Effects of haloperidol, olanzapine, ziprasidone, and PHA-543613 on spatial learning and memory in the Morris water maze test in naïve and MK-801-treated mice

Regulating effect of Qifu Yin on intestinal microbiota in mice with memory impairment induced by scopolamine hydrobromide

ETHNOPHARMACOLOGICAL RELEVANCE

Qifu Yin (QFY) originates from "Jingyue Quanshu · Volume 51 · New Fang Bazhen · Buzhen" a work by Zhang Jingyue, a distinguished Chinese medical practitioner from the Ming Dynasty. QFY is composed of Ginseng Radix et Rhizoma, Rehmanniae Radix Praeparata, Angelicae Sinensis Radix, Atractylodis Macrocephalae Rhizoma, Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle, Ziziphi Spinosae Semen, and Polygalae Radix. QFY is frequently employed to address memory loss and cognitive impairment stemming from vascular dementia, Alzheimer's disease (AD), and related conditions. Our findings indicate that QFY can mitigate nerve cell damage. Moreover, the study explores the impact of QFY on the calcium ion pathway and sphingolipid metabolism in mice with myocardial infarction, presenting a novel perspective on QFY's mechanism in ameliorating myocardial infarction through lipidomics. While this research provides an experimental foundation for the clinical application of QFY, a comprehensive and in-depth analysis of its improvement mechanism remains imperative.

AIM OF THE STUDY

To clarify the regulatory mechanism of QFY on intestinal microecology in mice with memory impairment (MI).

MATERIAL AND METHODS

The memory impairment mouse model was established by intraperitoneal injection of scopolamine hydrobromide. Kunming (KM) mice were randomly divided into blank group, Ginkgo tablet group (0.276 g/kg), QFY high, medium and low dose groups (17.2 g/kg, 8.6 g/kg, 4.3 g/kg). The effect on memory ability was evaluated by open field and step-down behavioral experiments. The morphological changes of nerve cells in the hippocampus of mice were observed by pathological method. The contents of superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT) and glutathione peroxidase (GSH-Px) in the brain tissue of mice were detected. The expression levels of CREB, Brain-Derived Neurotrophic Factor (BDNF) and Recombinant Amyloid Precursor Protein (APP) in the hippocampus of mice were determined using immunohistochemistry. The expression of N-methyl-D-aspartate receptor (NMDAR) and cAMP response element binding protein (CREB) related factors in the serum of mice was analyzed by ELISA. The levels of apoptosis signal-regulating kinase-1 (ASK1) and c-Jun N-terminal kinase (JNK) mRNA in the hippocampus were detected by quantitative real-time fluorescence polymerase chain reaction (qPCR). The intestinal feces of mice were collected, and the 16 S rDNA technology was used to detect the changes in intestinal microbiota microecological structure of feces in each group.

RESULTS

Behavioral experiments showed that the high-dose QFY group exhibited a significant increase in exercise time (P<0.05) and a decrease in diagonal time (P<0.05) compared to the model group. The medium-dose group of QFY showed a reduction in diagonal time (P<0.05). Additionally, the latency time significantly increased in the medium and high-dose groups of QFY (P<0.01). The number of errors in the low, medium and high dose groups was significantly decreased (P<0.05, P<0.01, P<0.01). The nerve cells in the CA1 and CA3 regions of QFY-treated mice demonstrated close arrangement and clear structure. Furthermore, the content of SOD significantly increased (P<0.01) and the content of MDA significantly decreased (P<0.05) in the low and high-dose QFY groups. The content of CAT in the medium-dose group significantly increased (P < 0.05). Immunohistochemical analysis showed a significant reduction in the number of APP expression particles in the CA1 and CA3 regions of all QFY groups. Moreover, BDNF expression significantly increased in the medium and high-dose groups, while CREB expression significantly increased in the low and medium-dose groups of QFY within the CA1 and CA3 regions. Serum analysis revealed significant increases in CREB content in the low, medium, and high dose groups of QFY (P<0.01, P<0.05, P<0.05), and decreases in NMDAR content across all QFY dose groups (P<0.01). PCR analysis showed a significant decrease in the contents of ASK1 and JNK in the medium-dose group (P<0.01). Microecological analysis of intestinal microbiota demonstrated a significant restoration trend in the relative abundance of Fusobacteria, Planctomycetes, and Verrucomicrobia (P<0.01 or P<0.05) at the phylum level in the QFY groups. At the genus level, Akkermansia, Paramuribaculum, Herminiimonas, Erysipelatoclostridium and other genera in the QFY groups showed a significant trend of relative abundance restoration (P<0.01 or P<0.05).

CONCLUSION

QFY can improve the memory of MI animals induced by scopolamine hydrobromide by restoring the homeostasis of intestinal microbiota and regulating related indexes in serum and brain tissue.

Cellular Mechanisms of Cognitive Enhancement: The In Vivo Modulation of the Firing Activity and the Responsiveness of Rat Hippocampal Neurons by Memantine and Alpha7 Nicotinic Acetylcholine Receptor Ligands

Promising new pharmacological strategies for the enhancement of cognition target either nicotinic acetylcholine receptors (nAChR) or N-methyl-D-aspartate receptors (NMDAR). There is also an increasing interest in low-dose combination therapies co-targeting the above neurotransmitter systems to reach greater efficacy over the monotreatments and to reduce possible side effects of high-dose monotreatments. In the present study, we assessed modulatory effects of the α7 nAChR-selective agonist PHA-543613 (PHA), a novel α7 nAChR positive allosteric modulator compound (CompoundX) and the NMDAR antagonist memantine on the in vivo firing activity of CA1 pyramidal neurons in the rat hippocampus. Three different test conditions were applied: spontaneous firing activity, NMDA-evoked firing activity and ACh-evoked firing activity. Results showed that high but not low doses of memantine decreased NMDA-evoked firing activity, and low doses increased the spontaneous and ACh-evoked firing activity. Systemically applied PHA robustly potentiated ACh-evoked firing activity with having no effect on NMDA-evoked activity. In addition, CompoundX increased both NMDA- and ACh-evoked firing activity, having no effects on spontaneous firing of the neurons. A combination of low doses of memantine and PHA increased firing activity in all test conditions and similar effects were observed with memantine and CompoundX but without spontaneous firing activity increasing effects. Our present results demonstrate that α7 nAChR agents beneficially interact with Alzheimer's disease medication memantine. Moreover, positive allosteric modulators potentiate memantine effects on the right time and the right place without affecting spontaneous firing activity. All these data confirm previous behavioral evidence for the viability of combination therapies for cognitive enhancement.

Olax subscorpioidea prevented scopolamine-induced memory impairment through the prevention of oxido-inflammatory damage and modulation of cholinergic transmission

ETHNOPHARMACOLOGICAL RELEVANCE

Olax subscorpioidea oliv. is a shrub plant of the Olacaceae family with reported usage in ethnomedicine as a nootropic agent for the management of Alzheimer's-like dementia.

AIM

The aim of this study is to investigate the nootropic potential of methanol extract of Olax subscorpioidea (MEOS) in scopolamine-induced Alzheimer's-like dementia.

MATERIALS AND METHODS

Thirty male mice, assigned into six groups (n = 8), were used for this study. Group, I received distilled water, group II received scopolamine (1 mg/kg, i.p.), groups iii-v received 25, 50, and 100 mg/kg, p.o. of MEOS and scopolamine (1 mg/kg/i.p.), and group vi received donepezil 5 mg/kg, p.o.and scopolamine (1 mg/kg, i.p.). The animals were pre-treated with MEOS and Donepezil for 14 days, and scopolamine from the 8th to 14th day. Followed by cognitive, oxidative stress, neuroinflammation, and histology assessments.

RESULTS

100 mg/kg MEOS significantly reduced transfer latency and increased discrimination index in the elevated plus maze and novel object recognition test cognitive assessments. 100 mg/kg MEOS, significantly reduced oxidative stress, protect endogenous antioxidants, suppressed neuroinflammation, and acetylcholinesterase (ACHE) activity. The histomorphometry study of the hippocampus revealed that MEOS prevented extensive pyknosis, karyolysis, chromatolysis, and loss of hippocampal neurons that accompanied scopolamine treatment.

CONCLUSION

MEOS protected against Alzheimer's-like dementia via the suppression of neuroinflammation and oxidative stress associated with scopolamine-induced amnesic behavior.

Neuroprotective effects of Petiveria alliacea on scopolamine-induced learning and memory impairment mouse model

ETHNOPHARMACOLOGY RELEVANCE

Petiveria alliacea L., commonly known as macura and gully root, is an important medicinal plant used in the Caribbean and Central America to treat ailments associated to the central nervous system, including poor memory.

AIM OF THE STUDY

To assess the effects of the P. alliacea leaves methanol fraction (PMF) on a scopolamine-induced learning and memory impairment mouse model related to acetylcholinesterase activity and oxidative stress.

MATERIAL AND METHODS

After PMF administration at doses of 500 or 900 mg/kg, cognitive ability was evaluated using the Morris water maze (MWM), Y-maze (YM) and novel object recognition (NOR) tests. The mouse brain tissue was further assessed for acetylcholinesterase activity and antioxidant activity. Levels of oxidative stress were also evaluated by measuring malondialdehyde (MDA) and glutathione activity. Acute toxicity was also evaluated.

RESULTS

PMF led to memory improvement in the behavioral tests in mice with scopolamine-induced cognitive impairment. Moreover, PMF inhibited acetylcholinesterase activity and showed antioxidant potential that in turn attenuated cholinergic degradation. Additionally, PMF increased glutathione levels and glutathione reductase activity and reduced MDA levels in the brain. Moreover, no acute toxicity was detected with the use of PMF.

CONCLUSION

In a mouse model of scopolamine-induced cognitive deficit, PMF exhibited protective effects, decreasing oxidative damage and regulating cholinergic function in the brain bearing significant memory enhancing potency. These data suggest that PMF is a promising candidate for developing therapies for neurodegenerative disorders.

The effect of acute and chronic formaldehyde exposure on learning and memory in male and female rats

AIM

Formaldehyde is a chemical that lies behind the various systemical failures in organism. Many products that people use contain formaldehyde. Owing to its tissue fixative properties, scientists who work in life sciences are exposed to this substance more than others. Several studies have shown that formaldehyde affects the CA1 and CA3 regions of the hippocampus, which play crucial roles in memory consolidation. In this study, we aimed to investigate anxiety levels and indicate the short and long term effects of formaldehyde and sex-related differences by exposing formaldehyde to male and female rats.

MATERIALS AND METHODS

Formaldehyde (10 mg/kg) was administered intraperitoneally for 7 days for acute exposure and 30 days for chronic exposure. Cognitive assessment was performed using fear conditioning, elevated plus maze, and Morris water maze tests. TUNEL staining was used to identify apoptosis in the brains obtained after decapitation.

RESULTS

Exposure to intraperitoneal formaldehyde does not impair learning and memory in acute and chronic periods and has no effect on depression or anxiety. After acute exposure, apoptosis was observed in the hippocampal CA1 and CA3 regions in males. When the cognitive test results were examined, no differences were found between the experimental and control groups. There was also no significant difference between males and females.

MK-801 and cognitive functions: Investigating the behavioral effects of a non-competitive NMDA receptor antagonist

RATIONALE

MK-801 (dizocilpine) is a non-competitive NMDA receptor antagonist originally explored for anticonvulsant potential. Despite its original purpose, its amnestic properties led to the development of pivotal models of various cognitive impairments widely employed in research and greatly impacting scientific progress. MK-801 offers several advantages; however, it also presents drawbacks, including inducing dose-dependent hyperlocomotion or ambiguous effects on anxiety, which can impact the interpretation of behavioral research results.

OBJECTIVES

The present review attempts to summarize and discuss the effects of MK-801 on different types of memory and cognitive functions in animal studies.

RESULTS

A plethora of behavioral research suggests that MK-801 can detrimentally impact cognitive functions. The specific effect of this compound is influenced by variables including developmental stage, gender, species, strain, and, crucially, the administered dose. Notably, when considering the undesirable effects of MK-801, doses up to 0.1 mg/kg were found not to induce stereotypy or hyperlocomotion.

CONCLUSION

Dizocilpine continues to be of significant importance in preclinical research, facilitating the exploration of various procognitive therapeutic agents. However, given its potential undesirable effects, it is imperative to meticulously determine the appropriate dosages and conduct supplementary evaluations for any undesirable outcomes, which could complicate the interpretation of the findings.

The Effects of Four Compounds That Act on the Dopaminergic and Serotonergic Systems on Working Memory in Animal Studies; A Literature Review

The dopaminergic and serotonergic systems are two of the most important neuronal pathways in the human brain. Almost all psychotropic medications impact at least one neurotransmitter system. As a result, investigating how they affect memory could yield valuable insights into potential therapeutic applications or unanticipated side effects. The aim of this literature review was to collect literature data from animal studies regarding the effects on memory of four drugs known to act on the serotonergic and dopaminergic systems. The studies included in this review were identified in the PubMed database using selection criteria from the PRISMA protocol. We analyzed 29 articles investigating one of four different dopaminergic or serotonergic compounds. Studies conducted on bromocriptine have shown that stimulating D2 receptors may enhance working memory in rodents, whereas inhibiting these receptors could have the opposite effect, reducing working memory performance. The effects of serotonin on working memory are not clearly established as studies on fluoxetine and ketanserin have yielded conflicting results. Further studies with better-designed methodologies are necessary to explore the impact of compounds that affect both the dopaminergic and serotonergic systems on working memory.

Developmental Manipulation-Induced Changes in Cognitive Functioning

Schizophrenia is a complex neurodevelopmental disorder with as-yet no identified cause. The use of animals has been critical to teasing apart the potential individual and intersecting roles of genetic and environmental risk factors in the development of schizophrenia. One way to recreate in animals the cognitive impairments seen in people with schizophrenia is to disrupt the prenatal or neonatal environment of laboratory rodent offspring. This approach can result in congruent perturbations in brain physiology, learning, memory, attention, and sensorimotor domains. Experimental designs utilizing such animal models have led to a greatly improved understanding of the biological mechanisms that could underlie the etiology and symptomology of schizophrenia, although there is still more to be discovered. The implementation of the Research and Domain Criterion (RDoC) has been critical in taking a more comprehensive approach to determining neural mechanisms underlying abnormal behavior in people with schizophrenia through its transdiagnostic approach toward targeting mechanisms rather than focusing on symptoms. Here, we describe several neurodevelopmental animal models of schizophrenia using an RDoC perspective approach. The implementation of animal models, combined with an RDoC framework, will bolster schizophrenia research leading to more targeted and likely effective therapeutic interventions resulting in better patient outcomes.

Moringa oleifera-supplemented diet protect against cortico-hippocampal neuronal degeneration in scopolamine-induced spatial memory deficit in mice: role of oxido-inflammatory and cholinergic neurotransmission pathway

The therapeutic and pharmacological management of Alzheimer's disease (AD) is generally considered a major concern in ethnomedicine. Moreover, plant-based foods containing flavonoids were previously reported to show neuroprotective effects by modulating self-aggregation of amyloid-β (Aβ)/or tau peptide into oligomers and fibrils, associated with the pathogenesis of AD. This study investigated the impact of Moringa oleifera-supplemented diet (MO-SD) in scopolamine-induced spatial memory deficit in mice. Mice were partitioned into two phases with five groups each (n=6) and pretreated intraperitoneally with scopolamine (1 mg/kg) prior the daily oral administration of MO-SD (1 %, 5 % and 10 %) for 7 and 14 days. Spatial memory function was assessed using the Morris water maze (MWM) test. Thereafter, markers of cholinergic system inhibition (Acetylcholinesterase; AChE) and oxido-inflammatory stress (Malonaldehyde, MDA; Nitrite; Superoxide Dismutase, SOD; Tumor necrosis factor-alpha, TNF-α) and histo-morphology of the cortico-hippocampal neuron were measured. The scopolamine treatment led to loss of spatial memory function in mice spatial exploration of the escape platform in the MWM test. Meanwhile, treatment with MO-SD attenuated loss of spatial memory function via significant decrease in escape latency, significant increase in the frequency of cross with time spent in the platform quadrant. Furthermore, scopolamine treatment altered the endogenous antioxidants and pro-inflammatory mediators, elevated acetylcholinesterase activity and promoted chromatolysis of the cortico-hippocampal neuron. However, MO-SD significantly ameliorated oxido-inflammatory stress, restored cholinergic transmission via acetylcholinesterase inhibition and maintains neuronal integrity in the mice brain at both phases. These results suggest that Moringa oleifera-supplemented diet may serve a potential therapeutic and possible pharmacological macromolecule for preventing loss of neuronal cells and management of Alzheimer's disease.

Dose Effects of Histone Deacetylase Inhibitor Tacedinaline (CI-994) on Antipsychotic Haloperidol-Induced Motor and Memory Side Effects in Aged Mice

Background: Elderly patients treated with antipsychotic drugs often experience increased severity and frequency of side effects, yet the mechanisms are not well understood. Studies from our group indicate age-related histone modifications at drug targeted receptor gene promoters may contribute to the increased side effects, and histone deacetylase (HDAC) inhibitors entinostat (MS-275) and valproic acid (VPA) could reverse typical antipsychotic haloperidol (HAL) induced motor-side effects. However, whether such effects could be dose dependent and whether HDAC inhibitors could improve memory function in aged mice is unknown. Methods: We co-treated selective class 1 HDAC inhibitor tacedinaline (CI-994) at different doses (10, 20, and 30 mg/kg) with HAL (0.05 mg/kg) in young (3 months) and aged (21 months) mice for 14 consecutive days, then motor and memory behavioral tests were conducted, followed by biochemical measurements. Results: CI-994 at doses of 10 and 20 mg/kg could decrease HAL-induced cataleptic episodes but only 20 mg/kg was sufficient to improve motor coordination in aged mice. Additionally, CI-994 at 10 and 20 mg/kg mitigate HAL-induced memory impairment in aged mice. Biochemical analyses showed increased acetylation of histone marks H3K27ac and H3K18ac at the dopamine 2 receptor (D2R) gene (Drd2) promoter and increased expression of the Drd2 mRNA and D2R protein in the striatum of aged mice after administration of CI-994 at 20 mg/kg. Conclusions: Our results suggest CI-994 can reduce HAL-induced motor and memory side effects in aged mice. These effects may act through an increase of acetylation at the Drd2 promoter, thereby restoring D2R expression and improving antipsychotic drug action.

Effects of dexmedetomidine on postoperative cognitive function of sleep deprivation rats based on changes in inflammatory response

We aimed to assess the effects of dexmedetomidine (DEX) on postoperative cognitive function of sleep deprivation (SD) rats based on changes in inflammatory response. Male rats were randomly divided into blank control (C), SD, DEX, and SD+DEX groups. The SD model was established through intraperitoneal injection of DEX. The escape latency was detected through Morris water maze test daily, and the mechanical withdrawal threshold and thermal withdrawal latency were detected for 8 d. The content of malondialdehyde (MDA) and activity of superoxide dismutase (SOD) in hippocampus homogenate were determined, and the morphological changes in neurons were detected through Nissl staining. The concentration of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-6 in the hippocampus was detected by enzyme-linked immunosorbent assay, and the Rac1/protein kinase B (AKT)/nuclear factor-κB (NF-κB) expressions were detected by Western blotting. The changes in immunofluorescence localization of NF-κB were observed by confocal microscopy. Compared with SD group, the escape latency was shortened, original platform-crossing times increased, MDA content declined, SOD activity rose, neurons were arranged orderly and number of Nissl bodies increased in the hippocampal CA1 region, levels of IL-1β, TNF-α, and IL-6 in the hippocampus decreased, Rac1/AKT/NF-κB expressions were down-regulated, and proportion of NF-κB entering the nucleus declined in SD+DEX group (P < 0.05). DEX can effectively alleviate postoperative hippocampal inflammation and improve cognitive function of SD rats. The ability of DEX to relieve oxidative stress of hippocampal neurons, restore damaged cells, and reduce hippocampal inflammation in SD rats may be related to the Rac1/AKT/NF-κB pathway.

Minireview: Animal model of schizophrenia from the perspective of behavioral pharmacology: Effect of treatment on cognitive functions

Schizophrenia is a debilitating mental disorder characterized by positive, negative and cognitive symptoms. Whereas positive symptoms are satisfactorily addressed by current antipsychotic treatment, negative and cognitive symptomatic treatment remains largely ineffective. This review investigates the treatment efficacy regarding cognitive symptoms and evaluates the contribution of different monoamine receptor systems involved in schizophrenia pathophysiology to cognition. In the review, we included preclinical studies assessing the effect of different treatments on cognition in pre-pulse inhibition and two spatial cognitive tests. While pre-pulse inhibition investigates pre-attentive processes operating outside of conscious awareness, the spatial tasks require continuous attention and active engagement in task solving for a successful outcome. The schizophrenia-like phenotype was attained by acute or subchronic administration of non-competitive NMDA receptor antagonist MK-801.

Acute effects of 2.856 GHz and 1.5 GHz microwaves on spatial memory abilities and CREB-related pathways

This study aimed to evaluate the acute effects of 2.856 GHz and 1.5 GHz microwaves on spatial memory and cAMP response element binding (CREB)-related pathways. A total of 120 male Wistar rats were divided into four groups: a control group (C); 2.856 GHz microwave exposure group (S group); 1.5 GHz microwave exposure group (L group); and 2.856 and 1.5 GHz cumulative exposure group (SL group). Decreases in spatial memory abilities, changes in EEG, structural injuries, and the downregulation of phosphorylated-Ak strain transforming (p-AKT), phosphorylated-calcium/calmodulin-dependent protein kinase II (p-CaMKII), phosphorylated extracellular signal regulated kinase (p-ERK) and p-CREB was observed 6 h after microwave exposure. Significant differences in the expression of p-CaMKII were found between the S and L groups. The power amplitudes of the EEG waves (θ, δ), levels of structural injuries and the expression of p-AKT, p-CaMK II, p-CREB, and p-ERK1/2 were significantly different in the S and L groups compared to the SL group. Interaction effects between the 2.856 and 1.5 GHz microwaves were found in the EEG and p-CREB changes. Our findings indicated that 2.856 GHz and 1.5 GHz microwave exposure induced a decline in spatial memory, which might be related to p-AKT, p-CaMK II, p-CREB and p-ERK1/2.

Behavioral Tasks Evaluating Schizophrenia-like Symptoms in Animal Models: A Recent Update

BACKGROUND

Schizophrenia is a serious mental illness that affects more than 21 million people worldwide. Both genetics and the environment play a role in its etiology and pathogenesis. Symptoms of schizophrenia are mainly categorized into positive, negative, and cognitive. One major approach to identify and understand these diverse symptoms in humans has been to study behavioral phenotypes in a range of animal models of schizophrenia.

OBJECTIVE

We aimed to provide a comprehensive review of the behavioral tasks commonly used for measuring schizophrenia-like behaviors in rodents together with an update of the recent study findings.

METHODS

Articles describing phenotypes of schizophrenia-like behaviors in various animal models were collected through a literature search in Google Scholar, PubMed, Web of Science, and Scopus, with a focus on advances over the last 10 years.

RESULTS

Numerous studies have used a range of animal models and behavioral paradigms of schizophrenia to develop antipsychotic drugs for improved therapeutics. In establishing animal models of schizophrenia, the candidate models were evaluated for schizophrenia-like behaviors using several behavioral tasks for positive, negative, and cognitive symptoms designed to verify human symptoms of schizophrenia. Such validated animal models were provided as rapid preclinical avenues for drug testing and mechanistic studies.

CONCLUSION

Based on the most recent advances in the field, it is apparent that a myriad of behavior tests are needed to confirm and evaluate the congruency of animal models with the numerous behaviors and clinical signs exhibited by patients with schizophrenia.

α7 nicotinic receptor agonist and positive allosteric modulators differently improved schizophrenia-like cognitive deficits in male rats

The majority of schizophrenia patients have cognitive deficits as a separate symptom cluster independent of positive or negative symptoms. Current medicines, unfortunately, cannot provide clear benefits for cognitive symptoms in patients. Recent findings showed decreased α7 nicotinic acetylcholine receptor (nAChR) expressions in subjects with schizophrenia. α7 nAChR full/partial agonists and positive allosteric modulators (PAMs) may be valuable drug candidates to treat cognitive deficits of disease. This study comparatively investigated the effect of α7 nAChR agonist (A-582941), type I PAM (CCMI), type II PAM (PNU-120596), and the antipsychotic drug (clozapine) on behavioral, molecular, and immunohistochemical parameters in a subchronic MK-801 model of schizophrenia in male rats. Novel object recognition (NOR) and Morris water maze (MWM) tests were performed to evaluate recognition and spatial memories, respectively. Gene and protein expressions of parvalbumin, glutamic acid decarboxylase-67 (GAD67), and α7 nAChR were examined in the rats' hippocampal tissue. The subchronic MK-801 administration produced cognitive deficits in the NOR and MWM tests. It also decreased the protein and gene expressions of parvalbumin, GAD67, and α7 nAChR in the hippocampus. Clozapine, A-582941, and PNU-120596 but not CCMI increased the parvalbumin and α7 nAChR expressions and provided benefits in recognition memory. Interestingly, clozapine and CCMI restored the MK-801 induced deficits on GAD1 expression and spatial memory while A-582941 and PNU-120596 were ineffective. These results indicated that α7 nAChR agonist, type I and type II PAMs may provide benefits in different types of cognitive deficits rather than a complete treatment in schizophrenia.

Metformin attenuates antipsychotic-induced metabolic dysfunctions in MK801-induced schizophrenia-like rats

RATIONALE

Second-generation antipsychotics are the first-line medications prescribed for schizophrenic patients; however, some of them, such as olanzapine and risperidone, may induce metabolic dysfunctions during short-term treatment. Metformin is an effective adjuvant that attenuates antipsychotic-induced metabolic dysfunctions (AIMD) in clinical practice. Whether metformin can reverse AIMD and whether metformin affects the therapeutic effects of antipsychotics in animal models of schizophrenia are questions that still need to be investigated.

METHODS

In this study, an animal model of schizophrenia was established by consecutive injections of MK801 during the neurodevelopmental period. In adulthood, different dosages of olanzapine or risperidone treatment were administered to the schizophrenia model animals for 14 days. Both therapeutic effects and metabolic adverse effects were measured by behavioral tests, histopathological tests, and biochemical tests. The coadministration of different doses of metformin with olanzapine or risperidone was used to evaluate the effects of metformin on both AIMD and the therapeutic effect of those antipsychotics.

RESULTS

The MK801-treated rats showed schizophrenia-like behavior and variations in the shape and volume of the hippocampus. Both olanzapine and risperidone reversed the MK801-induced behavioral abnormalities as the dosage increased; however, they degenerated the hepatocytes in the liver and influenced the blood lipid levels and blood glucose levels. The coadministration of metformin did not affect the therapeutic effects of olanzapine or risperidone on behavioral abnormalities but attenuated the metabolic dysfunctions induced by those antipsychotics.

CONCLUSION

Metformin attenuated the olanzapine- and risperidone-induced metabolic dysfunctions in MK801-induced schizophrenia-like rats without reducing the therapeutic effects of the antipsychotics.

AMPK-SIRT1-PGC1α Signal Pathway Influences the Cognitive Function of Aged Rats in Sevoflurane-Induced Anesthesia

To understand the effect of AMP-activated protein kinase (AMPK)-SIRT1 (silent information regulator 1)-PPARγ coactivator-1α (PGC1α) signaling pathway on the cognitive function of sevoflurane-anesthetized aged rats. Aged rats were divided into Normal group, Sevo group (Sevoflurane anesthesia), Sevo + AICAR (the AMPK activator) group, Sevo + EX527 group (the AMPK inhibitor), and Sevo + AICAR + EX527 group. The cognitive function of rats was determined by the Morris water maze. Hippocampal neuronal apoptosis was evaluated by TUNEL and Fluoro-Jade C (FJC) staining, and the expression of cleaved caspase-3 was detected by immunohistochemistry. ROS, SOD, and MDA levels and the fluorescence intensity of GFAP in the hippocampus were assayed. The mitochondrial membrane potential (MMP), mitochondrial mass, ATP level, and the expression of AMPK-SIRT1-PGC1α were determined by the corresponding methods. Rats in the Sevo group manifested significant extension in the escape latency, with fewer platform crossings; and meanwhile, the apoptotic rate, the number of FJC-positive cells, and the fluorescence intensity of GFAP of neurons were elevated, with up-regulation of cleaved caspase-3. Moreover, the level of MDA and ROS was increased evidently, with significant down-regulation of SOD activity, ATP, mitochondrial mass and MMP levels, and AMPK, SIRT1 and PGC-1α protein expressions. However, sevoflurane-induced changes above were improved after the administration of AICAR, and EX527 could reverse AICAR-induced improvements in Sevo-anesthetized aged rats. Activating AMPK-SIRT1-PGC1α pathway can improve the cognitive function and mitigate the neuronal injury in Sevo-anesthetized aged rats by antagonizing the oxidative stress and maintaining the mitochondrial function.

Action of Akt Pathway on La-Induced Hippocampal Neuron Apoptosis of Rats in the Growth Stage

This study investigated the influences of lanthanum (La) exposure on learning and memory and the expression of apoptosis-related proteins in offspring rats. Wistar female rats were randomly divided into a control group (NC) and 0.25%, 0.5% and 1.0% LaCl₃ treatment groups, with eight per group. La dye was transmitted to offspring rats through parental blood circulation and breast milk before delactation and through water drinking after delectation. Offspring rats were killed at 14, 28 and 42 days after birth. Hippocampal neurons were observed by microscope, and apoptosis and necrosis were tested. The expression levels of apoptosis-related proteins were detected by Western blot, and Morris water maze experiments were used to measure learning and memory abilities. LaCl₃ groups showed longer escape latency periods and swimming distances than the NC group (p < 0.05). The 1.0% LaCl₃ group passed across the target quadrants and platforms more times and stayed in the target quadrants for less time, than the NC group (p < 0.05). At 42 days, the apoptosis rate and necrosis in the hippocampus of the 1.0% LaCl₃ group were significantly higher than those of other groups. There was a significant difference among LaCl₃ groups in terms of protein expressions measured in the hippocampus. In LaCl₃ groups, caspase-3 and caspase-9 were significantly higher than in the NC group (p < 0.05). Therefore, La exposure can promote neuronal apoptosis by regulating the protein expressions of Akt, Bcl-2, Bcl-xl, Bax, Bad, caspase-3 and caspase-9, thus damaging learning and memory and the hippocampal neurons of offspring rats.

Cortico-hippocampal memory enhancing activity of hesperetin on scopolamine-induced amnesia in mice: role of antioxidant defense system, cholinergic neurotransmission and expression of BDNF

Alzheimer disease (AD) is an age related neurodegenerative disease causing severe cognitive and memory decline in elderly people. Flavonoids play neuroprotective role by inhibiting and/or modifying the self-assembly of the amyloid-β (Aβ) or tau peptide into oligomers and fibrils. This study sought to investigate the effect of hesperetin (HPT) on scopolamine-induced memory impairments in mice. Mice were orally pretreated with HPT (1, 5 or 50 mg/kg) or vehicle (normal saline; 10 ml/kg) for 3 consecutive days. One hour post-treatment on day 3, scopolamine (3 mg/kg, i.p.) was administered 5 min before locomotor activity (open field test) and memory function (novel object recognition test (NORT) for 2 consecutive days and Morris water maze task (MWM) for 5 consecutive days). Levels of oxidative stress markers / brain derived neurotrophic factors (BDNF) and acetylcholinesterase activity were determined in the hippocampus and prefrontal cortex after completion of MWM task. Scopolamine caused no significant change in mice exploration of the familiar or novel object in the test session whereas the HPT-treated mice spent more time exploring the novel object more than familiar object in NORT. Scopolamine also increased the escape latency in acquisition phase and decreases time spent in target quadrant in probe phase which were ameliorated by the pretreatment with HPT. Scopolamine-induced alteration of oxidant-antioxidant balance, acetylcholinesterase activity and neurogenesis in the hippocampus and prefrontal cortex were attenuated by HPT treatment. This study showed that HPT ameliorated non-spatial/spatial learning and memory impairment by scopolamine possibly through enhancement of antioxidant defense, cholinergic and BDNF signaling.

Metformin reverses the schizophrenia-like behaviors induced by MK-801 in rats

Schizophrenia is known to be a complex and disabling psychiatric disorder. Dopamine receptor antagonists have a significant therapeutic effect in improving the positive symptoms that are associated with the illness. Therefore, dopamine receptor antagonists are commonly used in the treatment of schizophrenia; however, they do not achieve satisfactory results in improving negative symptoms and cognitive impairment. Metformin, widely known as an antidiabetic drug, has been found to enhance spatial memory formation and improve anxiety-like behaviors in rodents. Metformin's neuroprotective effect has been well documented in several neurological disorders including Alzheimer's disease, Parkinson's disease, strokes, Huntington's disease, and seizures. In the present study, we used a rat model to explore the effect of metformin on schizophrenia-like behaviors induced by MK-801 (dizocilpine), an N-methyl-D-aspartate (NMDA) receptor antagonist. We found that the pre-pulse inhibition (PPI) deficit caused by MK-801 could be alleviated by metformin. The hyperlocomotion in the open field test induced by chronic treatment of MK-801 was reversed by administration of metformin. Metformin has no effect on the baseline level of anxiety in normal naive rats, while metformin could relieve the anxiety-like behaviors in MK-801-treatment rats, though this effect is not reaching a significant level. Additionally, metformin could significantly ameliorate working memory impairments induced by MK-801. Moreover, the increased level of phosphorylation of Akt and GSK3β in the frontal cortex induced by MK-801 was normalized by metformin. In conclusion, our results demonstrate that metformin improved schizophrenia-like symptoms in rats, and is therefore a potential agent for the treatment of schizophrenia.

Synergistic effects of combined vaccination with BCG and influenza vaccines on spatial cognition and hippocampal plasticity in rats

Previous study has demonstrated the neurobeneficial role of BCG and influenza vaccines. Based on this, our study concentrated on the synergistic effects on development of central nervous system by combined vaccination with BCG and influenza vaccines in rats. Our results displayed that pups combinedly vaccinated with BCG and influenza vaccines showed a significant enhance in spatial cognition, induction of LTP, hippocampal neurogenesis and morphology of dendritic spines compared with pups vaccinated with BCG solely. Furthermore, combined vaccination with BCG and influenza vaccines showed higher expression of BDNF, IGF-1, IL-4, IFN-γ and lower IL-1β, TNF-α and IL-6 than BCG. Taken together, combined vaccination with BCG and influenza vaccines presented synergistic effects on spatial cognition and hippocampal plasticity in rats.

The effects of donepezil on phencyclidine-induced cognitive deficits in a mouse model of schizophrenia

Donepezil is the first-line of treatment for Alzheimer's disease (AD), which improves cognitive impairment effectively, but whether it has an impact on cognitive impairment in schizophrenia remains unknown. In this study, we evaluated the effects and mechanisms of donepezil on schizophrenia-like cognitive deficits induced by phencyclidine (PCP). The cognitive deficits model of schizophrenia was established by injecting PCP into mice. Risperidone, an atypical antipsychotic drug, served as positive control drug. Three behavioral tests including novel object recognition (NOR) test, Morris Water Maze (MWM) and passive avoidance (PA) test were performed to evaluate the effect of donepezil on PCP-induced cognitive deficits. Furthermore, the content of BDNF and NGF in the hippocampus and cortex of mice was determined using ELISA. Expressions of p-GSK-3β/GSK-3β, p-Akt/Akt, Bcl-2/Bax and Caspase-3 in the hippocampus and cortex were detected by Western blot. Results revealed that donepezil has a protective effect on PCP-induced cognitive dysfunction. Moreover, donepezil can also improve PCP-induced schizophrenia-like cognitive deficits by inhibiting neuronal apoptosis and regulating synaptic plasticity, which was possible through the up-regulation of p-Akt, p-GSK-3β, Bcl-2 and the down-regulation of Bax, Caspase-3. The results indicated that donepezil might exhibit a beneficial effect on the treatment of cognitive dysfunction in schizophrenia.

Brain PET Imaging of α7-nAChR with [18F]ASEM: Reproducibility, Occupancy, Receptor Density, and Changes in Schizophrenia

BACKGROUND

The α7 nicotinic acetylcholine receptor increasingly has been implicated in normal brain physiology, as well as in neuropsychiatric disorders. The highly cortical distribution of α7 nicotinic acetylcholine receptor suggests a role in cognition.

METHODS

We expanded the first-in-human PET imaging of α7 nicotinic acetylcholine receptor with [18F]ASEM from 5 to 21 healthy nonsmoking volunteers and added a feasibility study in 6 male patients with schizophrenia. Study aims included: (1) confirmation of test-retest reproducibility of [18F]ASEM binding, (2) demonstration of specificity by competition with DMXB-A, an α7 nicotinic acetylcholine receptor partial agonist, (3) estimation of [18F]ASEM binding potentials and α7 nicotinic acetylcholine receptor density in vivo in humans, and (4) demonstrating the feasibility of studying α7 nicotinic acetylcholine receptor as a target for schizophrenia.

RESULTS

Test-retest PET confirmed reproducibility (>90%) (variability ≤7%) of [18F]ASEM volume of distribution (VT) estimates in healthy volunteers. Repeated sessions of PET in 5 healthy subjects included baseline and effect of inhibition after oral administration of 150 mg DMXB-A. From reduction of binding potentials, we estimated the dose-dependent occupancy of α7 nicotinic acetylcholine receptor by DMXB-A at 17% to 49% for plasma concentrations at 60 to 200 nM DMXB-A. In agreement with evidence postmortem, α7 nicotinic acetylcholine receptor density averaged 0.67 to 0.82 nM and inhibitor affinity constant averaged 170 to 385 nM. Median VT in a feasibility study of 6 patients with schizophrenia was lower than in healthy volunteers in cingulate cortex, frontal cortex, and hippocampus (P = 0.02, corrected for multiple comparions, Mann-Whitney test).

CONCLUSIONS

The current results confirm the reproducibility of [18F]ASEM VT estimates and the specificity of the tracer for α7 nicotinic acetylcholine receptor. Preliminary findings from our feasibility study of [18F]ASEM binding in patients with schizophrenia are suggestive and provide guidance for future studies with more subjects.

Effects of haloperidol, olanzapine, ziprasidone, and PHA-543613 on spatial learning and memory in the Morris water maze test in naïve and MK-801-treated mice

INTRODUCTION

Cognitive impairment is the core symptom of schizophrenia, significantly impacting the functional outcome. Improvement of cognitive function has been an important aspect of the treatment of schizophrenia. Therefore, this study is to demonstrate the effects of first-generation antipsychotic haloperidol, second-generation antipsychotic olanzapine and ziprasidone, and alpha-7 nicotinic acetylcholine receptor agonist PHA-543613 on spatial learning and memory.

MATERIAL AND METHODS

C57BL/6 mice received intraperitoneal injections of haloperidol (2 mg/kg), olanzapine (2.5 mg/kg), ziprasidone (2 mg/kg), and PHA-543613 (1 mg/kg), and cognitive dysfunctions were induced by MK-801 (0.1 mg/kg). Morris water maze was used for investigating the effects of all agents.

RESULTS

Mk-801 significantly increased the mean escape latency to the platform and decreased the number of platform area crossings. Ziprasidone had no effect on the mean escape latency to platform and the number of platform area crossings in naïve mice, but haloperidol, olanzapine, and PHA-543613 did not. Haloperidol and olanzapine significantly increased the mean escape latency to platform and decreased the number of platform area crossings, while ziprasidone and PHA-543613 did not. All the agents had no effect on swimming speed.

CONCLUSIONS

Ziprasidone and alpha-7 nicotinic acetylcholine receptor agonist PHA-543613 might be helpful in the treatment of CIAS.