Elevated Zero Maze Research Articles

(2R,6R)-Hydroxynorketamine Treatment of Rats Exposed to Repetitive Low-Level Blast Injury.

Many military veterans who experienced blast-related traumatic brain injuries (TBIs) in the conflicts in Iraq and Afghanistan suffer from chronic cognitive and mental health problems, including post-traumatic stress disorder (PTSD). Male rats subjected to repetitive low-level blast exposure develop chronic cognitive and PTSD-related traits that develop in a delayed manner. Ketamine has received attention as a treatment for refractory depression and PTSD. (2R,6R)-hydroxynorketamine [(2R,6R)-HNK] is a ketamine metabolite that exerts rapid antidepressant actions. (2R,6R)-HNK has become of clinical interest because of its favorable side-effect profile, low abuse potential, and oral route of administration. We treated three cohorts of blast-exposed rats with (2R,6R)-HNK, beginning 7-11 months after blast exposure, a time when the behavioral phenotype is established. Each cohort consisted of groups (n = 10-13/group) as follows: 1) Sham-exposed treated with saline, 2) blast-exposed treated with saline, and 3) blast-exposed treated with a single dose of 20 mg/kg of (2R,6R)-HNK. (2R,6R)-HNK rescued blast-induced deficits in novel object recognition (NOR) and anxiety-related features in the elevated zero maze (EZM) in all three cohorts. Exaggerated acoustic startle was reversed in cohort 1, but not in cohort 3. (2R,6R)-HNK effects were still present in the EZM 12 days after administration in cohort 1 and 27 days after administration in NOR testing of cohorts 2 and 3. (2R,6R)-HNK may be beneficial for the neurobehavioral syndromes that follow blast exposure in military veterans. Additional studies will be needed to determine whether higher doses or more extended treatment regimens may be more effective.

A 2-hit model of early life stress and later life restraint stress: Susceptibility or resilience to anxiety and alcohol drinking?

Early life stress adversely influences neurodevelopment and has profound long-term effects on brain function and behavior. Here we measure endogenous stress hormone and determine locomotor, anxiogenic, and operant binge drinking behavior of rats exposed to a 2-hit model of maternal deprivation (MD) stress in infancy followed by acute (ARS) or chronic restraint stress (CRS) paradigms during adolescence/adulthood to determine resiliency or susceptibility to the second stress exposure. Adolescents (n=40) exhibited higher baseline corticosterone (CORT) levels than adults (n=40) and with CRS exposure, showed significantly elevated circulating CORT irrespective of MD exposure status. In adults, MD females had lower baseline CORT levels than controls, whereas MD and control male CORT were indistinguishable. For behavior, N=40 was used in total. In the open field, locomotion was significantly decreased upon ARS, with MD having a significant sustained impact on ambulatory measures with CRS. When tested for anxiety-like behavior on an elevated zero maze, ARS interacted with MD to induce protracted and more profound anxiogenic behavior. Upon CRS, MD anxiogenic behavior was reversed to baseline levels whereas controls, especially males, exceeded baseline levels to spend significantly more time in the open arms of the EZM. Finally, in testing for binge drinking behavior, MD rats lever-pressed significantly more for 10% ethanol on an operant apparatus and exhibited a 3-fold greater drinking baseline than controls. Binge drinking behavior was further elevated with ARS, but quickly returned to the MD baseline even prior to reaching CRS. By contrast, controls had much lower baseline but significantly elevated binge drinking behavior by 3–5-fold in response to ARS which remained elevated through CRS, stabilizing at MD baseline levels. Sex differences were most evident in controls where males exhibited accelerated binge drinking behavior at consistently higher rates than females until Day 21 of CRS where their binge drinking behaviors were similar. There was also a main effect of alcohol binge behavior for MD males, and not females. This study illustrates that, depending on the biobehavioral output, males and females differ in reactivity to stressors where MD stress may confer sex-dependent resilience to subsequent stressors, and males are differently impacted than females.

Social isolation from early life induces anxiety-like behaviors in adult rats: Relation to neuroendocrine and neurochemical dysfunctions

Subjects suffering from psychosis frequently experience anxiety. However, mechanisms underlying this comorbidity remain still unclear. We investigated whether neurochemical and neuroendocrine dysfunctions were involved in the development of anxiety-like behavior in a rodent model of psychotic-like symptoms, obtained by exposing male rats to social isolation rearing from postnatal day 21 to postnatal day 70. In the elevated zero maze test, isolated rats showed a significant reduction in the time spent in the open arms, as well as an increase in the time spent in the closed arms, compared to controls. An increased grooming time in the open field test was also observed in isolated animals. Isolation-induced anxiety-like behavior was accompanied by a decrease of plasmatic oxytocin, prolactin, ghrelin and melatonin levels, whereas plasmatic amount of Neuropeptide S was not altered. Social isolation also caused a reduction of noradrenaline, serotonin and GABA levels, together with an increase of serotonin turnover and glutamate levels in the amygdala of isolated animals. No significant differences were found in noradrenaline and serotonin levels, as well as in serotonin turnover in hippocampus, while glutamate amount was increased and GABA levels were reduced in isolated rats. Furthermore, there was a reduction in plasmatic serotonin content, and an increase in plasmatic kynurenine levels following social isolation, while no significant changes in serotonin turnover were observed. Taken together, our data provide novel insights in the neurobiological alterations underlying the comorbidity between psychosis and anxiety, and open new perspectives for multi-target therapies acting on both neurochemical and neuroendocrine pathways. Data availability statementThe data presented in this study are available on request from the corresponding author.

Involvement of Microbiome Gut-Brain Axis in Neuroprotective Effect of Quercetin in Mouse Model of Repeated Mild Traumatic Brain Injury.

Repeated mild traumatic brain injury (rmTBI) poses adversity in the form of neurological deficits. The ignition of long-term neurological aberrations post-TBI is appended with the microbiota gut-brain axis perturbation. Herein, we examined whether quercetin, which is anti-inflammatory and antioxidant flavonoid, serves as a prebiotic and modifies the compromised microbiome gut-brain axis in rmTBI mouse model. Male C57BL/6 mice were subjected to rmTBI for 7 times. The quercetin (50mg/kg) was administered peroral from the day1 of first injury till 7days post-injury. The neurobehavioral assessments were performed using return of righting reflex (ROR), rotarod, forced swimming test (FST), elevated zero maze (EZM), novel object recognition test (NORT), and Y-maze. Mice fecal samples, brains, and intestines were collected for molecular studies. Mice underwent rmTBI showed significant neurological deficits in ROR and rotarod test and also exhibited long-term neuropsychiatric aberrations like anxiety- and depression-like phenotypes, and cognitive deficits in EZM, FST, and Y-maze assays, respectively. Repeated peroral administration of quercetin ameliorated these neuropsychiatric problems. Quercetin treatment also restored the increased expression of GFAP and decreased expression of occludin and doublecortin in the frontal cortex and hippocampus of rmTBI mice. The altered levels of acetate and propionate, and microbial phylum abundance in fecal samples were also normalized in the quercetin-treated group. We also noted an improved intestinal permeability indicated by reduced villi rupture, blunting, and mucosal thinning in quercetin-treated mice. We suggest that the neuroprotective effect of quercetin may be mediated via remodeling of the microbiome gut-brain axis in rmTBI mouse model.

Sex Differences in the Behavioural Aspects of the Cuprizone-Induced Demyelination Model in Mice.

Multiple sclerosis is an autoimmune disease characterised by demyelination in the central nervous system. The cuprizone-induced demyelination model is often used in mice to test novel treatments for multiple sclerosis. However, despite significant demyelination, behavioural deficits may be subtle or have mixed results depending on the paradigm used. Furthermore, the sex differences within the model are not well understood. In the current study, we have sought to understand the behavioural deficits associated with the cuprizone-induced demyelination model in both male and female C57BL/6J mice. Using Black gold II stain, we found that cuprizone administration over 6 weeks caused significant demyelination in the corpus callosum that was consistent across both sexes. Cuprizone administration caused increased mechanical sensitivity when measured using an electronic von Frey aesthesiometer, with no sex differences observed. However, cuprizone administration decreased motor coordination, with more severe deficits seen in males in the horizontal bar and passive wire hang tests. In contrast, female mice showed more severe deficits in the motor skill sequence test. Cuprizone administration caused more anxiety-like behaviours in males compared to females in the elevated zero maze. Therefore, this study provides a better understanding of the sex differences involved in the behavioural aspects of cuprizone-induced demyelination, which could allow for a better translation of results from the laboratory to the clinic.

Transgenerational transmission of aspartame-induced anxiety and changes in glutamate-GABA signaling and gene expression in the amygdala

We report the effects of aspartame on anxiety-like behavior, neurotransmitter signaling and gene expression in the amygdala, a brain region associated with the regulation of anxiety and fear responses. C57BL/6 mice consumed drinking water containing 0.015% or 0.03% aspartame, a dose equivalent of 8 to 15% of the FDA recommended maximum human daily intake, or plain drinking water. Robust anxiety-like behavior (evaluated using open field test and elevated zero maze) was observed in male and female mice consuming the aspartame-containing water. Diazepam, an allosteric modulator of the GABA-A receptor, alleviated the anxiety-like behavior. RNA sequencing of the amygdala followed by KEGG biological pathway analysis of differentially expressed genes showed glutamatergic and GABAergic synapse pathways as significantly enriched. Quantitative PCR showed upregulation of mRNA for the glutamate NMDA receptor subunit 2D (Grin2d) and metabotropic receptor 4 (Grm4) and downregulation of the GABA-A receptor associated protein (Gabarap) mRNA. Thus, taken together, our diazepam and gene expression data show that aspartame consumption shifted the excitation-inhibition equilibrium in the amygdala toward excitation. Even more strikingly, the anxiety-like behavior, its response to diazepam, and changes in amygdala gene expression were transmitted to male and female offspring in two generations descending from the aspartame-exposed males. Extrapolation of the findings to humans suggests that aspartame consumption at doses below the FDA recommended maximum daily intake may produce neurobehavioral changes in aspartame-consuming individuals and their descendants. Thus, human population at risk of aspartame's potential mental health effects may be larger than current expectations, which only include aspartame-consuming individuals.

Early life stress exacerbates bone resorption and inhibitsanxiety-like behaviour induced by apical periodontitis in rats.

To evaluate the influence of the early life stress (ELS) on the severity of the apical periodontitis (AP) in Wistar rats. Forty male Wistar rats were divided into four groups (n=10): Control rats; AP-rats with AP; ELS-rats subject to ELS; AP + ELS-rats exposed to ELS and subject to AP. ELS was induced by maternal separation (MS) for a period of 3h for 21 consecutive days. AP was induced via pulp exposure of the first and second right maxillary molars to the oral environment for 40 days. Three days before euthanasia, all rats underwent behavioural analysis to measure anxiety levels by elevated zero maze. Then, the rats were euthanized and the maxillas were removed to assess the occurrence and severity of AP. The periapical region was evaluated for the intensity of the inflammatory infiltrate and the extent of bone loss. The Mann-Whitney test was performed for nonparametric data, and the Tukey's or Student's t-test was performed for parametric data (p < .05). The intensity of the inflammatory infiltrate was significantly larger in the AP + ELS group when compared with AP group (p < .05). The AP + ELS group exhibited significantly greater alveolar bone loss, with a periapical lesion size of 103.5 ± 29.88, compared with 72.3 ± 22.28 in the AP group (p < .05). Rats with AP displayed higher anxiety-like behaviour in relation to the control group (p < .05). However, exposure to ELS abolished the AP-induced increased anxiety-like 'behaviour' throughout, since that rats from AP + ELS group attended more the open arms than non-stressed rats with AP (p < .05). Early life stress is predictive of the severity of AP exacerbating the inflammatory process and increasing periapical bone resorption.

DISP-13. FEMALE MICE HAVE GREATER SUSTAINED ACTIVITY SUPPRESSION AND HYPERSOMNOLENCE AFTER RADIATION THERAPY: EXPLORATION OF SEX DIFFERENCES IN A MODEL OF CRANIAL-RADIATION-INDUCED HYPERSOMNOLENCE (C-RIH)

Abstract Female cancer patients have a better prognosis but more adverse events with chemotherapy; less is known with other cancer treatments like radiation therapy. Previous literature has demonstrated sex-dependent effects on the hippocampi and behavioral tasks within post-natal mice after radiotherapy. We explored the differences in activity and sleep in adult male and female mice within our previously established mouse model of cranial-irradiation-induced hypersomnolence (C-RIH). Ten mice of each sex (B6 x B6D2 backcrossed with C57/b6NCr) were observed for general activity and sleep continuously over 10 days before and after therapeutic irradiation (whole brain, 15Gy, single fraction). Behavioral assessments aimed at measuring anxiety (Light Dark Box, Elevated Zero Maze) and depression (Sucrose Preference Test) related behaviors, and working memory (Y Maze) were then used to assess any radiation-induced changes in mood or cognition. Independent samples t-tests compared male and female cohorts before and after radiation. At baseline, females had significantly higher peak activity (p &amp;lt; 0.001), as well as day (p &amp;lt; 0.001), and night (p = 0.004) activity. Females also showed less anxiety in the Elevated Zero Maze (p &amp;lt; 0.001) and Light-Dark Box (p = 0.012). In the Y-Maze, females had significantly more alternations (entry into each arm without repeat) (p = 0.004). Males and females consumed the same proportion of sucrose solution in respect to water (p = 0.124). After radiation, males and females showed a significant decrease in activity, with females displaying a higher suppression of night activity both 1-3 days (t(18) = 2.162, p = 0.045) and 7-9 days (t(18) = 2.266, p = 0.037). Female mice also showed increased night hypersomnolence at 1-3 days (t(18) = 4.474, &amp;lt; p = 0.001) and 7-9 days (t(18) = 2.920, p = 0.01). Further analysis is underway on post-radiation sex differences in sleep and activity. Here we used a mouse model of C-RIH to assess the behavioral outcomes between the sexes and found marked effects on sleep and activity.

C-type natriuretic peptide preserves central neurological function by maintaining blood-brain barrier integrity.

C-type natriuretic peptide (CNP) is highly expressed in the central nervous system (CNS) and key to neuronal development; however, a broader role for CNP in the CNS remains unclear. To address this deficit, we investigated behavioral, sensory and motor abnormalities and blood-brain barrier (BBB) integrity in a unique mouse model with inducible, global deletion of CNP (gbCNP–/–). gbCNP–/– mice and wild-type littermates at 12 (young adult) and 65 (aged) weeks of age were investigated for changes in gait and motor coordination (CatWalk™ and rotarod tests), anxiety-like behavior (open field and elevated zero maze tests), and motor and sensory function (modified neurological severity score [mNSS] and primary SHIRPA screen). Vascular permeability was assessed in vivo (Miles assay) with complementary in vitro studies conducted in primary murine brain endothelial cells. Young adult gbCNP–/– mice had normal gait but reduced motor coordination, increased locomotor activity in the open field and elevated zero maze, and had a higher mNSS score. Aged gbCNP–/– animals developed recurrent spontaneous seizures and had impaired gait and wide-ranging motor and sensory dysfunction. Young adult and aged gbCNP–/– mice exhibited increased BBB permeability, which was partially restored in vitro by CNP administration. Cultured brain endothelial cells from gbCNP–/– mice had an abnormal ZO-1 protein distribution. These data suggest that lack of CNP in the CNS impairs tight junction protein arrangement and increases BBB permeability, which is associated with changes in locomotor activity, motor coordination and late-onset seizures.

Aconitum Alkaloid Songorine Exerts Potent Gamma-Aminobutyric Acid-A Receptor Agonist Action In Vivo and Effectively Decreases Anxiety without Adverse Sedative or Psychomotor Effects in the Rat.

Songorine (SON) is a diterpenoid alkaloid from Aconitum plants. Preparations of Aconitum roots have been employed in traditional oriental herbal medicine, however, their mechanisms of action are still unclear. Since GABA-receptors are possible brain targets of SON, we investigated which subtypes of GABA-receptors contribute to the effects of SON, and how SON affects anxiety-like trait behavior and psychomotor cognitive performance of rats. First, we investigated the effects of microiontophoretically applied SON alone and combined with GABA-receptor agents picrotoxin and saclofen on neuronal firing activity in various brain areas. Next, putative anxiolytic effects of SON (1.0–3.0 mg/kg) were tested against the GABA-receptor positive allosteric modulator reference compound diazepam (1.0–5.0 mg/kg) in the elevated zero maze (EOM). Furthermore, basic cognitive effects were assessed in a rodent version of the psychomotor vigilance task (PVT). Local application of SON predominantly inhibited the firing activity of neurons. This inhibitory effect of SON was successfully blocked by GABA(A)-receptor antagonist picrotoxin but not by GABA(B)-receptor antagonist saclofen. Similar to GABA(A)-receptor positive allosteric modulator diazepam, SON increased the time spent by animals in the open quadrants of the EOM without any signs of adverse psychomotor and cognitive effects observed in the PVT. We showed that, under in vivo conditions, SON acts as a potent GABA(A)-receptor agonist and effectively decreases anxiety without observable side effects. The present findings facilitate the deeper understanding of the mechanism of action and the widespread pharmacological use of diterpene alkaloids in various CNS indications.

Mice lacking proSAAS display alterations in emotion, consummatory behavior and circadian entrainment.

ProSAAS is a neuroendocrine protein that is cleaved by neuropeptide-processing enzymes into more than a dozen products including the bigLEN and PEN peptides, which bind and activate the receptors GPR171 and GPR83, respectively. Previous studies have suggested that proSAAS-derived peptides are involved in physiological functions that include body weight regulation, circadian rhythms and anxiety-like behavior. In the present study, we find that proSAAS knockout mice display robust anxiety-like behaviors in the open field, light-dark emergence and elevated zero maze tests. These mutant mice also show a reduction in cued fear and an impairment in fear-potentiated startle, indicating an important role for proSAAS-derived peptides in emotional behaviors. ProSAAS knockout mice exhibit reduced water consumption and urine production relative to wild-type controls. No differences in food consumption and overall energy expenditure were observed between the genotypes. However, the respiratory exchange ratio was elevated in the mutants during the light portion of the light-dark cycle, indicating decreased fat metabolism during this period. While proSAAS knockout mice show normal circadian patterns of activity, even upon long-term exposure to constant darkness, they were unable to shift their circadian clock upon exposure to a light pulse. Taken together, these results show that proSAAS-derived peptides modulate a wide range of behaviors including emotion, metabolism and the regulation of the circadian clock.

Lion's Mane (Hericium erinaceus) Exerts Anxiolytic Effects in the rTg4510 Tau Mouse Model.

Alzheimer’s disease (AD) significantly impairs the life of an individual both cognitively and behaviorally. Tau and beta-amyloid (Aβ) proteins are major contributors to the etiology of AD. This study used mice modeling AD through the presence of tau pathology to assess the effects of Hericium erinaceus (H. erinaceus), also known as Lion’s mane, on cognitive and non-cognitive behaviors. Despite neurocognitive and neurobiological effects of H. erinaceus being seen in both healthy and transgenic mice, no research to date has explored its effects on mice with solely tau pathology. In this study, mice were placed on a diet supplemented with H. erinaceus or a standard rodent diet for 4.5 months in order to determine the effect of this medicinal mushroom on behavior. Tau mice given H. erinaceus had significantly shorter latencies to enter the center of the open field (OF) (p < 0.05) and spent significantly more time in the open arms of the elevated zero maze (EZM) (p < 0.001) compared to tau control mice. Mice given H. erinaceus spent significantly more time in the open arms of and made more head dips in the elevated zero maze (EZM) (p < 0.05). While H. erinaceus had anxiolytic effects, no improvements were seen in spatial memory or activities of daily living. These findings provide additional support for the anxiolytic effects of H. erinaceus and point to its potential benefit as a therapeutic for anxiety in AD.

Nanocurcumin substantially alleviates noise stress-induced anxiety-like behavior: The roles of tight junctions and NMDA receptors in the hippocampus

Environmental noise stress affects non-auditory brain regions such as the hippocampus; an area of the brain implicated in cognition and emotion. Recent experimental data indicate that dysfunction of the blood-brain barrier (BBB) and overexpression of NMDA receptors may cause anxiety. In this experiment, we evaluated the effect of nanocurcumin on anxiety-like behavior and the expression of tight junctions and NMDA receptor subunits in the hippocampus of rats exposed to traffic noise. Forty rats were assigned to control (CON), stress (ST), nanocurcumin (NC), and nanocurcumin+stress (NC+ST) groups. Anxiety-like behavior was evaluated through an elevated zero maze apparatus. The gene expression of tight junctions and NMDA receptor subunits was examined by real-time PCR in the hippocampus. Statistical analysis showed that noise exposure developed anxiety-like behavior and elevated the corticosterone level in the ST group compared to the CON group. The nanocurcumin administration decreased the stress and anxiety in the NC+ST group compared to the ST animals. While the noise stress reduced the gene expression of tight junctions occludin, claudin-5, and ZO-1, the nanocurcumin administration increased them in the NC+ST animals. Furthermore, the noise stress elevated the gene expression of the NMDA receptor subunits GRIN1 and GRIN2B. The NC+ST animals showed a modification of these subunits compared to the ST animals. Our findings showed that noise exposure promotes stress and anxiety and impairs the NMDA receptor structure and BBB integrity. The nanocurcumin treatment partly restores the destructive effects of noise exposure.

Limbic Responses Following Shock Wave Exposure in Male and Female Mice.

Blast traumatic brain injury (bTBI) presents a serious threat to military personnel and often results in psychiatric conditions related to limbic system dysfunction. In this study, the functional outcomes for anxiety- and depressive-like behaviors and neuronal activation were evaluated in male and female mice after exposure to an Advanced Blast Simulator (ABS) shock wave. Mice were placed in a ventrally exposed orientation inside of the ABS test section and received primary and tertiary shock wave insults of approximately 15 psi peak pressure. Evans blue staining indicated cases of blood-brain barrier breach in the superficial cerebral cortex four, but not 24 h after blast, but the severity was variable. Behavioral testing with the elevated plus maze (EPM) or elevated zero maze (EZM), sucrose preference test (SPT), and tail suspension test (TST) or forced swim test (FST) were conducted 8 days–3.5 weeks after shock wave exposure. There was a sex difference, but no injury effect, for distance travelled in the EZM where female mice travelled significantly farther than males. The SPT and FST did not indicate group differences; however, injured mice were less immobile than sham mice during the TST; possibly indicating more agitated behavior. In a separate cohort of animals, the expression of the immediate early gene, c-Fos, was detected 4 h after undergoing bTBI or sham procedures. No differences in c-Fos expression were found in the cerebral cortex, but female mice in general displayed enhanced c-Fos activation in the paraventricular nucleus of the thalamus (PVT) compared to male mice. In the amygdala, more c-Fos-positive cells were observed in injured animals compared to sham mice. The observed sex differences in the PVT and c-Fos activation in the amygdala may correlate with the reported hyperactivity of females post-injury. This study demonstrates, albeit with mild effects, behavioral and neuronal activation correlates in female rodents after blast injury that could be relevant to the incidence of increased post-traumatic stress disorder in women.

Electroacupuncture Alleviates Anxiety-like Behavior in Pain Aversion Rats by Attenuating the Expression of Neuropeptide Y in Anterior Cingulate Cortex

Pain is considered as a multidimensional conscious experience that includes a sensory component and a negative affective-motivational component. Electroacupuncture (EA) is widely used to treat pain and pain-induced negative emotions, however, little is known about the mechanisms underlying the effect of EA. This study investigated the effect of EA on alleviating the anxiety-like behaviors in pain aversion rats and its anterior cingulate cortex (ACC) regulation mechanism. After a Freund's complete adjuvant (CFA)-conditioned place aversion (C-CPA) model was established in rats, EA treatment (2/100 Hz, 30 min, once/day, 4 days totally) was applied at bilateral Zusanli (ST36) and Kunlun (BL60) acupoints. Von Frey filaments were used to measure changes of pain withdrawal threshold (PWT) at indicated time points. Elevated zero maze (EZM) was used to investigate the changes of pain-related anxiety and CPA was used to investigate the changes of pain aversion. The protein expression levels of GAD67, PV, and NPY in ACC were detected by Western blotting. Compared with the control group, the staying time in the "CFA-paired compartment" was significantly reduced, and the PWT was decreased in model group. In the EZM assessment, the distance and the time in open arm, as well as the number of open arm entries of model group were significantly lower than those in the control group. In the CPA assessment, the time spent in the "CFA-paired compartment" was significantly decreased in model group compared with control group, and EA reversed the changes in pain sensation and in pain-related emotions. Western blotting showed that the NPY level, but not the levels of GAD67 and PV, was significantly increased in the ACC of the model group compared to that of the control group. The increased expression of NPY in the ACC was significantly downregulated by EA, while sham EA produced no such effect. EA can effectively relieve the pain and pain-related emotions, and its mechanism may be achieved by down-regulating the expression of NPY in the ACC. EA stimulation effectively reverses chronic inflammatory pain and its negative emotions by downregulating the expression of NPY protein in the ACC

The Impact of Chronic Unpredictable Mild Stress-Induced Depression on Spatial, Recognition and Reference Memory Tasks in Mice: Behavioral and Histological Study.

Depression-induced cognitive impairment has recently been given more attention in research. However, the relationship between depression and different types of memory is still not clear. Chronic unpredictable mild stress (CUMS) is a commonly used animal model of depression in which animals are exposed to chronic unpredictable environmental and psychological stressors, which mimics daily human life stressors. This study investigated the impact of different durations of CUMS on various types of memory (short- and long-term spatial memory and recognition memory) and investigated CUMS’ impact on the ultrastructural level by histological assessment of the hippocampus and prefrontal cortex. Twenty male C57BL/J6 mice (6 weeks old, 21.8 ± 2 g) were randomly divided into two groups (n = 10): control and CUMS (8 weeks). A series of behavioral tasks were conducted twice at weeks 5–6 (early CUMS) and weeks 7–8 (late CUMS). A tail-suspension test (TST), forced swimming test (FST), elevated zero maze (EZM), elevated plus maze (EPM), open field test (OFT), and sucrose-preference test (SPT) were used to assess anxiety and depressive symptoms. The cognitive function was assessed by the novel object recognition test (NORT; for recognition memory), Y-maze (for short-term spatial memory), and Morris water maze (MWM: for long-term spatial memory) with a probe test (for reference memory). Our data showed that 8 weeks of CUMS increased the anxiety level, reported by a significant increase in anxiety index in both EPM and EZM and a significant decrease in central preference in OFT, and depression was reported by a significant increase in immobility in the TST and FST and sucrose preference in the SPT. Investigating the impact of CUMS on various types of memory, we found that reference memory is the first memory to be affected in early CUMS. In late CUMS, all types of memory were impaired, and this was consistent with the abnormal histological features of the memory-related areas in the brain (hippocampus and prefrontal cortex).

Neonatal Opioid Withdrawal Syndrome in Mice: Acute Molecular and Long‐Term Behavioral Consequences

Populations affected by the ongoing opioid epidemic include pregnant women and their offspring. Infants exposed to opioids in utero are at risk of developing Neonatal Opioid Withdrawal Syndrome (NOWS), a combination of somatic withdrawal symptoms including high pitched crying, sleeplessness, irritability, and potentially seizures. Confounding environmental factors and difficulty in conducting longitudinal clinical studies have made it challenging to elucidate the long‐term consequences of NOWS. In order to investigate the molecular mechanisms and long‐term effects of NOWS, we have developed a mouse model of opioid exposure and withdrawal that encompasses the developmental equivalent of all three trimesters of the human pregnancy. Female mice are implanted with morphine minipumps (10 mg/kg/day) before mating, ensuring that pups are exposed to morphine in utero for the entirety of embryonic development. Mice are then given twice daily morphine injections (10 mg/kg/day, SC) for post‐natal days 1‐14. Mice are tested for developmental milestones during this period, including eye opening, extinguishing pivoting, surface righting, and forelimb grasp. Following the final morphine injection withdrawal behaviors were measured by ultrasonic vocalizations, 55°C hotplate analgesia latency, and somatic withdrawal signs. After reaching adulthood, mice were tested for changes in affective behavior (elevated zero maze, tail suspension test and learned helplessness), opioid response (conditioned place preference and intravenous self‐administration), social behavior (three‐chamber social behavior test), and sleep patterns. Mice exposed to this paradigm show delayed latency to reach developmental milestones and acute withdrawal phenotypes. In adulthood, social behavior and sleep patterns were affected in a sex‐dependent manner, while affective behavior and opioid response was unchanged. Bulk RNA sequencing of mice at post‐natal day 1 revealed changes in gene expression related to synapse development and function, the GABAergic system, and mitochondrial function. These transcriptome changes may underlie the behavioral long‐term effects of NOWS.

A role for BD2‐selective BET inhibitors in cocaine‐seeking behaviors

Epigenetic mechanisms play important roles in the maladaptive transcriptional and behavioral responses to drugs of abuse. Inhibition of bromodomain and extra‐terminal domain (BET) proteins, a class of histone acetylation reader proteins, has been shown to reduce cocaine‐seeking behaviors in animal models of addiction. To date, the role of BET protein in animal models of substance use disorder (SUD) has only been evaluated using pan‐BET inhibitors, small molecules that bind to both bromodomains (BD1 and BD2) in all BET proteins. Although these initial studies are encouraging, side effects associated with pan‐BET inhibitors may limit their clinical utility as a SUD treatment. In order to evaluate safer and more selective approaches, we utilized a clinically tested BD2 selective BET inhibitor, RVX‐208. We show that RVX‐208 dose‐dependently reduced cocaine conditioned place preference in male mice, similar to the pan‐BET inhibitor JQ1. Additionally, RVX‐208 did not alter other behaviors, such as: locomotor activity, elevated zero maze, or novel object recognition memory. At the transcriptional level, RVX‐208 attenuated the expression of multiple cocaine‐induced genes in the nucleus accumbens. RVX‐208 also produced a distinct transcriptional response in stimulated primary neurons compared to JQ1 but had little effect on gene expression in non‐stimulated neurons. Together, these data indicate that targeting domain‐specific BET mechanisms may be an effective and safer strategy to reduce cocaine‐induced neurobehavioral adaptations.

Effects of a psychedelic 5-HT2A receptor agonist on anxiety-related behavior and fear processing in mice.

Psychedelic-assisted psychotherapy gained considerable interest as a novel treatment strategy for fear-related mental disorders but the underlying mechanism remains poorly understood. The serotonin 2A (5-HT2A) receptor is a key target underlying the effects of psychedelics on emotional arousal but its role in fear processing remains controversial. Using the psychedelic 5-HT2A/5-HT2C receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) and 5-HT2A receptor knockout (KO) mice we investigated the effect of 5-HT2A receptor activation on emotional processing. We show that DOI administration did not impair performance in a spontaneous alternation task but reduced anxiety-like avoidance behavior in the elevated plus maze and elevated zero maze tasks. Moreover, we found that DOI did not block memory recall but diminished fear expression in a passive avoidance task. Likewise, DOI administration reduced fear expression in an auditory fear conditioning paradigm, while it did not affect retention of fear extinction when administered prior to extinction learning. The effect of DOI on fear expression was abolished in 5-HT2A receptor KO mice. Administration of DOI induced a significant increase of c-Fos expression in specific amygdalar nuclei. Moreover, local infusion of the 5-HT2A receptor antagonist M100907 into the amygdala reversed the effect of systemic administration of DOI on fear expression while local administration of DOI into the amygdala was sufficient to suppress fear expression. Our data demonstrate that activation of 5-HT2A receptors in the amygdala suppresses fear expression but provide no evidence for an effect on retention of fear extinction.

Iron Chelation Remits Memory Deficits Caused by the High-Fat Diet in a Mouse Model of Alzheimer's Disease.

Obesity is a worldwide health problem that has been implicated in many diseases, including Alzheimer's disease (AD). AD is one of the most common neurodegenerative disorders and is characterized by two pathologies, including extracellular senior plaques composed of amyloid-β (Aβ) and intracellular neurofibrillary tangles (NFTs) consisting of abnormally hyperphosphorylated tau. According to current research, a high-fat diet (HFD) could exacerbate Aβ accumulation, oxidative damage, and cognitive defects in AD mice. However, the accurate role of HFD in the pathogenesis of AD is far more unclear. To explore the accurate role of HFD in the pathogenesis of AD. Open Field, Barns Maze, Elevated zero-maze, Contextual fear condition, Tail suspension test, western blotting, immunofluorescence, Fluoro-Jade C Labeling, Perls' Prussian blue staining, and ELISA were used. HFD caused nonheme iron overload in the brains of APPswe/PS1dE9 (APP/PS1) mice. Furthermore, the administration of M30 (0.5 mg/kg) for iron chelation once every 2 days per os (p.o.) for 1 month remitted memory deficits caused by HFD in APP/PS1 mice. Notably, a variety of hematological parameters in whole blood had no difference after iron chelation. In addition, iron chelation effectively reduced synaptic impairment in hippocampus and neuronal degeneration in cortex in the HFD-fed APP/PS1 mice. Meanwhile, iron chelation decreased Aβ1-40 and Aβ1-42 level as well as neuroinflammation in HFD-fed APP/PS1 mice. These data enhance our understanding of how HFD aggravates AD pathology and cognitive impairments and might shed light on future preclinical studies.