Novel Object Recognition Memory Research Articles

Acute optogenetic induction of the prodromal endophenotype of CA1 hyperactivity causes schizophrenia-related deficits in cognition and salience attribution.

Hyperactivity of the human anterior hippocampus has been reported to spread from its CA1 subfield to the subiculum around the onset of first-episode psychosis and could be a cellular target for early therapeutic intervention in the schizophrenia prodrome. However, to what extent CA1 hyperactivity actually causes schizophrenia-related symptoms remains unknown. Here, we mimic this endophenotype by direct optogenetic activation of excitatory cells in the homologous mouse region, ventral CA1 (vCA1) and assess its consequence in multiple schizophrenia-related behavioural tests. We find that hyperactivity of vCA1 causes hyperlocomotion and impairments of spatial and object-related short-term habituation (spatial novelty-preference and novel-object recognition memory) and spatial working memory, whereas social interaction, spatial exploration, and anxiety remain unaltered. Stimulation of the ventral subiculum, in contrast, only increased locomotion and exploration. In conclusion, CA1 hyperactivity may be a direct driver of prodromal cognitive symptoms and of aberrant salience assignment leading to psychosis.

Neuroprotective mechanisms and ameliorative activities of quercetin in cisplatin-induced cerebellum neurotoxicity in rat models

Cisplatin (CP) is a highly effective antitumor agent, but its clinical use is limited due to critical adverse reactions including neurotoxicity. Quercetin (QC) is a naturally occurring phytochemical with promising bioactive effects. This study investigated the Neuroprotective mechanisms and ameliorative activities of quercetin in cisplatin-induced cerebellum neurotoxicity in rat models.The rats were randomly divided into five groups of six (n = 6) rats. Group A, served as control. Group B, received a single dose of 10 mg/kg body weight (bwt) of CP (i.p.) on the first day. Group C received 30 mg/kg bwt of QC. Group D received a single dose of 10 mg/kg bwt CP on the first day followed by 30 mg/kg bwt of QC. Group E received 30 mg/kg bwt of QC per day followed by a single dose of 10 mg/kg bwt of CP on the last day. The treatment lasted for 35 days after which the novel-object recognition memory test (NORT) was used to assess non-spatial memory function. Brain neurochemical status was assessed and brain tissues were processed for histology.Quercetin increased weight loss and cognitive performance in CP-treated rats by enhancing the exploration of unfamiliar objects. Quercetin protects the brain from CP-mediated alterations in oxidative status, as well as brain metabolic enzyme indicators. It also decreased IL-6, IL-1, and TNF-α, and NF-ĸB expression, restored brain metabolic enzyme activities, increased neurotransmitters, and prevented neuromorphological alterations.In conclusion, quercetin protects rats’ brains against CP-induced cerebellum neurotoxicity via oxidative stress inhibition and down-regulation of inflammation.

Acute exercise performed during the late consolidation phase improves memory persistence by hippocampal protein synthesis and catecholamine modulation

Memory persistence is a crucial aspect of long-term memory (LTM) and involves late consolidation processes that modulate memory stability over time. Acute physical exercise (PE) has emerged as a potential strategy to modulate memory consolidation and enhance memory persistence. While its effects have been extensively explored in the early consolidation phase, its impact on the late phase remains unexplored. In this study, we investigated the effects and mechanisms of an acute PE on the late consolidation window of novel object recognition (NOR) memory in rats. A 30-minute running session applied 11 h after NOR memory acquisition significantly increased memory persistence for at least 7 days. The inhibition of hippocampal protein synthesis immediately after acute PE using anisomycin (a ribosomal inhibitor) or rapamycin (an mTOR pathway inhibitor) impaired the effect of PE on memory persistence. Animals only presented memory 1 day after acquisition. The same effect was observed with the inhibition of beta-adrenergic receptors by timolol. Although there were no differences between the groups' comparison, blocking D1/D5 receptors after acute PE resulted in a lack of memory persistence in the dichotomous testing (remember/non-remember). Therefore, our exploration of the mechanisms underlying this enhancement revealed the involvement of protein synthesis and the requirement of beta-adrenergic and dopaminergic D1/D5 receptors in the dorsal hippocampus. These findings provide valuable insights into PE as a potential memory modulator, contributing to expanding our understanding of memory consolidation dynamics and acute PE effects.

Radiosensitivity-related Variation in MicroRNA-34a-5p Levels and Subsequent Neuronal Loss in the Hilus of the Dentate Gyrus after Irradiation at Postnatal Days 10 and 21 in Mice.

The radiosensitivity of mice differs between postnatal days 10 (P10) and 21(P21); these days mark different stages of brain development. In the present study, Ki67 and doublecotin (DCX) immunostaining and hematoxylin staining was performed, which showed that acute radiation exposure at postnatal day 10 induced higher cell apoptosis and loss in the hilus of the dentate gyrus at day 1 postirradiation than postnatal day 21. MicroRNA (miRNA) sequencing and real-time quantitative reverse transcription PCR (qRT-PCR) analysis indicated the upregulation of miRNA-34a-5p at days 1 and 7 after irradiation at postnatal day 10, but not at postnatal day 21. Down-regulation of T-cell intracytoplasmic antigen-1 pathway (Tia1) was indicated by qRT-PCR at day 1 day but not day 7 after irradiation at postnatal day 10. Neurobehavioral testing in mature mice irradiated at postnatal day 10 demonstrated the impairment of short-term memory in novel object recognition and spatial memory, compared to those irradiated at postnatal day 21. Combined with our previous luciferase assay showing the direct interaction of miRNA34a-5p and Tia1, these findings suggest that radiation-induced abnormal miR-34a-5p/Tial interaction at day 1 after irradiation at postnatal day 10 may be involved in apoptosis of the dentate gyrus hilar, impairment of neurogenesis and subsequent short-term memory loss as observed in the novel object recognition and Barnes maze tests.

Differences in memory performance: The effects of sex and reproductive experience on object recognition memory in high- and low-yawning Sprague‒Dawley rats

The novel object recognition (NOR) test is an efficient way to measure nonspatial memory in rodents. The NOR performance of female and male rats is sexually dimorphic because memory performance is better in the former than in the latter. In females, maternal experience enhances spatial memory. We used the NOR test to evaluate short- and long-term recognition memory in both sexes in the high- and low-yawning sublines of rats (HY and LY, respectively), which were generated via a strict inbreeding process from the Sprague‒Dawley (SD) strain for more than ninety generations. Additionally, we evaluated the effect of maternal experience using nulliparous, primiparous, biparous, and multiparous HY, LY and SD dams. Our results revealed that LY rats presented less thigmotaxis, with lower central square crosses and more vertical exploration in the open-field arena, suggesting that they experienced anxiety. Additionally, LY males performed significantly better than LY females in short- and long-term NOR memory, and LY males performed significantly better than SD rats did. Among females, two maternal experiences negatively affected short-term memory in the LY and HY sublines with respect to primiparous dams, and HY dams had better memory performance in the NOR test than did SD dams. Our findings suggest that the yawning sublines are suitable for studying the neurobiological basis of different memory processes under different endocrine conditions in highly inbred groups of rats.

Pegylated chitosan nanoparticles of fluoxetine enhance cognitive performance and hippocampal brain derived neurotrophic factor levels in a rat model of local demyelination

Cognitive impairment is a common feature in neurodegenerative diseases such as multiple sclerosis (MS). This study aims to explore the potential of enhancing the beneficial effects of fluoxetine (FLX), a neuroprotective agent known for its ability to increase neural plasticity by utilizing nanoparticles. The study specifically focuses on the synthesis and evaluation of PEGylated chitosan nanoparticles of FLX and its effect on demyelination and the subsequent cognitive impairment (CI) in the hippocampus of rats induced by local injection of lysophosphatidylcholine (LPC). Chitosan/polyethylene glycol nanoparticles were synthesized, and their properties were analyzed. Demyelination was induced in rats via hippocampal injections of lysolecithin. Behavioral assessments included open field maze, elevated plus maze, and novel object recognition memory (NORM) tests. Hippocampal levels of insulin-like growth factor (IGF-1) and brain-derived neurotrophic factor (BDNF) were measured using enzyme-linked immunoassay (ELISA). The extent of remyelination was quantified using Luxol fast blue staining. Nanoparticle size measured 240.2 nm with 53 % encapsulation efficacy. Drug release exhibited a slow pattern, with 76 % released within 4 h. Nanoparticle-treated rats displayed reduced anxiety-like behavior, improved memory, increased BDNF levels, and a reduced extent of demyelination, with no change in IGF- levels. In addition, FLX -loaded chitosan nanoparticles had better effect on cognitive improvement, BDNF levels in the hippocampus that FLX. Altering pharmacokinetics and possibly pharmacodynamics. These findings highlight the potential of innovative drug delivery systems, encouraging further research in this direction.

Acute physical exercise prevents memory amnesia caused by protein synthesis inhibition in rats' hippocampus

The benefits of physical exercise (PE) on memory consolidation have been well-documented in both healthy and memory-impaired animals. However, the underlying mechanisms through which PE exerts these effects are still unclear. In this study, we aimed to investigate the role of hippocampal protein synthesis in memory modulation by acute PE in rats. After novel object recognition (NOR) training, rats were subjected to a 30-min moderate-intensity acute PE on the treadmill, while control animals did not undergo any procedures. Using anisomycin (ANI) and rapamycin (RAPA), compounds that inhibit protein synthesis through different mechanisms, we manipulated protein synthesis in the CA1 region of the hippocampus to examine its contribution to memory consolidation. Memory was assessed on days 1, 7, and 14 post-training. Our results showed that inhibiting protein synthesis by ANI or RAPA impaired NOR memory consolidation in control animals. However, acute PE prevented this impairment without affecting memory persistence. We also evaluated brain-derived neurotrophic factor (BDNF) levels after acute PE at 0.5h, 2h, and 12h afterward and found no differences in levels compared to animals that did not engage in acute PE or were only habituated to the treadmill. Therefore, our findings suggest that acute PE could serve as a non-pharmacological intervention to enhance memory consolidation and prevent memory loss in conditions associated with hippocampal protein synthesis inhibition. This mechanism appears not to depend on BDNF synthesis in the early hours after exercise.

Esketamine enhances memory reconsolidation in the novel object recognition task

Esketamine, the right-handed optical isomer of racemic ketamine, is a rapidly acting antidepressant approved by the FDA for treatment-resistant depression in 2019. However, few studies have investigated esketamine's role in learning and memory, particularly in the context of memory reconsolidation. Herein, we evaluated esketamine's role in memory reconsolidation in 7-week-old male Institute of Cancer Research mice subjected to the novel object recognition (NOR) memory task. The NOR reconsolidation procedure comprised three phases: sampling, reactivation, and testing. Esketamine-enhanced NOR memory performance when injected into mice 0 h after reactivation rather than following a 6 h delay. Conversely, administering esketamine 24 h after sampling without reactivation did not enhance NOR memory performance. Notably, esketamine exhibited no discernible effects on nonspecific responses, such as locomotor activity and exploratory behavior. Furthermore, the α-amino-3‑hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type receptor antagonist NBQX effectively blocked the esketamine-induced enhancement of memory reconsolidation. In conclusion, esketamine treatment markedly improves memory reconsolidation in NOR tasks, and this effect is linked to AMPA receptor activity.

Memory impairment induced by aluminum nanoparticles is associated with hippocampal IL-1 and IBA-1 upregulation in mice

ABSTRACT Objectives Increasing evidence indicates a link between aluminum (Al) intake and Alzheimer’s disease (AD). The main entry of Al into the human body is through oral route, and in the digestive tract, under the influence of the pH change, Al can be transformed into Al nanoparticles (Al-NP). However, studies related to the effect of Al-NP on the brain are limited and need further investigation. Neuro-inflammation is considered as one of the principal features of AD. Microglial activation and expression of the inflammatory cytokine IL-1β (interleukin-1β) in the brain have been used as hallmarks of brain inflammation. Therefore, in the present study, the hippocampal levels of ionized calcium-binding adaptor molecule 1 (IBA-1), as the marker of microglia activation, and IL-1β were assessed. Methods Adult male NMRI mice were treated with Al-NP (5 or 10 mg/kg) for 5 days. A novel object recognition (NOR) test was used to assess memory. Following cognitive assessments, the hippocampal tissues were isolated to analyze the levels of IL-1β and IBA-1 as well as beta actin proteins using western blot technique. Results Al-NP in both doses of 5 and 10 mg/kg impaired NOR memory in mice. In addition, Al-NP increased IL-1β and IBA-1 in the hippocampus. Discussion These findings indicate that the memory impairing effect of Al-NP coincides with hippocampal inflammation. According to the proposed relationship between AD and Al toxicity, this study can increase the knowledge about the toxic effects of Al-NP and highlight the need to limit the use of this nanoparticle.

Diosmin alleviates doxorubicin-induced chemobrain in rats via inhibition of oxido-inflammation, apoptosis and modulation of autophagy

Background/aimDoxorubicin (DOX) is a highly effective chemotherapy medicine commonly used to treat breast cancer; yet, despite its clinical efficacy, it usually causes chemobrain. As a result, we investigated the neuroprotective effects of Diosmin (DIOS) on DOX-induced chemobrain in male rat brains. Animals and methodsIn the experimental protocol, Rats were divided into 4 groups: group I received solvent and saline for 56 days, group II received Dios and a concomitant dose of saline for 56 days, group III received DOX intraperitoneally on 7th, 14th, 21st, 28th, 35th, 42nd, 49th and 56th days, and Group IV received DIOS (40 mg/kg P.O.) for 56 days and DOX was administered one hour after DIOS oral administration. The novel-object recognition memory test (NORT) was used to assess non-spatial memory function. Following that, brain neurochemical status were assessed. ResultsDIOS increased cognitive performance in DOX-treated rats by enhancing exploration of unfamiliar objects. DIOS protects the brain from DOX-mediated alterations in oxidative status, as well as brain metabolic enzyme indicators. It also decreased MMP-6, IL-6, IL-β1, TNF-α and COX-2 expression, reduced apoptotic markers levels, boosted mTOR protein levels, lowered beclin-1, restored brain metabolic enzyme activities, increased neurotransmitter as well as cathepsin levels, and avoided the rise in α-synuclein and PON1 enzyme activity. ConclusionIn conclusion, DIOS protects rats' brains against DOX-induced chemobrain via oxidative stress inhibition, autophagy modulation, and down-regulation of inflammatory and apoptotic markers.

Memory interference in APPswe/PS1dE9 mice: Role of astrocytic β‐adrenoreceptors

AbstractBackgroundPrevious studies have reported that long‐term β‐adrenoceptor (β‐AR) agonist, isoproterenol hydrochloride (IPE), treatment brings about beneficial effects in an induced model of Alzheimer’s disease (AD) by neutralizing microglial inflammatory morphology against soluble amyloid β oligomers (PMID: 30093491). However, we do not have a clear understanding of how such treatment impacts astrocyte morphology, and whether that afford beneficial effects. Introducing a proactive memory interference step to the classical novel object recognition (NOR) paradigm impairs long‐term memory formation in 2‐month‐old familial model of AD ‐ APPswe/PS1dE9 (APP/PS1) mice. Long‐term IPE treatment rescued long‐term memory. In this study we attempt to understand the impact of long‐term IPE treatment on astrocyte morphology, and how they bring about the reversal in cognitive deficits.Method(1) Mice were taken through a proactive interference step in which they were exposed to objects of varied shape, size and colour before taking them through NOR paradigm. (2) Mice were treated with β‐AR agonist IPE at P26 (0.05g/litre) in drinking water for 21 days till P47. (3) They were sacrificed at 2‐months of age by transcardial perfusion and 100µm coronal sections of hippocampus were stained with astrocytic markers GFAP and S100β by immunohistochemistry. The number and morphology of astrocytes were analysed using ImageJ, SMorph (PMID: 34137444) and Imaris software.ResultOur observations suggest that NOR memory is intact in 2‐month‐old APP/PS1. However, introducing an object‐based short‐term interference before NOR leads to recognition memory deficits in APP/PS1 but not in wild‐type mice. Treatment with IPE restored long‐term memory of APP/PS1 mice to normal levels, thereby protecting them from the effects of interference during the NOR task. Our preliminary findings indicate that IPE impacts the morphology of astrocytes and thus contribute to the reversal of recognition deficits in APP/PS1 at 2 months of age.Conclusionβ‐AR activation can bring about morphological changes in astrocytes that in turn can modulate memory representations.

The hippocampal FTO-BDNF-TrkB pathway is required for novel object recognition memory reconsolidation in mice

Memory reconsolidation refers to the process by which the consolidated memory was restored after reactivation (RA). Memory trace becomes labile after reactivation and inhibition of memory reconsolidation may disrupt or update the original memory trace, which provided a new strategy for the treatment of several psychiatric diseases, such as drug addiction and post-traumatic stress disorder. Fat mass and obesity-associated gene (FTO) is a novel demethylase of N6-methyladenosine (m6A) and it has been intensively involved in learning and memory. However, the role of FTO in memory reconsolidation has not been determined. In the present study, the function of FTO in memory reconsolidation was investigated in the novel object recognition (NOR) model in mice. The results showed that RA of NOR memory increased hippocampal FTO expression in a time-dependent manner, while FTO inhibitor meclofenamic acid (MA) injected immediately, but not 6 h after RA disrupted NOR memory reconsolidation. MA downregulated BDNF expression during NOR memory reconsolidation in the hippocampus, while the TrkB agonist 7,8-Dihydroxyflavone (7,8-DHF) reversed the disruptive effects of MA on NOR memory reconsolidation. Furthermore, overexpression of FTO increased BDNF expression via decreasing mRNA m6A in HT22 cells. Taken together, these results indicate that FTO may up-regulate the BDNF-TrkB pathway to promote NOR memory reconsolidation through m6A modification.

Acute physical exercise improves recognition memory via locus coeruleus activation but not via ventral tegmental area activation

Both animals and humans have been studied to explore the impact of acute physical exercise (PE) on memory. In rats, a single session of PE enhances the persistence of novel object recognition (NOR) memory, which depends on dopamine and noradrenaline activity in the hippocampus. However, limited research has examined the involvement of other brain regions in this phenomenon. In this study, we investigated the role of the ventral tegmental area (VTA) and locus coeruleus (LC) in modulating the persistence of NOR memory induced by acute PE. After NOR training, some animals underwent a 30 min treadmill PE session, followed by infusion of either vehicle (VEH) or muscimol (MUS) in either the VTA or LC. Other animals did not undergo PE and only received VEH, MUS, or NMDA within the same time window. We evaluated memory recall 1, 7, and 14 days later. Acute PE promoted memory persistence for up to 14 days afterward, similar to NMDA glutamatergic stimulation of the VTA or LC. Moreover, only the LC region was required for the memory improvement induced by acute PE since blocking this region with MUS impaired NOR encoding. Our findings suggest that acute PE can improve learning within a closed time window, and this effect depends on LC, but not VTA, activity.

Agmatine prevents the memory impairment and the dysfunction of hippocampal GSK-3β and ERK signaling induced by aluminum nanoparticle in mice.

The growing usage of aluminum nanoparticles (Al-NP) and their exposure may influence body function. Considering the proposed relationship between Al and the pathogenesis of Alzheimer's disease and the concern about the effect of this nanoparticle on brain health and cognitive function, the use of neuroprotective agents might be helpful. According to the reported neuroprotective effects of agmatine, in the present study, the possible protective effect of agmatine was assessed in mice model of Al-NP-induced memory impairment. In addition, due to the roles of hippocampal Glycogen synthase kinase-3 beta (GSK-3β) and ERK signaling in memory and its disorders, these pathways were also investigated. Al-NP (10 mg/kg/p.o.) with/without agmatine (5 or 10 mg/kg/i.p.) was administered to adult male NMRI mice for 5 days. Novel object recognition (NOR) test session was used to assess cognitive function. Following the behavioral assessments, the hippocampi were used to determine the phosphorylated and total levels of GSK-3β and ERK as well as GAPDH using western blot analysis. The results showed that Al-NP impaired NOR memory in mice while agmatine 10 mg/kg prevented the memory deficit induced by Al-NP. Furthermore, Al-NP activated GSK-3β as well as ERK signals within the hippocampus while agmatine prevented the effects of Al-NP on GSK-3β and ERK signals within the hippocampus. Besides supporting the neuroprotective effects of agmatine, these findings suggest the possibility of the connection of hippocampal GSK-3β and ERK signaling in the neuroprotective effect of this polyamine against Al-NP.

The cognitive deficit induced by Al nanoparticle ingestion is associated with hippocampal inflammation in mice

AbstractBackgroundAlthough, both environmental and genetic factors are known as the predispositions to AD development, each of these factors are suggested to acts via increasing the Al content of brain tissue. Al nanoparticles are newer nanomaterials that have been significantly exposed to the human body. When Al reaches the nanosize, it may display different characteristics from natural Al, and its potential influence on body function is an interesting aspect of research as these particles might have more negative impact on human health. Activation of microglia and expression of the inflammatory cytokine IL‐1 (interleukin‐1) in the brain have been used as hallmarks of brain inflammation. Our recent findings suggest that administration of nano‐Al for a short period of 5 days can cause memory impairment. Given the importance of neuroinflammation in Alzheimer’s pathology, the question was whether 5‐day nano‐Al intake could lead to inflammatory changes in the hippocampus.MethodAdult male NMRI mice were treated with nano‐Al in doses 5 and 10 mg/kg/oral gavage for 5 days. The test session of novel object recognition (NOR) task was performed on day 5. Following the NOR test, the hippocampi were isolated. Considering the key roles of microglia activation and IL‐1β in neuroinflammation, the levels of hippocampal iba‐1 (as the speciefic marker of microglial activation) and IL‐1β were determined using western blot studies.ResultThe results showed that nano‐Al oral gavage in doses of 5 and 10 mg/kg impairs NOR memory in mice. Moreover, the memory impairing effect of nano‐Al coincided with a dose dependent increase in hippocampal iba‐1. It also increased the content of IL‐1 in the hippocampus.ConclusionThis study showed that nano‐Al in doses as low as 5 and 10 mg/ kg ingested for 5 days impairs memory and induces neuroinflammation in the hippocampus.

Memantine, an NMDA receptor antagonist, protected the brain against the long-term consequences of sepsis in mice

AimsLong-term neuroinflammation and brain dysfunction have frequently been reported in sepsis survivors. In this study, the protective effect of memantine (an NMDA receptor antagonist) on the long-term consequences of sepsis on the brain was investigated in mice. Materials and methodsEighty-five male C57 mice were included. Memantine was administrated through gavage at 5, 10, and 20 mg/kg three days before sepsis and continued for three days after sepsis induction. Sepsis was induced by intraperitoneal injection of 5 mg/kg LPS. A cohort of mice was sacrificed on the 4th day post sepsis to measure NF-κB, TNF-α, and IL-1β mRNA expression and oxidative stress markers in the brain. The second cohort was used for behavioral tests one month after sepsis induction and then sacrificed for oxidative stress markers and acetylcholinesterase (AChE) activity measurement. Key findingsMDA levels and mRNA expression of NF-κB, TNF-α, and IL-1β ameliorated by memantine at the early days of sepsis induction, and total thiol content and SOD activity were increased. Post-septic mice showed significant disruption of recognition memory in novel object recognition (NOR) and depressive and anxiety-like behaviors in tail suspension test, elevated plus maze (EPM), and open field tests one month after sepsis. Memantine at 10 and 20 mg/kg dose-dependently ameliorated behavioral abnormalities, reduced AChE activity and MDA levels, and enhanced SOD activity and thiol content one month after sepsis. SignificanceThese findings suggest that early treatment of septic mice with memantine could ameliorate brain inflammation and oxidative damage and prevent long-term behavioral consequences of sepsis.

Chronic morphine exposure and maternal separation induce impairments in cognition and locomotor activity of male adolescent rats.

Maternal morphine exposure reduces motivation for basic cognitive tasks, followed by executive function deficits in attention and accuracy. It also induces depression-like behaviors and has negative consequences for learning and memory in offspring. Interaction between mothers and pups has a crucial effect on the mammal's development. Maternal separation (MS) can originate behavioral and neuropsychiatric abnormalities later in life. It seems that adolescents are more susceptible to the effects of early-life stress; Therefore, this study aimed to evaluate the effects of chronic morphine consumption (21 days before and after mating and gestation) and MS (180 min/day from postnatal day [PND] 1-21) on the cognitive and behavioral performance of male offspring in mid-adolescence. Six groups, including control, MS, V (vehicle), morphine, V+MS, and morphine+MS, were tested for open field (OF), novel object recognition (NOR), and the Morris water maze (MWM). The results of the OF test showed that MS increased locomotor activity and movement velocity. Inner and outer zone durations did not differ among groups. The body stretching of the morphine+MS rats was significantly more than the MS rats. Moreover, the MS and morphine+MS groups showed significantly less sniffing behavior in the OF test. The MS group showed deficits in spatial learning in the MWM test, but recognition memory in the NOR and spatial memory in the MWM tests were not significantly different among groups. We concluded that MS could induce impairments in spatial learning and locomotor activity that could be worsened by maternal morphine exposure in adolescent male rats.

Effectiveness of coenzyme Q10 on learning and memory and synaptic plasticity impairment in an aged Aβ-induced rat model of Alzheimer's disease: a behavioral, biochemical, and electrophysiological study.

Aging is the major risk factor for Alzheimer's disease (AD), and cognitive and memory impairments are common among the elderly. Interestingly, coenzyme Q10 (Q10) levels decline in the brain of aging animals. Q10 is a substantial antioxidant substance, which has an important role in the mitochondria. We assessed the possible effects of Q10 on learning and memory and synaptic plasticity in aged β-amyloid (Aβ)-induced AD rats. In this study, 40 Wistar rats (24-36 months old; 360-450 g) were randomly assigned to four groups (n = 10 rats/group)-group I: control, group II: Aβ, group III: Q10; 50 mg/kg, and group IV: Q10+Aβ. Q10 was administered orally by gavage daily for 4 weeks before the Aβ injection. The cognitive function and learning and memory of the rats were measured by the novel object recognition (NOR), Morris water maze (MWM), and passive avoidance learning (PAL) tests. Finally, malondialdehyde (MDA), total antioxidant capacity (TAC), total thiol group (TTG), and total oxidant status (TOS) were measured. Q10 improved the Aβ-related decrease in the discrimination index in the NOR test, spatial learning and memory in the MWM test, passive avoidance learning and memory in the PAL test, and long-term potentiation (LTP) impairment in the hippocampal PP-DG pathway in aged rats. In addition, Aβ injection significantly increased serum MDA and TOS levels. Q10, however, significantly reversed these parameters and also increased TAC and TTG levels in the Aβ+Q10 group. Our experimental findings suggest that Q10 supplementation can suppress the progression of neurodegeneration that otherwise impairs learning and memory and reduces synaptic plasticity in our experimental animals. Therefore, similar supplemental Q10 treatment given to humans with AD could possibly provide them a better quality of life.

The differential effect of levetiracetam on memory and anxiety in rats

ObjectiveOne of the newest antiseizure medication is levetiracetam (LEV). It might be effective in various indications, not only related to convulsions. Central nervous system disorders are common during anticonvulsant therapy. The aim of this study was to assess the effect of LEV on various types of memory and anxiety in rats. MethodsAdult male Wistar rats (n = 58) were given LV p.o. as a single (100 mg/kg or 500 mg/kg) or repeated doses (300 mg/kg). The effect of the drug on memory was assessed in the Morris water maze (MWM) (spatial memory), the passive avoidance (PA) (emotional memory) and the novel object recognition (NOR) (recognition memory). The anxiety was evaluated in the elevated plus maze (EPM). ResultsLEV administered as repeated doses disturbed the long-term recognition memory in NOR and locomotor activity in EPM. A single dose affected emotional memory in PA. LEV did not alter spatial memory in MWM. ConclusionsLEV may cause memory and locomotor disturbances, but some of these adverse effects seem to be temporary and limited to the effect of acute dose.

Two distinct ways to form long-term object recognition memory during sleep and wakefulness

Memory consolidation is promoted by sleep. However, there is also evidence for consolidation into long-term memory during wakefulness via processes that preferentially affect nonhippocampal representations. We compared, in rats, the effects of 2-h postencoding periods of sleep and wakefulness on the formation of long-term memory for objects and their associated environmental contexts. We employed a novel-object recognition (NOR) task, using object exploration and exploratory rearing as behavioral indicators of these memories. Remote recall testing (after 1 wk) confirmed significant long-term NOR memory under both conditions, with NOR memory after sleep predicted by the occurrence of EEG spindle-slow oscillation coupling. Rats in the sleep group decreased their exploratory rearing at recall testing, revealing successful recall of the environmental context. By contrast, rats that stayed awake after encoding showed equally high levels of rearing upon remote testing as during encoding, indicating that context memory was lost. Disruption of hippocampal function during the postencoding interval (by muscimol administration) suppressed long-term NOR memory together with context memory formation when animals slept, but enhanced NOR memory when they were awake during this interval. Testing remote recall in a context different from that during encoding impaired NOR memory in the sleep condition, while exploratory rearing was increased. By contrast, NOR memory in the wake rats was preserved and actually superior to that after sleep. Our findings indicate two distinct modes of long-term memory formation: Sleep consolidation is hippocampus dependent and implicates event-context binding, whereas wake consolidation is impaired by hippocampal activation and strengthens context-independent representations.