Sucrose intake and preference by Wistar Han rats are not influenced by sex or food/water deprivation

Estradiol replacement enhances sweet taste preference in ovariectomized Rats: Interaction with energy intake regulation

Estrogens exert anorectic and anti-obesity effects via homeostatic regulation. However, their role in hedonic ingestive behavior, particularly in sweet taste preference, remains unclear. We examined the effects of estradiol replacement on the intake of sweetened solutions, water, and total energy in ovariectomized rats with concurrent access to sweetened solutions, water, and a standard rodent chow. Compared with the non-replaced (E2 (-)) group, the estradiol-replaced (E2 (+)) group exhibited a higher intake of various sweetened solutions, including those containing non-caloric artificial sweeteners and natural sugars. Food intake was lower in the E2 (+) group than in the E2 (-) group. Total energy intake was lower in the E2 (+) group than in the E2 (-) group when rats consumed water, sucralose, and fructose, but not when rats consumed glucose or sucrose. To explore the involvement of μ-opioid receptors in the estrogen-induced enhancement of sucrose intake, we chronically infused naltrexone (NTX), a partial μ-opioid receptor antagonist. NTX attenuated sucrose intake in the E2 (+) group but not in the E2 (-) group. By contrast, NTX reduced food intake in the E2 (-) group. Additionally, c-Fos expression in the nucleus accumbens shell was attenuated by NTX in the E2 (+) group during the short-term sucrose preference test. These findings suggest that estrogen enhances sweet taste preference and that available palatable glucose or sucrose diminishes the estrogen-induced attenuation of homeostatic energy intake. Moreover, μ-opioid receptors possibly play a role in the estrogen-induced enhancement of hedonic sweet taste preference, while they are involved in the enhancement of homeostatic food/energy intake in the absence of estrogen.

Alamandine enhanced spatial memory in rats by reducing neuroinflammation and altering BDNF levels in the hippocampus and prefrontal cortex

Our study aims to determine the effects of alamandine, the newest component of the renin-angiotensin system, on cognitive functions, neuroinflammation, and oxidative stress in the pathophysiology of depression. 35 male Sprague dawley rats, three months old, weighing between 300 and 350 g, were used. The chronic, unpredictable mild stress model of depression was performed. Experimental animals were divided into five groups: control (C), depression (D), alamandine (50 µg/kg, ip) (D + ALA), A779 (300 µg/kg, ip) (D + A779), and both alamandine and A779 treatment groups (D + ALA + A779). After confirming the development of depression through behavioral tests, the animals' learning and memory performances were measured using the Morris water maze test. At the end of the experiment, the animals' prefrontal cortex, hippocampus, and blood samples were isolated for biochemical studies and gene expression analyses. The sucrose preference, open field, elevated plus maze, tail suspension, and forced swimming tests were performed to determine the animals' anxiety levels. There was a significant increase in anxiety-like behaviors in the D group and the A779-treated group, while alamandine exhibited an anxiolytic effect. Moreover, improvements in cognitive skills observed in the Morris water maze test were paralleled by molecular changes, including an increase in BDNF protein levels and NMDA receptor expression and a decrease in GABA levels. In addition, the levels of TNF-α, IL-1β, IL-6, and oxidative stress markers were increased in the depression groups while significantly decreased with alamandine treatment. It was concluded that alamandine has an anxiolytic effect and facilitates spatial memory by reducing neuroinflammation and oxidative stress.

Postbiotics Made From Selected Lactic Acid Bacteria Improves Chronic Restraint Stress-Induced Anhedonia and Sleep Disorders

Sleep disorders have become one of the most prevalent neuropsychiatric disorders in recent years. This study aimed to investigate the effects of postbiotics derived from selected lactic acid bacteria on anhedonia and sleep disorders in chronic restraint stress (CRS)-induced mice, as well as their potential mechanisms. Mice were orally administered normal saline, low, medium, or high doses of postbiotics for 30 days, with CRS applied from days 1 to 21. The medium dose of postbiotics significantly increased the sucrose preference index, and the high dose of postbiotics significantly increased sleep duration. Postbiotic treatment effectively restored the diversity and composition of the gut microbiota to levels comparable to those observed in the vehicle (Veh) group. Furthermore, low and medium doses of postbiotics significantly reduced serum corticosterone levels, and medium and high doses significantly reduced serum IL-1β levels. Additionally, postbiotics administration significantly increased glutamate and GABA levels in both the prefrontal cortex and hypothalamus, as well as GABA levels in the feces. These results indicate that postbiotics alleviate CRS-induced anhedonia and sleep disorders in a dose-dependent manner. This effect may be mediated through the restoration of homeostasis in the MGB axis, HPA axis, inflammation pathways, and neurotransmitter balance.

(2R,6R)-hydroxynorketamine prevents opioid abstinence-related negative affect and stress-induced reinstatement in mice

BACKGROUND AND PURPOSE

Opioid use disorder (OUD) is a pressing public health concern marked by frequent relapse during periods of abstinence, perpetuated by negative affective states. Classical antidepressants or the currently prescribed opioid pharmacotherapies have limited efficacy to reverse the negative affect or prevent relapse.

EXPERIMENTAL APPROACH

Using mouse models, we investigated the effects of ketamine's metabolite (2R,6R)-hydroxynorketamine (HNK) on reversing conditioning to sub-effective doses of morphine in stress-susceptible mice, preventing conditioned-place aversion and alleviating acute somatic abstinence symptoms in opioid-dependent mice. Additionally, we evaluated its effects on anhedonia, anxiety-like behaviours and cognitive impairment during protracted opioid abstinence, while mechanistic studies examined cortical EEG oscillations and synaptic plasticity markers.

KEY RESULTS

(2R,6R)-HNK reversed conditioning to sub-effective doses of morphine in stress-susceptible mice and prevented conditioned-place aversion and acute somatic abstinence symptoms in opioid-dependent mice. In addition, (2R,6R)-HNK reversed anhedonia, anxiety-like behaviours and cognitive impairment emerging during protracted opioid abstinence plausibly via a restoration of impaired cortical high-frequency EEG oscillations, through a GluN2A-NMDA receptor-dependent mechanism. Notably, (2R,6R)-HNK facilitated the extinction of opioid conditioning, prevented stress-induced reinstatement of opioid-seeking behaviours and reduced the propensity for enhanced morphine self-consumption in mice previously exposed to opioids.

CONCLUSIONS AND IMPLICATIONS

These findings emphasize the therapeutic potential of (2R,6R)-HNK, which is currently in Phase II clinical trials, in addressing stress-related opioid responses. Reducing the time and cost required for development of new medications for the treatment of OUDs via drug repurposing is critical due to the opioid crisis we currently face.

Syringa oblata Lindl extract alleviated corticosterone-induced depression via the cAMP/PKA-CREB-BDNF pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Syringa oblata Lindl (ZDX) is a plant in the Oleaceae family that is the primary ingredient in the classic Tibetan medicine AKARU sinensis. The plant's stem is used as a medicine, and Tibetan doctors often use it as a sedative, a use with a history of nearly 100 years. Tibetan medicine mainly uses lilac to treat headache, forgetfulness, insomnia, irritability and other symptoms. Depression is a chronic mental disorder characterized by low mood, cognitive impairments, and physical discomfort, and it has become a significant public health issue. Given the limitations of existing treatments, interest in alternative therapies, including herbal medicines, is increasing.

AIM

To elucidate the mechanism of ZDX extract in the treatment of depression.

MATERIALS AND METHODS

A depression-like mouse model was established via the subcutaneous injection of corticosterone (CORT) into the groin, and a model of PC12 cell injury was established via CORT treatment. The antidepressant effect of the ZDX extract was subsequently evaluated via weight measurements, the sucrose preference test (SPT), the forced swimming test (FST), the open field test(OFT), the tail suspension test (TST), HE staining, Nissl staining and ELISA. Moreover, immunofluorescence staining, qRT‒PCR and Western blotting were used to determine whether ZDX extract can regulate the cAMP/PKA-CREB-BDNF pathway to prevent depression and neuronal apoptosis.

RESULTS

ZDX extract significantly improved depression-like behaviours; inhibited decreases in the protein levels of cAMP, PKA, CREB and BDNF; and increased proliferative activity in the hippocampus and cortex. In addition, in vitro, ZDX extract attenuated CORT-induced injury and apoptosis in hippocampal neurons and inhibited CORT-induced decreases in the mRNA expression levels of cAMP, PKA, CREB and BDNF.

CONCLUSIONS

These findings suggest that ZDX extract has potential as a novel antidepressant therapeutic agent, offering a complementary approach to current treatments by targeting multiple pathways involved in the pathogenesis of depression. Further research is warranted to explore the clinical applications of ZDX extract in the treatment of depression.

Brivaracetam and rufinamide combination increased seizure threshold and improved neurobehavioral deficits in corneal kindling model of epilepsy

BACKGROUND

Besides seizures, a myriad of overlapping neuropsychiatric and cognitive comorbidities occur in patients with epilepsy, which further debilitates their quality of life. This study provides an in-depth characterization of the impact of brivaracetam and rufinamide individually and in combination at 10 and 20 mg/kg doses, respectively, on corneal kindling-induced generalized seizures and behavioral alterations. Furthermore, observed convulsive frequency and behavioral changes were correlated to post-kindling-induced changes in the activity of markers of oxidative stress.

METHODS

Adult C57BL/6 mice were kindled via twice-daily transcorneal 50-Hz electrical stimulations (3 mA) for 3 s for 12 days until animals reached a fully kindled state. After the kindling procedure, animals were tested using a set of behavioral tests, and neurochemical alterations were assessed.

RESULTS

Corneal-kindled animals exhibited intense generalized convulsions, altered behavioral phenotypes typified by positive symptoms (hyperlocomotion), negative symptoms (anxiety and anhedonia), and deficits in semantic and working memory. BRV 10 + RFM 20 dual regime increased convulsive threshold and propensity toward the start of stage 4-5 seizures and improved phenotypical deficits, that is, anxiety, depression, and memory impairments. Moreover, this combination therapy mitigated kindling-induced redox impairments as evidenced by reduced malondialdehyde and acetylcholinesterase levels and increased glutathione antioxidant activity in the brain of animals subjected to repetitive brain insult.

CONCLUSION

Based on our outcomes, this dual therapy provides supporting evidence in alleviating epilepsy-induced neurobehavioral comorbidities and changes in redox homeostasis.

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

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

Sucrose binge-eating and increased anxiety-like behavior in Sprague-Dawley rats exposed to repeated LPS administration followed by chronic mild unpredictable stress

Exposure to persistent mild stress is a frequently encountered chronic challenge in a rapidly evolving society. Depending on various factors including sex, the response to stressors varies and is closely linked to the phenomenon of resilience. Depression and anxiety can be considered maladaptive responses to such stress. In this rat study, we investigated the sex-dependent effects of low-grade systemic inflammation during 1 week in combination with chronic unpredictable mild stress during the following 4 weeks on anxiety-like behavior and episodic feeding behavior. Increased anxiety-like behavior and increased sucrose intake were identified in stressed compared to control animals regardless of sex. Interestingly, two nearly equally distributed subpopulations were found in the stressed groups within each sex at the end of the 5-week protocol of combined stress exposure: the resistant and the susceptible, which were characterized by unchanged and increased sucrose intake, respectively. This difference in susceptibility to protracted combined mild stress and ensuing response to a sucrose eating binge demonstrates the complexity of the underlying regulatory mechanisms associated with emotional hyperreactivity. This model carries the potential for further investigation of the molecular basis of resilience and susceptibility to combined stressors and for testing treatments with potential preventive or therapeutic effects.

Neuroprotective potential of topiramate, pregabalin and lacosamide combination in a rat model of acute SE and intractable epilepsy: Perspectives from electroencephalographic, neurobehavioral and regional degenerative analysis

The lithium-pilocarpine model is commonly used to recapitulate characteristics of human intractable focal epilepsy. In the current study, we explored the impact of topiramate (TPM) alone and in combination with pregabalin and lacosamide administration for 6 weeks on the evolution of spontaneous recurrent seizures (SRS) and disease-modifying potential on associated neuropsychiatric comorbidities. In addition, redox impairments and neurodegeneration in hippocampus regions vulnerable to temporal lobe epilepsy (TLE) were assessed by cresyl violet staining. Results revealed that acute electrophysiological (EEG) profiling of the ASD cocktail markedly halted sharp ictogenic spikes as well as altered dynamics of brain wave oscillations thus validating the need for polytherapy vs. monotherapy. In TLE animals, pharmacological intervention for 6 weeks with topiramate 10 mg/kg in combination with PREG and LAC at the dose of 20 mg/kg exhibited marked protection from SRS incidence, improved body weight, offensive aggression, anxiety-like behavior, cognitive impairments, and depressive-like behavior (p < 0.05). Moreover, combination therapy impeded redox impairments as evidenced by decreased MDA and AchE levels and increased activity of antioxidant SOD, GSH enzymes. Furthermore, polytherapy rescued animals from SE-induced neurodegeneration with increased neuronal density in CA1, CA3c, CA3ab, hilus, and granular cell layer (GCL) of the dentate gyrus. In conclusion, early polytherapy with topiramate in combination with pregabalin and lacosamide prompted synergy and prevented epileptogenesis with associated psychological and neuropathologic alterations.

Pitavastatin attenuates hypercholesterolemia-induced decline in serotonin transporter availability

INTRODUCTION

Hypercholesterolemia is associated with increased inflammation and impaired serotonin neurotransmission, potentially contributing to depressive symptoms. However, the role of statins, particularly pitavastatin, in modulating serotonin transporter (SERT) function within this context remains underexplored. This study aimed to investigate whether pitavastatin counteracts the neurobiological effects of hypercholesterolemia.

METHODS

Low-density lipoprotein receptor knockout (LDLR-/-) mice on a C57BL/6 background were assigned to three groups: a control group fed a standard chow diet, a group fed a high-fat diet (HFD), and a third group fed a high-fat diet supplemented with pitavastatin (HFD + Pita). We evaluated the effects of HFD with or without pitavastatin on lipid profiles, inflammatory markers, and SERT availability using small-animal positron emission tomography (PET) scans with the radioligand 4-[18F]-ADAM over a 20-week period.

RESULTS

Pitavastatin treatment in HFD-fed mice significantly reduced both total cholesterol and LDL cholesterol levels in HFD-fed mice compared to those on HFD alone. Elevated inflammatory markers such as IL-1α, MCP-1/CCL2, and TNF-α in HFD mice were notably decreased in the HFD + Pita group. PET scans showed reduced SERT availability in the brains of HFD mice; however, pitavastatin improved this in brain regions associated with mood regulation, suggesting enhanced serotonin neurotransmission. Additionally, the sucrose preference test showed a trend towards increased preference in the HFD + Pita group compared to the HFD group, indicating a potential reduction in depressive-like behavior.

CONCLUSION

Our findings demonstrate that pitavastatin not only lowers cholesterol and reduces inflammation but also enhances SERT availability, suggesting a potential role in alleviating depressive symptoms associated with hypercholesterolemia. These results highlight the multifaceted benefits of pitavastatin, extending beyond its lipid-lowering effects to potentially improving mood regulation and neurotransmitter function.

Decoupling the mutual promotion of inflammation and oxidative stress mitigates cognitive decline and depression-like behavior in rmTBI mice by promoting myelin renewal and neuronal survival

BACKGROUND

Repetitive mild traumatic brain injury (rmTBI) can lead to somatic, emotional, and cognitive symptoms that persist for years after the initial injury. Although the ability of various treatments to promote recovery after rmTBI has been explored, the optimal time window for early intervention after rmTBI is unclear. Previous research has shown that hydrogen-rich water (HRW) can diffuse through the blood-brain - barrier, attenuate local oxidative stress, and reduce neuronal apoptosis in patients with severe traumatic brain injury. However, research on the effect of HRW on rmTBI is scarce.

AIMS

The objectives of this study were to explore the following changes after rmTBI and HRW treatment: (i) temporal changes in inflammasome activation and oxidative stress-related protein expression through immunoblotting, (ii) temporal changes in neuron/myelin-related metabolite concentrations in vivo through magnetic resonance spectroscopy, (iii) myelin structural changes in late-stage rmTBI via immunofluorescence, and (iv) postinjury anxiety/depression-like behaviors and spatial learning and memory impairment.

RESULTS

NLRP-3 expression in the rmTBI group was elevated at 7 and 14 DPI, and inflammasome marker levels returned to normal at 30 DPI. Oxidative stress persisted throughout the first month postinjury. HRW replacement significantly decreased Nrf2 expression in the prefrontal cortex and hippocampal CA2 region at 14 and 30 DPI, respectively. Edema and local gliosis in the hippocampus and restricted diffusion in the thalamus were observed on MR-ADC images. The tCho/tCr ratio in the rmTBI group was elevated, and the tNAA/tCr ratio was decreased at 30 DPI. Compared with the mice in the other groups, the mice in the rmTBI group spent more time exploring the open arms in the elevated plus maze (P < 0.05) and were more active in the maze (longer total distance traveled). In the sucrose preference test, the rmTBI group exhibited anhedonia. In the Morris water maze test, the latency to find the hidden platform in the rmTBI group was longer than that in the sham and HRW groups (P < 0.05).

CONCLUSION

Early intervention with HRW can attenuate inflammasome assembly and reduce oxidative stress after rmTBI. These changes may restore local oligodendrocyte function, promote myelin repair, prevent axonal damage and neuronal apoptosis, and alleviate depression-like behavior and cognitive impairment.

Efficacy of Chinese herbal formula Kai-Xin-San on rodent models of depression: A systematic review and meta-analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Kai-Xin-San (KXS, or Happy Feeling Powder), a typical Chinese herbal prescription, is frequently used for treating depression by the multi-level and multi-target mechanism.

AIM OF THE STUDY

To systematically investigate the efficacy and safety of KXS on depression in preclinic trials.

MATERIALS AND METHODS

We independently searched for preclinical animal studies of KXS on depression from inception to June 28, 2022, using electronic databases, e.g., PUBMED. The measurements were performed to assess the outcomes of behavioral tests.

RESULTS

This systematic review and meta-analysis included twenty-four studies and 608 animals. A remarkable effect of KXS in depression behavioral tests, including sucrose consumption test (SMD: 2.36, 95% CI: (1.81, 2.90); Z = 8.49, P < 0.00001)., forced swimming test (MD = -60.52, 95% CI: (-89.04, -31.99); Z = 4.16, P < 0.0001), rearing times (MD=4.48, 95% CI: (3.39, 5.57); Z = 8.05, P < 0.00001) and crossing times (MD = -33.7, 95% CI: (25.74, 41.67); Z = 8.29, P < 0.00001) in the open field test, showing KXS's excellent efficiency in improving depressive-like symptoms of animals.

CONCLUSIONS

Our meta-analysis showed KXS remarkably relieved animals' depressive-like symptoms, providing evidence that KXS can be a promising drug candidate for depression treatment.

Baccharis dracunculifolia DC Consumption Improves Nociceptive and Depressive-like Behavior in Rats with Experimental Osteoarthritis

Osteoarthritis (OA) persistently activates nociceptors, leading to chronic pain, which is often accompanied by the comorbid development of emotional impairments (anxiety and depression), an effect associated with microgliosis. Baccharis dracunculifolia DC (Asteraceae), a Brazilian edible plant, is an important source of active compounds with anti-inflammatory abilities. Thus, we evaluated its ability to reverse OA-induced nociceptive and emotional-like impairments in osteoarthritic ovariectomized female rats using the kaolin/carrageenan (K/C) model. Four weeks after OA induction, mechanical hyperalgesia was confirmed, and the treatment started. Control animals (SHAMs) were treated with phosphate-buffered saline (PBS), while arthritic animals (ARTHs) either received PBS or B. dracunculifolia 50 mg/kg (Bd50) and 100 mg/kg (Bd100), via gavage, daily for five weeks. At the end of the treatment, anxiety-like behavior was assessed using the Open Field Test (OFT), anhedonia was assessed using the Sucrose Preference Test (SPT), and learned helplessness was assessed using the Forced Swimming Test (FST). After occision, microglia were stained with IBA-1 and quantified in brain sections of target areas (prefrontal cortex, amygdala, and periaqueductal grey matter). Treatment with B. dracunculifolia extract reversed OA-induced mechanical hyperalgesia and partly improved depressive-like behavior in OA animals' concomitant to a decrease in the number of M1 microglia. Our findings suggest that B. dracunculifolia extracts can potentially be used in the food industry and for the development of nutraceuticals and functional foods.

Reliability of sucrose preference testing following short or no food and water deprivation-a Systematic Review and Meta-Analysis of rat models of chronic unpredictable stress

The sucrose preference test is a popular test for anhedonia in the chronic unpredictable stress model of depression. Yet, the test does not always produce consistent results. Long food and water deprivation before the test, while often implemented, confounds the results by introducing unwanted drives in the form of hunger and thirst. We assessed the reliability of the test when only short or no fasting was used. We searched PubMed, Embase, and Web of Science for studies in rats exposed to chronic unpredictable stress that used no more than 6 h of food and/or water deprivation before the test. Sweet consumptions, for stressed and control/antidepressant-treated animals, in 132 studies were pooled using random effects models. We found a decrease in sweet consumption in stressed rats, compared to controls, that was halved when a non-caloric sweetener was used and significantly reduced when sucrose consumption was corrected for body weight. What is more, the length of food and water deprivation was found to confound the effect. The effect was reversed when the stressed rats were treated with antidepressants. Methodological strategies meant to control for recognized sources of bias when conducting the test were often missing, and so was a clear and complete report of essential study information. Our results indicate that not only is food and water deprivation before the test unnecessary, but not recommended. Even in absence of long fasting, we found evidence of an additional effect on sweet consumption that is unrelated to anhedonia. Without properly controlling for non-hedonic drivers of consumption, the test is unreliable as a proxy measure of anhedonia. Strengthening the methodological rigor and addressing the confounding effect of metabolic factors in the sucrose preference test prevents misleading conclusions that harm the translatability of the associated research and perpetuates the use of animals for little gain.

Perampanel increases seizure threshold in pentylenetetrazole-kindled mice and improves behavioral dysfunctions by modifying mRNA expression levels of BDNF/TrkB and inflammatory markers

Perampanel (PER), a novel 3rd-generation antiseizure drug that modulates altered post-synaptic glutamatergic storming by selectively inhibiting AMPA receptors, is recently approved to treat intractable forms of seizures. However, to date, presumably consequences of long-term PER therapy on the comorbid deleterious psychiatric disturbances and its correlation with neuroinflammatory parameters are not fully investigated in chronic models of epilepsy. Therefore, we investigated the real-time effect of PER on brain electroencephalographic (EEG) activity, behavioral alterations, redox balance, and relative mRNA expression in pentylenetetrazole (PTZ) induced kindling. Male BALB/c mice were pretreated with PER (0.125, 0.25, and 0.5 mg/kg) for 3 weeks and challenged with 11 injections of PTZ at the sub-threshold dose of 40 mg/kg every other day. vEEG from implanted cortical electrodes was monitored to elucidate seizure propagation and behavioral manifestations. Recorded EEG signals exhibited that PER 0.5 mg/kg pretreatment exceptionally impeded the onset of sharp epileptic spike-wave discharges and associated motor symptoms. Additionally, qEEG analysis showed that PER prevented alterations in absolute mean spectral power and reduced RMS amplitude of epileptogenic spikes vs PTZ control. Furthermore, our outcomes illustrated that PER dose-dependently attenuated PTZ-evoked anxiety-like behavior, memory deficits, and depressive-like behavior that was validated by a series of behavioral experiments. Moreover PER, significantly reduced lipid peroxidation, AChE, and increased levels of SOD and total thiol in the mice brain via AMPAR antagonism. Post-PTZ kindling provoked overstimulation of BDNF/TrkB signaling and increased release of pro-inflammatory cytokines that were reversed by PER with suppression of iNOS in brain immune cells. In conclusion, our findings highlight that PER might play an auspicious preventive role in the proepileptic transformation of brain circuits via suppression of BDNF/TrkB signaling and reduced transcriptional levels of neuroinflammatory markers leading to improvised epilepsy-induced neurobehavioral and neurochemical effects.

Depressive-like behavior and impaired synaptic plasticity in the prefrontal cortex as later consequences of prenatal hypoxic-ischemic insult in rats

Perinatal hypoxia-ischemia (HI) is a leading cause of morbidity and mortality among newborns. Infants with HI encephalopathy may experience lasting consequences, such as depression, in adulthood. In this study, we examined depressive-like behavior, neuronal population, and markers of monoaminergic and synaptic plasticity in the prefrontal cortex (PFC) of adolescent rats subjected to a prenatal HI model. Pregnant rats underwent a surgery in which uterine and ovarian blood flow was blocked for 45 min at E18 (HI procedure). Sham-operated subjects were also generated (SH procedure). Behavioral tests were conducted on male and female pups from P41 to P43, and animals were histologically processed or dissected for western blotting at P45. We found that the HI groups consumed less sucrose in the sucrose preference test and remained immobile for longer periods in the forced swim test. Additionally, we observed a significant reduction in neuronal density and PSD95 levels in the HI group, as well as a smaller number of synaptophysin-positive cells. Our results underscore the importance of this model in investigating the effects of HI-induced injuries, as it reproduces an increase in depressive-like behavior and suggests that the HI insult affects circuits involved in mood modulation.

Effects of the dopamine depleting agent tetrabenazine in tests evaluating different components of depressive-like behavior in mice: sex-dependent response to antidepressant drugs with SERT and DAT blocker profiles

BACKGROUND

Depression is a disorder twice as common in women than in men. There are sex differences in the symptomatology and treatment response to this disorder. Impairments in behavioral activation (i.e. anergia, fatigue) are often seen in people with depression and are highly resistant to treatment. The role of mesolimbic dopamine (DA) in regulating behavioral activation has been extensively studied in male rodents, but little is known in female rodents.

OBJECTIVE

The present studies assessed potential sex differences in rodent paradigms used to study different components of depressive-like behavior, and in the treatment response to antidepressants with different mechanisms of action.

METHODS

Male and female CD1 mice received Tetrabenazine (TBZ), a VMAT-2 blocker that depletes DA and induces depressive symptoms in humans. Mice were tested on the Forced Swim Test, (FST), the Dark-Light box (DL), the elevated plus maze (EPM), Social Interaction (SI) test, and sucrose preference and consumption using the two bottles test. In addition, bupropion (a DA reuptake inhibitor) or fluoxetine (a serotonin reuptake inhibitor) were used to reverse TBZ-induced anergia.

RESULTS

In the FST, bupropion reversed TBZ effects in both sexes but fluoxetine was only effective in female mice. DA depletion did not affect other aspects of depression such as anxiety, sociability or sucrose consumption, and there was no interaction with bupropion on these parameters. In TBZ treated-females SERT-blockers may be effective at reversing anergia in aversive contexts (FST), and potentiating avoidance of anxiogenic stimuli.

CONCLUSIONS

Pro-dopaminergic antidepressants seem more efficacious at improving anergia in both sexes than SERT-blockers.

Sex-Dependent Effects of Chronic Restraint Stress on Mood-Related Behaviours and Neurochemistry in Mice

Anxiety and depressive disorders are closely associated; however, the pathophysiology of these disorders remains poorly understood. Further exploration of the mechanisms involved in anxiety and depression such as the stress response may provide new knowledge that will contribute to our understanding of these disorders. Fifty-eight 8-12-week-old C57BL6 mice were separated into experimental groups by sex as follows: male controls (n = 14), male restraint stress (n = 14), female controls (n = 15) and female restraint stress (n = 15). These mice were taken through a 4-week randomised chronic restraint stress protocol, and their behaviour, as well as tryptophan metabolism and synaptic proteins, were measured in the prefrontal cortex and hippocampus. Adrenal catecholamine regulation was also measured. The female mice showed greater anxiety-like behaviour than their male counterparts. Tryptophan metabolism was unaffected by stress, but some basal sex characteristics were noted. Synaptic proteins were reduced in the hippocampus in stressed females but increased in the prefrontal cortex of all female mice. These changes were not found in any males. Finally, the stressed female mice showed increased catecholamine biosynthesis capability, but this effect was not found in males. Future studies in animal models should consider these sex differences when evaluating mechanisms related to chronic stress and depression.

Gut microbiota from sigma-1 receptor knockout mice induces depression-like behaviors and modulates the cAMP/CREB/BDNF signaling pathway

Introduction

Depression is a common mental disorder that affects approximately 350 million people worldwide. Much remains unknown about the molecular mechanisms underlying this complex disorder. Sigma-1 receptor (Sig-1R) is expressed at high levels in the central nervous system. Increasing evidence has demonstrated a close association between the Sig-1R and depression. Recently, research has suggested that the gut microbiota may play a crucial role in the development of depression.

Methods

Male Sig-1R knockout (Sig-1R KO) and wild-type (WT) mice were used for this study. All transgenic mice were of a pure C57BL/6J background. Mice received a daily gavage of vancomycin (100 mg/kg), neomycin sulfate (200 mg/kg), metronidazole (200 mg/kg), and ampicillin (200 mg/kg) for one week to deplete gut microbiota. Fecal microbiota transplantation (FMT) was conducted to assess the effects of gut microbiota. Depression-like behaviors was evaluated by tail suspension test (TST), forced swimming test (FST) and sucrose preference test (SPT). Gut microbiota was analyzed by 16s rRNA and hippocampal transcriptome changes were assessed by RNA-seq.

Results

We found that Sig-1R knockout induced depression-like behaviors in mice, including a significant reduction in immobility time and an increase in latency to immobility in the FST and TST, which was reversed upon clearance of gut microbiota with antibiotic treatment. Sig-1R knockout significantly altered the composition of the gut microbiota. At the genus level, the abundance of Alistipes, Alloprevotella, and Lleibacterium decreased significantly. Gut microbiota dysfunction and depression-like phenotypes in Sig-1R knockout mice could be reproduced through FMT experiments. Additionally, hippocampal RNA sequencing identified multiple KEGG pathways that are associated with depression. We also discovered that the cAMP/CREB/BDNF signaling pathway is inhibited in the Sig-1R KO group along with lower expression of neurotrophic factors including CTNF, TGF-α and NGF. Fecal bacteria transplantation from Sig-1R KO mice also inhibited cAMP/CREB/BDNF signaling pathway.

Discussion

In our study, we found that the gut-brain axis may be a potential mechanism through which Sig-1R regulates depression-like behaviors. Our study provides new insights into the mechanisms by which Sig-1R regulates depression and further supports the concept of the gut-brain axis.

Behavioral abnormalities in C57BL/6 mice with chronic ulcerative colitis induced by DSS

BACKGROUND

Clinical epidemiological studies have found that some patients with ulcerative colitis (UC) are prone to mental disorders. DSS-induced acute and chronic UC models are often used to evaluate the efficacy of anti-UC drugs. However, whether DSS has an effect on mouse behavior has not been reported.

METHODS

Acute and chronic UC models were induced by 3% DSS and 1.5% DSS, respectively. The bloody stool, the changes in the colon length, and histopathological changes in the colon were used to evaluate the success of the animal model. The behavior of mice was evaluated by open field experiment, tail suspension experiment and Sucrose preference test.

RESULTS

The weight of mice in 3% DSS group decreased significantly, the DAI score increased significantly, the colon length of mice was significantly shortened, and the structure of colonic crypts was abnormal, which showed inflammatory cell infiltration and shrinkage of crypts. Compared with the control group, the immobility time of 3%DSS group mice in the tail suspension test and forced swimming test had no effect, the number of running and grooming times was significantly reduced, and there was no significant difference in the number of standing times. No abnormality was observed in HE staining of the hippocampus. However, in 1.5% DSS-induced chronic UC model, behavioral and hippocampal abnormalities were observed not only UC symptoms.

CONCLUSIONS

The acute UC model induced by 3% DSS has certain influence on the behavior of mice, but the mental state of mice is normal, which may be the abnormal behavior caused by UC symptoms; However, the chronic UC model induced by 1.5% DSS has a significant effect on the behavior of mice, and the mice have mental disorders, which are caused by mental disorders.

Sucrose Preference Test as a Measure of Anhedonic Behavior in a Chronic Unpredictable Mild Stress Model of Depression: Outstanding Issues

Despite numerous studies on the neurobiology of depression, the etiological and pathophysiological mechanisms of this disorder remain poorly understood. A large number of animal models and tests to evaluate depressive-like behavior have been developed. Chronic unpredictable mild stress (CUMS) is the most common and frequently used model of depression, and the sucrose preference test (SPT) is one of the most common tests for assessing anhedonia. However, not all laboratories can reproduce the main effects of CUMS, especially when this refers to a decrease in sucrose preference. It is also unknown how the state of anhedonia, assessed by the SPT, relates to the state of anhedonia in patients with depression. We analyzed the literature available in the PubMed database using keywords relevant to the topic of this narrative review. We hypothesize that the poor reproducibility of the CUMS model may be due to differences in sucrose consumption, which may be influenced by such factors as differences in sucrose preference concentration threshold, water and food deprivation, and differences in animals’ susceptibility to stress. We also believe that comparisons between animal and human states of anhedonia should be made with caution because there are many inconsistencies between the two, including in assessment methods. We also tried to offer some recommendations that should improve the reproducibility of the CUMS model and provide a framework for future research.