The use of the elevated plus maze as an assay of anxiety-related behavior in rodents

L-type calcium channel regulation of depression, anxiety and anhedonia-related behavioral phenotypes following chronic stress exposure

Exposure to chronic and unpredictable stressors can precipitate mood-related disorders in humans, particularly in individuals with pre-existing mental health challenges. L-type calcium channels (LTCCs) have been implicated in numerous neuropsychiatric disorders, as LTCC encoding genes have been identified as candidate risk factors for neuropsychiatric illnesses. In these sets of experiments, we sought to examine the ability of LTCC blockade to alter depression, anxiety, and anhedonic-related behavioral responses to chronic unpredictable stress (CUS) exposure in female and male rats. Rats first underwent either 21 days of CUS or no exposure to chronic stressors, serving as home cage controls (HCC). Then rats were examined for anhedonia-related behavior, anxiety and depression-like behavioral responses as measured by the sucrose preference test (SPT), elevated plus maze (EPM), and forced swim test (FST). CUS exposed females and males showed anhedonic and anxiogenic-like behavioral responses on the SPT and EPM, respectively, when compared to HCCs. In female and male rats, systemic administration of the LTCC blocker isradipine (0.4 mg/kg and 1.2 mg/kg, I.P.) attenuated the CUS-induced decrease in sucrose preference and reversed the CUS-induced decrease in open arm time. In the FST, systemic isradipine decreased immobility time across all groups, consistent with an antidepressant-like response. However, there were no significant differences in forced swim test immobility time between HCC and CUS exposed animals. Taken together, these data point to a role of LTCCs in the regulation of mood disorder-related behavioral phenotype responses to chronic stress exposure.

Acute Stress Affects the Relaxin/Insulin-Like Family Peptide Receptor 3 mRNA Expression in Brain of Pubertal Male Wistar Rats

The current literature suggests that relaxin-3/relaxin/insulin-like family peptide receptor 3 (RLN-3/RXFP-3) system is involved in the pathophysiology of affective disorders because the results of anatomical and pharmacological studies have shown that the RLN-3 signaling pathway plays a role in modulating the stress response, anxiety, arousal, depression-like behavior, and neuroendocrine homeostasis. The risk of developing mental illnesses in adulthood is increased by exposure to stress in early periods of life. The available data indicate that puberty is especially characterized by the development of the neural system and emotionality and is a "stress-sensitive" period. The presented study assessed the short-term changes in the expression of RLN-3 and RXFP-3 mRNA in the stress-dependent brain regions in male pubertal Wistar rats that had been subjected to acute stress. Three stressors were applied from 42 to 44 postnatal days (first day: a single forced swim; second day: stress on an elevated platform that was repeated three times; third day: restraint stress three times). Anxiety (open field, elevated plus maze test) and anhedonic-like behavior (sucrose preference test) were estimated during these tests. The corticosterone (CORT) levels and blood morphology were estimated. We found that the RXFP-3 mRNA expression decreased in the brainstem, whereas it increased in the hypothalamus 72 h after acute stress. These molecular changes were accompanied by the increased levels of CORT and anxiety-like behavior detected in the open field test that had been conducted earlier, that is, 24 h after the stress procedure. These findings shed new light on the neurochemical changes that are involved in the compensatory response to adverse events in pubertal male rats and support other data that suggest a regulatory interplay between the RLN-3 pathway and the hypothalamus-pituitary-adrenal axis activity in the mechanisms of anxiety-like behavior.

Neurolipidomic insights into anxiety disorders: Uncovering lipid dynamics for potential therapeutic advances

Anxiety disorders constitute a spectrum of psychological conditions affecting millions of individuals worldwide, imposing a significant health burden. Historically, the development of anxiolytic medications has been largely focused on neurotransmitter function and modulation. However, in recent years, neurolipids emerged as a prime target for understanding psychiatric pathogenesis and developing novel medications. Neurolipids influence various neural activities such as neurotransmission and cellular functioning, as well as maintaining cell membrane integrity. Therefore, this review aims to elucidate the alterations in neurolipids associated with an anxious mental state and explore their potential as targets of novel anxiolytic medications. Existing evidence tentatively associates dysregulated neurolipid levels with the etiopathology of anxiety disorders. Notably, preclinical investigations suggest that several neurolipids, including endocannabinoids and polyunsaturated fatty acids, may hold promise as potential pharmacological targets. Overall, the current literature tentatively suggests the involvement of lipids in the pathogenesis of anxiety disorders, hinting at potential prospects for future pharmacological interventions.

Quercetin ameliorates cognitive deficit, expression of amyloid precursor gene, and pro-inflammatory cytokines in an experimental models of Alzheimer's disease in Wistar rats

Chronic stress (CS) is critically involved in the Alzheimer's disease (AD) pathogenesis resulting in cognitive disturbance. Also, amyloid precursor protein (APP) related gens, pro-inflammatory cytokines, and stress increases AD-related pathogenesis through increasing APP, all are important players in the development of AD. Herein, we explore the possible neuroprotective and anti-amnestic effect of quercetin (QUER) on cognitive deficits induced by scopolamine (SCOP) in stressed rats. Stress induction was performed by exposed of rats to 2-h chronic restraint stress for 10 days. Then rats were supplemented with QUER (25 mg/kg/day oral gavage, for 1 month). Ratswere submitted to intraperitoneal (i.p.) injection of SCOP (1 mg/kg) during the final 9 days of QUER supplementation to induce dementia like condition. Following the interventions, behavioral tests [elevated plus maze (EPM) and novel object recognition memory (NORM)] was examined to analysis the cognitive functions. Meanwhile, prefrontal cortex (PFC) and hippocampus of brain were used for gene expression and biochemical studies. Also, the plasma corticosterone (CORT) level was measured. We established that administration of QUER ameliorated the SCOP-related memory impairment. Also, QUER decreased stress related anxiety like behaviors in the EPM. QUER also altered the interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels in both PFC and hippocampus of SCOP treated rats in stress and non-stress conditions. We found that QUER increased APP and amyloid precursor-like protein 2 (APLP2) mRNA expression in both non-stress and stressed rats. Also, our findings imply that QUER suppress the effect of SCOP on cognitive functions. Moreover, decreased APP mRNA expression in the hippocampus were observed following pretreatment of rats with QUER in both stress and non-stress groups. Given that decreased amyloid beta (Aβ) expression in the hippocampus of stressed rats, it can be proposed that elevations in APP mRNA expression by QUER activates non-amyloidogenic pathways leading to reduction in Aβ levels. However, our findings indicate that QUER can be a therapeutic candidate, which exerts an anti-amnesic property against SCOP-induced memory decline. On the other hand, prior QUER administration in stress condition could be a promising approach against AD prevention.

Chronic administration of caffeine, modafinil, AVL-3288 and CX516 induces time-dependent complex effects on cognition and mood in an animal model of sleep deprivation

OBJECTIVE

Caffeine and modafinil are used to reverse effects of sleep deprivation. Nicotinic alpha-7 receptor and AMPA receptor positive allosteric modulators (PAM) are also potential substances in this context. Our objective is to evaluate the effects of caffeine, modafinil, AVL-3288 (nicotinic alpha-7 PAM) and CX516 (AMPA receptor PAM) on cognition and mood in a model of sleep deprivation.

METHOD

Modified multiple platform model is used to sleep-deprive mice for 24 days, for 8 h/day. Vehicle, Modafinil (40 mg/kg), Caffeine (5 mg/kg), CX516 (10 mg/kg), and AVL3288 (1 mg/kg) were administered intraperitoneally daily. A cognitive test battery was applied every six days for four times. The battery that included elevated plus maze, novel object recognition, and sucrose preference tests was administered on consecutive days.

RESULTS

Sleep deprivation decreased novel object recognition skill, but no significant difference was found in anxiety and depressive mood. Caffeine administration decreased anxiety-like behavior in short term, but this effect disappeared in chronic administration. Caffeine administration increased memory performance in chronic period. AVL group showed better memory performance in short term, but this effect disappeared in the rest of experiment. Although, in the modafinil group, no significant change in mood and memory was observed, anhedonia was observed in the chronic period in vehicle, caffeine and modafinil groups, but not in AVL-3288 and CX-516 groups.

CONCLUSION

Caffeine has anxiolytic effect in acute administration. The improvement of memory in chronic period may be associated with the neuroprotective effects of caffeine. AVL-3288 had a short-term positive effect on memory, but tolerance to these effects developed over time. Furthermore, no anhedonia was observed in AVL-3288 and CX516 groups in contrast to vehicle, caffeine and modafinil groups. This indicates that AVL-3288 and CX516 may show protective effect against depression.

IL-10 and Cdc42 modulate astrocyte-mediated microglia activation in methamphetamine-induced neuroinflammation

Methamphetamine (Meth) use is known to induce complex neuroinflammatory responses, particularly involving astrocytes and microglia. Building upon our previous research, which demonstrated that Meth stimulates astrocytes to release tumor necrosis factor (TNF) and glutamate, leading to microglial activation, this study investigates the role of the anti-inflammatory cytokine interleukin-10 (IL-10) in this process. Our findings reveal that the presence of recombinant IL-10 (rIL-10) counteracts Meth-induced excessive glutamate release in astrocyte cultures, which significantly reduces microglial activation. This reduction is associated with the modulation of astrocytic intracellular calcium (Ca2+) dynamics, particularly by restricting the release of Ca2+ from the endoplasmic reticulum to the cytoplasm. Furthermore, we identify the small Rho GTPase Cdc42 as a crucial intermediary in the astrocyte-to-microglia communication pathway under Meth exposure. By employing a transgenic mouse model that overexpresses IL-10 (pMT-10), we also demonstrate in vivo that IL-10 prevents Meth-induced neuroinflammation. These findings not only enhance our understanding of Meth-related neuroinflammatory mechanisms, but also suggest IL-10 and Cdc42 as putative therapeutic targets for treating Meth-induced neuroinflammation.

Effects of sleep deprivation on anxiety-depressive-like behavior and neuroinflammation

BACKGROUND

Depression is defined by a persistent low mood and disruptions in sleep patterns, with the WHO forecasting that major depression will rank as the third most prevalent contributor to the global burden of disease by the year 2030. Sleep deprivation serves as a stressor that triggers inflammation within the central nervous system, a process known as neuroinflammation. This inflammatory response plays a crucial role in the development of depression by upregulating the expression of inflammatory mediators that contribute to symptoms such as anxiety, hopelessness, and loss of pleasure.

METHODS

In this study, sleep deprivation was utilized as a method to induce anxiety and depressive-like behaviors in mice. The behavioral changes in the mice were then evaluated using the EZM, EPM, TST, FST, and SPT. H&E staining and Nissl staining was used to detect morphological changes in the medial prefrontal cortical (mPFC) regions. Elisa to assess serum CORT levels. Detection of mRNA levels and protein expression of clock genes, high mobility genome box-1 (Hmgb1), silent message regulator 6 (Sirt6), and pro-inflammatory factors by RT-qPCR, Western blotting, and immunofluorescence techniques.

RESULTS

Sleep deprivation resulted in decreased exploration of unfamiliar territory, increased time spent in a state of despair, and lower sucrose water intake in mice. Additionally, sleep deprivation led to increased secretion of serum CORT and upregulation of clock genes, IL6, IL1β, TNFα, Cox-2, iNOS, Sirt6, and Hmgb1. Sleep.

CONCLUSIONS

Sleep deprivation induces anxiety-depressive-like behaviors and neuroinflammation in the brain. Transcription of clock genes and activation of the Sirt6/Hmgb1 pathway may contribute to inflammatory responses in the mPFC.

Accumulated HIIT inhibits anxiety and depression, improves cognitive function, and memory-related proteins in the hippocampus of aged rats

This study aimed to compare the effects of High-Intensity Interval Training (HIIT) performed in a single session(1xHIIT) versus three daily sessions (3xHIIT) on fitness level and behavior of aged rats. Eighteen-month-old Wistar rats were assigned to Untrained (UN), 1xHIIT, or 3xHIIT (n = 12/group). Both groups, 1xHIIT and 3xHIIT, performed 15 min of a treadmill running HIIT protocol during 8 weeks. 1xHIIT protocol consisted of a single daily session of 15 min, while the 3xHIIT performed three daily sessions of 5 min with a 4 h interval between the sessions. Morris Water Maze (MWM) task was used to evaluate spatial learning and memory. Splash test, Forced Swim test, and Elevated Plus Maze task (EPM) were used to evaluate anhedonic, depressive-like, and anxious behaviors, respectively. Rats were euthanized, and the hippocampus was harvested for western blot analyses (CaMKII and BDNF). Both HIIT protocols improved VO2max and spatial memory. Notably, only the 3xHIIT protocol attenuated anxious and depressive-like behaviors. Western blot analyses of the hippocampus revealed that both HIIT protocols increased BDNF levels. BDNF levels were higher in the 3xHIIT when compared with 1xHIIT group, and we observed increasement of the CamKII levels just in the 3x HIIT group. Therefore, this study provides evidence indicating that accumulated HIIT sessions is more effective than traditional daily HIIT sessions in improving fitness level, cognitive function, memory, inhibiting the development of mood disorders, and enhancing BDNF and CaMKII levels in the hippocampus of aged rats.

Understanding the role of early life stress and schizophrenia on anxiety and depressive like outcomes: An experimental study

BACKGROUND

Adverse experiences due to early life stress (ELS) or parental psychopathology such as schizophrenia (SZ) have a significant implication on individual susceptibility to psychiatric disorders in the future. However, it is not fully understood how ELS affects social-associated behaviors as well as the developing prefrontal cortex (PFC).

OBJECTIVE

The aim of this study was to investigate the impact of ELS and ketamine induced schizophrenia like symptoms (KSZ) on anhedonia, social behavior and anxiety-like behavior.

METHODS

Male and female Sprague-Dawley rat pups were allocated randomly into eight experimental groups, namely control, gestational stress (GS), GS+KSZ, maternal separation (MS), MS+KSZ pups, KSZ parents, KSZ parents and Pups and KSZ pups only. ELS was induced by subjecting the pups to GS and MS, while schizophrenia like symptoms was induced through subcutaneous administration of ketamine. Behavioral assessment included sucrose preference test (SPT) and elevated plus maze (EPM), followed by dopamine testing and analysis of astrocyte density. Statistical analysis involved ANOVA and post hoc Tukey tests, revealing significant group differences and yielding insights into behavioral and neurodevelopmental impacts.

RESULTS

GS, MS, and KSZ (dams) significantly reduced hedonic response and increased anxiety-like responses (p < 0.05). Notably, the presence of normal parental mental health demonstrated a reversal of the observed decline in Glial Fibrillary Acidic Protein-positive astrocytes (GFAP+ astrocytes) (p < 0.05) and a reduction in anxiety levels, implying its potential protective influence on depressive-like symptoms and PFC astrocyte functionality.

CONCLUSION

The present study provides empirical evidence supporting the hypothesis that exposure to ELS and KSZ on dams have a significant impact on the on development of anxiety and depressive like symptoms in Sprague Dawley rats, while positive parenting has a reversal effect.

Long-term Treatment with a 5-Alpha-Reductase Inhibitor AlleviatesDepression-like Behavior in Obese Male Rats

Several studies have reported side effects of finasteride (FIN), such as anxiety/depression in young men. Obesity is also positively associated with anxiety/depression symptoms; however, the impacts of long-term FIN treatment and FIN withdrawal in young obese individuals are still elusive. The present study aimed to investigate the effect of long-term treatment and its withdrawal on anxiety/depression and brain pathologies in lean and obese adult male rats. Forty-eight male Wistar rats were equally divided into two groups and fed either a normal or high-fat diet. At age 13 weeks, rats in each dietary group were divided into three subgroups: 1) the control group receiving drinking water, 2) the long-term treatment group receiving FIN orally at 5mg/kg/day for 6 weeks, and 3) the withdrawal group receiving FIN orally at 5mg/kg/day for 2 weeks followed by a 4-week withdrawal period. Anxiety/depression-like behaviors, biochemical analysis, brain inflammation, oxidative stress, neuroactive steroids, brain metabolites, and microglial complexity were tested. The result showed that lean rats treated with long-term FIN and its withdrawal exhibited metabolic disturbances, depressive-like behavior, and both groups showed increased neurotoxic metabolites and reduced microglial complexity. Obesity itself led to metabolic disturbances and brain pathologies, including increased inflammation, oxidative stress, and quinolinic acid, as well as reduced microglial complexity, resulting in increased anxiety- and depression-like behaviors. Interestingly, the long-term FIN treatment group in obese rats showed attenuation of depressive-like behaviors, brain inflammation, and oxidative stress, along with increased brain antioxidants, suggesting the possible benefits of FIN in obese conditions.

A Prelimbic Cortex-Thalamus Circuit Bidirectionally Regulates Innate and Stress-Induced Anxiety-Like Behavior

Anxiety-related disorders respond to cognitive behavioral therapies, which involved the medial prefrontal cortex (mPFC). Previous studies have suggested that subregions of the mPFC have different and even opposite roles in regulating innate anxiety. However, the specific causal targets of their descending projections in modulating innate anxiety and stress-induced anxiety have yet to be fully elucidated. Here, we found that among the various downstream pathways of the prelimbic cortex (PL), a subregion of the mPFC, PL-mediodorsal thalamic nucleus (MD) projection, and PL-ventral tegmental area (VTA) projection exhibited antagonistic effects on anxiety-like behavior, while the PL-MD projection but not PL-VTA projection was necessary for the animal to guide anxiety-related behavior. In addition, MD-projecting PL neurons bidirectionally regulated remote but not recent fear memory retrieval. Notably, restraint stress induced high-anxiety state accompanied by strengthening the excitatory inputs onto MD-projecting PL neurons, and inhibiting PL-MD pathway rescued the stress-induced anxiety. Our findings reveal that the activity of PL-MD pathway may be an essential factor to maintain certain level of anxiety, and stress increased the excitability of this pathway, leading to inappropriate emotional expression, and suggests that targeting specific PL circuits may aid the development of therapies for the treatment of stress-related disorders.

Targeting fear memories: Examining pharmacological disruption in a generalized fear framework

Labilization-reconsolidation, which relies on retrieval, has been considered an opportunity to attenuate the negative aspects of traumatic memories. A therapeutic strategy based on reconsolidation blockade is deemed more effective than current therapies relying on memory extinction. Nevertheless, extremely stressful memories frequently prove resistant to this process. Here, after inducing robust fear memory in mice through strong fear conditioning, we examined the possibility of rendering it susceptible to pharmacological modulation based on the degree of generalized fear (GF). To achieve this, we established an ordered gradient of GF, determined by the perceptual similarity between the associated context (CA) and non-associated contexts (CB, CC, CD, and CE) to the aversive event. We observed that as the exposure context became less similar to CA, the defensive pattern shifted from passive to active behaviors in both male and female mice. Subsequently, in conditioned animals, we administered propranolol after exposure to the different contexts (CA, CB, CC, CD or CE). In males, propranolol treatment resulted in reduced freezing time and enhanced risk assessment behaviors when administered following exposure to CA or CB, but not after CC, CD, or CE, compared to the control group. In females, a similar change in behavioral pattern was observed with propranolol administered after exposure to CC, but not after the other contexts. These results highlight the possibility of indirectly manipulating a robust contextual fear memory by controlling the level of generalization during recall. Additionally, it was demonstrated that the effect of propranolol on reconsolidation would not lead to a reduction in fear memory per se, but rather to its reorganization resulting in greater behavioral flexibility (from passive to active behaviors). Finally, from a clinical viewpoint, this would be of considerable relevance since following this strategy could make the treatment of psychiatric disorders associated with traumatic memory formation more effective and less stressful.

Semaphorin 6D tunes amygdalar circuits for emotional, metabolic, and inflammatory outputs

Regulated neural-metabolic-inflammatory responses are essential for maintaining physiological homeostasis. However, the molecular machinery that coordinates neural, metabolic, and inflammatory responses is largely unknown. Here, we show that semaphorin 6D (SEMA6D) coordinates anxiogenic, metabolic, and inflammatory outputs from the amygdala by maintaining synaptic homeostasis. Using genome-wide approaches, we identify SEMA6D as a pleiotropic gene for both psychiatric and metabolic traits in human. Sema6d deficiency increases anxiety in mice. When fed a high-fat diet, Sema6d-/- mice display attenuated obesity and enhanced myelopoiesis compared with control mice due to higher sympathetic activity via the β3-adrenergic receptor. Genetic manipulation and spatial and single-nucleus transcriptomics reveal that SEMA6D in amygdalar interneurons is responsible for regulating anxiogenic and autonomic responses. Mechanistically, SEMA6D is required for synaptic maturation and γ-aminobutyric acid transmission. These results demonstrate that SEMA6D is important for the normal functioning of the neural circuits in the amygdala, coupling emotional, metabolic, and inflammatory responses.

Chlordiazepoxide reduces anxiety-like behavior in the adolescent mouse elevated plus maze: A pharmacological validation study

This report evaluates the effects of chlordiazepoxide, a benzodiazepine commonly prescribed to manage anxiety-related disorders in adolescent/pediatric populations, on elevated plus maze (EPM) performance in juvenile mice. This approach was taken because chlordiazepoxide produces anxiolytic-like effects in multiple models in adult rodents, however, less is known about the behavioral effects of this benzodiazepine in juveniles. Thus, we administered a single intraperitoneal injection of chlordiazepoxide (0, 5, or 10 mg/kg) to postnatal day 35 male C57BL/6 mice. Thirty minutes later, mice were allowed to explore the EPM for 5-min. We found that chlordiazepoxide-treated mice (5 and 10 mg/kg) spent more time exploring the open arms of the EPM. No differences in velocity (cm/s) or distance traveled (cm) were observed between the groups. These results indicate that chlordiazepoxide induces anxiolytic-related behavior in adolescent male mice.

Complement C5a receptor 1 blockade reverses cognitive deficits following cranial radiation therapy for brain cancer

Cranial radiation therapy (RT) for brain cancers leads to an irreversible decline in cognitive function without an available remedy. Radiation-induced cognitive deficits (RICD) are particularly a pressing problem for the survivors of pediatric and low grade glioma (LGG) patients who often live long post-RT. Radiation-induced elevated neuroinflammation and gliosis, triggered by the detrimental CNS complement cascade, lead to excessive synaptic and cognitive loss. Using intact and brain cancer-bearing mouse models, we now show that targeting anaphylatoxin complement C5a receptor (C5aR1) is neuroprotective against RICD. We used a genetic knockout, C5aR1 KO mouse, and a pharmacologic approach, employing the orally active, brain penetrant C5aR1 antagonist PMX205, to reverse RICD. Irradiated C5aR1 KO and WT mice receiving PMX205 showed significant neurocognitive improvements in object recognition memory and memory consolidation tasks. C5aR1 inhibition reduced microglial activation, astrogliosis, and synaptic loss in the irradiated brain. Importantly, C5aR1 inhibition in the syngeneic, orthotopic astrocytoma, and glioblastoma-bearing mice protected against RICD without interfering with the therapeutic efficacy of RT to reduce tumor volume in vivo . PMX205 is currently in clinical trials for amyotrophic lateral sclerosis (ALS). Thus, C5aR1 inhibition is a translationally feasible approach to address RICD, an unmet medical need.

Polycomb repressive complex 2 is critical for mouse cortical glutamatergic neuron development

The Polycomb Repressive Complex 2 (PRC2) regulates corticogenesis, yet the consequences of mutations to this epigenetic modifier in the mature brain are poorly defined. Importantly, PRC2 core genes are haploinsufficient and causative of several human neurodevelopmental disorders. To address the role of PRC2 in mature cortical structure and function, we conditionally deleted the PRC2 gene Eed from the developing mouse dorsal telencephalon. Adult homozygotes displayed smaller forebrain structures. Single-nucleus transcriptomics revealed that glutamatergic neurons were particularly affected, exhibiting dysregulated gene expression profiles, accompanied by aberrations in neuronal morphology and connectivity. Remarkably, homozygous mice performed well on challenging cognitive tasks. In contrast, while heterozygous mice did not exhibit clear anatomical or behavioral differences, they displayed dysregulation of neuronal genes and altered neuronal morphology that was strikingly different from homozygous phenotypes. Collectively, these data reveal how alterations to PRC2 function shape the mature brain and reveal a dose-specific role for PRC2 in determining glutamatergic neuron identity.

Repeated stress triggers seeking of a starvation-like state in anxiety-prone female mice

Elevated anxiety often precedes anorexia nervosa and persists after weight restoration. Patients with anorexia nervosa often describe self-starvation as pleasant, potentially because food restriction can be anxiolytic. Here, we tested whether repeated stress can cause animals to prefer a starvation-like state. We developed a virtual reality place preference paradigm in which head-fixed mice can voluntarily seek a starvation-like state induced by optogenetic stimulation of hypothalamic agouti-related peptide (AgRP) neurons. Prior to stress exposure, males but not females showed a mild aversion to AgRP stimulation. Strikingly, following multiple days of stress, a subset of females developed a strong preference for AgRP stimulation that was predicted by high baseline anxiety. Such stress-induced changes in preference were reflected in changes in facial expressions during AgRP stimulation. Our study suggests that stress may cause females predisposed to anxiety to seek a starvation state and provides a powerful experimental framework for investigating the underlying neural mechanisms.

Vitamin D attenuates monosodium glutamate-induced behavioural anomalies, metabolic dysregulation, cholinergic impairment, oxidative stress, and astrogliosis in rats

BACKGROUND

Monosodium glutamate (MSG) is a commonly used flavor enhancer that has raised concerns due to its potential adverse effects on various organs. This study explored the neuroprotective potential of Vitamin D, a beneficial micronutrient, in mitigating MSG-induced neurotoxicity.

MATERIALS AND METHODS

Adult male Wistar rats were categorized into five groups: control (2 ml/kg PBS orally for 30 days), MSG (40 mg/kg orally for 30 days), VIT-D (oral cholecalciferol; 500 IU/kg for 30 days), MSG+VIT-D (MSG for 30 days followed by VIT-D for another 30 days), and VIT-D/MSG (concurrent VIT-D and MSG for 30 days). The rats underwent neurobehavioral, histochemical, and biochemical analyses following the treatments.

RESULTS

MSG treatment caused a decline in both long and short-term memory, along with reduced exploratory and anxiogenic behavior, mitigated by vitamin D treatment. MSG exposure also induced impaired behavior, dyslipidemia, oxidative stress, lipid peroxidation, altered cholinergic transmission, and increased chromatolysis and neuroinflammation in the frontal cortex, hippocampus, and cerebellum.

CONCLUSIONS

VIT-D demonstrated a mitigating effect on MSG-induced adverse outcomes, highlighting its potential to attenuate neurodegenerative cascades. This investigation contributes to understanding MSG-associated neurotoxicity and suggests vitamin D as a valuable and potential intervention for neuroprotection.

Motor behavior induced by bergamot essential oil in experimental tasks is differentially modulated by pretreatment with metabotropic glutamate receptor 2/3 or 5 antagonists

Bergamot essential oil shows anxiolytic-relaxant effects devoid of sedative action and motor impairment typical of benzodiazepines. Considering the potential for clinical of these effects, it is important to understand the underlying mechanisms of the phytocomplex. Modulation of glutamate group I and II metabotropic receptors is involved in stress and anxiety disorders, in cognition and emotions and increases locomotor activity and wakefulness. Interestingly, early data indicate that bergamot essential oil modulates glutamatergic transmission in specific manifestations of the central nervous system. The aim of this work is to investigate if selective antagonists of metabotropic glutamate 2/3 and 5 receptors affect behavioral parameters modulated by the phytocomplex. Male Wistar rats were used to measure behavioral parameters to correlate anxiety and motor activity using elevated plus maze (EPM), open field (OF), and rotarod tasks. Bergamot essential oil increases in EPM the time spent in open/closed arms and reduces total number of entries. The essential oil also increases immobility in EPM and OF and not affect motor coordination in rotarod. Pretreatment with the metabotropic glutamate antagonists does not affect the time spent in open/close arms, however, differently affects motor behavior measured after administration of phytocomplex. Particularly, glutamate 2/3 antagonist reverts immobility and glutamate 5 antagonist potentiates this parameter induced by the phytocomplex. Our data show that modulation of both metabotropic glutamate receptors is likely involved in some of behavioral effects of bergamot essential oil.

Cyclooxygenase-2 inhibitors alleviated depressive and anxious-like behaviors in mice exposed to lipopolysaccharide: Involvement of oxidative stress and neuroinflammation

Depression and anxiety disorders have their pathophysiologies linked to inflammation and oxidative stress. In this context, celecoxib (CLX) and etoricoxib (ETR) inhibit cyclooxygenase 2 (COX-2), an enzyme expressed by cells involved in the inflammatory process and found in the brain. Studies have been using CLX as a possible drug in the treatment of depression, although its mechanisms at the central nervous system level are not fully elucidated. In this study, the effects of CLX and ETR on behavioral, oxidative, and inflammatory changes induced by systemic exposure to Escherichia coli lipopolysaccharide (LPS) were evaluated in adult male swiss mice. For ten days, the animals received intraperitoneal injections of LPS at 0.5 mg/kg. From the sixth to the tenth day, one hour after LPS exposure, they were treated orally with CLX (15 mg/kg), ETR (10 mg/kg), or fluoxetine (FLU) (20 mg/kg). Twenty-four hours after the last oral administration, the animals underwent evaluation of locomotor activity (open field test), predictive tests for depressive-like behavior (forced swim and tail suspension tests), and anxiolytic-like effect (elevated plus maze and hole board tests). Subsequently, the hippocampus, prefrontal cortex and striatum were dissected for the measurement of oxidative and nitrosative parameters (malondialdehyde, nitrite, and glutathione) and quantification of pro-inflammatory cytokines (IL-1β and IL-6). LPS induced depressive and anxious-like behavior, and treatment with CLX or ETR was able to reverse most of the behavioral changes. It was evidenced that nitrosative stress and the degree of lipid peroxidation induced by LPS were reduced in different brain areas after treatment with the drugs, as well as the endogenous defense system against free radicals was strengthened. CLX and ETR also significantly reduced LPS-induced cytokine levels. These data are expected to expand information on the role of inflammation in depression and anxiety and provide insights into possible mechanisms of COX-2 inhibitors in psychiatric disorders with a neurobiological basis in inflammation and oxidative stress.

Disfunction of dorsal raphe nucleus-hippocampus serotonergic-HTR3 transmission results in anxiety phenotype of Neuroplastin 65-deficient mice

Anxiety disorders are the most common psychiatric condition, but the etiology of anxiety disorders remains largely unclear. Our previous studies have shown that neuroplastin 65 deficiency (NP65-/-) mice exhibit abnormal social and mental behaviors and decreased expression of tryptophan hydroxylase 2 (TPH2) protein. However, whether a causal relationship between TPH2 reduction and anxiety disorders exists needs to be determined. In present study, we found that replenishment of TPH2 in dorsal raphe nucleus (DRN) enhanced 5-HT level in the hippocampus and alleviated anxiety-like behaviors. In addition, injection of AAV-NP65 in DRN significantly increased TPH2 expression in DRN and hippocampus, and reduced anxiety-like behaviors. Acute administration of exogenous 5-HT or HTR3 agonist SR57227A in hippocampus mitigated anxiety-like behaviors in NP65-/- mice. Moreover, replenishment of TPH2 in DRN partly repaired the impairment of long-term potentiation (LTP) maintenance in hippocampus of NP65-/- mice. Finally, we found that loss of NP65 lowered transcription factors Lmx1b expression in postnatal stage and replenishment of NP65 in DRN reversed the decrease in Lmx1b expression of NP65-/- mice. Together, our findings reveal that NP65 deficiency induces anxiety phenotype by downregulating DRN-hippocampus serotonergic-HTR3 transmission. These studies provide a novel and insightful view about NP65 function, suggesting an attractive potential target for treatment of anxiety disorders.

The role of mGluR5 on the therapeutic effects of ketamine in Wistar rats

RATIONALE

Ketamine produces dissociative, psychomimetic, anxiolytic, antidepressant, and anesthetic effects in a dose dependent manner. It has a complex mechanism of action that involve alterations in other glutamate receptors. The metabotropic glutamate receptor 5 (mGluR5) has been investigated in relation to the psychotic and anesthetic properties of ketamine, while its role in mediating the therapeutic effects of ketamine remains unknown.

OBJECTIVES

We investigated the role of mGluR5 on the antidepressant, anxiolytic and fear memory-related effects of ketamine in adult male Wistar rats.

METHODS

Two sets of experiments were conducted. We first utilized the positive allosteric modulator CDPPB to investigate how acute mGluR5 activation regulates the therapeutic effects of ketamine (10 mg/kg). We then tested the synergistic antidepressant effect of mGluR5 antagonism and ketamine by combining MTEP with a sub-effective dose of ketamine (1 mg/kg). Behavioral despair, locomotor activity, anxiety-like behavior, and fear memory were respectively assessed in the forced swim test (FST), open field test (OFT), elevated plus maze (EPM), and auditory fear conditioning.

RESULTS

Enhancing mGluR5 activity via CDPPB occluded the antidepressant effect of ketamine without changing locomotor activity. Furthermore, concomitant administration of MTEP and ketamine exhibited a robust synergistic antidepressant effect. The MTEP + ketamine treatment, however, blocked the anxiolytic effect observed by sole administration of MTEP or the low dose ketamine.

CONCLUSIONS

These findings suggest that suppressed mGluR5 activity is required for the antidepressant effects of ketamine. Consequently, the antagonism of mGluR5 enhances the antidepressant effectiveness of low dose ketamine, but eliminates its anxiolytic effects.

Body weight modulates the impact of oxytocin on chronic cold-immobilization stress response

By activating the stress system, stress modulates various physiological parameters including food intake, energy consumption, and, consequently, body weight. The role of oxytocin in the regulation of stress and obesity cannot be disregarded. Based on these findings, we aimed to investigate the effect of intranasal oxytocin on stress response in high-fat-diet (HFD)--fed and control-diet-fed rats exposed to chronic stress. Cold-immobilization stress was applied for 5 consecutive days to male Sprague-Dawley rats fed either with a control diet (n=20) or HFD (n=20) for 6 weeks. Half of the animals in each group received oxytocin. Stress response was evaluated via plasma and salivary cortisol levels as well as elevated plus maze scores. Prefrontal cortex and hypothalamic oxytocin receptor (OxtR) expression levels were identified using western blot analysis. The results showed higher stress response in HFD-fed animals than in control animals both under basal and post-stress conditions. Oxytocin application had a prominent anxiolytic effect in the control group but an insignificant effect in the HFD group. While OxtR expression levels in the prefrontal cortex did not vary according to the body weight and oxytocin application, OxtR levels in the hypothalamus were higher in the HFD- and/or oxytocin-treated animals. Our results indicated that the peripheral and central effects of oxytocin vary with body weight. Moreover, obesity masks the anxiolytic effects of oxytocin, probably by reinforcing the stress condition via central OxtRs. In conclusion, elucidating the mechanisms underlying the central effect of oxytocin is important to cope with stress and obesity.

Loss of Sigma-2 Receptor/TMEM97 Is Associated with Neuropathic Injury-Induced Depression-Like Behaviors in Female Mice

Previous studies have shown that ligands that bind to sigma-2 receptor/TMEM97 (s2R/TMEM97), a transmembrane protein, have anxiolytic/antidepressant-like properties and relieve neuropathic pain-like effects in rodents. Despite medical interest in s2R/TMEM97, little affective and pain behavioral characterization has been done using transgenic mice, which limits the development of s2R/TMEM97 as a viable therapeutic target. Using wild-type (WT) and global Tmem97 knock-out (KO) mice, we sought to identify the contribution of Tmem97 in modulating affective and pain-like behaviors using a battery of affective and pain assays, including open field, light/dark preference, elevated plus maze, forced swim test, tail suspension test, and the mechanical sensitivity tests. Our results demonstrate that female Tmem97 KO mice show less anxiety-like and depressive-like behaviors in light/dark preference and tail suspension tests but not in an open field, elevated plus maze, and forced swim tests at baseline. We next performed spared nerve injury in WT and Tmem97 KO mice to assess the role of Tmem97 in neuropathic pain-induced anxiety and depression. WT mice, but not Tmem97 KO mice, developed a prolonged neuropathic pain-induced depressive-like phenotype when tested 10 weeks after nerve injury in females. Our results show that Tmem97 plays a role in modulating anxiety-like and depressive-like behaviors in naive animals with a significant change in the presence of nerve injury in female mice. Overall, these data demonstrate that Tmem97 could be a target to alleviate affective comorbidities of pain disorders.

In Vivo Assays for Amyloid-Related Diseases

Amyloid-related diseases, such as Alzheimer's and Parkinson's disease, are devastating conditions caused by the accumulation of abnormal protein aggregates known as amyloid fibrils. While assays involving animal models are essential for understanding the pathogenesis and developing therapies, a wide array of standard analytical techniques exists to enhance our understanding of these disorders. These techniques provide valuable information on the formation and propagation of amyloid fibrils, as well as the pharmacokinetics and pharmacodynamics of candidate drugs. Despite ethical concerns surrounding animal use, animal models remain vital tools in the search for treatments. Regardless of the specific animal model chosen, the analytical methods used are usually standardized. Therefore, the main objective of this review is to categorize and outline the primary analytical methods used in in vivo assays for amyloid-related diseases, highlighting their critical role in furthering our understanding of these disorders and developing effective therapies.

Effect of high fat diet on maternal behavior, brain-derived neurotrophic factor and neural stem cell proliferation in mice expressing human placental lactogen during pregnancy

Maternal obesity is a serious health concern because it increases risks of neurological disorders, including anxiety and peripartum depression. In mice, a high fat diet (HFD) in pregnancy can negatively affect placental structure and function as well as maternal behavior reflected by impaired nest building and pup-retrieval. In humans, maternal obesity in pregnancy is associated with reduced placental lactogen (PL) gene expression, which has been linked to a higher risk of depression. PL acting predominantly through the prolactin receptor maintains energy homeostasis and is a marker of placenta villous trophoblast differentiation during pregnancy. Impaired neurogenesis and low serum levels of brain-derived neurotrophic factor (BDNF) have also been implicated in depression. Augmented neurogenesis in brain during pregnancy was reported in the subventricular zone (SVZ) of mice at gestation day 7 and linked to increased prolactin receptor signaling. Here, we used transgenic CD-1 mice that express human (h) PL during pregnancy to investigate whether the negative effects of diet on maternal behavior are mitigated in these (CD-1[hGH/PL]) mice. Specifically, we examined the effect of a HFD on nest building prepartum and pup retrieval postpartum, as well as on brain BDNF levels and neurogenesis. In contrast to wild-type CD-1[WT]mice, CD-1[hGH/PL] mice displayed significantly less anxiety-like behavior, and showed no impairment in prepartum nest building or postpartum pup-retrieval when fed a HFD. Furthermore, the HFD decreased prepartum and increased postpartum BDNF levels in CD-1[WT] but not CD-1[hGH/PL] mice. Finally, neurogenesis in the SVZ as well as phosphorylated mitogen-activated protein kinase, indicative of lactogenic signaling, appeared unaffected by pregnancy and diet at gestation day 7 in CD-1[hGH/PL] mice. These observations indicate that CD-1[hGH/PL] mice are resistant to the negative effects of HFD reported for CD-1[WT] mice, including effects on maternal behaviors and BDNF levels, and potentially, neurogenesis. This difference probably reflects a direct or indirect effect of the products of the hGH/PL transgene.

Pregestational fructose-induced metabolic syndrome in Wistar rats causes sexually dimorphic behavioral changes in their offspring

Metabolic syndrome (MetS), marked by enduring metabolic inflammation, has detrimental effects on cognitive performance and brain structure, influencing behavior. This study aimed to investigate whether maternal MetS could negatively impact the neurodevelopment and metabolism of offspring. To test this hypothesis, 2 months old female Wistar rats were subjected to a 10-week regimen of tap water alone or supplemented with 20% fructose to induce MetS. Dams were mated with healthy males to generate litters: OC (offspring from control dams) and OMetS (offspring from dams with MetS). To isolate prenatal effects, all pups were breastfed by control nurse dams, maintaining a standard diet and water ad libitum until weaning. Behavioral assessments were conducted between postnatal days (PN) 22 and 95, and metabolic parameters were analyzed post-sacrifice on PN100. Results from the elevated plus maze, the open field, and the marble burying tests revealed a heightened anxiety-like phenotype in OMetS females. The novel object recognition test showed that exclusively OMetS males had long-term memory impairment. In the reciprocal social interaction test, OMetS displayed a lower number of social interactions, with a notable increase in "socially inactive" behavior observed exclusively in females. Additionally, in the three-chamber test, social preference and social novelty indexes were found to be lower solely among OMetS females. An increase in visceral fat concomitantly with hypertriglyceridemia was the relevant postmortem metabolic finding in OMetS females. In summary, maternal MetS leads to enduring damage and adverse effects on offspring neurobehavior and metabolism, with notable sexual dimorphism.

A novel role for microtubule affinity-regulating kinases in neuropathic pain

BACKGROUND AND PURPOSE

Neuropathic pain affects millions of patients, but there are currently few viable therapeutic options available. Microtubule affinity-regulating kinases (MARKs) regulate the dynamics of microtubules and participate in synaptic remodelling. It is unclear whether these changes are involved in the central sensitization of neuropathic pain. This study examined the role of MARK1 or MARK2 in regulating neurosynaptic plasticity induced by neuropathic pain.

EXPERIMENTAL APPROACH

A rat spinal nerve ligation (SNL) model was established to induce neuropathic pain. The role of MARKs in nociceptive regulation was assessed by genetically knocking down MARK1 or MARK2 in amygdala and systemic administration of PCC0105003, a novel small molecule MARK inhibitor. Cognitive function, anxiety-like behaviours and motor coordination capability were also examined in SNL rats. Synaptic remodelling-associated signalling changes were detected with electrophysiological recording, Golgi-Cox staining, western blotting and qRT-PCR.

KEY RESULTS

MARK1 and MARK2 expression levels in amygdala and spinal dorsal horn were elevated in SNL rats. MARK1 or MARK2 knockdown in amygdala and PCC0105003 treatment partially attenuated pain-like behaviours along with improving cognitive deficit, anxiogenic-like behaviours and motor coordination in SNL rats. Inhibition of MARKs signalling reversed synaptic plasticity at the functional and structural levels by suppressing NR2B/GluR1 and EB3/Drebrin signalling pathways both in amygdala and spinal dorsal horn.

CONCLUSION AND IMPLICATIONS

These results suggest that MARKs-mediated synaptic remodelling plays a key role in the pathogenesis of neuropathic pain and that pharmacological inhibitors of MARKs such as PCC0105003 could represent a novel therapeutic strategy for the management of neuropathic pain.

Prenatal exposure to vortioxetine and vilazodone: Impact on depressive- and anxiety-like behavioral manifestations in young rat offspring

Major depressive disorder (MDD) affects millions of people worldwide, with women at a higher risk during the childbearing age. Vortioxetine (VOX) and Vilazodone (VLZ) are newer antidepressants with improved therapeutic profile commonly used, but their safety during pregnancy and long-term effects on offspring are poorly understood due to paucity of literature in preclinical and clinical studies. This study aimed to investigate whether prenatal exposure to VOX and VLZ impacts depressive- and anxiety-like neurobehavioral alterations in offspring, focusing on neurotransmitter-mediated mechanisms. Pregnant Wistar dams received either VOX or VLZ, 1 mg/day and 2 mg/day of the drug orally from gestation day (GD) 6-21. The dams naturally delivered their offspring and reared until they reached postnatal day (PND) 21. Offspring of both sexes were tested for display of depressive-and anxiety-like behaviors from PND 56-70. After PND 70, offspring were sacrificed, and their brains were collected to estimate neurotransmitter levels. As per protocol, controls were maintained simultaneously for each experimental design. Prenatal exposure to VOX or VLZ induced an increased state of depressive- and anxiety-like behaviors in both male and female offspring. Additionally, neurotransmitter (serotonin, dopamine, and nor-epinephrine) levels in the prefrontal cortex region of the brain were substantially reduced in exposed offspring. No sex specific neurobehavioral and neurochemical implications were observed in the present study. Our findings suggest that prenatal exposure to VOX and VLZ disrupts neurochemical balance in the fetal brain, leading to long-lasting neurobehavioral impairments in offspring of both sexes.

Activity of ventral hippocampal parvalbumin interneurons during anxiety

Anxiety plays a key role in guiding behavior in response to potential threats. Anxiety is mediated by the activation of pyramidal neurons in the ventral hippocampus (vH), whose activity is controlled by GABAergic inhibitory interneurons. However, how different vH interneurons might contribute to anxiety-related processes is unclear. Here, we investigate the role of vH parvalbumin (PV)-expressing interneurons while mice transition from safe to more anxiogenic compartments of the elevated plus maze (EPM). We find that vH PV interneurons increase their activity in anxiogenic EPM compartments concomitant with dynamic changes in inhibitory interactions between PV interneurons and pyramidal neurons. By optogenetically inhibiting PV interneurons, we induce an increase in the activity of vH pyramidal neurons and persistent anxiety. Collectively, our results suggest that vH inhibitory microcircuits may act as a trigger for enduring anxiety states.

Hippocampal astrocytes induce sex-dimorphic effects on memory

Astrocytic receptors influence cognitive function and can promote behavioral deficits in disease. These effects may vary based on variables such as biological sex, but it is not known if the effects of astrocytic receptors are dependent on sex. We leveraged in vivo gene editing and chemogenetics to examine the roles of astrocytic receptors in spatial memory and other processes. We show that reductions in metabotropic glutamate receptor 3 (mGluR3), the main astrocytic glutamate receptor in adults, impair memory in females but enhance memory in males. Similarly, increases in astrocytic mGluR3 levels have sex-dependent effects and enhance memory in females. mGluR3 manipulations also alter spatial search strategies during recall in a sex-specific manner. In addition, acute chemogenetic stimulation of Gi/o-coupled or Gs-coupled receptors in hippocampal astrocytes induces bidirectional and sex-dimorphic effects on memory. Thus, astrocytes are sex-dependent modulators of cognitive function and may promote sex differences in aging and disease.

Top-down brain circuits for operant bradycardia

Heart rate (HR) can be voluntarily regulated when individuals receive real-time feedback. In a rat model of HR biofeedback, the neocortex and medial forebrain bundle were stimulated as feedback and reward, respectively. The rats reduced their HR within 30 minutes, achieving a reduction of approximately 50% after 5 days of 3-hour feedback. The reduced HR persisted for at least 10 days after training while the rats exhibited anxiolytic behavior and an elevation in blood erythrocyte count. This bradycardia was prevented by inactivating anterior cingulate cortical (ACC) neurons projecting to the ventromedial thalamic nucleus (VMT). Theta-rhythm stimulation of the ACC-to-VMT pathway replicated the bradycardia. VMT neurons projected to the dorsomedial hypothalamus (DMH) and DMH neurons projected to the nucleus ambiguus, which innervates parasympathetic neurons in the heart.

Prosapip1 in the dorsal hippocampus mediates synaptic protein composition, long-term potentiation, and spatial memory

Prosapip1 is a brain-specific protein localized to the postsynaptic density, where it promotes dendritic spine maturation in primary hippocampal neurons. However, nothing is known about the role of Prosapip1 in vivo . To examine this, we utilized the Cre-loxP system to develop a Prosapip1 neuronal knockout mouse. We found that Prosapip1 controls the synaptic localization of its binding partner SPAR, along with PSD-95 and the GluN2B subunit of the NMDA receptor (NMDAR) in the dorsal hippocampus (dHP). We next sought to identify the potential contribution of Prosapip1 to the activity and function of the NMDAR and found that Prosapip1 plays an important role in NMDAR-mediated transmission and long-term potentiation (LTP) in the CA1 region of the dHP. As LTP is the cellular hallmark of learning and memory, we examined the consequences of neuronal knockout of Prosapip1 on dHP-dependent memory. We found that global or dHP-specific neuronal knockout of Prosapip1 caused a deficit in learning and memory whereas developmental, locomotor, and anxiety phenotypes were normal. Taken together, Prosapip1 in the dHP promotes the proper localization of synaptic proteins which, in turn, facilitates LTP driving recognition, social, and spatial learning and memory.

Inhibition of Protein Synthesis Attenuates Formation of Traumatic Memory and Normalizes Fear-Induced c-Fos Expression in a Mouse Model of Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is a debilitating psychosomatic condition characterized by impairment of brain fear circuits and persistence of exceptionally strong associative memories resistant to extinction. In this study, we investigated the neural and behavioral consequences of inhibiting protein synthesis, a process known to suppress the formation of conventional aversive memories, in an established PTSD animal model based on contextual fear conditioning in mice. Control animals were subjected to the conventional fear conditioning task. Utilizing c-Fos neural activity mapping, we found that the retrieval of PTSD and normal aversive memories produced activation of an overlapping set of brain structures. However, several specific areas, such as the infralimbic cortex and the paraventricular thalamic nucleus, showed an increase in the PTSD group compared to the normal aversive memory group. Administration of protein synthesis inhibitor before PTSD induction disrupted the formation of traumatic memories, resulting in behavior that matched the behavior of mice with usual aversive memory. Concomitant with this behavioral shift was a normalization of brain c-Fos activation pattern matching the one observed in usual fear memory. Our findings demonstrate that inhibiting protein synthesis during traumatic experiences significantly impairs the development of PTSD in a mouse model. These data provide insights into the neural underpinnings of protein synthesis-dependent traumatic memory formation and open prospects for the development of new therapeutic strategies for PTSD prevention.

Anti-PD-1 cancer immunotherapy induces central nervous system immune-related adverse events by microglia activation

Cancer treatment with anti-PD-1 immunotherapy can cause central nervous system immune-related adverse events (CNS-irAEs). The role of microglia in anti-PD-1 immunotherapy-induced CNS-irAEs is unclear. We found that anti-PD-1 treatment of mice caused morphological signs of activation and major histocompatibility complex (MHC) class II up-regulation on microglia. Functionally, anti-PD-1 treatment induced neurocognitive deficits in mice, independent of T cells, B cells, and natural killer cells. Instead, we found that microglia mediated these CNS-irAEs. Single-cell RNA sequencing revealed major transcriptional changes in microglia upon anti-PD-1 treatment. The anti-PD-1 effects were mediated by anti-PD-1 antibodies interacting directly with microglia and were not secondary to peripheral T cell activation. Using a proteomics approach, we identified spleen tyrosine kinase (Syk) as a potential target in activated microglia upon anti-PD-1 treatment. Syk inhibition reduced microglia activation and improved neurocognitive function without impairing anti-melanoma effects. Moreover, we analyzed CNS tissue from a patient cohort that had received anti-PD-1 treatment. Imaging mass cytometry revealed that anti-PD-1 treatment of patients was associated with increased surface marker expression indicative of microglia activation. In summary, we identified a disease-promoting role for microglia in CNS-irAEs driven by Syk and provide an inhibitor-based approach to interfere with this complication after anti-PD-1 immunotherapy.

Assessment of Hippocampal-Related Behavioral Changes in Adolescent Rats of both Sexes Following Voluntary Intermittent Ethanol Intake and Noise Exposure: A Putative Underlying Mechanism and Implementation of a Non-pharmacological Preventive Strategy

Ethanol (EtOH) intake and noise exposure are particularly concerning among human adolescents because the potential to harm brain. Unfortunately, putative underlying mechanisms remain to be elucidated. Moreover, implementing non-pharmacological strategies, such as enriched environments (EE), would be pertinent in the field of neuroprotection. This study aims to explore possible underlying triggering mechanism of hippocampus-dependent behaviors in adolescent animals of both sexes following ethanol intake, noise exposure, or a combination of both, as well as the impact of EE. Adolescent Wistar rats of both sexes were subjected to an intermittent voluntary EtOH intake paradigm for one week. A subgroup of animals was exposed to white noise for two hours after the last session of EtOH intake. Some animals of both groups were housed in EE cages. Hippocampal-dependent behavioral assessment and hippocampal oxidative state evaluation were performed. Results show that different hippocampal-dependent behavioral alterations might be induced in animals of both sexes after EtOH intake and sequential noise exposure, that in some cases are sex-specific. Moreover, hippocampal oxidative imbalance seems to be one of the potential underlying mechanisms. Additionally, most behavioral and oxidative alterations were prevented by EE. These findings suggest that two frequently found environmental agents may impact behavior and oxidative pathways in both sexes in an animal model. In addition, EE resulted a partially effective neuroprotective strategy. Therefore, it could be suggested that the implementation of a non-pharmacological approach might also potentially provide neuroprotective advantages against other challenges. Finally, considering its potential for translational human benefit might be worth.

Increased anxiolytic effect in aged female rats and increased motoric behavior in aged male rats to acute alcohol administration: Comparison to younger animals

The population of most countries in the world is increasing and understanding risk factors that can influence the health of the older population is critical. Older adults consume alcohol often in a risky, binge manner. Previous work has demonstrated that aged rats are more sensitive to many of the effects of acute ethanol. In the current project aged, adult, and adolescent female and male rats were tested on the elevated plus maze and open field following either a 1.0 g/kg alcohol injection or a saline injection. We report sex- and age-dependent effects whereas aged female rats, but not aged male rats, showed an increased anxiolytic effect of alcohol in the elevated plus maze while aged male rats, but not aged female rats, showed increased stimulatory movement in the open field. In addition, significant age effects were found for both female and male rats. It is proposed that the sex- and age-dependent effects reported in the current studies may be due to differential levels of alcohol-induced allopregnanolone for the anxiolytic effects and differential levels of alcohol-induced dopamine for the stimulatory effects. The current work provides insights into factors influencing alcohol consumption in older adults.

Synergistic anxiolytic efficacy exploring the combined effects of diazepam and zinc chloride in wistar albino rats

Combinations of medications are frequently employed when their effects are similar. Beyond aiding in the reduction of medication dosages, this approach may yield additional positive outcomes. Studies have shown that zinc can mitigate anxiety-related behavior in laboratory animals. This study aimed to investigate the potential stabilizing effects of zinc chloride and diazepam in Wistar albino rats.Five groups, each comprising six animals. Test groups included two combinations of zinc chloride and diazepam, each with two different doses of diazepam (1 and 2 mg/kg) and 10 mg/kg of zinc chloride. Four established anxiety models-the Elevated Plus Maze (EPM), the hole board, the light and dark box, and the mirror chamber-were employed to assess the anxiolytic effects. The combination of zinc chloride and diazepam proved to be more effective than the individual doses of zinc chloride and diazepam, indicating enhanced anxiolytic effects.

Different emotional states engage distinct descending pathways from the prefrontal cortex

Emotion regulation, essential for adaptive behavior, depends on the brain's capacity to process a range of emotions. Current research has largely focused on individual emotional circuits without fully exploring how their interaction influences physiological responses or understanding the neural mechanisms that differentiate emotional valence. Using in vivo calcium imaging, electrophysiology, and optogenetics, we examined neural circuit dynamics in the medial prefrontal cortex (mPFC), targeting two key areas: the basal lateral amygdala (BLA) and nucleus accumbens (NAc). Our results demonstrate distinct activation patterns in the mPFC→BLA and mPFC→NAc pathways in response to social stimuli, indicating a mechanism for discriminating emotions: increased mPFC→BLA activity signals anxiety, while heightened mPFC→NAc responses are linked to exploration. Additionally, chronic emotional states amplify activity in these pathways-positivity enhances mPFC→NAc, while negativity boosts mPFC→BLA. This study sheds light on the nuanced neural circuitry involved in emotion regulation, revealing the pivotal roles of mPFC projections in emotional processing. Identifying these specific circuits engaged by varied emotional states advances our understanding of emotional regulation's biological underpinnings and highlights potential targets for addressing emotional dysregulation in psychiatric conditions.

Significance statement

While existing circuitry studies have underscored the significance of emotional circuits, the majority of research has concentrated on individual circuits. The assessment of whether and how the balance among multiple circuits influences overall physiological outcomes is often overlooked. This study delves into the neural underpinnings of emotion regulation, focusing on how positive and negative valences are discriminated and managed. By examining the specific pathways from the medial prefrontal cortex (mPFC) to key emotional centers-the basal lateral amygdala (BLA) for negative valence and the nucleus accumbens (NAc) for positive one-we uncovered a novel dual-balanced neural circuit mechanism that enables this essential aspect of human cognition.

Tiger nut/coconut dietary intervention as antidotal nutritional remediation strategy against neurobehavioural deficits following organophosphate-induced gut-brain axis dysregulation in mice

Organophosphate poisoning remains a global health crisis without efficacious treatments to prevent neurotoxicity. We examined whether antidotal tiger nut and coconut dietary intervention could ameliorate neurobehavioral deficits from organophosphate dichlorvos-induced gut-brain axis dysregulation in a mouse model. Mice were divided into groups given control diet, dichlorvos-contaminated diets, or dichlorvos plus nut-enriched diets. They were exposed to a DDVP-contaminated diet for 4 weeks before exposure to the treatment diets for another 8 weeks. This was followed by behavioural assessments for cognitive, motor, anxiety-, and depressive-like behaviours. Faecal samples (pre- and post-treatment), as well as blood, brain, and gut tissues, were collected for biochemical assessments following euthanasia. Dichlorvos-exposed mice displayed impairments in cognition, motor function, and mood along with disrupted inflammatory and antioxidant responses, neurotrophic factor levels, and acetylcholinesterase activity in brain and intestinal tissues. Weight loss and altered short-chain fatty acid levels additionally indicated gut dysfunction. However, intervention with tiger nut and/or coconut- enriched diet after dichlorvos exposure attenuated these neurobehavioral, and biochemical alterations. Our findings demonstrate organophosphate-induced communication disruptions between the gut and brain pathways that manifest in neuropsychiatric disturbances. Overall, incorporating fibre-rich nuts may represent an antidotal dietary strategy to reduce neurotoxicity and prevent brain disorders associated with organophosphate poisoning.

Downregulation of lncRNAs Gomafu, NONMMUT033604.2, and NONMMUT064397.2 in the hippocampus of mice with model of post-traumatic stress disorder

OBJECTIVES

Molecular mechanisms of post-traumatic stress disorder (PTSD) development have been analysed by evaluati-ng changes in the expression level of long non-coding RNA (lncRNA) as a potential biomarker of the disease and as one of the molecular aspects associated with the disease development.

METHODS

In our study, we used quantitative polymerase chain reaction (qPCR) to evaluate changes in the expression level of long non-coding RNA - Gomafu, NONMMUT033604.2, and NONMMUT064397.2 - in the hippocampus of mice that were subjected to an artificially induced middle single prolonged stress (mSPS) model of post-traumatic stress disorder.

RESULTS

We found a significant reduction in the expression levels of each of the three lncRNAs tested: Gomafu in 45.4 times, NONMMUT033604.2 in 53.4 times, and NONMMUT064397.2 in 5.2 times. The results of the present study provide evidence that the mSPS model effectively induces PTSD-like behaviour in mice leading to a significant decrease in the expression level of Gomafu, NONMMUT033604.2 and NONMMUT064397.2 lncRNA in mice hippocampus.

CONCLUSIONS

This data provides evidence that the three studied lncRNAs could be potential biomarkers of PTSD development.

Timp1 Deletion Induces Anxiety-like Behavior in Mice

The hippocampus is essential for learning and memory, but it also plays an important role in regulating emotional behavior, as hippocampal excitability and plasticity affect anxiety and fear. Brain synaptic plasticity may be regulated by tissue inhibitor of matrix metalloproteinase 1 (TIMP1), a known protein inhibitor of extracellular matrix (ECM), and the expression of TIMP1 in the hippocampus can be induced by neuronal excitation and various stimuli. However, the involvement of Timp1 in fear learning, anxiety, and hippocampal synaptic function remains to be established. Our study of Timp1 function in vivo revealed that Timp1 knockout mice exhibit anxiety-like behavior but normal fear learning. Electrophysiological results suggested that Timp1 knockout mice showed hyperactivity in the ventral CA1 region, but the basic synaptic transmission and plasticity were normal in the Schaffer collateral pathway. Taken together, our results suggest that deletion of Timp1 in vivo leads to the occurrence of anxiety behaviors, but that Timp1 is not crucial for fear learning.

Rehmanniae Radix Preparata ameliorates behavioral deficits and hippocampal neurodevelopmental abnormalities in ADHD rat model

Objectives

Abnormal hippocampal neurodevelopment, particularly in the dentate gyrus region, may be a key mechanism of attention-deficit/hyperactivity disorder (ADHD). In this study, we investigate the effect of the most commonly used Chinese herb for the treatment of ADHD, Rehmanniae Radix Preparata (RRP), on behavior and hippocampal neurodevelopment in spontaneously hypertensive rats (SHR).

Methods

Behavior tests, including Morris water maze (MWM) test, open field test (OFT) and elevated plus maze (EPM) test were performed to assess the effect of RRP on hyperactive and impulsive behavior. Hippocampal neurodevelopment was characterized by transmission electron microscopy, immunofluorescence, Golgi staining and Nissl staining approaches. Regulatory proteins such as Trkb, CDK5, FGF2/FGFR1 were examined by Western blot analysis.

Results

The results showed that RRP could effectively control the impulsive and spontaneous behavior and improve the spatial learning and memory ability. RRP significantly reduced neuronal loss and increased the number of hippocampal stem cells, and promoted synaptic plasticity. In addition, FGF/FGFR signaling was upregulated after RRP treatment.

Conclusion

RRP can effectively reduce impulsive and spontaneous behavior and ameliorate hippocampal neurodevelopmental abnormalities in ADHD rat model.

Differential effects of perigestational consumption of sucrose-sweetened beverages on anxiety and depression-related behaviors in adult offspring: Sex disparity in a mouse model

Consumption of sucrose-sweetened drinks (SSDs) during pregnancy and breastfeeding can lead to various health and metabolism issues, but the potential impact on neurodevelopment and long-term effects remains unclear. This study aims to examine how maternal consumption of SSDs during gestation and lactation influences anxiety and depression-related behavior in adult offspring. Adult female CD-1 mice were randomly assigned to a control group (CG) or a sucrose group (SG) 2 weeks before gestation. The SG had 2 h of access to an SSD (15% w/w, 0.6 kcal/ml) for 2 weeks before mating, during pregnancy, and throughout lactation, totaling 8 weeks. Adult offspring were then evaluated for depressive-related behaviors and anxiety-related behaviors. Our findings reveal that perigestational consumption of SSDs does not lead to offspring presenting behaviors related to depression, but it does increase swimming behavior. However, maternal consumption of SSDs could impact the fighting response due to a diminished motivational component. In contrast, perigestational consumption of SSDs has apparent effects on anxiety-related behavior. Furthermore, female offspring appeared to be particularly vulnerable, exhibiting a higher anxiety index compared with controls. These findings indicate that females could be more vulnerable to the effects of maternal consumption of SSDs, being more susceptible to the presence of anxiety-related behaviors.

Circadian Synchronization of Feeding Attenuates Rats' Food Restriction-Induced Anxiety and Amygdalar Thyrotropin-Releasing Hormone Downregulation

Anxiety is a common comorbidity of obesity, resulting from prescribing long-term caloric restriction diets (CRDs); patients with a reduced food intake lose weight but present anxious behaviors, poor treatment adherence, and weight regain in the subsequent 5 years. Intermittent fasting (IF) restricts feeding time to 8 h during the activity phase, reducing patients' weight even with no caloric restriction; it is unknown whether an IF regime with ad libitum feeding avoids stress and anxiety development. We compared the corticosterone blood concentration between male Wistar rats fed ad libitum or calorie-restricted with all-day or IF food access after 4 weeks, along with their anxiety parameters when performing the elevated plus maze (EPM). As the amygdalar thyrotropin-releasing hormone (TRH) is believed to have anxiolytic properties, we evaluated its expression changes in association with anxiety levels. The groups formed were the following: a control which was offered food ad libitum (C-adlib) or 30% of C-adlib's energy requirements (C-CRD) all day, and IF groups provided food ad libitum (IF-adlib) or 30% of C-adlib's requirements (IF-CRD) with access from 9:00 to 17:00 h. On day 28, the rats performed the EPM and, after 30 min, were decapitated to analyze their amygdalar TRH mRNA expression by in situ hybridization and corticosterone serum levels. Interestingly, circadian feeding synchronization reduced the body weight, food intake, and animal anxiety levels in both IF groups, with ad libitum (IF-adlib) or restricted (IF-CRD) food access. The anxiety levels of the experimental groups resulted to be negatively associated with TRH expression, which supported its anxiolytic role. Therefore, the low anxiety levels induced by synchronizing feeding with the activity phase would help patients who are dieting to improve their diet therapy adherence.

Antidepressant-like Effects of Chinese Quince (Chaenomeles sinensis) Fruit Based on In Vivo and Molecular Docking Studies

In this study, we examined the potential antidepressant-like effects of Chinese quince fruit extract (Chaenomeles sinensis fruit extract, CSFE) in an in vivo model induced by repeated injection of corticosterone (CORT)-induced depression. HPLC analysis determined that chlorogenic acid (CGA), neo-chlorogenic acid (neo-CGA), and rutin (RT) compounds were major constituents in CSFE. Male ICR mice (5 weeks old) were orally administered various doses (30, 100, and 300 mg/kg) of CSFE and selegiline (10 mg/kg), a monoamine oxidase B (MAO-B) inhibitor, as a positive control following daily intraperitoneal injections of CORT (40 mg/kg) for 21 days. In our results, mice treated with CSFE exhibited significant improvements in depressive-like behaviors induced by CORT. This was evidenced by reduced immobility times in the tail suspension test and forced swim test, as well as increased step-through latency times in the passive avoidance test. Indeed, mice treated with CSFE also exhibited a significant decrease in anxiety-like behaviors as measured by the elevated plus maze test. Moreover, molecular docking analysis indicated that CGA and neo-CGA from CSFE had stronger binding to the active site of MAO-B. Our results indicate that CSFE has potential antidepressant effects in a mouse model of repeated injections of CORT-induced depression.

The impact of psychopathic traits on anxiety-related behaviors in a mixed reality environment

There is an ongoing debate about anxiety deficits in psychopathy and their possible impact on individual behavior. Data on actual anxiety- and threat-related behavior associated with psychopathy is still limited. We performed a mixed reality study using the elevated plus-maze (EPM) in a non-clinical sample (N = 160) to test anxiety-related behavior in relation to psychopathic personality traits measured through the Brief Questionnaire of Psychopathic Personality Traits (FPP). The psychopathy sum score correlated significantly with all measures of anxiety-related behavior on the EPM. Sensation seeking, but not general levels of acrophobia was moreover associated with psychopathic traits. Multivariate analyses revealed that the subscales Fearlessness and Lack of Empathy of the FPP predicted anxious behavior. Our findings are the first to demonstrate the relationship between psychopathic traits and actual behavior in an anxiety-inducing environment. This supports the low-anxiety hypothesis in psychopathy research. Implications for potentially harmful or risky behavior are discussed.

Intranasal Delivery of Near-Infrared and Magnetic Dual-Response Nanospheres to Rapidly Produce Antidepressant-Like and Cognitive Enhancement Effects

Restricted by synaptic plasticity, dopamine receptor (DR) upregulation takes a long time to work. Moreover, the impact of the blood-brain barrier (BBB) on delivery efficiency restricts the development of drugs. Taking inspiration from snuff bottles, a convenient, fast-acting, and nonaddictive nasal drug delivery system has been developed to rapidly reshape the balance of synaptic transmitters. This optical and magnetic response system called CFs@DP, comprised of carbonized MIL-100 (Fe) frameworks (CFs) and domperidone (DP), which can enter the brain via nasal administration. Under dual stimulation of near-infrared (NIR) irradiation and catecholamine-induced complexation, CFs@DP disintegrates to release iron ions and DP, causing upregulation of the dopamine type 1 (D1), type 2 (D2) receptors, and brain-derived neurotrophic factor (BDNF) to achieve a therapeutic effect. In vivo experiments demonstrate that the DR density of mice (postnatal day 50-60) increased in the prefrontal cortex (PFC) and the hippocampus (HPC) after 10 days of therapy, resulting in antidepressant-like and cognitive enhancement effects. Interestingly, the cognitive enhancement effect of CFs@DP is even working in noniron deficiency (normal fed) mice, making it a promising candidate for application in enhancing learning ability.

Adolescent activity-based anorexia has a substantial and prolonged impact on social behavior in young adult female rats

Activity-based anorexia (ABA) is a rodent model of anorexia nervosa (AN) that induces several key components of AN, including voluntary reduction in food intake, reduced body weight, hyperactivity, and alterations to the hypothalamic-pituitary-adrenal (HPA) axis. Previous research has demonstrated persistently increased anxiety-like behavior in the elevated plus maze (EPM), a test measuring avoidance of novel and open areas in adult female rats that experienced ABA during adolescence and are weight-restored in adulthood. Whether the same behavioral effects of two bouts of adolescent ABA emerge in response to different anxiety-provoking stimuli, however, has not been explored. We used the social partition (SP), novelty suppressed feeding (NSF), marble burying, and EPM tests to explore whether two bouts of adolescent ABA have persistent effects on anxiety-like behavior in weight restored young adult female rats. One-way ANOVA analyses revealed that female rats that experienced two bouts of ABA during adolescence had increased anxiety-like behavior in the EPM and SP tests in young adulthood following weight restoration compared with controls. These data demonstrate that the enduring behavioral effects of two bouts of adolescent ABA are specific to particular anxiety-provoking stimuli and suggest that adolescent ABA has enduring effects on social relationships.

The effects of paternal dietary fat versus sugar on offspring body composition and anxiety-related behavior

Increasing evidence suggests that the pre-conception parental environment has long-term consequences for offspring health and disease susceptibility. Though much of the work in this field concentrates on maternal influences, there is growing understanding that fathers also play a significant role in affecting offspring phenotypes. In this study, we investigate effects of altering the proportion of dietary fats and carbohydrates on paternal and offspring body composition and anxiety-related behavior in C57Bl/6-JArc mice. We show that in an isocaloric context, greater dietary fat increased body fat and reduced anxiety-like behavior of studs, whereas increased dietary sucrose had no significant effect. These dietary effects were not reflected in offspring traits, rather, we found sex-specific effects that differed between offspring body composition and behavioral traits. This finding is consistent with past paternal effect studies, where transgenerational effects have been shown to be more prominent in one sex over the other. Here, male offspring of fathers fed high-fat diets were heavier at 10 weeks of age due to increased lean body mass, whereas paternal diet had no significant effect on female offspring body fat or lean mass. In contrast, paternal dietary sugar appeared to have the strongest effects on male offspring behavior, with male offspring of high-sucrose fathers spending less time in the closed arms of the elevated plus maze. Both high-fat and high-sugar paternal diets were found to reduce anxiety-like behavior of female offspring, although this effect was only evident when offspring were fed a control diet. This study provides new understanding of the ways in which diet can shape the behavior of fathers and their offspring and contribute to the development of dietary guidelines to improve obesity and mental health conditions, such as anxiety.