheral zone in OFT (p < 0.05). The present findings have shown that Tf-GNP induces anxiety-like behavior without altering spontaneous firing rate of hippocampal neurons. We suggest that neurobiological effects of Tf-GNP should be pre-determined before using in medical applications.

Neurotoxicity of Bisphenol A and the Impact of Melatonin Administration on Oxidative Stress, ERK/NF-kB Signaling Pathway, and Behavior in Rats.

Bisphenol A (BPA) exposure can be associated with neurodevelopmental disorders due to impairment of cell proliferation and synaptic development. Our study evaluated the effects of melatonin (MEL) on ambulatory activity, lipid peroxidation, cytokines, ERK/NF-kB signaling pathway in the hippocampus and frontal lobe, and histopathological changes in the hippocampus of the BPA-treated rats. The animals were divided into 4 groups: control, BPA, BPA + MEL I, and BPA + MEL II. MEL I (20mg/kg b.w.) and MEL II (40mg/kg b.w.) were orally administered for 28days. On the 29th day, BPA (1mg/kg b.w.) was intraperitoneally administered, and, after 24h, an open field test (OFT) and an elevated plus maze (EPM) were conducted. The results showed that the MEL II group made significantly more entries in the open arms of EPM, traveled significantly greater distance, and spent more time in the central part of OFT. Malondialdehyde levels were diminished by MEL II in the hippocampus and by MEL I in the frontal lobe. In the hippocampus, the MAPK level was significantly lowered by both doses of MEL (p < 0.05) while in the frontal lobe, only MEL II reduced the MAPK activation. MEL I and II significantly decreased the γH2AX and upregulated the NFkB and pNFkB expressions in the hippocampus while MEL II downregulated the MCP1 expression. Both doses of MEL attenuated the BPA-evoked histopathological alterations in the hippocampus. These data indicate that MEL can mediate the neuroprotection against BPA-induced neurotoxicity and improves behavioral changes suggesting a real potential as a protective agent in brain toxicity.

Evaluation of the posterior insular cortex involvement in anxiogenic response to emotional stress in male rats: Functional topography along the rostrocaudal axis

The insular cortex (IC) is engaged in behavioral and physiological responses to emotional stress. Control of physiological functions and behavioral responses has been reported to occur in a site-specific manner along the rostrocaudal axis of the IC. However, a functional topography of the IC regulation of anxiogenic responses caused by stress has never been evaluated. Therefore, we investigated the role of rostrocaudal subregions in the posterior IC in anxiogenic-like effect caused by exposure to acute restraint stress in male rats. For this, rats received bilateral microinjection of the non-selective synaptic inhibitor CoCl2 or vehicle into either the rostral, intermediate or caudal portions of the posterior IC before exposure to acute restraint stress. Then, behavior in the elevated plus maze (EPM) was evaluated immediately after restraint stress. The behavior of non-stressed animals in the EPM was also investigated. We observed that acute restraint stress decreased the exploration of the EPM open arms in animals treated with vehicle in all regions of the posterior IC, thus indicating an anxiogenic-like effect. The avoidance of the EPM open arms was completely inhibited in animals subjected to microinjection of CoCl2 into the intermediate posterior IC. Nevertheless, the same pharmacological treatment into either the rostral or caudal subregions of the posterior IC did not affect the restraint-evoked behavioral changes in the EPM. Taken together, these results suggest that regulation of anxiogenic-like effect to emotional stress along the rostrocaudal axis of the posterior IC might occur in a site-specific manner, indicating a role of the intermediate subregion.

Stress resilience-associated behaviors following predator scent stress are accompanied by upregulated nucleus accumbens mGlu5 transcription in female Sprague Dawley rats

Despite the higher prevalence of post-traumatic stress disorder (PTSD) in women, the majority of preclinical research has been conducted utilizing male subjects. We have found that male rats exposed to the predator scent 2,4,5-trimethyl-3-thiazoline (TMT) show heterogenous long-term anxiety-like behavior and conditioned fear to the TMT environment. Stress-Resilient males exhibit increased mGlu5 mRNA expression in the basolateral amygdala (BLA) and prefrontal cortex (PFC). Here we sought to determine whether the same behavioral and genetic responses would be observed in female rats exposed to TMT. Female Sprague-Dawley rats were exposed to TMT for ten minutes, while Controls were exposed to an unscented environment. Anxiety and anhedonia were assessed 7–14 days later with elevated plus maze (EPM), acoustic startle response, light-dark box, and sucrose preference test (SPT). TMT-exposed females spent less time in the EPM open arms, exhibited greater startle amplitude, and reduced sucrose intake compared to Controls. Median split analyses conducted on EPM and SPT data yielded stress-Susceptible and -Resilient phenotypes that displayed behavior in the light-dark box consistent with EPM and SPT behavior. Susceptible females displayed greater BLA mGlu5 mRNA expression than Resilient and Control rats and did not show conditioned fear, in contrast to previous results in males. Resilient females displayed greater mGlu5 mRNA expression in the nucleus accumbens. These data indicate that the predator scent stress model of PTSD produces distinct stress-Susceptible and Resilient phenotypes in female rats that are associated with changes in mGlu5 mRNA expression in several brain regions.

LOSARTAN, ANGIOTENSIN II TYPE 1 RECEPTOR BLOCKER, REDUCED AORTIC STIFFNESS AND IMPROVED COGNITIVE FUNCTION IN DAHL SALT SENSITIVE RAT MODEL OF AGE-ASSOCIATED VASCULAR DEMENTIA

Cardiovascular diseases are the major contributors to the pathogenesis of vascular dementia. The Dahl salt sensitive (Dahl-S) rat model is characterized by the development of central arterial stiffness (CAS), hypertension and cognitive decline with age on a normal salt diet. We hypothesized that treatment with losartan (LOS), angiotensin II type 1 receptor (AT1R) blocker, via reduction of blood pressure (BP) and CAS, will improve cognitive function in aged Dahl-S rats.Male Dahl-S rats (n = 30) were kept on a normal salt diet (0.5% NaCl) for the duration of the study. Baseline measurements were taken at 3- and/or 6-mo of age following by the treatment with LOS in drinking water (30 mg/kg/day, n = 14) or control treatment (n = 16) for 6-mo. Measurements were taken every 3 months and included systolic and diastolic BP (SBP, DBP), pulse wave velocity (PWV), a measure of CAS, left ventricular posterior wall thickness in diastole (LVPWd), fractional shortening (FS) and LV mass (by echocardiography). At 12-mo of age the rats were tested in operant chambers using a simple reaction task to assess attention and impulsivity, and in elevated plus maze (EPM) to assess anxiety-like behavior. Statistical analyses were performed using 2-way ANOVA and t-test. Data are presented as mean ± SEM.Prior to the treatment, LOS and control groups did not display differences in any parameter analyzed. Following the treatment, LOS rats had lower SBP, DBP, PWV, thinner LVPWd, higher FS and smaller LV mass at 9- and 12-mo of age vs. control group (Fig.1A-F). In the reaction task, LOS rats demonstrated more correct responses and fewer premature responses. The LOS rats exhibited lower anxiety level, because they spent more time in the open arm of EPM vs. control rats (Fig.1G,H).Beneficial effect of LOS on cognitive function in aged male Dahl-S rats was associated with the improvement of cardiovascular function and remodeling. The CAS stabilizing and BP reduction by LOS treatment was associated with improved attentional performance, lower impulsivity and lower anxiety. The mechanistic basis of these effects of LOS on cognition via cerebrovascular and brain changes will be further investigated.

STREStrogen: The Dichotomous Role of Estrous Cycle on Anxiety‐like Behavior is Dependent upon Stress History

Stress‐induced psychiatric disorders are some of the most debilitating conditions worldwide and occur more often in women than men. Increased risk coincides with the reproductive years when circulating estrogen (E) levels peak, alluding to a critical role of ovarian hormones in susceptibility. Human stress studies support this association as E is linked to negative mood and anxiety during social stressors. However, preclinical research often reports opposing findings of protective effects of E in non‐stressed subjects, indicating reduced anxiety‐like behavioral responses. Yet, rodent studies often neglect to acknowledge the latent effects of stress on E‐induced behavioral differences, like the negative impact of a traumatic experience that perpetuates future interactions. Thus, this divergence between clinical and preclinical findings limits the capability of identifying adequate pharmacological targets for use in naturally cycling females. Therefore, we investigated if prior exposure to stress in intact adult female rats sensitized behavioral outcomes during anxiogenic tasks and whether this was contingent upon the current phase of estrous. Rats were exposed for 15 mins/day over 5 consecutive days to either control handling (CON) or witness stress (WS), a modified social defeat paradigm whereby a female observes social defeat from within a protected compartment of the aggressive resident’s cage. Forty‐eight hours after the 5th and final CON/WS exposure, rats underwent elevated plus maze (EPM) testing, and then acoustic startle response (ASR) testing the next day. Vaginal lavage was obtained immediately following EPM and ASR to confirm estrous phase. Analyses were conducted in a 2 x 2 fashion: stress exposure x estrous phase, in which metestrus/diestrus (M/D) signified putatively low levels of E, and proestrus/estrus (P/E) signified high levels. Results revealed a prominent stress exposure x estrous phase interaction for percentage of time spent in the closed and open arms of EPM. First, CON rats demonstrated reduced avoidance of the open arms when tested during P/E vs M/D. This is in line with studies reporting an anxiolytic effect of E. However, our findings in WS rats supports the notion that E is a critical component of sensitizing anxiety‐like responses in females with a history of stress. Specifically, WS rats demonstrated greater avoidance of open arms in the EPM during P/E vs M/D. Importantly, we also found that not all tests are impacted by cycle stage. Females with a history of stress demonstrated a sensitized startle amplitude compared with CON rats, independent of estrous phase, when tested for magnitude of the innate startle response. Further investigations into E receptor expression and subsequent signaling mechanisms in stress‐sensitive brain regions are necessary to determine how a history of stress modifies behavioral outcomes in the presence of high circulating E. These data can then elucidate novel therapeutic targets important for decreasing the high incidence of psychological disorders in this susceptible population.

Swimming Exercise Modulates Gut Microbiota in CUMS-Induced Depressed Mice.

BackgroundGut microbiota is associated with anxiety and depression, while exercise has been proved to alleviate depressive symptoms. However, the interaction of exercise, depression, and gut microbiota remains unclear.MethodsMale C57/BL6J mice were exposed to chronic unpredictable mild stress (CUMS) for 6 weeks and then were subjected to a 5-week swimming program. Behavioral tests, including sucrose preference test (SPT), open field test (OFT), elevated plus-maze (EPM) test, and tail suspension test (TST), were conducted to assess the anxiety-like and depressive behaviors. Gut microbiota analysis was carried out after sample collection.ResultsThis study showed that CUMS induced depressive behaviors, but swimming exercise increased sucrose preference rate in the SPT, increased time in the center and number of rearing in the OFT, decreased time in the closed arm and increased time in the open arm in EPM, and decreased immobility time in the TST. Firmicutes were the predominant phylum in the gut microbiome, followed by the phyla Bacteroidetes and Proteobacteria. We further found that CUMS and swimming influenced the relative abundance of the genus Desulfovibrio, genus Streptococcus, genus p-75-a5. Among the metabolic pathways, aromatic biogenic amine degradation (PWY-7431), mono-trans and polycis decaprenyl phosphate biosynthesis (PWY-6383), chlorosalicylate degradation (PWY-6107), mycothiol biosynthesis (PWY1G-0), mycolyl-arabinogalactan-peptidoglycan complex biosynthesis (PWY-6397), toluene degradation I (aerobic) (via o-cresol) (PWY-5180), toluene degradation II (aerobic) (via 4-methylcatechol) (PWY-5182), and starch degradation III (PWY-6731) may be related to the mechanism of anti-depression effect.ConclusionSwimming exercise reverses CUMS-induced depressive behaviors, and the alteration of gut microbiota composition and regulation of microbiota metabolic pathways are involved.

Swimming exercise reverses chronic unpredictable mild stress-induced depression-like behaviors and alleviates neuroinflammation and collapsing response mediator protein-2-mediated neuroplasticity injury in adult male mice.

ObjectiveImpaired neuroplasticity and neuroinflammation are vital in the mechanisms of depression. Exercise alleviates depressive symptoms and ameliorates body functions. Swimming is one of the most common exercises; however, whether swimming alters depressive behaviors and the underlying mechanism has not been fully elucidated.MethodsMale C57/BL6J mice were exposed to chronic unpredictable mild stress (CUMS) for 6 weeks and then were subjected to a 5-week swimming program. Behavioral test, including sucrose preference test (SPT), open field test (OFT), elevated plus-maze (EPM) test, and tail suspension test (TST), was conducted to assess the anxiety-like and depressive behaviors. Western blotting and immunofluorescence staining were carried out after tissue collection.ResultsThis study showed that CUMS-induced depressive behaviors but swimming exercise increased sucrose preference in SPT, increased time and velocity in the center on OFT, decreased time in the closed arm, increased time in the open arm in EPM, and decreased immobility time in TST. We further found swimming exercise increased hippocampal collapsing response mediator protein-2 (CRMP2) expression and decreased p-CRMP2 expression in CUMS mice. CUMS inhibited the levels of α-tubulin and CRMP2, and the expression of ionized calcium-binding adaptor molecule 1 and caspase-1, whereas swimming reversed them in CUMS-exercised mice.ConclusionOur study confirmed that swimming exercise reverses CUMS-induced depressive behaviors, and neuroinflammation and CRMP2-mediated neuroplasticity are involved, which may provide a new insight into the antidepression therapy of exercise.

Behavioral effects of a low molecular weight peptide fraction from Phaseolus vulgaris in rats.

Seminal studies stated that bean proteins are efficient neuronal tracers with affinity for brain tissue. A low molecular weight peptide fraction (<3kDa) from Phaseolus vulgaris (PV3) was previously reported to be antioxidant, non-cytotoxic, and capable of reducing reactive oxygen species and increasing nitric oxide in cells. We evaluated the effects of PV3 (5, 50, 100, 500, and 5000 µg/kg) on behavior and the molecular routes potentially involved. Acute and chronic PV3 treatments were performed before testing Wistar rats: i) in the elevated plus-maze (EPM) to assess the anxiolytic-like effect; ii) in the open field (OF) to evaluate locomotion and exploration; and iii) for depression-like behavior in forced swimming (FS). Catecholaminergic involvement was tested using the tyrosine hydroxylases (TH) enzyme inhibitor, α-methyl-DL-tyrosine (AMPT). Brain areas of chronically treated groups were dissected to assess: i) lipid peroxidation (LPO); ii) carbonylated proteins (CP); iii) superoxide dismutase (SOD) and catalase (CAT) enzymatic activities. Neuronal nitric oxide synthases (nNOS) and argininosuccinate synthase (ASS) protein expression was evaluated by western blotting. Acute treatment with PV3 increased the frequency and time spent in the EPM open arms, suggesting anxiolysis. PV3 increased crossing episodes in the OF. These PV3 effects on anxiety and locomotion were absent in the chronically treated group. Acute and chronic PV3 treatments reduced the immobility time in the FS test, suggesting an antidepressant effect. TH inhibition by AMPT reverted acute PV3 effects. PV3 decreased LPO and CP levels and SOD and CAT activities, whereas nNOS and ASS were reduced in few brain areas. In conclusion, PV3 displayed central antioxidant actions that are concomitant to catecholaminergic-dependent anxiolytic and antidepressant effects.

Assessment of homeopathic medicine Aconitum napellus in the treatment of anxiety in an animal model

Background: Aconitum napellus is a classic resource of complementary medicine for the treatment of patients exhibiting neurological symptoms of anxiety. Aim: To assess the action of homeopathic medicine Acon in the treatment of generalized anxiety in an experimental model using rats. Methods: 48 adult (two to three months old) male Wistar rats (Rattus rattus) were randomly divided in six groups (n= 8/treatment) and given the following treatments by gastric tube along 10 days: 1) control (diazepam 1 mg/kg/day); 2) negative control (0.15 mL saline solution/day); 3) ACH6 (0.15 mL Acon (6cH/day); 4) ACH12 (0.15 mL Acon 12cH/day); 5) ACH30 (0.15 mL Acon 30cH/day); and 6) ALC30 (0.15 mL 30% cereal alcohol/day). Behavioral effects were blindly and randomly assessed in elevated plus maze (EPM) and open field test. Results: Acon in dilutions 12cH and 30cH exhibited possible anxiolytic effects on the central nervous system (CNS) since they increased the number of entries in the EPM open arms (12cH and 30cH) and the permanence time in the EPM open arms (30cH only). In the open field test the homeopathic preparations did not show effects on the locomotor system of rats. Conclusion: Dilutions 12cH and 30cH of Acon exhibited anxiolytic effects on the CNS in an animal experimental model.

Putative Role of Monoaminergic Systems in Antidepressant and Anxiolytic Effects of Naringin in Mice: An Interaction Study with Receptor Antagonists

Aim: Stress-related disorders like depression and anxiety represent one of the greatest therapeutic challenges globally. Although previous studies have revealed the antidepressant-like potentials of naringin, the neurotransmitter receptor interaction mechanisms of action have not been studied, hence, this study was carried out to evaluate the role of neurotransmitter-receptor antagonists in the antidepressant-like effects of naringin in mice.&#x0D; Method: Male Swiss mice were subjected to chronic unpredictable mild stress (CUMS) apart from mice in the control group. The mice were then pretreated with different neurotransmitter antagonists; metergoline (4 mg /kg i.p.), a 5-HT1 - and 5-HT2 -receptor antagonist; propranolol; (0.2 mg/kg i.p.), β1,2-noradrenoceptor antagonist or haloperidol (0.2 mg/kg i.p.), D 2 -dopaminergic receptor antagonists prior to the administration of naringin or vehicle (10 mL/kg). The antidepressant-like and anxiolytic effects of naringin were evaluated 30 min later using the tail suspension test (TST), open-field test (OFT), sucrose preference test (SPT) and elevated plus maze (EPM) tests paradigms.&#x0D; Results: Administration of naringin following CUMS significantly decrease immobility time and locomotion activity in TST and OFT respectively, relative to control while increasing preference to sucrose in SPT, open arm entries as well as time spent in open arm in EPM, relative to control suggesting antidepressant-like property. Pretreatment with metergoline, propranolol, and haloperidol following CUMS increased immobility time in TST, locomotor activity in OFT and IOAA in the EPM. Reduced preference for sucrose in SPT, open arm entry and duration in EPM relative to control (p &lt; 0.05), however, these effects were attenuated by naringin.&#x0D; Conclusion: These findings suggest that the antidepressant-like activity exhibited by naringin might be mediated via interactions with 5-HTergic, noradrenergic, and dopaminergic receptors, while the anxiolytic effect might involve interaction with both 5-HTergic and noradrenergic receptors.

Systemic LPS-induced microglial activation results in increased GABAergic tone: A mechanism of protection against neuroinflammation in the medial prefrontal cortex in mice

Neuroinflammation with excess microglial activation and synaptic dysfunction are early symptoms of most neurological diseases. However, how microglia-associated neuroinflammation regulates synaptic activity remains obscure. We report here that acute neuroinflammation induced by intraperitoneal injection of lipopolysaccharide (LPS) results in cell-type-specific increases in inhibitory postsynaptic currents in the glutamatergic, but not the GABAergic, neurons of medial prefrontal cortex (mPFC), coinciding with excessive microglial activation. LPS causes upregulation in levels of GABAAR subunits, glutamine synthetase and vesicular GABA transporter, and downregulation in brain-derived neurotrophic factor (BDNF) and its receptor, pTrkB. Blockage of microglial activation by minocycline ameliorates LPS-induced abnormal expression of GABA signaling-related proteins and activity of synaptic and network. Moreover, minocycline prevents the mice from LPS-induced aberrant behavior, such as a reduction in total distance and time spent in the centre in the open field test; decreases in entries into the open arm of elevated-plus maze and in consumption of sucrose; increased immobility in the tail suspension test. Furthermore, upregulation of GABA signaling by tiagabine also prevents LPS-induced microglial activation and aberrant behavior. This study illustrates a mode of bidirectional constitutive signaling between the neural and immune compartments of the brain, and suggests that the mPFC is an important area for brain–immune system communication. Moreover, the present study highlights GABAergic signaling as a key therapeutic target for mitigating neuroinflammation-induced abnormal synaptic activity in the mPFC, together with the associated behavioral abnormalities.