Ketamine impairs recognition memory consolidation and prevents learning-induced increase in hippocampal brain-derived neurotrophic factor levels

Age-related differences in long-term memory performance and astrocyte morphology in rat hippocampus

Astrocytes are neuromodulator cells. Their complex and dynamic morphology regulates neuronal signaling, synaptic plasticity, and neurogenesis. The impact of aging on astrocyte morphology is still under ongoing debate. Therefore, this study aimed to characterize astrocyte morphology in the hippocampus of older rats. 2-, 18-, and 20-month-old male Wistar rats were submitted to the object recognition test to assess their short- and long-term memories. CA1, CA2, CA3, and the dentate gyrus were collected for immunohistochemistry analysis and glial fibrillary acid protein (GFAP) immunostaining. Our results indicate that 20-month-old rats did not recognize or discriminate the novel object in the long-term memory test. Also, GFAP staining was greater in the oldest group for all analyzed areas. Morphometric and fractal analysis indicated shorter branch lengths and smaller sizes for astrocytes of 20-month-old rats. Overall, our results suggest that 20-month-old rats have long-term memory impairment, increased GFAP staining, and astrocyte dystrophy. These age-related alterations in astrocyte morphology are a resource for future studies exploring the role of astrocytes in age-related cognitive decline and age-related diseases.

Artificial intelligence-based drug repurposing with electronic health record clinical corroboration: A case for ketamine as a potential treatment for amphetamine-type stimulant use disorder

BACKGROUND AND AIMS

Amphetamine-type stimulants are the second-most used illicit drugs globally, yet there are no US Food and Drug Administration (FDA)-approved treatments for amphetamine-type stimulant use disorders (ATSUD). The aim of this study was to utilize a drug discovery framework that integrates artificial intelligence (AI)-based drug prediction, clinical corroboration and mechanism of action analysis to identify FDA-approved drugs that can be repurposed for treating ATSUD.

DESIGN AND SETTING

An AI-based knowledge graph model was first utilized to prioritize FDA-approved drugs in their potential efficacy for treating ATSUD. Among the top 10 ranked candidate drugs, ketamine represented a novel candidate with few studies examining its effects on ATSUD. We therefore conducted a retrospective cohort study to assess the association between ketamine and ATSUD remission using US electronic health record (EHR) data. Finally, we analyzed the potential mechanisms of action of ketamine in the context of ATSUD.

PARTICIPANTS AND MEASUREMENTS

ATSUD patients who received anesthesia (n = 3663) or were diagnosed with depression (n = 4328) between January 2019 and June 2022. The outcome measure was the diagnosis of ATSUD remission within one year of the drug prescription.

FINDINGS

Ketamine for anesthesia in ATSUD patients was associated with greater ATSUD remission compared with other anesthetics: hazard ratio (HR) = 1.58, 95% confidence interval (CI) = 1.15-2.17. Similar results were found for ATSUD patients with depression when comparing ketamine with antidepressants and bupropion/mirtazapine with HRs of 1.51 (95% CI = 1.14-2.01) and 1.68 (95% CI = 1.18-2.38), respectively. Functional analyses demonstrated that ketamine targets several ATSUD-associated pathways including neuroactive ligand-receptor interaction and amphetamine addiction.

CONCLUSIONS

There appears to be an association between clinician-prescribed ketamine and higher remission rates in patients with amphetamine-type stimulant use disorders.

Effects of a mitochondrial calcium uniporter and P-selectin inhibitors on neural injury induced by global cerebral ischemia-reperfusion in male rats

Neural injury following ischemia-reperfusion (I/R) is induced by multiple pathophysiological pathways. This study aimed to use mitochondrial calcium channel and p-selectin inhibitors to weaken these pathways. One hundred and two rats were randomly divided into six groups. In the sham group, cerebral I/R induction and drug intervention were not performed. In the I/R group, cerebral I/R induction was induced. In the RR + FCN group, animals received only ruthenium red (RR) and fucoidan (FCN) intraperitoneally without I/R induction. In the I/R + RR group, animals received RR during the cerebral I/R period. In the I/R + FCN group, FCN was administered along with cerebral I/R. In the I/R +(RR + FCN) group, animals exposed to cerebral I/R received a combination of RR and FCN simultaneously. The shuttle box and new object tests were used to assess learning and memory. The superoxide dismutase (SOD), malondialdehyde (MDA), interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) levels in the hippocampus were measured. Neuronal death in the hippocampal CA1 area was assessed via hematoxylin-eosin staining. FCN and RR significantly decreased the tissue MDA, IL-1β, TNF-α levels while increased the SOD level. These inhibitors significantly reduced learning disorders and cerebral edema following I/R. The rate of neuronal death was significantly lower in each of the receiving RR and FCN groups. This study revealed that the use of FCN and RR significantly attenuated the pathways associated with oxidative stress and inflammation as well as neuronal death following cerebral I/R, thereby reducing learning and memory impairments. The effects of neuroprotection were further determined when two inhibitors were used simultaneously. HIGHLIGHTS: Cerebral ischemia-reperfusion is associated with many neurological, sensory and motor defects. Multiple pathways of neural pathophysiology are activated during cerebral ischemia-reperfusion. The Administration of ruthenium and fucoidan weakens inflammatory pathways, oxidative stress, and learning dysfunctions caused by cerebral ischemia and reperfusion. Stronger Neuroprotective effects were observed during the simultaneous administration of ruthenium and fucoidan.

Neuroprotective Effect of Curcumin-Metavanadate in the Hippocampus of Aged Rats

Brain aging is a multifactorial process that includes a reduction in the biological and metabolic activity of individuals. Oxidative stress and inflammatory processes are characteristic of brain aging. Given the current problems, the need arises to implement new therapeutic approaches. Polyoxidovanadates (POV), as well as curcumin, have stood out for their participation in a variety of biological activities. This work aimed to evaluate the coupling of metavanadate and curcumin (Cuma-MV) on learning, memory, redox balance, neuroinflammation, and cell death in the hippocampal region (CA1 and CA3) and dentate gyrus (DG) of aged rats. Rats 18 months old were administered a daily dose of curcumin (Cuma), sodium metavanadate (MV), or Cuma-MV for two months. The results demonstrated that administration of Cuma-MV for 60 days in aged rats improved short- and long-term recognition memory, decreased reactive oxygen species, and substantially improved lipoperoxidation in the hippocampus. Furthermore, the activity of superoxide dismutase and catalase increased in animals treated with Cuma-MV. It is important to highlight that the treatment with Cuma-MV exhibited a significantly greater effect than the treatments with MV or Cuma in all the parameters evaluated. Finally, we conclude that Cuma-MV represents a potential therapeutic option in the prevention and treatment of cognitive decline associated with aging.

The Role of Intravenous Anesthetics for Neuro: Protection or Toxicity?

The primary intravenous anesthetics employed in clinical practice encompass dexmedetomidine (Dex), propofol, ketamine, etomidate, midazolam, and remimazolam. Apart from their established sedative, analgesic, and anxiolytic properties, an increasing body of research has uncovered neuroprotective effects of intravenous anesthetics in various animal and cellular models, as well as in clinical studies. However, there also exists conflicting evidence pointing to the potential neurotoxic effects of these intravenous anesthetics. The role of intravenous anesthetics for neuro on both sides of protection or toxicity has been rarely summarized. Considering the mentioned above, this work aims to offer a comprehensive understanding of the underlying mechanisms involved both in the central nerve system (CNS) and the peripheral nerve system (PNS) and provide valuable insights into the potential safety and risk associated with the clinical use of intravenous anesthetics.

Effects of Quetiapine on Novelty-Related Object Recognition Memory and Hippocampal BDNF Level in Sleep-Deprived Rats

BACKGROUND

The underlying mechanism of quetiapine (QET) in treating cognitive impairment in sleep deprivation is unclear. The present study aimed to evaluate the effects of treatment with QET on novel object recognition and hippocampal (hippo) brain-derived neurotrophic factor (BDNF) levels in rats submitted to 72 h sleep deprivation (SD).

MATERIALS AND METHODS

A total of 42 adult male Wistar albino rats were assigned into six experimental groups: non-sleep-deprived (NSD) control, short-term control group (n = 7) received a single intraperitoneal (i.p.) injection 10 mg/kg QET of 1 mL saline (4 days) (NSD-STQET), long-term control group (n = 7) received single i.p. injection 10 mg/kg QET of 1 mL saline (30 days) (NSD-LTQET); 72 h sleep-deprived (SD) group, 72 h SD short-term group received short-term i.p. injection 10 mg/kg QET of either (n = 7) (SD-STQET), and 72 h SD long-term group received long-term i.p. injection 10 mg/kg QET of either (n = 7) QET (SD-LTQET). SD was performed using the modified multiple-platform technique in a water tank for 72 h. Additionally, we aim to reveal the consequences of 72 h SD and QET effects on memory processes with hippo BDNF levels by testing rats in the novel object recognition (NOR) test and ELISA method.

RESULTS

Long-term QET administration in healthy rats decreased NOR and BDNF protein expression in the hippocampus, as did 72 h SD. Long- and short-term QET administration reversed SD effects, but only short-term QET administration increased hippo BDNF.

CONCLUSION

These results suggest that the beneficial effects of QET on SD may be partly related to the upregulation of recognition memory and neuroprotective proteins such as BDNF. However, long-term QET treatment in the absence of a disease model may have the potential to negatively impact recognition memory and BDNF levels, which support synaptic plasticity and cognitive function.

Effects of psychedelics on neurogenesis and broader neuroplasticity: a systematic review

In the mammalian brain, new neurons continue to be generated throughout life in a process known as adult neurogenesis. The role of adult-generated neurons has been broadly studied across laboratories, and mounting evidence suggests a strong link to the HPA axis and concomitant dysregulations in patients diagnosed with mood disorders. Psychedelic compounds, such as phenethylamines, tryptamines, cannabinoids, and a variety of ever-growing chemical categories, have emerged as therapeutic options for neuropsychiatric disorders, while numerous reports link their effects to increased adult neurogenesis. In this systematic review, we examine studies assessing neurogenesis or other neurogenesis-associated brain plasticity after psychedelic interventions and aim to provide a comprehensive picture of how this vast category of compounds regulates the generation of new neurons. We conducted a literature search on PubMed and Science Direct databases, considering all articles published until January 31, 2023, and selected articles containing both the words "neurogenesis" and "psychedelics". We analyzed experimental studies using either in vivo or in vitro models, employing classical or atypical psychedelics at all ontogenetic windows, as well as human studies referring to neurogenesis-associated plasticity. Our findings were divided into five main categories of psychedelics: CB1 agonists, NMDA antagonists, harmala alkaloids, tryptamines, and entactogens. We described the outcomes of neurogenesis assessments and investigated related results on the effects of psychedelics on brain plasticity and behavior within our sample. In summary, this review presents an extensive study into how different psychedelics may affect the birth of new neurons and other brain-related processes. Such knowledge may be valuable for future research on novel therapeutic strategies for neuropsychiatric disorders.

VNS paired with training enhances recognition memory: mechanistic insights from proteomic analysis of the hippocampal synapse

Introduction

Recognition memory, an essential component of cognitive health, can suffer from biological limitations of stress, aging, or neurodegenerative disease. Vagus nerve stimulation (VNS) is a neuromodulation therapy with the potential to improve cognitive function. This study investigated the effectiveness of multiple sessions of VNS to enhance recognition memory in healthy rodents and the underlying cognitive benefits of VNS by proteomic analysis of the synaptosome.

Methods

Rats demonstrated VNS-induced recognition memory improvements using a novel object recognition (NOR) task. Using the LC-MS/MS method, roughly 3,000 proteins in the synaptosome of the hippocampus were analyzed.

Results

Protein-protein interaction (PPI) enrichment analysis found differentially expressed proteins related to synaptic signaling and neurotransmitter pathways. PPI network analysis identified six unique protein clusters, including a cluster of synaptic signaling related pathways. Using ingenuity pathway analysis (IPA), rapamycin-insensitive companion of mTOR was identified as an upstream regulator of synaptosome changes due to VNS-paired training.

Discussion

Based on these results, it is proposed that VNS may mediate cognitive enhancement via increases in glutamatergic signaling and early LTP during the consolidation period, followed by sustained synaptic plasticity via modified post-synaptic receptor expression and dendritic outgrowth. Further investigation is required to determine if VNS is a good candidate to ameliorate cognitive impairment.

Exercise protects impairments in memory recognition in the iron-deficient male rat model of Restless Legs Syndrome

Restless Legs Syndrome (RLS) is a neurological disorder characterized by an irresistible urge to move the legs and is associated with decreased quality of life and sleep, and may result in cognitive changes. Physical exercise generates cognitive improvements and improves RLS symptoms. Our objective is to analyze recognition memory in the iron-deficient rodent model of RLS, and the effect of exercise. The animals (male Wistar rats) were distributed at 21 days of age into a control group (CTRL) (standard diet) or an ID group (iron-deficient diet). After performance classification (at 77 days of age), the animals were redistributed into CTRL (no exercise), CTRL EX (exercise), ID (no exercise) and ID EX (exercise), totaling 9 animals per group. The exercise groups performed treadmill exercise for four weeks. In the 14th week of the diet, the sleep recording of CTRL and ID animals was carried out to validate the RLS model. The Novel Object Recognition Memory test (NOR) was performed before the start of exercise (8th week of diet) and after the end (14th week) in all groups. The ID group demonstrated worsening sleep parameters and increased paw movements compared to the control group. The ID group demonstrated impairment of recognition memory after 14 weeks of diet compared to the CTRL group, and, the CTRL improved recognition memory in the 14th week compared to the 8th week. No differences were found for the exercise groups. Our findings indicate that the RLS animal model exhibited cognitive alterations associated with recognition memory, and long-term aerobic exercise intervention demonstrated a protective influence against these effects.

Ketamine differentially affects implicit and explicit memory processes in rats

RATIONALE

Ketamine, a non-competitive NMDA receptor antagonist, produces antidepressant effects at subanesthetic doses. The therapeutic effect, however, is often accompanied by cognitive side effects, including memory impairments. Yet, the specific effects of ketamine on different processes of implicit and explicit memory remain to be elucidated.

OBJECTIVES

We examined the effect of an antidepressant dose of ketamine (10 mg/kg, IP) on the encoding, retrieval, and modulation processes of fear memory and spatial memory in adult Wistar rats.

METHODS

Ketamine was administered before the fear acquisition, retrieval, or extinction procedures in a Pavlovian fear conditioning task. In another set of experiments, it was administered before the training, probe trial, or reversal training phases of the Morris Water Maze (MWM).

RESULTS

The antidepressant dose of ketamine partially impaired fear extinction when administered before the acquisition or retrieval. In contrast, it facilitated memory modulation and decreased the escape latency in the first day of reversal training in the MWM when administered before the training or reversal training sessions. Encoding or retrieval performance in either type of memory was not affected.

CONCLUSIONS

These findings show that ketamine does not impair the acquisition or retrieval processes of cued fear or spatial memory; but exerts differential effects on memory modulation of these implicit and explicit memory paradigms, by disrupting fear extinction and facilitating reversal spatial learning.

Neuroglycome alterations of hippocampus and prefrontal cortex of juvenile rats chronically exposed to glyphosate-based herbicide

Introduction

Glyphosate-based herbicides (GBHs) have been shown to have significant neurotoxic effects, affecting both the structure and function of the brain, and potentially contributing to the development of neurodegenerative disorders. Despite the known importance of glycosylation in disease progression, the glycome profile of systems exposed to GBH has not been thoroughly investigated.

Methods

In this study, we conducted a comprehensive glycomic profiling using LC-MS/MS, on the hippocampus and prefrontal cortex (PFC) of juvenile rats exposed to GBH orally, aiming to identify glyco-signature aberrations after herbicide exposure.

Results

We observed changes in the glycome profile, particularly in fucosylated, high mannose, and sialofucosylated N-glycans, which may be triggered by GBH exposure. Moreover, we found major significant differences in the N-glycan profiles between the GBH-exposed group and the control group when analyzing each gender independently, in contrast to the analysis that included both genders. Notably, gender differences in the behavioral test of object recognition showed a decreased performance in female animals exposed to GBH compared to controls (p < 0.05), while normal behavior was recorded in GBH-exposed male rats (p > 0.05).

Conclusion

These findings suggest that glycans may play a role in the neurotoxic effect caused by GBH. The result suggests that gender variation may influence the response to GBH exposure, with potential implications for disease progression and specifically the neurotoxic effects of GBHs. Understanding these gender-specific responses could enhance knowledge of the mechanisms underlying GBH-induced toxicity and its impact on brain health. Overall, our study represents the first detailed analysis of N-glycome profiles in the hippocampus and PFC of rats chronically exposed to GBH. The observed alterations in the expression of N-glycan structures suggest a potential neurotoxic effect associated with chronic GBH exposure, highlighting the importance of further research in this area.

Myosin Va-dependent Transport of NMDA Receptors in Hippocampal Neurons

N-methyl-D-aspartate receptor (NMDAR) trafficking is a key process in the regulation of synaptic efficacy and brain function. However, the molecular mechanism underlying the surface transport of NMDARs is largely unknown. Here we identified myosin Va (MyoVa) as the specific motor protein that traffics NMDARs in hippocampal neurons. We found that MyoVa associates with NMDARs through its cargo binding domain. This association was increased during NMDAR surface transport. Knockdown of MyoVa suppressed NMDAR transport. We further demonstrated that Ca2+/calmodulin-dependent protein kinase II (CaMKII) regulates NMDAR transport through its direct interaction with MyoVa. Furthermore, MyoVa employed Rab11 family-interacting protein 3 (Rab11/FIP3) as the adaptor proteins to couple themselves with NMDARs during their transport. Accordingly, the knockdown of FIP3 impairs hippocampal memory. Together, we conclude that in hippocampal neurons, MyoVa conducts active transport of NMDARs in a CaMKII-dependent manner.

D-Limonene reduces depression-like behaviour and enhances learning and memory through an anti-neuroinflammatory mechanism in male rats subjected to chronic restraint stress

D-limonene is a widely used flavouring additive in foods, beverages and fragrances due to its pleasant lemon-like odour. This study aimed to investigate the effects of D-limonene on the central nervous system when subjected to chronic restraint stress in rats for 21 days. Forty rats were randomly divided into five groups: i) control, ii) D-limonene, iii) restraint stress, iv) restraint stress+D-limonene and v) restraint stress+fluoxetine. Following the induction of restraint stress, the sucrose preference test, the open field test, the novel object recognition test and the forced swimming test were performed. The levels of BDNF, IL-1β, IL-6 and caspase-1 were measured from hippocampal tissue using the ELISA method. Sucrose preference test results showed an increase in consumption rate in the stress+D-limonene and a decrease in the stress group. The stress+D-limonene group reversed the increased defensive behaviour observed in the open-field test compared to the stress group. In the novel object recognition test, the discrimination index of the stress+D-limonene group increased compared to the stress group. BDNF levels increased in the stress+limonene group compared to the stress group. In contrast, IL-1β and caspase-1 levels increased in the stress group compared to the control and decreased in the stress+limonene group compared to the stress group. In this study, D-limonene has been found to have antidepressant-like properties, reducing anhedonic and defensive behaviours and the impairing effects of stress on learning and memory tests. It was observed that D-limonene showed these effects by alleviating neuroinflammation induced by chronic restraint stress in rats.

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.

Enhancing Cognitive Functions and Neuronal Growth through NPY1R Agonist and Ketamine Co-Administration: Evidence for NPY1R-TrkB Heteroreceptor Complexes in Rats

This study investigates the combined effects of the neuropeptide Y Y1 receptor (NPY1R) agonist [Leu31-Pro34]NPY at a dose of 132 µg and Ketamine at 10 mg/Kg on cognitive functions and neuronal proliferation, against a backdrop where neurodegenerative diseases present an escalating challenge to global health systems. Utilizing male Sprague-Dawley rats in a physiological model, this research employed a single-dose administration of these compounds and assessed their impact 24 h after treatment on object-in-place memory tasks, alongside cellular proliferation within the dorsal hippocampus dentate gyrus. Methods such as the in situ proximity ligation assay and immunohistochemistry for proliferating a cell nuclear antigen (PCNA) and doublecortin (DCX) were utilized. The results demonstrated that co-administration significantly enhanced memory consolidation and increased neuronal proliferation, specifically neuroblasts, without affecting quiescent neural progenitors and astrocytes. These effects were mediated by the potential formation of NPY1R-TrkB heteroreceptor complexes, as suggested by receptor co-localization studies, although further investigation is required to conclusively prove this interaction. The findings also highlighted the pivotal role of brain-derived neurotrophic factor (BDNF) in mediating these effects. In conclusion, this study presents a promising avenue for enhancing cognitive functions and neuronal proliferation through the synergistic action of the NPY1R agonist and Ketamine, potentially via NPY1R-TrkB heteroreceptor complex formation, offering new insights into therapeutic strategies for neurodegenerative diseases.

Protective effect of Baoyuan Jieyu formula on long-term spaceflight composite stress-induced depressive-like behavior and memory deficits through regulation of Ca2+ channel currents

Long-term spaceflight composite stress (LSCS) can cause adverse effects on human systems, especially the central nervous system. This study aimed to identify the underlying mechanisms of the protective effect of Baoyuan Jieyu Formula (BYJYF) on LSCS-induced depressive-like behavior and memory deficits. In this experiment, we simulated the real space station environment for a period of 42 days. Novel object recognition test and forced swimming test were used to assess the memory abilities and depression level of rats as well as test the therapeutic effects of BYJYF treatment. Results showed LSCS could induce depressive-like behavior and damage short-term memory in the behavioral level, and BYJYF could enhance the ability to resist LSCS. Meanwhile, LSCS increased the levels of CRH, ACTH, and CORT and induced HPA axis hyperactivity, which can be relieved by BYJYF. Further, we predicted and verified the potential signaling pathways of BYJYF. Results showed BYJYF may reverse the inhibition of LSCS on Ca2+ channel currents. And we also found that BYJYF may exert its medicinal effects via four main active components including saikosaponin A. Overall, BYJYF exhibited protective effects against LSCS-induced depressive-like behavior and memory deficits, which might be ascribed to the regulation of Ca2+ channel currents and four active components. And it might become a promising candidate medicine for diseases induced by LSCS.

Ganglioside GD3 regulates neural stem cell quiescence and controls postnatal neurogenesis

The postnatal neural stem cell (NSC) pool hosts quiescent and activated radial glia-like NSCs contributing to neurogenesis throughout adulthood. However, the underlying regulatory mechanism during the transition from quiescent NSCs to activated NSCs in the postnatal NSC niche is not fully understood. Lipid metabolism and lipid composition play important roles in regulating NSC fate determination. Biological lipid membranes define the individual cellular shape and help maintain cellular organization and are highly heterogeneous in structure and there exist diverse microdomains (also known as lipid rafts), which are enriched with sugar molecules, such as glycosphingolipids. An often overlooked but key aspect is that the functional activities of proteins and genes are highly dependent on their molecular environments. We previously reported that ganglioside GD3 is the predominant species in NSCs and that the reduced postnatal NSC pools are observed in global GD3-synthase knockout (GD3S-KO) mouse brains. The specific roles of GD3 in determining the stage and cell-lineage determination of NSCs remain unclear, since global GD3S-KO mice cannot distinguish if GD3 regulates postnatal neurogenesis or developmental impacts. Here, we show that inducible GD3 deletion in postnatal radial glia-like NSCs promotes NSC activation, resulting in the loss of the long-term maintenance of the adult NSC pools. The reduced neurogenesis in the subventricular zone (SVZ) and the dentate gyrus (DG) of GD3S-conditional-knockout mice led to the impaired olfactory and memory functions. Thus, our results provide convincing evidence that postnatal GD3 maintains the quiescent state of radial glia-like NSCs in the adult NSC niche.

Review on the Impact of Milk Oligosaccharides on the Brain and Neurocognitive Development in Early Life

Milk Oligosaccharides (MOS), a group of complex carbohydrates found in human and bovine milk, have emerged as potential modulators of optimal brain development for early life. This review provides a comprehensive investigation of the impact of milk oligosaccharides on brain and neurocognitive development of early life by synthesizing current literature from preclinical models and human observational studies. The literature search was conducted in the PubMed search engine, and the inclusion eligibility was evaluated by three reviewers. Overall, we identified 26 articles for analysis. While the literature supports the crucial roles of fucosylated and sialylated milk oligosaccharides in learning, memory, executive functioning, and brain structural development, limitations were identified. In preclinical models, the supplementation of only the most abundant MOS might overlook the complexity of naturally occurring MOS compositions. Similarly, accurately quantifying MOS intake in human studies is challenging due to potential confounding effects such as formula feeding. Mechanistically, MOS is thought to impact neurodevelopment through modulation of the microbiota and enhancement of neuronal signaling. However, further advancement in our understanding necessitates clinical randomized-controlled trials to elucidate the specific mechanisms and long-term implications of milk oligosaccharides exposure. Understanding the interplay between milk oligosaccharides and cognition may contribute to early nutrition strategies for optimal cognitive outcomes in children.

Inhaled molecular hydrogen reduces hippocampal neuroinflammation, glial reactivity and ameliorates memory impairment during systemic inflammation

Sepsis is associated with numerous physiological and biochemical abnormalities that result in a life-threatening condition. The involvement of the Central Nervous System (CNS) during sepsis has received considerable attention, especially the hippocampus which plays a key role in the learning and memory processes. The increased interest in this limbic region during systemic inflammation (SI) is related to the number of sepsis survivor patients who have cognitive impairments. A single injection of lipopolysaccharide (LPS)-induced systemic inflammation is the most commonly used murine endotoxemia model because it replicates several pathophysiological changes observed in severe sepsis. Molecular hydrogen (H₂) has been used as an anti-inflammatory therapeutic strategy to prevent neuroinflammation. However, the mechanisms by which inhaled H₂ mitigate memory loss during SI remains unknown. To understand how H₂ acts in the hippocampus, the current study focused on specific mechanisms that may be involved in reducing neuroinflammation in rats during SI. We hypothesized that inhaled H₂ decreases LPS-induced hippocampal pro-inflammatory cytokines surges and this effect is associated with reduced memory loss. Using different and integrative approaches, i.e., from hippocampal cells electrophysiology to animal behavior, we report that inhaled H₂ decreased LPS-induced peripheral and hippocampal inflammation, decreased microglial and astrocytic activation, lessen memory loss without affecting long-term potentiation (LTP). To our knowledge, this is the first evidence showing that inhaled H₂ reduces hippocampal microglial and glial cells inflammation, which may be associated with a reduced memory impairment induced by SI.

Reduction of brain stem pathology and transient amelioration of early cognitive symptoms in transgenic mice treated with a monoclonal antibody against α-synuclein oligomers/protofibrils

Immunotherapy against alpha-synuclein (α-syn) is a promising novel treatment strategy for Parkinson's disease (PD) and related α-synucleinopathies. We have previously shown that systemic treatment with the monoclonal oligomer/protofibril-selective antibody mAb47 targeting cytotoxic α-syn leads to reduced central nervous system levels of such species as well as an indication of reduced late-stage symptoms in aged (Thy-1)-h[A30P] α-syn transgenic mice. Here, we performed an early-onset long-term treatment study with this antibody to evaluate effects on brain pathology and behavioral outcomes in the same mouse model. Compared to the placebo group, the treatment strongly reduced phosphorylated α-syn (pS129 α-syn) pathology in the upper brain stem. Moreover, a preserved recognition memory and risk assessment behavior could be seen in antibody-treated mice at six months of age, even although these effects were no longer significant at eleven months of age. Importantly, no evidence of inflammatory responses or other potential toxic effects was seen with the treatment. Taken together, this study supports the strategy to target α-syn oligomers/protofibrils with monoclonal antibodies to counteract early symptoms and slow down the progression of PD and other α-synucleinopathies.

The Effects of Acute and Repeated Administration of Ketamine on Memory, Behavior, and Plasma Corticosterone Levels in Female Mice

Ketamine is an anesthetic drug that has recently been approved for the treatment of treatment-resistant depression. Females are diagnosed with Major Depressive Disorder at higher rates than males, yet most of the pre-clinical research on ketamine has been conducted in male subjects. Additionally, the literature on the acute and long-term behavioral and cognitive effects of ketamine shows conflicting results. It is important to examine the acute and long-term cognitive and behavioral effects of ketamine exposure at lower sub-anesthetic doses, as the recreational use of the drug at higher doses is associated with cognitive and memory impairments. The current study examined the effects of acute and repeated ketamine exposure on anxiety-like behavior, novel object recognition memory, depression-like behavior, and plasma corticosterone levels in 20 adult female C57BL/6J mice. Mice were exposed acutely or repeatedly for 10 consecutive days to saline or 15 mg/kg ketamine and behavior was measured in the open field test, novel object recognition test, and the Porsolt forced swim test. Plasma corticosterone levels were measured following behavioral testing. Acute ketamine exposure decreased locomotor activity and increased anxiety-like behavior in the open field test compared to controls, while repeated ketamine exposure impaired memory in the novel object recognition test. There were no effects of acute or repeated ketamine exposure on depression-like behavior in the Porsolt forced swim test or on plasma corticosterone levels. These findings suggest that a subanesthetic dose of ketamine alters behavior and cognition in female mice and the effects are dependent on the duration of exposure.

Amplification of olfactory signals by Anoctamin 9 is important for mammalian olfaction

Sensing smells of foods, prey, or predators determines animal survival. Olfactory sensory neurons in the olfactory epithelium (OE) detect odorants, where cAMP and Ca2+ play a significant role in transducing odorant inputs to electrical activity. Here we show Anoctamin 9, a cation channel activated by cAMP/PKA pathway, is expressed in the OE and amplifies olfactory signals. Ano9-deficient mice had reduced olfactory behavioral sensitivity, electro-olfactogram signals, and neural activity in the olfactory bulb. In line with the difference in olfaction between birds and other vertebrates, chick ANO9 failed to respond to odorants, whereas chick CNGA2, a major transduction channel, showed greater responses to cAMP. Thus, we concluded that the signal amplification by ANO9 is important for mammalian olfactory transduction.

Expression changes of c-Fos and D1R/p-ERK1/2 signal pathways in nucleus accumbens of rats after ketamine abuse

Ketamine is a commonly used dissociative anesthetic in clinical applications. However, the abuse potential has posted limits to its use and the mechanism remains to be studied. We aimed to investigate the changes of dopamine D1 receptors (D1R), phosphorylation of extracellular-regulated protein kinase 1/2 (p-ERK1/2), and c-Fos expression in the nucleus accumbens (NAc) of ketamine abuse rats. Ketamine induced severe anxiety in rats, as shown by an open field test. Nissl staining demonstrated clearly different morphologies between neurons of ketamine abuse rats and normal rats. The molecular expression changes were examined using immunohistochemistry assay and western blotting. D1R, p-ERK1/2, and c-Fos were significantly highly-expressed in NAc during ketamine exposure and were decreased by D1R antagonist SCH23390 and MAPK kinases inhibitor U0126. Taken together, the results suggest that ketamine abuse may induce the overexpression of c-Fos in NAc by up-regulating the expression of D1R and p-ERK1/2.

The α2C-adrenoceptor antagonist JP-1302 controls behavioral parameters, tyrosine hydroxylase activity and receptor expression in a rat model of ketamine-induced schizophrenia-like deficits

Schizophrenia is a chronic disabling disease affecting 1 % of the population. Current antipsychotics have limited efficacy in mitigating the severity of the symptoms of the disease. Therefore, searching for new therapeutic targets is essential. Previous studies have shown that α_2C-adrenoceptor antagonists may have antipsychotic and pro-cognitive effects. Therefore, the current study evaluates the behavioral and neurochemical effects of JP-1302, a selective α_2C-adrenoceptor antagonist, in a model of schizophrenia-like deficits induced by sub-chronic ketamine (KET) administration. Here, we administered ketamine (25 mg/kg, i.p.) to male and female Wistar rats for eight consecutive days. On the last two days of ketamine administration, rats were pretreated with either JP-1302 (1-3-10 μmol/kg, i.p.), chlorpromazine (0.1 mg/kg, i.p.), or saline, and the behavioral tests were performed. Behaviors related to positive (locomotor activity), negative (social interaction), and cognitive (novel object recognition) symptoms of schizophrenia were assessed. Glutamate, glutamine, GABA levels, and α_2C-adrenoceptor expression were measured in the frontal cortex and the hippocampus. Tyrosine hydroxylase immunocytochemical reactivity was also shown in the midbrain regions. Sub-chronic ketamine administration increased locomotor activity and produced robust social interaction and object recognition deficits, and JP-1302 significantly ameliorated ketamine-induced cognitive deficits. Ketamine induced a hyperdopaminergic activity in the striatum, which was reversed by the treatment with JP-1302. Also, the α_2C-adrenoceptor expression was higher in the frontal cortex and hippocampus in the ketamine-treated rats. Our findings confirm that α_2C-adrenoceptor antagonism may be a potential drug target for treating cognitive disorders related to schizophrenia.

Perinatal exposure to glyphosate-based herbicides induced neurodevelopmental behaviors impairments and increased oxidative stress in the prefrontal cortex and hippocampus in offspring

Glyphosate is the organophosphate pesticide most widely used in the world. Recent studies correlate exposure to glyphosate and the emergence of neurodevelopmental disorders. Therefore, it was objective to propose a rat model of perinatal exposure to glyphosate-based herbicides (GBH) to study associated neurodevelopmental disorders. Behavioral aspects and brain pathways were assessed in the prepubertal phase. For this, maternal treatment occurred throughout the entire gestation period (from GD0) until weaning on postnatal day 22 (PND 22). Control group received oral gavage with 5 mL/kg of saline per day and GBH group received oral gavage with 50 mg/kg of GBH per day (n = 10 per group). Maternal behavior was evaluated in PND 2-6. Offspring were evaluated for quantification of ultrasonic vocalizations (PND 5); homing behavior test (PND 13); and hole board, social play behavior, open field, and object recognition tests (PND 28-32). Prefrontal cortex and hippocampus of the offspring were processed to evaluate oxidative stress. Maternal exposure to GBH impaired early social communication, olfactory discrimination, social play behavior, and the exploration of objects, in addition to increasing repetitive and stereotyped movements. GBH also increased oxidative stress. Therefore, perinatal GBH exposure induced behavioral and oxidative stress impairments in rats associated with neurodevelopmental disorders. The manifestations found in the offspring are in accordance with symptoms of autism spectrum disorder.

Repeated social defeat stress exacerbates lipopolysaccharide-induced behavioural deficits in mice: ameliorative role of Chrysophyllum albidum fruit extract through anti-neuroinflammation, antioxidant and neurochemical balance

Development of neuropsychiatric disorder is associated with stress-related increase in pro-inflammatory cytokines. Chrysophyllum albidum fruit is an edible tropical fruit containing vitamins and phenolic compounds, well known for their anti-inflammatory and antioxidant activities. This study was designed to investigate the neuroprotective effect of C. albidum fruit extract (CAFE) on stress and lipopolysaccharide (LPS)-induced behavioral and neurochemical impairments in mice. Male Swiss mice were divided into 6 groups (n = 6). Groups 1-3 were orally treated daily for 14 days with normal saline (0.1 mL/10 g), CAFE (100 mg/kg) and Ferulic acid (FA, 10 mg/kg), and left in home cage as controls. Groups 4-6 were treated similarly but subjected to repeated social defeat (RSD) stress using the resident-intruder model from days 1-14. The RSD-animals were injected with LPS (125 µg/kg, i.p) 60 min after each RSD session from days 8-14. Neurobehavioral functions: locomotor, cognitive and anxiety-like behaviors were assessed 24 h after the last treatment. Pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α), dopamine, acetylcholinesterase, glutamic acid decarboxylase (GAD), malondialdehyde, nitrites, and reduced glutathione (GSH) were determined in brain tissue. CAFE significantly attenuated RSD and LPS-induced hypolocomotion, cognitive impairment and anxiety-like behavior when compared to the control. Treatment with CAFE also significantly reversed the negative effects of RSD and LPS on pro-inflammatory cytokines, dopamine, acetylcholinesterase, GAD, and oxidative-nitrosative stress levels. The findings clearly indicated that Chrysophyllum albidum fruit demonstrated neuroprotective effects and can play a key role in mitigating against chronic stress and inflammation linked to neuropsychiatric disorders.

Decoupling astrocytes in adult mice impairs synaptic plasticity and spatial learning

The mechanisms by which astrocytes modulate neural homeostasis, synaptic plasticity, and memory are still poorly explored. Astrocytes form large intercellular networks by gap junction coupling, mainly composed of two gap junction channel proteins, connexin 30 (Cx30) and connexin 43 (Cx43). To circumvent developmental perturbations and to test whether astrocytic gap junction coupling is required for hippocampal neural circuit function and behavior, we generate and study inducible, astrocyte-specific Cx30 and Cx43 double knockouts. Surprisingly, disrupting astrocytic coupling in adult mice results in broad activation of astrocytes and microglia, without obvious signs of pathology. We show that hippocampal CA1 neuron excitability, excitatory synaptic transmission, and long-term potentiation are significantly affected. Moreover, behavioral inspection reveals deficits in sensorimotor performance and a complete lack of spatial learning and memory. Together, our findings establish that astrocytic connexins and an intact astroglial network in the adult brain are vital for neural homeostasis, plasticity, and spatial cognition.

Lipoic acid prevents mirtazapine-induced weight gain in mice without impairs its antidepressant-like action in a neuroendocrine model of depression

Mirtazapine (MIRT) is a multi-target antidepressant used in treatment of severe depression with promising efficacy, but also with important side effects, mainly sedation and weight gain. Thus, the present study aimed to test the effects of the neuroprotective antioxidant lipoic acid (ALA) in the reversal of weight and metabolic changes induced by MIRT in corticosterone-induced depression model in mice, as well as proposed mechanisms for their association antidepressant and pro-cognitive effects. To do these male Swiss mice received Tween 80 (control), corticosterone (CORT 20 mg / kg), MIRT (3 mg / kg) and ALA (100 or 200 mg / kg), alone or associated for 21 days. After this, the animals were subjected to behavioral tests for affective and cognitive domains. Daily weight changes, blood cholesterol fractions and corticosterone were measured. Also, hippocampus (HC) protein expression of the serotonin transporter (SERT), synaptophysin, protein kinase B-Akt (total and phosphorylated) and the cytokines IL-4 and IL-6 were investigated. CORT induced a marked depression-like behavior, memory deficits, metabolic changes (total cholesterol and LDL) and increased serum corticosterone. Also, CORT increased SERT expression in the HC. MIRT alone or combined with ALA sustained its antidepressant-like effect, as well as reversed CORT-induced impairment in spatial recognition memory. Additionally, the association MIRT+ALA200 reversed the weight gain induced by the former antidepressant, as well as reduced serum corticosterone levels and SERT expression in the HC. ALA alone induced significant weight loss and reduced total cholesterol and HDL fraction. Our findings provide promising evidence about the ALA potential to prevent metabolic and weight changes associated to MIRT, without impair its antidepressant and pro-cognition actions. Therefore, ALA+MIRT combination could represent a new therapeutic strategy for treating depression with less side effects.

Effects of subanesthetic ketamine and (2R,6R) hydroxynorketamine on working memory and synaptic transmission in the nucleus reuniens in mice

RATIONALE

Acute cognitive impairment and abuse potential of ketamine incentivizes the search for alternatives to ketamine for clinical management of treatment-resistant depression. Recently, (2R,6R) hydroxynorketamine ((2R,6R)-HNK), a metabolite of ketamine, has shown promise due to its reported lack of ketamine-like reinforcing properties. Nonetheless, the effect of (2R,6R)-HNK on cognition has not been reported.

METHOD

Adult male mice were placed in a Y-maze to measure spatial working memory (SWM) 24 h after treatment with either a single or repeated subanesthetic dose of (2R,6R)-HNK or ketamine. To determine the effect of the drug regimens on synaptic mechanisms in neural circuits deemed critical for SWM, we conducted patch-clamp electrophysiological recordings from neurons in the midline thalamic nucleus reuniens (RE) in response to optogenetic stimulation of medial prefrontal cortex (mPFC) inputs in acutely prepared brain slices.

RESULTS

Single or repeated treatment with a 10 mg/kg dose of either drug did not impact performance in a Y-maze. However, single administration of a ½-log higher dose (32 mg/kg) of ketamine significantly reduced SWM. The same dose of (2R,6R)-HNK did not produce SWM deficits. Interestingly, repeated administration of either drugs at the 32 mg/kg had no effect on SWM performances. Concomitant to these effects on SWM, only single injection of 32 mg/kg of ketamine was found to increase the mPFC-driven action potential firing activity in the RE neurons. Conversely, both single and repeated administration of the 32 mg/kg dose of (2R,6R)-HNK but not ketamine, increased the input resistance of the RE neurons.

CONCLUSION

Our results indicate that acute treatment of ketamine at 32 mg/kg increases mPFC-driven firing activity of RE neurons, and this contributes to the ketamine-mediated cognitive deficit. Secondly, sub-chronic treatment with the same dose of ketamine likely induces tolerance. Although single or repeated administration of the 32 mg/kg dose of (2R,6R)-HNK can alter intrinsic properties of RE neurons, this dose does not produce cognitive deficit or changes in synaptic mechanism in the RE.

Quercetin mitigates memory deficits in scopolamine mice model via protection against neuroinflammation and neurodegeneration

AIMS

Neurodegenerative disorders like Alzheimer's disease (AD) are outcomes of neuroinflammatory processes that result in memory impairment. Quercetin (QT), a plant based flavonoid, has demonstrated notable effects against neurodegeneration and inflammation in models of dementia. However, the underlying mechanisms have not been well elucidated. This study evaluated the possible effects of QT against neuroinflammation and neurodegeneration in scopolamine (SC) induced memory impairment.

MAIN METHODS

SC was used to induce memory loss in mice after which novel object recognition test (NORT) was used to assess memory function. Enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in the brain tissues of the animals. Brain histology was carried out on the hippocampus (cornus ammonis 1, cornus ammonis 3 and dentate gyrus), and the prefrontal cortex. The population of healthy neuronal cells was counted, using ImageJ software. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) was employed for the identification of cells undergoing apoptosis.

KEY FINDINGS

QT reversed memory impairment in the NORT. Increases in TNF-α and IL-6 were attenuated by QT, and histology revealed that QT attenuated SC-induced cell degeneration and death in the hippocampal sub-regions and prefrontal cortex. QT diminished the population of dead cells in SC-treated mice, and also reversed the process of apoptosis induced by SC.

SIGNIFICANCE

Findings from the study suggest that QT mitigates pro-inflammatory mediators and reverses neurodegeneration to restore memory function.

Ketamine enhances novel object recognition memory reconsolidation via the BDNF/TrkB pathway in mice

In addition to the antidepressant properties of ketamine at subanesthetic doses, studies have revealed ketamine's influence on memory acquisition, consolidation, and reconsolidation. The effects of acute low-dose ketamine administration on conditioned memory have been investigated extensively in rodents through conditioned fear memory and morphine-induced conditioned place preference. In contrast to conditioned memory, the novel object recognition (NOR) task assesses the natural format of memory by exploiting the rodents' natural preference for novelty. Acute low-dose ketamine administration impairs NOR acquisition and consolidation, but its influence on reconsolidation remains unclear. We investigated the issue as well as the involvement of BDNF/TrkB pathway in this process by administering ketamine (i.p., 10 mg/kg, immediately or 6 h after reactivation, or without reactivation) and ANA-12 (i.p., 0.5 mg/kg, 5 min after ketamine/vehicle administration). ANA-12 is a selective antagonist for the BDNF TrkB receptor. Ketamine administration, immediately after (rather than without) reactivation, significantly increased the NOR preference index, thus suggesting an enhanced memory reconsolidation rather than consolidation. Ketamine exerted no significant effect when administered 6 h after reactivation, thereby suggesting 6 h to be an effective time window. ANA-12 administration significantly reduced the ketamine-induced NOR preference index increase, thus suggesting that the blockage of ketamine improves NOR reconsolidation. However, this blockage had no significant effect on the ketamine-induced hippocampal BDNF level increase. In conclusion, acute low-dose ketamine administration improves NOR memory reconsolidation by increasing hippocampal BDNF levels and subsequent BDNF binding to the TrkB receptor.

A standardized black pepper seed extract containing β-caryophyllene improves cognitive function in scopolamine-induced amnesia model mice via regulation of brain-derived neurotrophic factor and MAPK proteins

β-caryophyllene (BCP), a natural sesquiterpene present in plants, is a selective agonist of cannabinoid receptor type-2 (CB2) of the endocannabinoid system. In this study, we have prepared an extract from Piper nigrum (black pepper) seeds using supercritical fluid extraction, standardized to contain 30% BCP (Viphyllin^TM ). The beneficial effects of prophylactic treatment with Viphyllin on cognitive functions were demonstrated in Scopolamine-induced dementia model mice. Male Swiss albino mice (25-30 g) were administered with Viphyllin (50 mg and 100 mg/kg body weight p.o.) or donepezil (1.60 mg/kg) for 14 days. Subsequently, cognitive deficits were induced by treating the animals intraperitoneally with Scopolamine (0.75 mg/kg). The cognitive behavior of mice was evaluated using a novel object recognition test (NORT) and Morris water maze (MWM) test. The brain homogenates were studied for biochemical parameters including cholinesterase activities and antioxidant status. Western blot analysis was performed to investigate the mechanism of action. Viphyllin dose dependently improved the recognition and spatial memory and cholinergic functions in Scop-treated mice. The extract was found protective against Scop-induced oxidative damage and histopathologic changes in the brain. At 100 mg/kg Viphyllin markedly reduced the proBDNF/mBDNF ratio (p < .05) and augmented the TrkB expression (p < .01). Viphyllin (100 mg/kg) was found to be neuroprotective by reducing the Scop-induced upregulation of p-JNK and p-p38 MAPK proteins, Bax/Bcl-2 ratio, and caspase activation in the brain. Viphyllin also exerted anti-inflammatory effects by downregulating Cox-2, TNF-α, and NOS-2 in Scop-induced mice (p < .05). To summarize, our data encourage Viphyllin as a functional ingredient/dietary supplement for brain health and cognition. PRACTICAL APPLICATIONS: Black pepper is a culinary spice having several medicinal attributes. Essential oils in the seeds of the plant give aroma and flavor to it. Here we have prepared an extract from the seeds of black pepper using supercritical fluid extraction, characterized for the presence of β-caryophyllene (not <30%). This research work further validates the neuroprotective mechanism of the extract in Scopolamine-induced cognitive impairment model mice. The findings from this study strongly suggest the beneficial neuroactive properties of black pepper seed extract having the presence of BCP, a CB2 receptor agonist. It can thus be used potentially as a functional food ingredient for cognition and brain function.

Quercetin exhibits potent antioxidant activity, restores motor and non-motor deficits induced by rotenone toxicity

The rotenone-induced animal model of Parkinson's disease (PD) has been used to investigate the pathogenesis of PD. Oxidative stress is one of the main contributors of neurodegeneration in PD. Flavonoids have the potential to modulate neuronal function and combat various neurodegenerative diseases. The pre- and post-supplementation of quercetin (50 mg/kg, p.o) was done in rats injected with rotenone (1.5 mg/kg, s.c). After the treatment, behavioral activities were monitored for motor activity, depression-like behavior, and cognitive changes. Rats were decapitated after behavioral analysis and the brain samples were dissected out for neurochemical and biochemical estimation. Results showed that supplementation of quercetin significantly (p<0.01) restored rotenone-induced motor and non-motor deficits (depression and cognitive impairments), enhanced antioxidant enzyme activities (p<0.01), and attenuated neurotransmitter alterations (p<0.01). It is suggested that quercetin supplementation improves neurotransmitter levels by mitigating oxidative stress via increasing antioxidant enzyme activity and hence improves motor activity, cognitive functions, and reduces depressive behavior. The results of the present study showed that quercetin pre-supplementation produced more significant results as compared to post-supplementation. These findings show that quercetin can be a potential therapeutic agent to reduce the risk and progression of PD.

The selective TAAR1 partial agonist RO5263397 promoted novelty recognition memory in mice

RATIONALE

Trace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor that has a particular role in regulating dopaminergic, serotonergic, and glutamatergic transmission. TAAR1 agonists have shown pro-cognitive activities. However, it remains largely unknown of the effects of TAAR1 agonists on memory performance.

OBJECTIVES

Here, by using the mice novel object recognition (NOR) test, we examined the effects of the selective TAAR1 partial agonist RO5263397 on recognition memory.

RESULTS

We found that RO5263397 significantly enhanced the retrieval of short-term memory (STM; 20 min after training) both in male and female mice. RO5263397 promoted the retrieval of STM in the wild-type (WT) littermates but not TAAR1-KO mice, indicating that the effects of RO5263397 were dependent on TAAR1. Interestingly, compared to their WT litters, TAAR1-KO mice showed similar levels of STM, suggesting that genetic deletion of taar1 gene did not affect the STM retrieval. Furthermore, RO5263397 also promoted the retrieval of long-term NOR memory (24 h after training).

CONCLUSIONS

These results indicate that TAAR1 activation promotes NOR memory retrieval. Consistent with previous studies, our finding further suggests that TAAR1 agonists have pro-cognitive properties.

Post-acute delivery of α5-GABAA antagonist, S 44819, improves functional recovery in juvenile rats following stroke

Hypo-excitability was reported in the peri-infarct tissue following stroke, an effect counteracted by a blockage of α5-GABAA receptors in adult rodents. Our present study aims to evaluate the effect of a selective α5-GABAA receptor antagonist, S 44819, in stroke in juvenile animals. We have set up and characterized an original model of transient ischemic stroke in 28 day-old Sprague-Dawley rats (45-min occlusion of the middle cerebral artery by intraluminal suture). In this model, S 44819 (1, 3 and 10 mg/kg, b.i.d) was orally administered from day 3 to day 16 after stroke onset. Sensorimotor recovery was assessed on day 1, day 9 and day 16 after stroke onset. Results show that rats treated with S 44819 at the doses of 3 and 10 mg/kg displayed a significant improvement of the neurological deficits (neuroscore) on day 9 and day 16, when compared with animals treated with vehicle. Grip-test data analysis reveals that rats treated with S 44819 at the dose of 3 mg/kg displayed a better recovery on day 9 and day 16. These results are in agreement with those previously observed in adult rats, demonstrating that targeting α5-GABAA receptors improves neurological recovery after stroke in juvenile rats.

Promoting and Optimizing the Use of 3D-Printed Objects in Spontaneous Recognition Memory Tasks in Rodents: A Method for Improving Rigor and Reproducibility

Spontaneous recognition memory tasks are widely used to assess cognitive function in rodents and have become commonplace in the characterization of rodent models of neurodegenerative, neuropsychiatric and neurodevelopmental disorders. Leveraging an animal’s innate preference for novelty, these tasks use object exploration to capture the what, where and when components of recognition memory. Choosing and optimizing objects is a key feature when designing recognition memory tasks. Although the range of objects used in these tasks varies extensively across studies, object features can bias exploration, influence task difficulty and alter brain circuit recruitment. Here, we discuss the advantages of using 3D-printed objects in rodent spontaneous recognition memory tasks. We provide strategies for optimizing their design and usage, and offer a repository of tested, open-source designs for use with commonly used rodent species. The easy accessibility, low-cost, renewability and flexibility of 3D-printed open-source designs make this approach an important step toward improving rigor and reproducibility in rodent spontaneous recognition memory tasks.

Effects of general anesthetics on synaptic transmission and plasticity

General anesthetics depress excitatory and/or enhance inhibitory synaptic transmission principally by modulating the function of glutamatergic or GABAergic synapses, respectively, with relative anesthetic agent-specific mechanisms. Synaptic signaling proteins, including ligand- and voltage-gated ion channels, are targeted by general anesthetics to modulate various synaptic mechanisms, including presynaptic neurotransmitter release, postsynaptic receptor signaling, and dendritic spine dynamics to produce their characteristic acute neurophysiological effects. As synaptic structure and plasticity mediate higher-order functions such as learning and memory, long-term synaptic dysfunction following anesthesia may lead to undesirable neurocognitive consequences depending on the specific anesthetic agent and the vulnerability of the population. Here we review the cellular and molecular mechanisms of transient and persistent general anesthetic alterations of synaptic transmission and plasticity.

Probiotic alleviate fluoride-induced memory impairment by reconstructing gut microbiota in mice

Fluoride which is widespread in our environment and food due to its geological origin and industrial pollution has been identified as a developmental neurotoxicant. Gut-brain axis provides new insight into brain-derived injury. We previously found the psychoactive effects of a probiotic strain, Lactobacillus johnsonii BS15 against fluoride-induced memory dysfunction in mice by modulating the gut-brain axis. In this study, we aimed to detect the link between the reconstruction of gut microbiota and gut-brain axis through which probiotic alleviate fluoride-induced memory impairment. We also added an hour of water avoidance stress (WAS) before behavioral tests and sampling, aiming to demonstrate the preventive effects of the probiotic on fluoride-induced memory impairment after psychological stress. Mice were given fluoridated drinking water (sodium fluoride 100 ppm, corresponding to 37.8 ± 2.4 ppm F¯) for 70 days and administered with PBS or a probiotic strain, Lactobacillus johnsonii BS15 for 28 days prior to and throughout a 70 day exposure to sodium fluoride. Results showed that fluoride increases the hyperactivity of hypothalamic-pituitary-adrenal (HPA) axis and reduces the exploration ratio in novel object recognition (NOR) test and the spontaneous exploration during the T-maze test in mice following WAS, which were significantly improved by the probiotic. 16S rRNA sequencing showed a significant separation in ileal microbiota between the fluoride-treated mice and control mice. Lactobacillus was the main targeting bacteria and significantly reduced in fluoride-treated mice. BS15 reconstructed the fluoride-post microbiota and increased the relative abundance of Lactobacillus. D-lactate content and diamine oxidase (DAO) activity, two biomarkers of gut permeability were reduced in the serum of probiotic-inoculated mice. ZO-1, an intestinal tight junction protein was reduced by fluoride in mRNA, and its protein levels were increased by the probiotic treatment. Moreover, the hippocampus which is essential to learning and memory, down-regulated mRNA level of both the myelin-associated glycoprotein (MAG), and protein levels of brain-derived neurotrophic factor (BDNF), including the improvement of cAMP response element-binding protein (CREB) by BS15 in fluoride-exposed mice after WAS. Via spearman correlation analysis, Lactobacillus displayed significantly positive associations with the behavioral tests, levels of nerve development related factors, and intestinal tight junction proteins ZO-1, and negative association with TNF-α of the hippocampus, highlighting regulatory effects of gut bacteria on memory potential and gut barrier. These results suggested the psychoactive effects of BS15 on fluoride-induced memory dysfunction after psychological stress. In addition, there may be some correlations between fluoride-induced memory dysfunction and reconstruction of gut microbiota. AVAILABILITY OF DATA AND MATERIALS: 16S rRNA sequencing reads have uploaded to NCBI. The accession code of 16S rRNA sequencing reads in the National Center for Biotechnology Information (NCBI) BioProject database: PRJNA660154.

Effects of Eugenol on Memory Performance, Neurogenesis, and Dendritic Complexity of Neurons in Mice Analyzed by Behavioral Tests and Golgi Staining of Brain Tissue

Eugenol, as the main component in clove, has neuroprotective abilities, including its effect to learning memory of mice. However, there is no evidence showing whether eugenol can expand the growth of dendrites in the brain. The objective of this research was to examine the effects of eugenol towards dendritic complexity of neurons, neurogenesis, and memory performance in hippocampus. A total of 21 mice were divided into three groups; (i) mice were administered 30 mg/kg bw eugenol orally, (ii) mice were administered 100 mg/kg bw eugenol orally, and (iii) mice were administered distilled water as control. Mice were kept for 30 consecutive days following the standard animal housing. The memory performance was observed through the Y-arm maze alternation, Novel Object Recognition (NOR), and Morris Water Maze (MWM) test. The brain was dissected and stained with FD Rapid Golgi StainingTM kit to observe dendrites in the dentate gyrus (DG) and cornu ammonis 1 (CA1) region; and Haematoxylin-Eosin (HE) staining to assess neurogenesis in the DG. Our results showed that eugenol enhanced putative neural stem cells (NPCs) and granular cells (GC) number, and also decrease neuronal cell death in DG (p<0.0001). Eugenol also increased dendritic complexity of neurons in DG region; while in CA1, eugenol has given a positive effect only on the basal area. Eugenol increased spatial and recognition memory in mice, indicated by a higher number of correct alternations and discrimination ratio compared to the control group (p<0.05), although escape latency in MWM did not show significant effect (p>0.05). As analyzed by behavioral tests and Golgi staining of brain tissue, eugenol can increase memory performance, neurogenesis, and dendritic complexity of neurons in the DG and CA1 basal region of brain in mice.

Ketamine anesthesia enhances fear memory consolidation via noradrenergic activation in the basolateral amygdala

Trauma patients treated with ketamine during emergency care present aggravated early post- traumatic stress reaction which is highly predictive of post-traumatic stress disorder (PTSD) development and severity. The use of ketamine in the acute trauma phase may directly or indirectly interfere with neural processes of memory consolidation of the traumatic event, thus leading to the formation of maladaptive memories, a hallmark symptom of PTSD. We have recently shown that ketamine anesthesia, immediately after a traumatic event, enhances memory consolidation and leads to long-lasting alterations of social behavior in rats. Based on the evidence that ketamine induces a robust central and peripheral adrenergic/noradrenergic potentiation and that activation of this system is essential for the formation of memory for stressful events, we explored the possibility that the strong sympathomimetic action of ketamine might underlie its memory enhancing effects. We found that rats given immediate, but not delayed, post-training ketamine anesthesia (125 mg/kg) presented enhanced 48-h memory retention in an inhibitory avoidance task and that these effects were blocked by adrenal medullectomy, lesions of the locus coeruleus, systemic or intra-basolateral amygdala ß-adrenergic receptor antagonism. Thus, the memory enhancing effects of ketamine anesthesia are time-dependent and mediated by a combined peripheral-central sympathomimetic action. We elucidated a mechanism by which ketamine exacerbates acute post-traumatic reaction, possibly leading to development of PTSD symptomatology later in life. These findings will help guide for a better management of sedation/anesthesia in emergency care to promote the prophylaxis and reduce the risk of developing trauma-related disorders in trauma victims.

Investigation of the Role of Stimulation and Blockade of 5-HT7 Receptors in Ketamine Anesthesia

Although several pieces of evidence have indicated the ability of the serotonin-7 receptor (5-HTR₇) to modulate N-methyl-_D-aspartate receptor (NMDAR) activation, the possible impact on ketamine anesthesia has not been examined directly. The purpose of the present study is thus to investigate the possible role of the 5-HTR₇ in ketamine anesthesia using a 5-HTR₇ agonist and/or antagonist. The influence of a 5-HTR₇ agonist/antagonist on ketamine anesthesia for behavioral impact was assessed by testing potential anesthetic parameters. Its functional impact was assessed by mRNA expression with real-time PCR and immunostaining in the hippocampus and prefrontal cortex of mice. Two different doses of ketamine-high and low-were administered to induce anesthesia. In the high-dose ketamine-applied group in particular, the administration of both the 5-HTR₇ agonist and antagonist intensified the anesthetic effect of ketamine. The reflection of the change in anesthesia parameters to 5-HTR₇ expression was observed as an increase in the hippocampus and a decrease in the prefrontal cortex in the anesthetized groups by stimulation of 5-HTR₇. It is noteworthy that the results of NMDAR expressions are parallel to the results of the 5-HTR₇ expressions of both the hippocampus and the prefrontal cortex. The 5-HTR₇ may play a role in ketamine anesthesia. It may act through NMDAR in ketamine anesthesia, depending on the parallelism between both receptors.

Lipin1 Is Involved in the Pathogenesis of Diabetic Encephalopathy through the PKD/Limk/Cofilin Signaling Pathway

Diabetic encephalopathy is a type of central diabetic neuropathy resulting from diabetes mainly manifested as cognitive impairments. However, its underlying pathogenesis and effective treatment strategies remain unclear. In the present study, we investigated the effect of Lipin1, a phosphatidic acid phosphatase enzyme, on the pathogenesis of diabetic encephalopathy. We found that in vitro, Lipin1 exerts protective effects on high glucose-induced reductions of PC12 cell viability, while in vivo, Lipin1 is downregulated within the CA1 hippocampal region in a type I diabetes rat model. Increased levels of Lipin1 within the CA1 region are accompanied with protective effects including amelioration of dendritic spine and synaptic deficiencies, phosphorylation of the synaptic plasticity-related proteins, LIM kinase 1 (p-limk1) and cofilin, as well as increases in the synthesis of diacylglycerol (DAG), and the expression of phosphorylated protein kinase D (p-PKD). These effects are associated with the rescue of cognitive disorders as shown in this rat model of diabetes. In contrast, knockdown of Lipin1 within the CA1 region enhanced neuronal abnormalities and the genesis of cognitive impairment in rats. These results suggest that Lipin1 may exert neuroprotective effects involving the PKD/Limk/Cofilin signaling pathway and may serve as a potential therapeutic target for diabetic encephalopathy.

Ketamine disrupted storage but not retrieval of information in male rats and apomorphine counteracted its impairing effect

Ketamine, a non-competitive NMDA receptor antagonist, has been reported to mimic the cognitive symptoms of schizophrenia in animals. It has been reported to produce learning and memory deficits in rodents. However, there have limited number of reports that investigated the specific components of memory process that are affected with ketamine. In the present study, we investigated the effects of ketamine [8 and 20 mg/kg, intraperitoneally, (i.p.)] on storage and retrieval of information in rats using an object recognition test. We examined also whether a low dose range of the D1/D2 dopamine receptor agonist apomorphine (0.05 and 0.1 mg/kg, i.p.) would counteract the effects of ketamine. The results show that ketamine dose-dependently impaired storage of information while it did not affect rats' retrieval abilities. Administration of apomorphine reversed the ketamine-induced performance deficits in the ORT. The current findings show a differential modulation of post-training memory components (storage and retrieval of information) by ketamine and suggest a functional interaction between dopamine and NMDA receptors in the control of memory storage which may be of relevance to cognitive deficits a core feature of schizophrenia.

Caffeic acid phenethyl ester counteracts doxorubicin-induced chemobrain in Sprague-Dawley rats: Emphasis on the modulation of oxidative stress and neuroinflammation

Chemotherapy-induced cognitive dysfunction (chemobrain) is one of the major complaints for cancer patients treated with chemotherapy such as Doxorubicin (DOX). The induction of oxidative stress and neuroinflammation were identified as major contributors to such adverse effect. Caffeic acid phenethyl ester (CAPE) is a natural polyphenolic compound, that exhibits unique context-dependent antioxidant activity. It exhibits pro-oxidant effects in cancer cells, while it is a potent antioxidant and cytoprotective in normal cells. The present study was designed to investigate the potential neuroprotective effects of CAPE against DOX-induced cognitive impairment. Chemobrain was induced in Sprague Dawley rats via systemic DOX administration once per week for 4 weeks (2 mg/kg/week, i.p.). CAPE was administered at 10 or 20 μmol/kg/day, i.p., 5 days per week for 4 weeks. Morris water maze (MWM) and passive avoidance tests were used to assess learning and memory functions. Oxidative stress was evaluated via the colorimetric determination of GSH and MDA levels in both hippocampal and prefrontal cortex brain regions. However, inflammatory markers, acetylcholine levels, and neuronal cell apoptosis were assessed in the same brain areas using immunoassays including either ELISA, western blotting or immunohistochemistry. DOX produced significant impairment in learning and memory as indicated by the data generated from MWM and step-through passive avoidance tests. Additionally DOX-triggered oxidative stress as evidenced from the reduction in GSH levels and increased lipid peroxidation. Treatment with DOX resulted in neuroinflammation as indicated by the increase in NF-kB (p65) nuclear translocation in addition to boosting the levels of pro-inflammatory mediators (COX-II/TNF-α) along with the increased levels of glial fibrillary acid protein (GFAP) in the tested tissues. Moreover, DOX reduced acetylcholine levels and augmented neuronal cell apoptosis as supported by the increased active caspase-3 levels. Co-treatment with CAPE significantly counteracted DOX-induced behavioral and molecular abnormalities in rat brain tissues. Our results provide the first preclinical evidence for CAPE promising neuroprotective activity against DOX-induced neurodegeneration and memory deficits.

Cannabidiol Modulates the Motor Profile and NMDA Receptor-related Alterations Induced by Ketamine

Cannabidiol (CBD) is a non-addictive ingredient of cannabis with antipsychotic potential, while ketamine (KET), an uncompetitive NMDA receptor inhibitor, has been extensively used as a psychotomimetic. Only few studies have focused on the role of CBD on the KET-induced motor profile, while no study has investigated the impact of CBD on KET-induced alterations in NMDA receptor subunit expression and ERK phosphorylation state, in brain regions related to the neurobiology and treatment of schizophrenia. Therefore, the aim of the present study is to evaluate the role of CBD on KET-induced motor response and relevant glutamatergic signaling in the prefrontal cortex, the nucleus accumbens, the dorsal and ventral hippocampus. The present study demonstrated that CBD pre-administration did not reverse KET-induced short-lasting hyperactivity, but it prolonged it over time. CBD alone decreased motor activity at the highest dose tested (30 mg/kg) while KET increased motor activity at the higher doses (30, 60 mg/kg). Moreover, KET induced regionally-dependent alterations in NR1 and NR2B expression and ERK phosphorylation that were reversed by CBD pre-administration. Interestingly, in the nucleus accumbens KET per se reduced NR2B and p-ERK levels, while the CBD/KET combination increased NR2B and p-ERK levels, as compared to control. This study is the first to show that CBD prolongs KET-induced motor stimulation and restores KET-induced effects on glutamatergic signaling and neuroplasticity-related markers. These findings contribute to the understanding of CBD effects on the behavioral and neurobiological profiles of psychotogenic KET.

The Neuroprotective Action of Amidated-Kyotorphin on Amyloid β Peptide-Induced Alzheimer's Disease Pathophysiology

Kyotorphin (KTP, l-tyrosyl-l-arginine) is an endogenous dipeptide initially described to have analgesic properties. Recently, KTP was suggested to be an endogenous neuroprotective agent, namely for Alzheimer’s disease (AD). In fact, KTP levels were shown to be decreased in the cerebrospinal fluid of patients with AD, and recent data showed that intracerebroventricular (i.c.v.) injection of KTP ameliorates memory impairments in a sporadic rat model of AD. However, this administration route is far from being a suitable therapeutic strategy. Here, we evaluated if the blood-brain permeant KTP-derivative, KTP-NH₂, when systemically administered, would be effective in preventing memory deficits in a sporadic AD animal model and if so, which would be the synaptic correlates of that action. The sporadic AD model was induced in male Wistar rats through i.c.v. injection of amyloid β peptide (Aβ). Animals were treated for 20 days with KTP-NH₂ (32.3 mg/kg, intraperitoneally (i.p.), starting at day 3 after Aβ administration) before memory testing (Novel object recognition (NOR) and Y-maze (YM) tests). Animals were then sacrificed, and markers for gliosis were assessed by immunohistochemistry and Western blot analysis. Synaptic correlates were assessed by evaluating theta-burst induced long term potentiation (LTP) of field excitatory synaptic potentials (fEPSPs) recorded from hippocampal slices and cortical spine density analysis. In the absence of KTP-NH₂ treatment, Aβ-injected rats had clear memory deficits, as assessed through NOR or YM tests. Importantly, these memory deficits were absent in Aβ-injected rats that had been treated with KTP-NH₂, which scored in memory tests as control (sham i.c.v. injected) rats. No signs of gliosis could be detected at the end of the treatment in any group of animals. LTP magnitude was significantly impaired in hippocampal slices that had been incubated with Aβ oligomers (200 nM) in the absence of KTP-NH₂. Co-incubation with KTP-NH₂ (50 nM) rescued LTP toward control values. Similarly, Aβ caused a significant decrease in spine density in cortical neuronal cultures, and this was prevented by co-incubation with KTP-NH₂ (50 nM). In conclusion, the present data demonstrate that i.p. KTP-NH₂ treatment counteracts Aβ-induced memory impairments in an AD sporadic model, possibly through the rescuing of synaptic plasticity mechanisms.

Ketamine Blocks Morphine-Induced Conditioned Place Preference and Anxiety-Like Behaviors in Mice

Patients suffering from opioid use disorder often relapse during periods of abstinence, which is posited to be caused by negative affective states that drive motivated behaviors. Here, we explored whether conditioning mice with morphine in a conditioned place preference (CPP) training paradigm evoked anxiety-like behavior during morphine abstinence. To do this, mice were conditioned with morphine (10 mg/kg, i.p.) for 5 days. Twenty-four hours following conditioning, anxiety levels were tested by measuring time in the open arms of the elevated plus-maze. The next day, mice were placed in the three-compartment chamber to measure morphine-induced CPP. Our results show that following morphine conditioning, mice spent significantly less time in the open arm of the elevated plus-maze and expressed robust morphine CPP on CPP test day. Furthermore, we found that an acute treatment with (R,S)-ketamine (10 mg/kg, i.p.), a medication demonstrating promise for preventing anxiety-related phenotypes, 30 min before testing on post-conditioning day 1, increased time spent in the open arm of the elevated plus-maze in saline- and morphine-conditioned mice. Additionally, we found that the second injection of ketamine 30 min before CPP tests on post-conditioning day 2 prevented morphine-induced CPP, which lasted for up to 28 days post-conditioning. Furthermore, we found that conditioning mice with 10% (w/v) sucrose using an oral self-administration procedure did not evoke anxiety-like behavior, but elicited robust CPP, which was attenuated by ketamine treatment 30 min before CPP tests. Overall, our results suggest that the ketamine-induced block of morphine CPP may not be attributed solely to alleviating negative affective states, but potentially through impaired memory of morphine-context associations.

The Combination Effects of Resveratrol and Swimming HIIT Exercise on Novel Object Recognition and Open-field Tasks in Aged Rats

INTRODUCTION

Resveratrol, a natural polyphenol abundant in grapes and red wine, has been reported to exert numerous beneficial health effects in the body. High-Intensity Interval Exercise (HIIT) is a form of interval training that provides improved athletic capacity and has a protective effect on health. The purpose of this study was to investigate the interactive effects of swimming HIIT and Resveratrol supplementation on behavioral function in Novel object recognition and open-field tests in aged rats.

METHODS

A total of 45 aged male Wistar rats with an age of 20 months were randomly assigned into five groups of control (C), swimming HIIT (SW-HIIT), swimming HIIT with Resveratrol supplementation (SW-HIIT-R), Resveratrol supplementation (R), and solvent of Resveratrol supplementation (SR). There was also another group that included young animals (2-month-old) and was used to compare with older animals. Swimming HIIT and Resveratrol supplementation groups performed the exercise and received Resveratrol (10 mg/kg/day, gavage) for six weeks. Novel object recognition and open-field tests were used for evaluating the behavioral functions in animals.

RESULTS

The results showed that HIIT and Resveratrol significantly improved recognition memory compared to old animals. Moreover, it seems that HIIT and Resveratrol partly could modulate anxiety-like behaviors compared to old animals in the open-field test.

Exogenous GM1 Ganglioside Attenuates Ketamine-Induced Neurocognitive Impairment in the Developing Rat Brain

BACKGROUND

A prolonged exposure to ketamine triggers significant neurodegeneration and long-term neurocognitive deficits in the developing brain. Monosialotetrahexosylganglioside (GM1) can limit the neuronal damage from necrosis and apoptosis in neurodegenerative conditions. We aimed to assess whether GM1 can prevent ketamine-induced developmental neurotoxicity.

METHODS

Postnatal day 7 (P7) rat pups received 5 doses of intraperitoneal ketamine (20 mg/kg per dose) at 90-minute intervals for 6 hours. Cognitive functions, determined by using Morris water maze (MWM) including escape latency (at P32-36) and platform crossing (at P37), were compared among the ketamine-exposed pups treated with or without exogenous GM1 (30 mg/kg; n = 12/group). The effect of GM1 on apoptosis in hippocampus was determined by terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick end labeling (TUNEL) staining and activated caspase 3 measurement. The hippocampal expression of brain-derived neurotrophic factor (BDNF), along with the phosphorylation of protein kinase B (AKT) and extracellular signal-related kinases 1 and 2 (ERK1/2), was detected by western blotting (n = 6/group). Anti-BDNF antibody (2 μg per rat) administered before GM1 treatment was applied to determine the neuroprotective mechanisms of GM1.

RESULTS

The rats receiving ketamine exposure experinced cognitive impairment in MWM test compared to the control rats, indicated by prolonged escape latency at P34 (P = .006), P35 (P = .002), and P36 (P = .005). However, in GM1-pretreated rats, ketamine exposure did not induce prolonged escape latency. The exogenous GM1 increased the platform-crossing times at P37 (3.00 ± 2.22 times vs 5.40 ± 1.53 times, mean ± standard deviation; P = .041) and reduced the hippocampal TUNEL-positive cells and cleaved-caspase 3 expression in ketamine-exposed young rats. Ketamine decreased BDNF expression and phosphorylation of AKT and ERK in the hippocampus, whereas exogenous GM1 blocked these ketamine-caused effects. However, for the ketamine-exposed rat pups receiving exogenous GM1, compared to immunoglobulin Y (IgY) isotype control, the BDNF-neutralizing antibody treatment counteracted the exogenous GM1-induced improvement of the escape latency at P36 (41.32 ± 12.37 seconds vs 25.14 ± 8.97 seconds, mean ± standard deviation; P = .036), platform-crossing times at P37 (2.16 ± 1.12 times vs 3.92 ± 1.97 times, mean ± standard deviation; P < .036), apoptotic activity, as well as AKT and ERK1/2 phosphorylation in the hippocampus of ketamine-challenged young rats.

CONCLUSIONS

Our data suggest that the exogenous GM1 acts on BDNF signaling pathway to ameliorate the cognitive impairment and hippocampal apoptosis induced by ketamine in young rats. Our study may indicate a potential use of GM1 in preventing the cognitive deficits induced by ketamine in the young per se.