Factors influencing behavior in the forced swim test

A novel butyrylcholinesterase inhibitor induces antidepressant, pro-cognitive, and anti-anhedonic effects in Flinders Sensitive Line rats: The role of the ghrelin-dopamine cascade

BACKGROUND AND PURPOSE

Major depressive disorder (MDD) is often treatment resistant, particularly in addressing anhedonia and cognitive deficits. Novel pharmacological strategies are needed. While butyrylcholinesterase, ghrelin, and dopamine (DA) have been well studied in the context of stress and MDD, their interaction remains unclear.

EXPERIMENTAL APPROACH

The dose-dependent antidepressant effects of a novel butyrylcholinesterase inhibitor (BChEI) were evaluated in the Flinders Sensitive Line (FSL) rat model of MDD. Behavioural assessments included the forced swim test (despair), sucrose preference test (reward-related), and novel object recognition test (cognition). Brain-derived neurotrophic factor (BDNF), acetylcholine (ACh), and brain monoamines were analysed, as well as serum growth hormone and acyl- and desacyl-ghrelin. To confirm the role of ghrelin, pharmacological exploration was undertaken using the ghrelin receptor antagonist, D-Lys-3-GHRP-6.

KEY RESULTS

FSL rats had significantly lower ghrelin ratios, BDNF, ACh, DA and growth hormone levels. In FSL rats, both BChEI and escitalopram significantly reduced despair. BChEI significantly outperformed escitalopram in enhancing reward-related and cognitive behaviours. Biochemically, BChEI treatment significantly increased ghrelin ratios and brain DA levels without altering brain 5-HT, ACh or BDNF. D-Lys-3-GHRP-6 significantly reversed the antidepressant-like, rewarding, and pro-cognitive effects of BChEI, accompanied by significant reductions in BDNF and DA.

CONCLUSIONS AND IMPLICATIONS

FSL rats display impaired ghrelin, DA, serotonin, growth hormone, and BDNF signalling, akin to MDD. BChEI exerts antidepressant-like effects across despair, reward, and cognitive domains, most likely via the BChE-ghrelin-DA cascade. Reversal of these effects by ghrelin antagonism underscores the critical role of ghrelin, specifically via growth hormone secretagogue receptor-ghrelin interaction. These findings suggest a potentially novel multimodal neurobiological target for the treatment of MDD.

Psilocybin mitigates behavioral despair and cognitive impairment in treatment-resistant depression model using wistar kyoto rats

Major depressive disorder (MDD) is a leading cause of disability that affects over 300 million people globally. Despite multiple antidepressant trials, approximately one-third of MDD patients remain symptomatic, progressing to treatment-resistant depression (TRD). This persistence possibly is due to the multifaceted etiology of TRD, encompassing biological, psychological, and environmental factors. Chronic stress, prevalent in modern life, significantly contributes to mental health disorders and complicates TRD treatment. This study investigated psilocybin as a potential TRD treatment using a diathesis-stress animal model. Twenty-two male Wistar-Kyoto (WKY) rats were divided into control and stress groups, with the stress group further subdivided to receive either sham treatment or psilocybin as early intervention. Behavioral assessments demonstrated a significant and sustained beneficial effect of psilocybin on behavioral despair and cognitive impairment. Biochemical analyses revealed psilocybin-induced increases in thyroid-stimulating hormone (TSH) levels without significant changes in the hypothalamic-pituitary-adrenal (HPA) axis. The ability of psilocybin to counter stress-induced TSH reductions suggested that TSH may serve as a proxy marker of therapeutic response, although its causal role in mood regulation remains unclear. Additionally, following psilocybin administration, changes in cannabinoid receptor type I (CB1R) suggest a potential modulation of psilocybin intervention on the component of the endocannabinoid system (ECS), though causal links remain unconfirmed without antagonist studies. These findings highlight the potential of psilocybin to treat TRD through the targeting of previously unexplored biological pathways.

Behavioral manifestations and underlying mechanisms of amphetamine in constructing animal models of mania: a comprehensive review

Mania is a mind disorder with heightened emotions, etc. Amphetamine (AMPH), a drug with central nervous system excitatory effects, can disrupt neurotransmitter release and metabolism, causing mania. AMPH-induced animal models of mania show increased risk and reward-seeking behaviors and excessive locomotion like mania patients, verifiable by tests like Elevated Plus Maze (EPM). It also impacts neurotransmitter balance in different brain regions, aligning with the imbalance in mania patients. Multiple signaling pathways including extracellular regulated protein kinases and others are involved, and their altered activities link to mania symptoms. In the AMPH-induced mania model, regions like the frontal cortex have increased oxidative stress and inflammatory response. Moreover, AMPH changes neurotrophin levels, potentially causing neuronal damage and cognitive impairment. In summary, the AMPH-induced mania animal model is crucial for studying mania's pathogenesis. However, further in-depth studies on neurotransmitter regulation, signaling pathway intervention, and neurotrophic factors are needed to develop more effective and personalized treatment plans.

When Silence Breaks: The Influence of Pure Tones and White Noises on Conditioned Flight Responses

BACKGROUND

The flight response is part of the repertoire of adaptive behavioral responses all animals possess and use to face threats coming from their environment. Compared to the other responses, flight requires a high degree of physical effort and is thought to be related to those active coping strategies that can be observed in several psychopathological conditions, including anxiety and depressive disorders. In recent years, a new protocol of auditory fear conditioning has been shown to induce a learned flight response in mice, based on a conditioned stimulus that includes pure tones and white noise, the serial compound stimulus (SCS).

METHODS

In this review, we examine the effects of stimulus characteristics in fear learning paradigms, particularly in the context of the recently developed SCS paradigm. We will discuss how factors such as conditioned stimulus (CS) modality (e.g., tone versus white noise), stimulus salience, and the temporal relationship between stimuli influence conditioned flight responses.

RESULTS

For the study of both physiological and maladaptive behaviors, fear conditioning still represents the paradigm of choice, e.g., for the modeling of psychiatric conditions such as post-traumatic stress disorder or phobias. Albeit its relevance in this context, up to now only a few studies have focused on developing procedures for eliciting conditioned flight responses in the laboratory, in favor of freezing/immobilization, the so-called fright response. The SCS protocol poses new interesting questions on the impact of noises and other stimuli on learning and behavioral responses.

CONCLUSION

The discovery of SCS already led to interesting findings in the neurobiology of fear learning and shows great potential for the study of maladaptive responses in animal models of psychopathology.

Indomethacin Partially Alleviates Depressive-Like Behaviors in Maternally Separated Mice: Targeting Neuroinflammatory Response in the Hippocampus

Experiencing early-life stress (ELS) plays a fundamental role in the development of mood disorders like depression in adulthood. Neuro-immune response in the brain is coupled with depressive-like behaviors following maternal separation (MS) stress. Indomethacin (IND) is a nonsteroidal anti-inflammatory drug. This study aimed to assess the antidepressant-like effect of IND in a mouse model of MS stress, focusing on its potential effect on neuro-inflammatory response in the hippocampus. To do this, male NMRI mice were treated with IND at doses of 5, 10, and 20 mg/kg, saline (10 mL/kg) or fluoxetine (30 mg/kg). Drugs were injected intraperitoneally for 7 days. Behavioral tests including forced swimming test, splash test, and open field test were performed. Quantitative reverse transcription-PCR was used for evaluation of gene expression of inflammatory mediators including of iNOS, TLR4, NLRP3, TNF-α, and IL-1β in the hippocampus. Results showed that MS provoked depressive-like behavior in mice as observed by a decrease in the grooming activity time in the splash test and an increase in the immobility time in the forced swimming test. Depressive-like behaviors were coupled with neuroinflammation in the hippocampus. IND attenuated depressive-like behaviors as well as decreased the gene expression of neuroinflammation-related mediators in the hippocampus of MS mice. In conclusion, results showed that IND, at least in part, via alleviation of neuro-inflammatory response in the hippocampus, exerted antidepressant-like effects in a mouse model of MS stress.

Reversing the impact of an obesogenic diet on emotion regulation and brain metabolism: A rat model study

The global rise in obesity and poor dietary habits, particularly the consumption of high-fat, high-sucrose (HFS) diets, is a growing public health concern. These diets, especially when consumed during critical developmental periods, such as gestation and early life, are linked to long-term consequences on both physical and mental health. Early exposure to obesogenic diets has been shown to disrupts brain function and increases the risk of anxiety, depression, and additional emotional disorders. However, it has been suggested that dietary changes during early life may reverse these effects. This study investigated whether switching from an HFS diet to a standard diet (SD) after weaning could reverse abnormal emotional responses (o anxiety- and depression-like behavior) and brain energy metabolic capacity in rats. Male and female Wistar rats were divided into three groups: one on continuous SD, one on an HFS diet from gestation until adulthood, and one that shifted from HFS to SD after weaning. Emotional behavior was assessed using the saccharin preference test, forced swimming test, and elevated zero maze test. Brain metabolism was evaluated by measuring cytochrome c oxidase (CCO) activity in key regions involved in emotion regulation, such as the nucleus accumbens, ventral pallidum, dorsal striatum, and the bed nucleus of stria terminalis. Adult animals exposed to the HFS diet exhibited increased depression and anxiety-like behaviors, and elevated CCO activity. Notably, sex differences were observed, with males showing more pronounced anxiety- and depression-like behaviors, although both sexes improved after diet switching. These findings suggest that early dietary interventions can mitigate diet-induced emotional and metabolic disturbances, thereby underscoring the importance of nutrition during critical developmental periods.

The light-dark forced swim test for simultaneous assessment of behavioral 'despair' and anxiety-like behavior in female mice

Animal models are a valuable tool to study anxiety and depression, two common and severely debilitating brain disorders. Probing them experimentally typically relies on various rodent behavioral assays, such as the light-dark and the forced swim tests. However, the growing importance of testing novel CNS concepts and neuroactive drugs calls for further refinement of existing behavioral tests, as well as the development of new assays. One research strategy in this direction involves combining principles of several tests into one 'hybrid' assay. Using this approach, here we develop a novel 'hybrid' mouse assay, the light-dark forced swim test, combining features of the two conventional assays to simultaneously assess animal anxiety-like (light-dark preference during swimming) and depression-like behaviors ('despair'-like immobility). Overall, the anxiety-like dark preference of female white outbred mice in this test is sensitive to physiological anxiogenic stressors (daily swimming or administration of prednisolone and dexamethasone), whereas clinically active antidepressants (fluoxetine and paroxetine) reduce despair-like immobility in this test. Collectively, these findings suggest that this novel assay may simultaneously evaluate anxiety- and depression-like behaviors, and can be applied to testing neuroactive drugs.

Vitamin D3 administration ameliorates the anxiety and depressive-like behaviour induced by nicotine withdrawal: a mechanistic focus on oxidative stress, inflammatory response, and serotonergic transmission

BACKGROUND

The present study conducted to assess whether vitamin D3 (Vit D) could ameliorate the anxiety and depression induced by nicotine (Nic) withdrawal in male adult rats.

METHODS

To this end, behavioural tests were done in male Wistar rats undergone adolescent Nic exposure (2 mg/kg) and then withdrawal and the effect of Vit D (100, 1000, and 10,000 IU/kg) was assessed at both behavioural and biochemical levels.

RESULTS

Results indicated that Vit D treatment could effectively prevent anxiety, depression, and biochemical alterations induced by Nic withdrawal.

CONCLUSION

Vit D has strong potential to be used for prevention of anxiety- and depressive-like behaviours following Nic withdrawal; however, further investigation is needed in larger sample size to discuss more confidently.

Behavioural assessment of neuropsychiatric outcomes in rodent stroke models

Stroke-associated mood disorders are less recognised than sensorimotor impairment, despite their high prevalence. Similarly, few experimental stroke studies assess non-sensorimotor functions. This study examined the prevalence and implementation of non-sensorimotor tests in three stroke-focused journals over the last twenty years. Of 965 experimental ischaemic stroke papers which used behavioural testing in rodents, 932 included sensorimotor testing, while 137 used non-sensorimotor tests (most commonly the Morris water maze, open field, Y-maze, and novel object recognition tests, but with a more diverse range of tests introduced in recent years). Cognition, anxiety and depression were assessed in 70%, 27% and 3% of these 137 papers. Non-sensorimotor deficits were typically observed after recovery of sensorimotor function. Potential confounding factors and challenges for data interpretation were identified in the most prevalent tests. More generally, experimental rigor (a priori power calculation, randomisation, blinding, and pre-defined inclusion/exclusion) improved over the years, but remained unsatisfactory with only 26% of studies providing some evidence of adequate statistical power. Furthermore, most studies focused on male animals, limiting external validity. This review confirms the disparity between sensorimotor and non-sensorimotor testing in experimental stroke but shows that the share of the studies including the latter is increasing. It is essential that research into the neuropsychiatric sequalae of stroke addresses methodological issues noted and continues to expand to improve patient outcomes post-stroke.

Hyperactivity in male and female mice manifests differently following early, acute prenatal alcohol exposure and mild juvenile stress

Introduction

Chronic prenatal alcohol exposure (PAE) and severe juvenile stress independently contribute to hyperactive and depressive behavioral phenotypes, with their combination exacerbating these effects. However, while chronic PAE and traumatic juvenile stress are well-studied, little is known about the impact of early, acute PAE and mild juvenile stress on hyperactivity and depression. This knowledge gap is clinically relevant, as these milder early-life insults are common in Western societies. Here, we provide the first investigation into the effects of early, acute PAE and juvenile sub-chronic, unpredictable, mild stress (SUMS)-both independently and in combination-on hyperactivity and depressive-like behaviors in mice throughout the lifespan.

Methods

We assessed hyperactivity through movement-related measures (i.e., distance traveled, thigmotaxis, and rearing), whereas depressive-like behaviors were evaluated using the u-shaped two-choice field and forced swim tests. Behavioural testing was performed on equivalent numbers of male and female offspring and repeated at juvenile, adolescent, and adult timepoints to enable assessment of sex and age effects.

Results

Neither early, acute PAE, juvenile SUMS, nor their combination induced depressive-like behaviors at any age; findings in contrast to the more severe chronic PAE and stress insults used in previous studies. However, these milder early-life insults did result in various hyperactivity phenotypes in both the male and female offspring. For example, juvenile SUMS had the strongest impact on hyperactive behaviors across both sexes, but only the adolescent females exhibited increased emotionality-associated activity. Moreover, early, acute PAE-both alone and in combination with juvenile SUMS significantly increased movement during adolescence and adulthood exclusively in male offspring.

Discussion

Thus, our collective findings not only indicate that early, acute PAE and juvenile SUMS influence hyperactivity in a sex- and age-dependent manner, but also highlight that their influence on hyperactive and depressive phenotypes do not simply mirror those of the more severe early-life insults. Given the potential prevalence of early, acute alcohol exposure and juvenile stress in Western society, further research is warranted to fully understand their long-term behavioral consequences.

Mice lacking the serotonin transporter do not respond to the behavioural effects of psilocybin

BACKGROUND AND PURPOSE

Psilocybin is a serotonergic psychedelic with therapeutic potential for several neuropsychiatric disorders, including depression and anxiety disorders. Serotonin transporter (5-HTT) knockout mice (KO) are a well-validated mouse model of anxiety/depression and are relevant to both chronic treatment with serotonin transporter reuptake inhibitors (SSRIs) and polymorphisms in the serotonin transporter-linked polymorphic region (5-HTTLPR) associated with depression/anxiety and resistance to classic antidepressant treatments. However, there is yet to be a study assessing the effect of psilocybin in 5-HTT KO mice.

EXPERIMENTAL APPROACH

We investigated the effects of a single dose of psilocybin (1 mg/kg) on locomotor activity and the head-twitch response as well as anxiety- and depressive-like behaviour in KO versus wild-type (WT) mice using the light-dark box and Porsolt swim test respectively.

KEY RESULTS

We found that both the psilocybin-induced head-twitch and hyperlocomotor responses observed in WT mice were completely absent in KO animals. In female WT mice only, psilocybin was also able to block the weight loss observed one day after intraperitoneal injection. While psilocybin did not alter anxiety- and depression-like behaviours for both genotypes, we revealed a genotype-specific trend for a main effect of treatment for WT females (p = 0.054) in the Porsolt swim test. Finally, we found that only female KO mice exhibit anhedonia-like behaviour in the saccharin-preference test.

CONCLUSION AND IMPLICATIONS

Our findings highlight the complexity of psilocybin's effects and suggest that functional integrity of 5-HTT is essential for psilocybin's acute behavioural effects. This could also have implications for pharmacogenetics, including individuals with polymorphisms or mutations in 5-HTT.

Possible GABAkine-Mediated Sedative-Like Antidepressant Effects of Phytol: Molecular Interventions Through In Vitro, In Vivo and In Silico Approaches

BACKGROUND

A previous report suggests that phytol (PHY) may exert its antidepressant effects in mice, possibly through GABAA receptor interaction pathways.

AIM

We aimed to check its antidepressant effect with possible molecular mechanisms through behavioral and in silico studies.

METHODS

For this, adult mice were randomly divided into different groups (n = 6), namely control (vehicle), standards (DZP: diazepam at 2 mg/kg, FLU: flumazenil at 0.1 mg/kg, FLUX: fluoxetine at 20 mg/kg), PHY (25, 50, and 75 mg/kg), and combined groups (PHY-75 with DZP-2 and/or FLU-0.1, and FLUX-20). Thirty minutes after treatment, each animal was subjected to tail suspension and forced swimming tests, and their immobility time (IMT) was counted for 5 min. In silico studies were performed with the GABAA receptor α1, α2, α3, α5, and γ2 subunits and 5HT1A to investigate possible molecular mechanisms. Additionally, in vitro GABA activity of PHY and/or reference drugs was also performed by using the colorimetric method.

RESULTS

The results demonstrated that PHY and/or DZP significantly (p < 0.05) and concentration-dependently inhibited GABA, while FLU alone or its combination with PHY reversed it. In mice, PHY dose-dependently reduced the IMT in both protocols, while FLUX-20 showed lower IMT compared to the control and DZP, indicating elevated locomotion in mice. It showed a reduced IMT value in male animals than in female animals. In both sexes, PHY at 75 mg/kg significantly (p < 0.05) increased the IMT values with DZP-2, while reducing this parameter with FLU-0.1. In silico studies demonstrated that PHY exhibited higher binding affinities with the α2 and α3 subunits of the GABAA and 5HT1A receptors by -6.5, -7.2 and 6.7 kcal/mol, respectively.

CONCLUSION

Taken together, PHY exerted sedative-like antidepressant effects in mice and modulated the effects of GABAergic drugs DZP and FLU and serotonergic drug FLUX. PHY may be a potential candidate for the management of depression.

Mechanism of Wuling powder modulating proBDNF/p75NTR/sortilin and BDNF/TrkB pathways in the treatment of ulcerative colitis complicated with depression

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory disease affecting the colon. The most common psychological issue in UC patients is varying degrees of depression, which affects the condition and quality of life of UC patients and may lead to deterioration of the patient's condition. UC drugs combined with antianxiety and antidepression drugs can alleviate symptoms of both depression and UC. Brain-derived neurotrophic factor (BDNF) precursor (proBDNF)/p75 neurotrophin receptor (p75NTR)/sortilin and BDNF/tropomyosin receptor kinase B (TrkB) signalling balance is essential for maintaining brain homeostasis and preventing the development of depressive behaviours.

AIM

To explore the mechanism by which Wuling powder regulates the proBDNF/p75NTR/sortilin and BDNF/TrkB pathways in the treatment of UC with depression.

METHODS

Depression was established in C57BL/6J mice via chronic restraint stress, and the UC model was induced with dextran sodium sulfate (DSS). In the treatment stage, mesalazine (MS) was the basic treatment, Wuling powder was the experimental treatment, and fluoxetine was the positive control drug for treating depression. Changes in intestinal mucosal inflammation, behaviour, and the proBDNFp75NTR/sortilin and BDNF/TrkB pathways were evaluated.

RESULTS

In the depression groups, Wuling powder decreased the immobility time, increased the distance travelled in the central zone and the total distance travelled, and restored balance in the proBDNF/p75NTR/sortilin and BDNF/TrkB signalling pathways. In the DSS and chronic restraint stress + DSS groups, immobility time increased, distance travelled in the central zone and total distance travelled decreased, activity of the proBDNF/p75NTR/sortilin pathway was upregulated, and activity of the BDNF/TrkB pathway was downregulated, indicating that mice with UC often have comorbid depression. Compared with those of MS alone, Wuling powder combined with MS further decreased the colon histopathological scores and the expression levels of tumor necrosis factor-alpha and interleukin-6 mRNAs.

CONCLUSION

This study confirmed that Wuling powder may play an antidepressant role by regulating the balance of the proBDNF/p75NTR/sortilin and BDNF/TrkB signalling pathways and further relieve intestinal inflammation in UC.

An Updated Bio-Behavioral Profile of the Flinders Sensitive Line Rat: Reviewing the Findings of the Past Decade

The Flinders sensitive line (FSL) rat is an accepted rodent model for depression that presents with strong face, construct, and predictive validity, thereby making it suitable to investigate novel antidepressant mechanisms. Despite the translatability of this model, available literature on this model has not been reviewed for more than ten years. The PubMed, ScienceDirect and Web of Science databases were searched for relevant articles between 2013 and 2024, with keywords relating to the Flinders line rat, and all findings relevant to treatment naïve animals, included. Following screening, 77 studies were included and used to create behavioral reference standards and calculate FSL favor ratios for the various behavioral parameters. The GRADE and SYRCLE risk of bias tools were used to scale the quality of these studies. Based on these results, FSL rats display reliable and reproducible depressive-like behavior in the forced swim test, together with hyperlocomotor activity across various behavioral tests. Despite reports of increased anhedonia, anxiety-like behavior, and cognitive dysfunction, the reviewed findings indicate that these parameters are comparable between strains. For the various neuro- and biological constructs, oxidative stress, energy production, and glutamatergic, noradrenergic and serotonergic neurotransmission received the most support for strain differences. Taken together, the FSL remains a reliable, popular, and translatable rodent model of depression, with strong face and construct validity. As for predictive validity, similar review approaches should be considered to establish whether the mentioned behavioral aspects and neurochemical constructs may be more sensitive (or resistant) to certain antidepressant strategies.

Tryptophan-induced effects on the behavior and physiology of aging in tryptophan hydroxylase-2 heterozygous mice C57BL/6N

Background and Aim

Tryptophan (Trp), a precursor of serotonin, plays a critical role in cognitive and emotional processes. Its metabolism through serotonin and kynurenine pathways impacts neuropsychiatric functions and lipid metabolism. This study investigates Trp's effects on the behavioral, physiological, and molecular parameters of aging female wild-type (WT) and heterozygous tryptophan hydroxylase-2 (HET) mice.

Materials and Methods

A 68-day experiment was conducted on 13-month-old WT and HET mice. Groups received either distilled water or Trp supplementation (400 mg/kg/day). Behavioral tests (Open Field, Elevated Zero Maze, Forced Swim, and Extrapolation Escape Task) assessed locomotion, anxiety, and cognition. Physiological assessments included body composition through NMR relaxometry, lipid histology, serotonin content in the brain (ELISA), and serotonergic gene expression (RT-PCR). Blood biochemistry and organ weights were also analyzed.

Results

Trp supplementation reduced growth rates and adipose tissue while increasing muscle mass in both genotypes, more markedly in HET mice. Behavioral tests revealed a decrease in anxiety and enhanced cognitive performance in HET+Trp mice but an increase in immobility. Trp increased brain serotonin content in HET mice and altered serotonergic gene expression. Histological studies showed hepatoprotective effects in HET+Trp mice, reducing liver lipid infiltration compared to WT+Trp mice.

Conclusion

Trp exhibited genotype-specific effects, with HET mice showing anabolic, hepatoprotective, and neuropsychiatric changes. These findings highlight Trp's potential in neuro-nutrition for conditions like depression and cognitive decline. Further studies are needed to explore Trp's metabolic pathways and their implications for personalized dietary interventions.

Simultaneous 5-HT1BR agonist/5-HT6R antagonist action as a potential treatment of Parkinson's disease and its comorbidities

Parkinson's disease (PD) treatment focuses mainly on the augmentation of dopamine transmission, but to alleviate adverse motor effects accompanying L-DOPA use, additional treatments with serotonergic (5-HT) medications may be considered. We propose a novel concept based on the simultaneous activation of 5-HT1BR and 5-HT6R blockade as a putative therapeutic option for PD treatment. We have developed PZKKN-94, a dual human 5-HT1BR agonist (EC50 = 39 nM) and human 5-HT6R antagonist (KB = 7.7 nM), with selectivity over 43 targets, favorable drug-like properties, and brain penetration. Importantly, PZKKN-94 potency was increased or retained at rat 5-HT1B and 5-HT6 orthologs but not at mouse 5-HT6. Therefore, PZKKN-94 was tested in 2 rat disease models: haloperidol-induced catalepsy and 6-hydroxydopamine-induced sensorimotor deficits in rats, showing antiparkinsonian-like effects in both. Of note, PZKKN-94 did not affect the therapeutic effects of L-DOPA and attenuated L-DOPA-induced motor fluctuation ("on-off" phenomena) in the stepping and vibrissae tests. PZKKN-94 had no effect on L-DOPA-induced contralateral rotation, suggesting no impact on dopamine-mimetic medication effects. In addition, PZKKN-94 reversed scopolamine-, phencyclidine-, and aged-induced learning deficits in the rat novel object recognition test, increased cognitive flexibility in the attention set-shifting task, and displayed antidepressant-like actions in the forced swim test in rats. Our data suggest that dual-acting 5-HT1BR agonists/5-HT6R antagonists provide a novel therapeutic approach to alleviate both motor symptoms and accompanying cognitive and depression comorbidities in PD. Our present findings highlight the dual 5-HT1BR agonist/5-HT6R antagonist strategy to simultaneously spare L-DOPA's action and alleviate motor fluctuations related to L-DOPA treatment. SIGNIFICANCE STATEMENT: The commonly used L-DOPA-based medications for Parkinson's disease, though effective in alleviating initial disease states, are limited in long-term use due to the motor (dyskinesia and on-off phenomena) and nonmotor (psychotic-like) side effects. A novel nondopaminergic strategy for treatment of Parkinson's disease based on simultaneous activation of the 5-HT1B receptor and blockade of the 5-HT6 receptor is proposed. The compound PZKKN-94 produces an antiparkinsonian-like effect and attenuates motor fluctuations, preserving the efficacy of L-DOPA. In addition, PZKKN-94 demonstrates procognitive and antidepressant-like properties.

Ascorbic acid supplementation in adolescent rats ameliorates anxiety-like and depressive-like manifestations of nicotine-ethanol abstinence: Role of oxidative stress, inflammatory, and serotonergic mechanisms

BACKGROUND

The present study aims to assess the therapeutic potential of vitamin C (Vit C) on anxiety- and depressive-like behavior induced by abstinence from chronic nicotine-ethanol co-exposure in adolescent male rats.

MATERIALS AND METHODS

Adolescent male rats were divided into seven experimental groups with ten rats as follows: 1) vehicle, 2) Nicotine (Nic)-Ethanol (Eth): received Nic (2 mg/kg) and Eth (20%) in drinking water from 21 to 42 days of age, 3-5) Nic-Eth-Vit C 100/200/400: received Nic and Eth from 21 to 42 days of age and received Vit C 100/200/400 mg/kg from 43 to 63 days of age, 6) Nic-Eth-Bupropion (Bup)- Naloxone (Nal): received Nic and Eth from 21 to 42 days of age and received Bup and Nal from 43 to 63 days of age, and 7) Vit C 400 mg/kg: received Vit C 400 mg/kg from 43 to 63 days of age. Behavioral assessments were done by elevated plus maze (EPM), forced swimming test (FST), marble burring test (MBT), and open field tests (OFT). Furthermore, specific biochemical variables associated with oxidative, inflammatory, and serotonergic profiles were quantified.

RESULTS

According to the obtained results, Nic and Eth induced anxiety and depression in treated rats. We showed that two higher doses of Vit C increases the active struggling time in FST and decreases both the time spent in the peripheral zone of OFT and the time spent in the closed arms of EPM. In addition, animals treated by Vit C buried less number of marbles in MBT compared to their control counterparts. Nic and Eth induced oxidative stress and inflammation in cortical tissues of treated rats. Biochemical parameters were improved in the Nic-Eth group receiving Vit C 200/400 mg/kg and Bup-Nal through establishing a balance between oxidant/anti-oxidant and inflammatory/anti-inflammatory mediators. In addition, serotonin level was increased, while Monoamine oxidase (MAO) activity was notably decreased.

CONCLUSION

The present findings support the beneficial effect of Vit C on anxiety- and depressive-like behavior induced by Nic-Eth withdrawal through various mechanisms such as the promotion of antioxidant defense, suppression of inflammatory mediators, and enhancement of serotoninergic function.

Evaluation of Nanocurcumin Effects on Depressive-Like Behaviors in Rats and Determination of Serum BDNF and Serotonin Levels

INTRODUCTION

Major depressive disorder (MDD) is a highly prevalent psychiatric condition worldwide, and it is the leading cause of disability globally. Turmeric, an aromatic perennial herb widely used in traditional Asian medicine and cuisine, contains curcumin, which has several biological effects, including a pseudoantidepressant effect. However, curcumin's low bioavailability limits its effectiveness. This study evaluated nanocurcumin (NCUR) effects on depressive-like behaviors and examined serum BDNF and serotonin levels in a chronic stress model in rats. Behavioral assessments and biochemical indicators elucidated NCUR's antidepressant-like properties.

METHODS

In this experimental study, 30 adult male rats were randomly divided into six groups and exposed to unexpected chronic mild stress (UCMS). The groups included: control (CG), stress control (SCG), fluoxetine (FLU) treatment (20 mg/kg), and three NCUR doses (20, 40, and 80 mg/kg). Before UCMS exposure, rats underwent a sucrose preference test (SPT). Depressive behaviors were then assessed using the open field test (OFT), forced swimming test (FST), and tail suspension test (TST) on days 27 and 28. Blood samples were collected on day 28 to measure serum Brain derived neurotrophic factor (BDNF) and serotonin levels using enzyme-linked immunosorbent assay (ELISA).

RESULTS

NCUR treatment significantly alleviated depressive-like behaviors in stressed rats. The sucrose preference index of the SCG decreased after 26 days of stress, while NCUR (all doses) and FLU reversed this effect. In the FST and TST, immobility time was significantly reduced in the NCUR and FLU groups compared to the SCG (p < 0.05). The OFT also showed that the SCG had significantly fewer crossings compared to treated groups (p < 0.05). Additionally, NCUR treatment significantly increased serum BDNF and serotonin levels compared to the SCG.

CONCLUSIONS

This study demonstrates that NCUR exerts antidepressant-like effects, improving depressive behaviors and increasing BDNF and serotonin levels in rats exposed to chronic stress. NCUR may offer a promising alternative for the treatment of MDD.

The molecular mechanism of Xiaoyaosan in treating major depressive disorder: Integrated analysis of DNA methylation and RNA sequencing of the arcuate nucleus in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaoyaosan, a classic Chinese herbal formula, exhibits promising antidepressant effects. However, its specific antidepressant mechanisms remain incompletely understood. Previous studies have highlighted the significant role of DNA methylation in the pathogenesis of major depressive disorder (MDD). Yet, whether the effects of Xiaoyaosan are linked to DNA methylation and its regulation remains unclear.

AIM OF THE STUDY

This study aims to explore and verify the molecular mechanism of Xiaoyaosan in treating MDD via integrated analysis of DNA methylation and RNA sequencing.

MATERIALS AND METHODS

In this study, a chronic unpredictable mild stress (CUMS) model was established to induce MDD in rats, which were subsequently orally treated with Xiaoyaosan, with fluoxetine as a positive control. Antidepressant effects were assessed by the open field test, sucrose preference test, and forced swimming test. Whole-genome bisulfite sequencing (WGBS) and bulk RNA sequencing were performed in the arcuate nucleus of hypothalamus to assess methylation changes and identify differentially expressed genes. Bioinformatics analyses were conducted to explore methylation alterations, RNA sequencing profiles, and their shared epigenetic as well as gene expression changes, to identify candidate genes. Finally, RT-PCR was used to validate the key differential genes.

RESULTS

Xiaoyaosan effectively reversed depressive-like behaviors. Further, Xiaoyaosan treatment involved multiple epigenetic modifications. The results of differentially methylated genes showed that there were 1353 overlapped genes between M-vs-C-hypo gene and X-vs-M-hyper gene, 5326 overlapped genes between M-vs-C-hyper gene and X-vs-M-hypo gene. GO and KEGG enrichment analyses indicated these intersecting genes were involved in biological regulation, transcription factors, appetite and endocrine control systems, etc. The analysis of differentially expressed genes from RNA sequencing revealed that there were 25 overlapping genes between the M vs C hypomethylated group and the X vs M hypermethylated group, while 81 overlapping genes were identified between the M vs C hypermethylated group and the X vs M hypomethylated group. Those differential genes regulated by methylation enriched in processes related to brain and neuronal growth, neuropeptide and hormone activation, as well as biological processes and molecular functions associated with protein translation, synthesis, transport, and localization. The integrated analysis of DNA methylation and RNA sequencing screened 14 potentially differential genes, which were associated with appetite regulation, energy metabolism, and neuroreceptor ligands. PCR verification found that Lmx1b, Abcc5, Gpc3 and Cfb showed statistical differences.

CONCLUSIONS

The antidepressant mechanism of Xiaoyaosan involves the biological regulation in the arcuate nucleus of hypothalamus, including transcription factors, neurotransmitter regulation, neural development, appetite regulation peptides, and endocrine control systems. The methylation level and regulation at the gene locus of Lmx1b, Abcc5, Gpc3, and Cfb may play a key role in the treatment of Xiaoyaosan. These findings provide new insights into the therapeutic mechanisms of Xiaoyaosan.

Potential antihyperlipidemic effects of myrcenol and curzerene in high-fat fed rats

The study evaluated the anti-hyperlipidemic effects of myrcenol and curzerene on a high fat diet induced hyperlipidemia rat model. Thirty male albino rats were fed on a high-fat diet for four months. The HFD-induced hyperperlipidemia rats were treated with rosuvastatin (10 mg/kg), curzerene (130 mg/kg) and myrcenol (100 mg/kg) for four weeks. Blood samples were collected for further analysis. Aorta and heart were harvested for histopathological evaluation. Hepatic lipase and HMG-CoA reductase were determined by ELISA. FST and Y-maze tests were performed to assess the stress level in hyperlipidemia rats. The phytochemical compounds (Curzerene and Myrcenol) and the standard drug (Rosuvastatin) resulted in decreased body weight as well as reduced levels of LDL, TG, TC, AST and ALT as compared to the diseased group. Additionally, the treated groups displayed improved HDL levels and less depressed behavior. The ELISA results revealed that the Curzerene and myrcenol had significantly increased the protein concentration of hepatic lipase than the diseased group whereas both compounds significantly lowered the HMG-CoA reductase concentrations compared to the diseased group. The findings suggested that myrcenol and curzerene had the potential to be therapeutic agents for managing hyperlipidemia and reducing the risk of heart-related conditions associated with high lipid levels.

Effectiveness of positive allosteric modulators of metabotropic glutamate receptor 2/3 (mGluR2/3) in animal models of schizophrenia

Schizophrenia (SZ) is a deleterious brain disorder characterised by its heterogeneity and complex symptomatology consisting of positive, negative and cognitive deficits. Current antipsychotic drugs ameliorate the positive symptomatology, but are inefficient in treating the negative symptomatology and cognitive deficits. The neurodevelopmental glutamate hypothesis of SZ has opened new avenues in the development of drugs targeting the glutamatergic system. One of these new therapies involves the positive allosteric modulators (PAMs) of metabotropic glutamate receptors, mainly types 2/3 (mGluR2/3). mGluR2/3 PAMs are selective for the receptor, present high tolerability and can modulate the activity of the receptor for long periods. There is not much research in clinical trials regarding mGluR2/3 PAMs. However, several lines of evidence from animal models have indicated the efficiency of mGluR2/3 PAMs. In this review, focusing on in vivo animal studies, we will specifically discuss the utilization of SZ animal models and the various methods employed to assess animal behaviour before summarising the evidence obtained to date in the field of mGluR2/3 PAMs. By doing so, we aim to deepen our understanding of the underlying mechanisms and the potential efficiency of mGluR2/3 PAMs in treating SZ. Overall, mGluR2/3 PAMs have demonstrated efficiency in attenuating SZ-like behavioural and molecular deficits in animal models and could be useful for the early management of the disorder or to treat specific subsets of patients.

Agmatine diminishes behavioral and endocrine alterations in a rat model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD), is a severe anxiety disorder characterized by associative fear conditioning. Single prolonged stress (SPS) is a widely accepted reliable animal model to stimulate PTSD. Agmatine is an endogenous neuromodulator of stress; however, its effect on PTSD remains to be investigated. This study explored the role of agmatine in conditioned fear response (CFR) in PTSD and highlighted the role of imidazoline receptors in the effect of agmatine. Intra-cerebroventricular (icv) surgery was done in order to facilitate drug administration. Animals were subjected to SPS. Agmatine and the involvement of imidazoline receptors (I1 and I2) were assessed for their effect in fear conditioning apparatus. During weeks 1, 2, and 3, in CFR, agmatine (40 µg/rat, icv) showed significantly decreased freezing time whereas other doses of agmatine (10 and 20 µg/rat, icv). Imidazoline (I1 and I2) receptor agonists Moxonidine (25 µg/rat, icv) and 2-BFI, (10 µg/rat, icv) respectively, at their sub-effective doses, with a submaximal dose of agmatine (20 µg/rat, icv) significantly decreased the altered freezing time during weeks 1, 2 and 3 compared to SPS animals. Moreover, the effective dose of agmatine (40 µg/rat, icv) with imidazoline (I1 and I2) receptor antagonists Efaroxan (10 µg/rat, icv) and Idazoxan (4 µg/rat, icv) respectively does not reversed the effect of agmatine on freezing. Agmatine and its combination with I1 and I2 agonists, normalized the altered freezing behavior, corticosterone level, organ coefficient of adrenal gland, neuroinflammatory and neurotrophic factor due to SPS during CFR projecting its strong therapeutic effect in SPS induced PTSD.

Early psilocybin intervention alleviates behavioral despair and cognitive impairment in stressed Wistar rats

Chronic stress exerts profound effects on mental health, contributing to disorders such as depression, anxiety, and cognitive impairment. This study examines the potential of psilocybin to alleviate behavioral despair and cognitive deficits in a rodent model of chronic stress, focusing on the interplay between the Hypothalamic-Pituitary-Adrenal (HPA) axis and the Endocannabinoid System (ECS). Twenty-two male Wistar rats were divided into control and stress groups. Animals within the stress group were exposed to predator odor and chronic social instability to induce chronic stress, and were either sham treated, or given psilocybin. Behavioral assessments were conducted using the Open Field Test, Sucrose Preference Test, Novel Object Recognition, Elevated Plus Maze, and Forced Swimming Test to evaluate locomotion, anhedonia, memory, anxiety, and behavioral despair, respectively. Blood and brain samples were analyzed for biochemical markers. Results indicated that psilocybin significantly reduced stress-induced behavioral despair and cognitive impairments, likely through ECS-mediated downregulation of the HPA axis. These findings suggest that early intervention with psilocybin has sustained beneficial effects on stress-related behavioral and cognitive disturbances, underscoring its potential as a novel therapeutic approach for stress-related mental health disorders.

Subchronic Exposure to Mixture of Cadmium, Copper, and Nickel Induces Neurobehavioral Deficits and Hippocampal Oxidative Stress of Wistar Rats

The present study was aimed at evaluating the influence of the subchronic exposure of cadmium (Cd), copper (Cu), and nickel (Ni) mixtures on affective behaviors, memory impairment, and oxidative stress (OS) in the hippocampus. Thirty male Wistar rats were divided into 5 equal groups. Group 1 (control) received a saline solution (NaCl 0.9%). Groups 2, 3, and 4 received Cd (0.25 mg/kg), Cu (0.5 mg/kg), and Ni (0.25 mg/kg), respectively, while group 5 received a Cd, Cu, and Ni mixture through intraperitoneal injections for 2 months. After the exposure period, all rats were submitted to behavioral tests. Subsequently, OS markers and histological changes in the rats' hippocampi were assessed. Results showed that a 2-month exposure to the mixtures of metals (MM) has led to higher anxiety-like and depression-like behaviors and cognitive deficits in rats when compared to the control group and the individual metals. Furthermore, the MM induced heightened OS, evidenced by the rise in lipid peroxidation and nitric oxide levels. These effects were accompanied by a decrease in superoxide dismutase and catalase activities in the hippocampus. The histopathological analysis also supported that MM caused a neuronal loss in the CA3 sub-region. Overall, this study underscores that subchronic exposure to the Cd, Cu, and Ni mixture induces an OS status and histological changes in the hippocampus, with important affective and cognitive behavior variations in rats.

A New Augmentation Strategy against Depression Combining SSRIs and the N-terminal Fragment of Galanin (1-15)

Depression is one of the most disabling mental disorders, with the second highest social burden; its prevalence has grown by more than 27% in recent years, affecting 246 million in 2021. Despite the wide range of antidepressants available, more than 50% of patients show treatment-resistant depression. In this review, we summarized the progress in developing a new augmentation strategy based on combining the N-terminal fragment of Galanin (1-15) and SSRI-type antidepressants in animal models.

Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice

BACKGROUND

Insulin-like growth factor-1 (IGF-1) promotes neurogenesis, cell survival, and glial function, making it a promising candidate therapy in Alzheimer's disease (AD).

OBJECTIVE

Long arginine 3-IGF-1 (LR3-IGF-1) is a potent IGF-1 analogue. We sought to determine whether intranasal (IN) LR3 treatment would delay cognitive decline and pathology in 5XFAD mice.

METHODS

Wildtype and 5XFAD male mice were treated for 7 months (3-10 months of age), with IN LR3-IGF-1 or IN Vehicle (Veh) (n = 19-27 mice/group). Behavior, memory, and brain imaging were assessed at 8-9 months of age and tissues collected at 10 months. A comprehensive amyloid-β (Aβ) profile and other pathologic features were conducted and supportive in vitro stimulation studies in BV-2 microglial cells were also performed.

RESULTS

In male 5XFAD mice, IN LR3-IGF-1 treatment improved body composition, but did not significantly alter cognitive symptoms, as assessed by multiple assays. In cortex, LR3 treatment improved some facets of pathology, including a reduction in filamentous plaques, and increase in inert plaques, corresponding with a reduction in low molecular weight Aβ oligomers. In vitro, uptake of Aβ1-42 peptide by BV2 cells was enhanced by LR3-IGF-1, which was also found to promote gene pathways implicated in actin remodeling and endocytosis.

CONCLUSIONS

LR3 promotes favorable effects on Aβ plaque remodeling in cortex of male 5XFAD mice but fails to preserve aspects of behavior or memory. While these data do not support LR3 as a monotherapy per se, they do warrant further investigation into its potential for combinatorial formulations aimed at targeting the complexity of AD.

Nelumbo nucifera Petals Ameliorate Depressive-like Symptom and Cognitive Deficit in Unpredictable Chronic Mild Stress Mouse Model

Background Chronic stress exposure has been widely recognized as a significant contributor to numerous central nervous system (CNS) disorders, leading to debilitating behavioral changes such as anxiety, depression, and cognitive impairments. The prolonged activation of the hypothalamic-pituitary-adrenal (HPA) axis during chronic stress disrupts the neuroendocrine balance and has detrimental effects on neuronal function and survival. Nelumbo nucifera (N. nucifera) Gaertn., commonly known as the lotus flower, is a traditional medicinal plant consumed for its purported benefits on mental and physical well-being. Despite its traditional use, limited scientific evidence supports these claims. Methods The present study explores the effects of N. nucifera, commonly known as the lotus flower, on cognitive performance and stress resilience in a mouse model subjected to unpredictable chronic mild stress (UCMS). Results Daily treatment significantly improved cognitive performance, alleviated depressive-like behaviors, and normalized hypothalamic-pituitary-adrenal (HPA) axis activity, as indicated by a 60.97% reduction in serum corticosterone. At the molecular level, N. nucifera petals also downregulated serum- and glucocorticoid-inducible kinase 1 (SGK1) mRNA expression while upregulating brain-derived neurotrophic factor (BDNF) mRNA expression and cyclic-adenosine monophosphate (cAMP) responsive element-binding protein (CREB) mRNA expression in the hippocampus and frontal cortex. These normalizations are critical, as chronic stress dysregulates HPA axis function, exacerbating behavioral changes. Furthermore, a phytochemical analysis resulted in the isolation of five major compounds, kaempferol (1), trifolin (2), kaempferol-3-neohesperidoside (3), icariside D2 (4), and β-sitosterol (5), each demonstrating significant monoamine oxidase (MAO) inhibitory activity. Conclusions These compelling findings suggest that N. nucifera petals not only alleviate stress-induced mood and cognitive deficits but also offer a promising avenue for modulating the HPA axis and promoting neuroprotection via essential neurotrophic factors and enzymatic pathways. We advocate for its potential as a complementary and alternative medicine for effective stress management. Future investigations should further explore its mechanisms of action and evaluate its clinical applicability in stress-related disorders.

Antidepressant-like and antistress effects of the ACTH(4-10) synthetic analogs Semax and Melanotan II on male rats in a model of chronic unpredictable stress

Current antidepressant therapy shows substantial limitations, and there is an urgent need for the development of new treatment strategies for depression. Stressful events and hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis play an important role in the pathogenesis of depression. HPA axis activity is self-regulated by negative feedback at several levels including adrenocorticotropic hormone (ACTH)-mediated feedback. Here, we investigated whether noncorticotropic synthetic analogs of the ACTH(4-10) fragment, ACTH(4-7)-Pro-Gly-Pro (Semax) and Ac-Nle4-cyclo[Asp5-His6-D-Phe7-Arg8-Trp9-Lys10]ACTH(4-10)-NH2 (Melanotan II (MTII), a potent agonist of melanocortin receptors), have potential antidepressant activity in a chronic unpredictable stress (CUS) rat model of depression. Stressed and control male adult Sprague-Dawley rats received daily intraperitoneal injections of saline or a low dose (60 nmol/kg of body weight (BW)) of Semax or MTII. Rats were monitored for BW and hedonic status, as measured in the sucrose preference test. We found that chronic treatment with Semax and MTII reversed or substantially attenuated CUS-induced anhedonia, BW gain suppression, adrenal hypertrophy and a decrease in the hippocampal levels of BDNF. In the forced swim test, no effects of the CUS procedure or peptides on the duration of rat immobility were detected. Our findings show that in the CUS paradigm, systemically administered ACTH(4-10) analogs Semax and MTII exert antidepressant-like effects on anhedonia and hippocampal BDNF levels, and attenuate markers of chronic stress load, at least in male rats. The results support the argument that ACTH(4-10) analogs and other noncorticotropic melanocortins may have promising therapeutic potential for the treatment and prevention of depression and other stress-related pathologies.

Systemic Administration of a Site-Targeted Complement Inhibitor Attenuates Chronic Stress-Induced Social Behavior Deficits and Neuroinflammation in Mice

Chronic stress, a risk factor for many neuropsychiatric conditions, causes dysregulation in the immune system in both humans and animal models. Additionally, inflammation and synapse loss have been associated with deficits in social behavior. The complement system, a key player of innate immunity, has been linked to social behavior impairments caused by chronic stress. However, it is not known whether complement inhibition can help prevent neuroinflammation and behavioral deficits caused by chronic stress. In this study, we investigated the potential of a site-targeted complement inhibitor to ameliorate chronic stress-induced changes in social behavior and inflammatory markers in the prefrontal cortex (PFC) and hippocampus. Specifically, we investigated the use of C2-Crry, which comprises a natural antibody-derived single-chain antibody (ScFv) targeting domain-designated C2, linked to Crry, a C3 activation inhibitor. The C2 targeting domain recognizes danger-associated molecular patterns consisting of a subset of phospholipids that become exposed following cell stress or injury. We found that systemic administration of C2-Crry attenuated chronic stress-induced social behavioral impairments in mice. Furthermore, C2-Crry administration significantly decreased microglia/macrophage and astrocyte activation markers in the PFC and hippocampus. These findings suggest that site-targeted complement inhibition could offer a promising, safe, and effective strategy for treating chronic stress induced behavioral and immune function disorders.

Antidepressant-like effects of the leaf extract of Mallotus oppositifolius (Geiseler) Müll. Arg. (Euphorbiaceae) in the chronic unpredictable mild stress model: A role of the gut-brain axis

The gut microbiota has been posited as a target for the treatment of major depressive disorder. Herein, we investigated the effect of the hydroethanolic leaf extract of Mallotus oppositifolius (MOE) on the gut microbiota of mice and how this contributes to its known antidepressant-like effect. A 6-week chronic unpredictable mild stress (CUMS) procedure was employed in 7 groups of mice to induce depression. From the third week, oral MOE treatments (10, 30, 100 mg/kg) and two reference drugs, fluoxetine (12 mg/kg) and minocycline (40 mg/kg), known to affect the gut microbiota, were administered. The sixth and seventh groups were the vehicle stressed (VEH-S) and non-stressed groups (VEH-NS). Changes in depressive-like behaviors were assessed using sucrose preference test while the forced swimming test (FST) was used to assess sustained antidepressant-effect after treatment discontinuation. Moreover, changes in prefrontal cortex (PFC) and hippocampal serotonin (5-HT) levels were evaluated using enzyme-linked immunosorbent assay (ELISA). The effect of treatment on the profile of the gut microbiota of the groups was elucidated using 16S rRNA Oxford Nanopore sequencing. MOE and reference drugs reversed the depression-associated reduction in sucrose preference when compared to VEH-S. MOE (with peak effect at 30 mg/kg) reduced immobility while increasing swimming and climbing behaviors. MOE reversed CUMS-induced reduction of 5-HT concentration in PFC and hippocampus. The behavioral effects of MOE were associated with shifts in the gut microbiota of CUMS-exposed mice. The study has provided seminal evidence that MOE ameliorates CUMS-induced depressive symptoms by modulating gut microbiota and increasing brain 5-HT levels.

Recent advances in the synthesis of antidepressant derivatives: pharmacologic insights for mood disorders

Mood disorders, including depression, remain a significant global health concern, necessitating continuous efforts to develop novel and more effective antidepressant therapies. Although there have been significant advancements in comprehending the biology of Major Depressive Disorder (MDD), a considerable number of people suffering from depression do not exhibit positive responses to the pharmacologic treatments now available. This study specifically examines emerging targets and potential future approaches for pharmaceutical interventions in the treatment of MDD. The discussion revolves around novel therapeutic agents and their effectiveness in treating depression. The focus is on the specific pathophysiological pathways targeted by these agents and the amount of evidence supporting their use. While conventional antidepressants are anticipated to continue being the primary treatment for MDD in the foreseeable future, there is currently extensive research being conducted on numerous new compounds to determine their effectiveness in treating MDD. Many of these compounds have shown encouraging results. This review highlighted the recent advances in the synthesis of antidepressant derivatives and explores their pharmacologic insights for the treatment of mood disorders.

Stress-induced c-fos expression in the medial prefrontal cortex differentially affects the main residing cell phenotypes

Stress poses a challenge to the body's equilibrium and triggers a series of responses that enable organisms to adapt to stressful stimuli. The medial prefrontal cortex (mPFC), particularly in acute stress conditions, undergoes significant physiological changes to cope with the demands associated with cellular activation. The proto-oncogene c-fos and its protein product c-Fos have long been utilized to investigate the effects of external factors on the central nervous system (CNS). While c-Fos expression has traditionally been attributed to neurons, emerging evidence suggests its potential expression in glial cells. In this study, our main objective was to explore the expression of c-Fos in glial cells and examine how acute stress influences these activity patterns. We conducted our experiments on male Wistar rats, subjecting them to acute stress and sacrificing them 2 h after the stressor initiation. Using double-labelling fluorescent immunohistochemistry targeting c-Fos, along with markers such as GFAP, Iba-1, Olig2, NG2, and NeuN, we analyzed 35 μm brain slices obtained from the mPFC. Our findings compellingly demonstrate that c-Fos expression extends beyond neurons and is present in astrocytes, oligodendrocytes, microglia, and NG2 cells-the diverse population of glial cells. Moreover, we observed distinct regulation of c-Fos expression in response to stress across different subregions of the mPFC. These results emphasize the importance of considering glial cells and their perspective in studies investigating brain activity, highlighting c-Fos as a response marker in glial cells. By shedding light on the differential regulation of c-Fos expression in response to stress, our study contributes to the understanding of glial cell involvement in stress-related processes. This underscores the significance of including glial cells in investigations of brain activity and expands our knowledge of c-Fos as a potential marker for glial cell responses.

Behavioral Assays for Comprehensive Evaluation of Cognitive and Neuropsychiatric Comorbidities of Traumatic Brain Injury and Chronic Neurological Disorders

Neurological deficits, psychiatric disorders, and cognitive impairments often accompany stroke, brain injury, epilepsy, and many neurological disorders, which present intricate comorbidities that challenge recognition and management. There are many tools and paradigms for evaluating learning, memory, anxiety, and depression-like behaviors in lab animal models of brain disorders. However, there is a significant gap between clinical observations and experimental models, which limit understanding of the complex interplay between chronic brain conditions and their impact on cognitive dysfunction and psychiatric impairments. This article describes an overview of experimental rationale, methods, protocols, and strategies for evaluating sensorimotor, affective and cognitive-associated comorbid behaviors in epilepsy, traumatic brain injury (TBI), stroke, spinal cord injury (SCI), and many other neurological disorders. First, we delve into clinical evidence elucidating the profound impact of comorbidities, e.g., psychiatric disorders and cognitive deficits, in individuals with epilepsy. Then, we discuss diverse approaches to assess these comorbidities in experimental models of brain diseases. Finally, we explore the methodologies for assessing motor function, sensorimotor, behavior, and psychiatric health. We cover strategies and protocols enabling these assays, including implementing behavioral paradigms to assess learning and memory, anxiety, and depression-like behaviors in rodents in health and disease conditions. It is essential to consider a comprehensive battery of tests to investigate various behavioral deficits, considering environment, age, and sex differences relevant to the disease, such as TBI, SCI, epilepsy, stroke, and other complex neurological conditions. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC.

Antidepressant-like effects of Cimicifuga dahurica (Turcz.) Maxim. via modulation of monoamine regulatory pathways

Sheng-ma is recorded in the Compendium of Materia Medica and mainly originates from the rhizomes of Cimicifuga dahurica (Turcz.) Maxim. (CD), Cimicifuga heracleifolia Kom. and Cimicifuga foetida L. The alcoholic extract of Cimicifuga foetida L. (Brand name: Ximingting®) has been approved for the treatment of perimenopausal symptoms accompanying hot flash, depression and anxiety in China. However, there's no further study about the antidepressant-like effects of C. dahurica (CD). The aim of this study is to investigate the antidepressant-like effect of CD extracted by 75% ethanol and its possible mechanisms.The neuro-protective effects of CD on injured PC12 cells induced by corticosterone was measured firstly. Then, forced swim test (FST), tail suspension test (TST), reserpine-induced hypothermia, 5-hydroxytryptophan (5-HTP) induced head twitch response in mice and chronic unpredictable mild stress (CUMS) on sucrose preference tests were executed. Moreover, the potential mechanisms were explored by measuring levels of monoamine neurotransmitter in mice frontal cortex and hippocampus, testing monoamine oxidase enzyme A (MAO-A) activities in the brains of CUMS-exposed mice. Results showed that CD (60, 120 mg/kg) can significantly decreased the immobility period in FST and TST in mice without affecting locomotor activity. CD (30 mg/kg, 60 mg/kg, 120 mg/kg) could significantly counteracted reserpine-induced hypothermia and increased the number of head-twitches in 5-HTP induced head twitch response. It was also found that the monoamine neurotransmitter levels in the hippocampus and frontal cortex were significantly increased in 60 mg/kg and 120 mg/kg CD treated mice. In addition, CD (60 and 120 mg/kg) significantly inhibited MAO-A after 6-week CUMS exposure. CD can effectively produce an antidepressant-like effect, which involved with modulation of monoamine regulatory pathways.

Amitriptyline and cholecalciferol amend hippocampal histological structure and myelination during stress in Wistar rats via regulating miR200/BMP4/Olig-2 signaling

Chronic stress is a universal condition commonly associated with many psychiatric diseases. An extensive body of evidence discussed hippocampal affection upon chronic stress exposure, however, the underlying molecular pathways still need to be identified. We investigated the impact of chronic stress on miR200/BMP/Olig-2 signaling and hippocampal myelination. We also compared the effects of chronic administration of amitriptyline and cholecalciferol on chronically stressed hippocampi. Both amitriptyline and cholecalciferol significantly decreased serum cortisol levels, reduced immobility time in the forced swim test, increased the number of crossed squares in open field test, decreased the hippocampal expression of bone morphogenetic protein 4 (BMP4) and its messenger RNA (mRNA) levels, reduced miR200 expression as compared to untreated chronically stressed rats. Also, both drugs amended the hippocampal neuronal damage, enhanced the surviving cell count, and increased the pyramidal layer thickness of Cornu Ammonis subregion 1 (CA1) and granule cell layer of the dentate gyrus. Cholecalciferol was more effective in increasing the area percentage of myelin basic protein (MBP) and Olig-2 positive cells count in hippocampi of chronic stress-exposed rats than amitriptyline, thus enhancing myelination. We also found a negative correlation between the expression of BMP4, its mRNA, miR200, and the immunoexpression of MBP and Olig-2 proteins. This work underscores the amelioration of the stress-induced behavioral changes, inhibition of miR200/BMP4 signaling, and enhancement of hippocampal myelination following chronic administration of either amitriptyline or cholecalciferol, though cholecalciferol seemed more effective in brain remyelination.

Long-term Treatment with a 5-Alpha-Reductase Inhibitor Alleviates Depression-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 5 mg/kg/day for 6 weeks, and 3) the withdrawal group receiving FIN orally at 5 mg/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.

Histone 3 Trimethylation Patterns are Associated with Resilience or Stress Susceptibility in a Rat Model of Major Depression Disorder

Major Depressive Disorder (MDD) is a severe and multifactorial psychiatric condition. Evidence has shown that environmental factors, such as stress, significantly explain MDD pathophysiology. Studies have hypothesized that changes in histone methylation patterns are involved in impaired glutamatergic signaling. Based on this scenario, this study aims to investigate histone 3 involvement in depression susceptibility or resilience in MDD pathophysiology by investigating cellular and molecular parameters related to i) glutamatergic neurotransmission, ii) astrocytic functioning, and iii) neurogenesis. For this, we subjected male Wistar rats to the Chronic Unpredictable Mild Stress (CUMS) model of depression. We propose that by evaluating the sucrose consumption, open field, and object recognition test performance from animals submitted to CUMS, it is possible to predict with high specificity rats with susceptibility to depressive-like phenotype and resilient to the depressive-like phenotype. We also demonstrated, for the first time, that patterns of H3K4me3, H3K9me3, H3K27me3, and H3K36me3 trimethylation are strictly associated with the resilient or susceptible to depressive-like phenotype in a brain-region-specific manner. Additionally, susceptible animals have reduced DCx and GFAP and resilient animals present increase of AQP-4 immunoreactivity. Together, these results provide evidence that H3 trimethylations are related to the development of the resilient or susceptible to depressive-like phenotype, contributing to further advances in the pathophysiology of MDD and the discovery of mechanisms behind resilience.

Phenotype Distinctions in Mice Deficient in the Neuron-Specific α3 Subunit of Na,K-ATPase: Atp1a3tm1Ling/+ and Atp1a3 +/D801Y

ATP1A3 is a Na,K-ATPase gene expressed specifically in neurons in the brain. Human mutations are dominant and produce an unusually wide spectrum of neurological phenotypes, most notably rapid-onset dystonia parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). Here we compared heterozygotes of two mouse lines, a line with little or no expression (Atp1a3tm1Ling/+) and a knock-in expressing p.Asp801Tyr (D801Y, Atp1a3 +/D801Y). Both mouse lines had normal lifespans, but Atp1a3 +/D801Y had mild perinatal mortality contrasting with D801N mice (Atp1a3 +/D801N), which had high mortality. The phenotypes of Atp1a3tm1Ling/+ and Atp1a3 +/D801Y were different, and testing of each strain was tailored to its symptom range. Atp1a3tm1Ling/+ mice displayed little at baseline, but repeated ethanol intoxication produced hyperkinetic motor abnormalities not seen in littermate controls. Atp1a3 +/D801Y mice displayed robust phenotypes: hyperactivity, diminished posture consistent with hypotonia, and deficiencies in beam walk and wire hang tests. Symptoms also included qualitative motor abnormalities that are not well quantified by conventional tests. Paradoxically, Atp1a3 +/D801Y showed sustained better performance than wild type on the accelerating rotarod. Atp1a3 +/D801Y mice were overactive in forced swimming and afterward had intense shivering, transient dystonic postures, and delayed recovery. Remarkably, Atp1a3 +/D801Y mice were refractory to ketamine anesthesia, which elicited hyperactivity and dyskinesia even at higher dose. Neither mouse line exhibited fixed dystonia (typical of RDP patients), spontaneous paroxysmal weakness (typical of AHC patients), or seizures but had consistent, measurable neurological abnormalities. A gradient of variation supports the importance of studying multiple Atp1a3 mutations in animal models to understand the roles of this gene in human disease.

The sinking platform test: a novel paradigm to measure persistence in animal models

Persistence is the propensity to maintain goal-directed actions despite adversities. While this temperamental trait is crucial to mitigate depression risk, its neurobiological foundations remain elusive. Developing behavioral tasks to capture persistence in animal models is crucial for understanding its molecular underpinnings. Here, we introduce the Sinking Platform Test (SPT), a novel high-throughput paradigm to measure persistence. Mice were trained to exit a water-filled tank by ascending onto a platform above water level. Throughout the training, mice were also occasionally exposed to "failure trials," during which an operator would submerge a platform right after the mouse climbed onto it, requiring the mouse to reach and ascend a newly introduced platform. Following training, mice were subjected to a 5-min test exclusively consisting of failure trials. Male and female mice exhibited comparable persistence, measured by the number of climbed platforms during the test. Furthermore, this index was increased by chronic administration of fluoxetine or imipramine; conversely, it was reduced by acute and chronic haloperidol. Notably, six weeks of social isolation reduced SPT performance, and this effect was rescued by imipramine treatment over the last two weeks. A 4-week regimen of voluntary wheel running also improved persistence in socially isolated mice. Finally, comparing transcriptomic profiles of the prefrontal cortex of mice with high and low SPT performance revealed significant enrichment of immediate-early genes known to shape susceptibility for chronic stress. These findings highlight the potential of SPT as a promising method to uncover the biological mechanisms of persistence and evaluate novel interventions to enhance this response.

Activation of CRF/CRFR1 Signaling in the Central Nucleus of the Amygdala Contributes to Chronic Stress-Induced Exacerbation of Neuropathic Pain by Enhancing GluN2B-NMDA Receptor-Mediated Synaptic Plasticity in Adult Male Rats

Exacerbation of pain by chronic stress and comorbidity of pain with stress-related disorders such as depression and post-traumatic stress disorder, represent significant clinical challenges. Previously we have documented that chronic forced swim (FS) stress exacerbates neuropathic pain in spared nerve injury (SNI) rats, associated with an up-regulation of GluN2B-containing N-methyl-D-aspartate receptors (GluN2B-NMDARs) in the central nucleus of the amygdala (CeA). However, the molecular mechanisms underlying chronic FS stress (CFSS)-mediated exacerbation of pain sensitivity in SNI rats still remain unclear. In this study, we demonstrated that exposure of CFSS to rats activated the corticotropin-releasing factor (CRF)/CRF receptor type 1 (CRFR1) signaling in the CeA, which was shown to be necessary for CFSS-induced depressive-like symptoms in stressed rats, and as well, for CFSS-induced exacerbation of pain hypersensitivity in SNI rats exposed to chronic FS stress. Furthermore, we discovered that activation of CRF/CRFR1 signaling in the CeA upregulated the phosphorylation of GluN2B-NMDARs at tyrosine 1472 (pGluN2BY1472) in the synaptosomal fraction of CeA, which is highly correlated to the enhancement of synaptic GluN2B-NMDARs expression that has been observed in the CeA in CFSS-treated SNI rats. In addition, we revealed that activation of CRF/CRFR1 signaling in the CeA facilitated the CFSS-induced reinforcement of long-term potentiation as well as the enhancement of NMDAR-mediated excitatory postsynaptic currents in the basolateral amygdala (BLA)-CeA pathway in SNI rats. These findings suggest that activation of CRF/CRFR1 signaling in the CeA contributes to chronic stress-induced exacerbation of neuropathic pain by enhancing GluN2B-NMDAR-mediated synaptic plasticity in rats subjected to nerve injury. PERSPECTIVE: Our present study provides a novel mechanism for elucidating stress-induced hyperalgesia and highlights that the CRF/CRFR1 signaling and the GluN2B-NMDAR-mediated synaptic plasticity in the CeA may be important as potential therapeutic targets for chronic stress-induced pain exacerbation in human neuropathic pain. DATA AVAILABILITY: The data that support the findings of this study are available from the corresponding author upon reasonable request.

A TrkB cleavage fragment in hippocampus promotes Depressive-Like behavior in mice

Decreased hippocampal tropomyosin receptor kinase B (TrkB) level is implicated in the pathophysiology of stress-induced mood disorder and cognitive decline. However, how TrkB is modified and mediates behavioral responses to chronic stress remains largely unknown. Here the effects and mechanisms of TrkB cleavage by asparagine endopeptidase (AEP) were examined on a preclinical murine model of chronic restraint stress (CRS)-induced depression. CRS activated IL-1β-C/EBPβ-AEP pathway in mice hippocampus, accompanied by elevated TrkB 1-486 fragment generated by AEP. Specifi.c overexpression or suppression of AEP-TrkB axis in hippocampal CaMKIIα-positive cells aggravated or relieved depressive-like behaviors, respectively. Mechanistically, in addition to facilitating AMPARs internalization, TrkB 1-486 interacted with peroxisome proliferator-activated receptor-δ (PPAR-δ) and sequestered it in cytoplasm, repressing PPAR-δ-mediated transactivation and mitochondrial function. Moreover, co-administration of 7,8-dihydroxyflavone and a peptide disrupting the binding of TrkB 1-486 with PPAR-δ attenuated depression-like symptoms not only in CRS animals, but also in Alzheimer's disease and aged mice. These findings reveal a novel role for TrkB cleavage in promoting depressive-like phenotype.

Environmental enrichment enhances the antidepressant effect of ketamine and ameliorates spatial memory deficits in adult rats

Ketamine is a rapid-acting antidepressant associated with various cognitive side effects. To mitigate these side effects while enhancing efficacy, it can be co-administered with other antidepressants. In our study, we adopted a similar strategy by combining ketamine with environmental enrichment, a potent sensory-motor paradigm, in adult male Wistar rats. We divided the animals into four groups based on a combination of housing conditions and ketamine versus vehicle injections. The groups included those housed in standard cages or an enriched environment for 50 days, which encompassed a 13-day-long behavioral testing period. Each group received either two doses of ketamine (20 mg/kg, IP) or saline as a vehicle. We tested the animals in the novel object recognition test (NORT), forced swim test (FST), open field test (OFT), elevated plus maze (EPM), and Morris water maze (MWM), which was followed by ex vivo c-Fos immunohistochemistry. We observed that combining environmental enrichment with ketamine led to a synergistic antidepressant effect. Environmental enrichment also ameliorated the spatial memory deficits caused by ketamine in the MWM. There was enhanced neuronal activity in the habenula of the enrichment only group following the probe trial of the MWM. In contrast, no differential activity was observed in enriched animals that received ketamine injections. The present study showed how environmental enrichment can enhance the antidepressant properties of ketamine while reducing some of its side effects, highlighting the potential of combining pharmacological and sensory-motor manipulations in the treatment of mood disorders.

Therapeutic potential of cannabidiol in depression

Major depressive disorder (MDD) is a widespread and debilitating condition affecting a significant portion of the global population. Traditional treatment for MDD has primarily involved drugs that increase brain monoamines by inhibiting their uptake or metabolism, which is the basis for the monoaminergic hypothesis of depression. However, these treatments are only partially effective, with many patients experiencing delayed responses, residual symptoms, or complete non-response, rendering the current view of the hypothesis as reductionist. Cannabidiol (CBD) has shown promising results in preclinical models and human studies. Its mechanism is not well-understood, but may involve monoamine and endocannabinoid signaling, control of neuroinflammation and enhanced neuroplasticity. This chapter will explore CBD's effects in preclinical and clinical studies, its molecular mechanisms, and its potential as a treatment for MDD.

RE104: Synthesis and Activity of a Novel Serotonergic Psychedelic Prodrug of 4-Hydroxy-N,N-diisopropyltryptamine

Results from randomized clinical trials of psilocybin in depressive disorders highlight the therapeutic potential of serotonergic psychedelic compounds in mental health disorders. The synthetic 5-hydroxytryptamine 2A receptor agonist 4-hydroxy-N,N-diisopropyltryptamine (4-OH-DiPT) is structurally similar to psilocin but is reported to have a shorter duration (2-3 h) of psychedelic effects, suggesting the potential for psilocybin-like therapeutic activity with reduced clinical resource burden. Here, we describe the preclinical and translational characterization of RE104, a 4-OH-DiPT prodrug comprising a glutarate moiety designed to cleave rapidly in situ and thus provide reasonable bioavailability of the active drug. Plasma concentration of 4-HO-DiPT over time in PK experiments in rats was correlated with head-twitch intensity. The half-life of 4-OH-DiPT was 40 min after subcutaneous administration of RE104 in rats. In a forced swim test, a single dose of RE104 (1 mg/kg) significantly reduced mean immobility time at 1 week compared with vehicle (P < 0.001), confirming translational antidepressant potential. Taken together, these data with RE104 show that the glutarate ester can act as an efficient prodrug strategy for 4-HO-DiPT, a unique short-duration psychedelic with potential in depressive disorders.

A scoping review of the effects of mushroom and fungus extracts in rodent models of depression and tests of antidepressant activity

One of the most important developments in psychopharmacology in the past decade has been the emergence of novel treatments for mood disorders, such as psilocybin for treatment-resistant depression. Psilocybin is most commonly found in different species of mushroom; however, the literature on mushroom and fungus extracts with potential antidepressant activity extends well beyond just psilocybin-containing mushrooms, and includes both psychedelic and non-psychedelic species. In the current review, we systematically review the preclinical literature on mushroom and fungus extracts, and their effects of animal models of depression and tests of antidepressant activity. The PICO structure, PRISMA checklist and the Cochrane Handbook for systematic reviews of intervention were used to guide the search strategy. A scoping search was conducted in electronic databases PubMed, CINAHL, Embase and Web of Science. The literature search identified 50 relevant and suitable published studies. These included 19 different species of mushrooms, as well as seven different species of other fungi. Nearly all studies reported antidepressant-like effects of treatment with extracts. Treatments were most commonly delivered orally, in both acute and chronically administered studies to predominantly male rodents. Multiple animal models of depression were used, the most common being unpredictable chronic mild stress, while the tail suspension test and forced swim test were most frequently used as standalone antidepressant screens. Details on each experiment with mushroom and fungus species are discussed in detail, while an evaluation is provided of the strengths and weaknesses of these studies.

Folic Acid Ameliorates Anxiety- and Depressive-Like Behavior Induced by Nicotine Withdrawal Through Restoration of Behavioral and Biochemical Alterations in Adolescent Male Rats

BACKGROUND

The present study aimed to assess the efficacy of folic acid (FA) on withdrawal following nicotine (Nic) administration in adolescent male rats.

AIMS AND METHODS

Adolescent male rats were divided into two groups: (1) vehicle and (2) Nic (Nic-2 mg/kg), and were under treatment from 21 to 42 days of age. After that, they continued the experiment without treatment and returned to a regular diet, except for one of those who received Nic. The rats were divided into four groups where they were treated with different doses of FA (5, 10, and 15 mg/kg) and bupropion (Bup) by oral gavage, and the final group included normal rats that received only FA (15 mg/kg) from 42 days of age for three weeks during which withdrawal occurred.

RESULTS

Results showed that adolescent Nic exposure exacerbated the behavioral indices of anxiety- and depression-like behaviors, while FA attenuated the effects of Nic withdrawal on anxiety and depression as well as Bup. In support, the biochemical results demonstrated a balance between oxidant and antioxidant mediators in addition to the increase and decrease of serotonin and monoamine oxidase (MAO) activity in cortical tissue. TNF-α as an inflammatory agent was decreased, whereas IL-10 as an anti-inflammatory parameter was increased.

CONCLUSIONS

The present findings suggest anxiety and depression caused by Nic withdrawal were attenuated by FA more likely through the reduction activity of MAO, the important enzyme responsible for serotonin metabolism along with balance between oxidant/antioxidant and pro-inflammatory/anti-inflammatory mediators. However, various mechanisms might be involved, which requires further investigation.

IMPLICATIONS

Nic withdrawal-induced depression and anxiety like behavior in rats followed by neuro-oxidative damage and neuro-inflammation. FA supplementation as well as Bup improved cognitive disorders induced by Nic withdrawal by increasing neuro-inflammation and neuro-oxidative damage.

Rodent tests of depression and anxiety: Construct validity and translational relevance

Behavioral testing constitutes the primary method to measure the emotional states of nonhuman animals in preclinical research. Emerging as the characteristic tool of the behaviorist school of psychology, behavioral testing of animals, particularly rodents, is employed to understand the complex cognitive and affective symptoms of neuropsychiatric disorders. Following the symptom-based diagnosis model of the DSM, rodent models and tests of depression and anxiety focus on behavioral patterns that resemble the superficial symptoms of these disorders. While these practices provided researchers with a platform to screen novel antidepressant and anxiolytic drug candidates, their construct validity-involving relevant underlying mechanisms-has been questioned. In this review, we present the laboratory procedures used to assess depressive- and anxiety-like behaviors in rats and mice. These include constructs that rely on stress-triggered responses, such as behavioral despair, and those that emerge with nonaversive training, such as cognitive bias. We describe the specific behavioral tests that are used to assess these constructs and discuss the criticisms on their theoretical background. We review specific concerns about the construct validity and translational relevance of individual behavioral tests, outline the limitations of the traditional, symptom-based interpretation, and introduce novel, ethologically relevant frameworks that emphasize simple behavioral patterns. Finally, we explore behavioral monitoring and morphological analysis methods that can be integrated into behavioral testing and discuss how they can enhance the construct validity of these tests.

Cynaroside improved depressive-like behavior in CUMS mice by suppressing microglial inflammation and ferroptosis

Depression is a common mental health disorder, and in recent years, the incidence of various forms of depression has been on the rise. Most medications for depression are highly dependency-inducing and can lead to relapse upon discontinuation. Therefore, novel treatment modalities and therapeutic targets are urgently required. Traditional Chinese medicine (TCM) offers advantages in the treatment of depression owing to its multi-target, multi-dimensional approach that addresses the root cause of depression by regulating organ functions and balancing Yin and Yang, with minimal side effects. Cynaroside (CNS), an extract from the traditional Chinese herb honeysuckle, is a flavonoid compound with antioxidant properties. In this study, network pharmacology identified 44 potential targets of CNS associated with depression and several highly correlated inflammatory signaling pathways. CNS alleviated LPS-induced M1 polarization and the release of inflammatory factors in BV-2 cells. Transcriptomic analysis and validation revealed that CNS reduced inflammatory polarization, lipid peroxidation, and ferroptosis via the IRF1/SLC7A11/GPX4 signaling pathway. In vivo experiments showed that CNS treatment had effects similar to those of fluoxetine (FLX). It effectively ameliorated anxiety-, despair-, and anhedonia-like states in chronic unpredictable mild stress (CUMS)-induced mice and reduced microglial activation in the hippocampus. Thus, we conclude that CNS exerts its therapeutic effect on depression by inhibiting microglial cells from polarizing into the M1 phenotype and reducing inflammation and ferroptosis levels. This study provides further evidence that CNS is a potential antidepressant, offering new avenues for the treatment of depression.

Prenatal and perinatal exposure to Per- and polyfluoroalkyl substances (PFAS)-contaminated drinking water impacts offspring neurobehavior and development

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants ubiquitous in the environment and humans. In-utero PFAS exposure is associated with numerous adverse health impacts. However, little is known about how prenatal PFAS mixture exposure affects offspring's neurobehavioral function. This study aims to determine the causal relationship between in-utero PFAS mixture exposure and neurobehavioral changes in Sprague-Dawley rat offspring. Dams were exposed via drinking water to the vehicle (control), an environmentally relevant PFAS mixture, or a high-dose PFAS mixture. The environmentally relevant mixture was formulated to resemble measured tap water levels in Pittsboro, NC, USA (10 PFAS compounds; sum PFAS =758.6 ng/L). The high-dose PFAS load was 3.8 mg/L (5000×), within the range of exposures in the experimental literature. Exposure occurred seven days before mating until birth. Following exposure to PFAS-laden water or the vehicle during fetal development, neurobehavioral toxicity was assessed in male and female offspring with a battery of motor, cognitive, and affective function tests as juveniles, adolescents, and adults. Just before weaning, the environmentally relevant exposure group had smaller anogenital distances compared to the vehicle and high-dose groups on day 17, and males in the environmentally relevant exposure group demonstrated lower weights than the high-dose group on day 21 (p < 0.05). Reflex development delays were seen in negative geotaxis acquisition for both exposure groups compared to vehicle-exposed controls (p = 0.009). Our post-weaning behavioral measures of anxiety, depression, and memory were not found to be affected by maternal PFAS exposure. In adolescence (week five) and adulthood (week eight), the high PFAS dose significantly attenuated typical sex differences in locomotor activity. Maternal exposure to an environmentally relevant PFAS mixture produced developmental delays in the domains of pup weight, anogenital distance, and reflex acquisition for rat offspring. The high-dose PFAS exposure significantly decreased typical sex differences in locomotor activity.

Evidence for a Role of 5-HT-glutamate Co-releasing Neurons in Acute Stress Mechanisms

A major subpopulation of midbrain 5-hydroxytryptamine (5-HT) neurons expresses the vesicular glutamate transporter 3 (VGLUT3) and co-releases 5-HT and glutamate, but the function of this co-release is unclear. Given the strong links between 5-HT and uncontrollable stress, we used a combination of c-Fos immunohistochemistry and conditional gene knockout mice to test the hypothesis that glutamate co-releasing 5-HT neurons are activated by stress and involved in stress coping. Acute, uncontrollable swim stress increased c-Fos immunoreactivity in neurons co-expressing VGLUT3 and the 5-HT marker tryptophan hydroxylase 2 (TPH2) in the dorsal raphe nucleus (DRN). This effect was localized in the ventral DRN subregion and prevented by the antidepressant fluoxetine. In contrast, a more controllable stressor, acute social defeat, had no effect on c-Fos immunoreactivity in VGLUT3-TPH2 co-expressing neurons in the DRN. To test whether activation of glutamate co-releasing 5-HT neurons was causally linked to stress coping, mice with a specific deletion of VGLUT3 in 5-HT neurons were exposed to acute swim stress. Compared to wildtype controls, the mutant mice showed increased climbing behavior, a measure of active coping. Wildtype mice also showed increased climbing when administered fluoxetine, revealing an interesting parallel between the behavioral effects of genetic loss of VGLUT3 in 5-HT neurons and 5-HT reuptake inhibition. We conclude that 5-HT-glutamate co-releasing neurons are recruited by exposure to uncontrollable stress. Furthermore, natural variation in the balance of 5-HT and glutamate co-released at the 5-HT synapse may impact stress susceptibility.