Evaluation of acetylcholinesterase activity and behavioural alterations induced by ketamine in an animal model of schizophrenia

Evaluation of possible neuroprotective effects of virgin coconut oil on aluminum-induced neurotoxicity in an in vitro Alzheimer's disease model

Alzheimer's disease (AD) is a progressive neurological disorder that affects various cognitive functions, behavior, and personality. AD is thought to be caused by a combination of genetic and environmental factors, including exposure to aluminum (Al). Virgin coconut oil (VCO) may have potential as a natural neuroprotectant against AD. Aim of this study was to determine neuroprotective effects of VCO on Al-induced neurotoxicity in an in vitro AD model. SH-SY5Y cells were initially cultured in normal growth medium and then differentiated by reducing fetal bovine serum content and adding retinoic acid (RA). Later, brain-derived neurotrophic factor (BDNF) was added along with RA. The differentiation process was completed on the seventh day. Study groups (n = 3) were designed as control group, VCO group, Al group, Al-VCO group, Alzheimer model (AD) group, AD + Al-exposed group (AD+Al), AD + VCO applied group (AD + VCO) and AD + Al-exposed + VCO applied group (AD + Al + VCO). Specific markers of AD (hyperphosphorylated Tau protein, amyloid beta 1-40 peptide, and amyloid precursor protein) were measured in all groups. In addition, oxidative stress parameters (total antioxidant capacity, lipid peroxidase, protein carbonyl, and reactive oxygen species) and neurotransmitter-related parameters (dopamine, dopamine transporter acetylcholine, and synuclein alpha levels, acetylcholinesterase activity) were measured comparatively in the study groups. VCO reduced amyloid beta and hyperphosphorylated Tau protein levels in the study groups. In addition, oxidative stress levels decreased, and neurotransmitter parameters improved with VCO. Our study shows that VCO may have potential therapeutic effects in Alzheimer's disease and further experiments are needed to determine its efficacy.

Coconut oil ameliorates behavioral and biochemical alterations induced by D-GAL/AlCl3 in rats

Alzheimer's disease (AD) is a chronic, progressive neurodegenerative condition marked by cognitive impairment. Although coconut oil has been shown to be potentially beneficial in reducing AD-related cognitive deficits, information on its mechanism of action is limited. Thus, we investigated the effects of coconut oil on spatial cognitive ability and non-cognitive functions in a rat model of AD induced by G-galactose (D-GAL) and aluminum chloride (AlCl3), and examined the changes in synaptic transmission, cholinergic activity, neurotrophic factors and oxidative stress in this process. The AD model was established by administering D-GAL and AlCl3 for 90 days, while also supplementing with coconut oil during this time. Cognitive and non-cognitive abilities of the rats were evaluated at the end of the 90-day supplementation period. In addition, biochemical markers related to the pathogenesis of the AD were measures in the hippocampus tissue. Exposure to D-GAL/AlCl3 resulted in a reduction in locomotor activity, an elevation in anxiety-like behavior, and an impairment of spatial learning and memory (P < 0.05). The aforementioned behavioral disturbances were observed to coincide with increased oxidative stress and cholinergic impairment, as well as reduced synaptic transmission and levels of neurotrophins in the hippocampus (P < 0.05). Interestingly, treatment with coconut oil attenuated all the neuropathological changes mentioned above (P < 0.05). These findings suggest that coconut oil shows protective effects against cognitive and non-cognitive impairment, AD pathology markers, oxidative stress, synaptic transmission, and cholinergic function in a D-GAL/AlCl3-induced AD rat model.

Influence of the dose of ketamine used on schizophrenia-like symptoms in mice: A correlation study with TH, GAD67, and PPAR-γ

Schizophrenia is a chronic, debilitating mental illness that has not yet been completely understood. In this study, we aimed to investigate the effects of different doses of ketamine, a non-competitive NMDA receptor antagonist, on the positive- and negative-like symptoms of schizophrenia. We also explored whether these effects are related to changes in the immunoreactivity of GAD67, TH, and PPAR-γ in brain structures. To conduct the study, male mice received ketamine (20-40 mg/kg) or its vehicle (0.9 % NaCl) intraperitoneally for 14 consecutive days. We quantified stereotyped behavior, the time of immobility in the forced swimming test (FST), and locomotor activity after 7 or 14 days. In addition, we performed ex vivo analysis of the immunoreactivity of GAD, TH, and PPAR-γ, in brain tissues after 14 days. The results showed that ketamine administration for 14 days increased the grooming time in the nose region at all tested doses. It also increased immobility in the FST at 30 mg/kg doses and decreased the number of rearing cycles during stereotyped behavior at 40 mg/kg. These behavioral effects were not associated with changes in locomotor activity. We did not observe any significant alterations regarding the immunoreactivity of brain proteins. However, we found that GAD and TH were positively correlated with the number of rearing during the stereotyped behavior at doses of 20 and 30 mg/kg ketamine, respectively. GAD was positively correlated with the number of rearing in the open field test at a dose of 20 mg/kg. TH was inversely correlated with immobility time in the FST at a dose of 30 mg/kg. PPAR-γ was inversely correlated with the number of bouts of stereotyped behavior at a dose of 40 mg/kg of ketamine. In conclusion, the behavioral alterations induced by ketamine in positive-like symptoms were reproduced with all doses tested and appear to depend on the modulatory effects of TH, GAD, and PPAR-γ. Conversely, negative-like symptoms were associated with a specific dose of ketamine.

Exposure of adult zebrafish (Danio rerio) to SARS-CoV-2 at predicted environmentally relevant concentrations: Outspreading warns about ecotoxicological risks to freshwater fish

While the multifaceted social, economic, and public health impacts associated with the COVID-19 pandemic are known, little is known about its effects on non-target aquatic ecosystems and organisms. Thus, we aimed to evaluate the potential ecotoxicity of SARS-CoV-2 lysate protein (SARS.CoV2/SP02.2020.HIAE.Br) in adult zebrafish (Danio rerio) at predicted environmentally relevant concentrations (0.742 and 2.226 pg/L), by 30 days. Although our data did not show locomotor alterations or anxiety-like or/and anxiolytic-like behavior, we noticed that exposure to SARS-CoV-2 negatively affected habituation memory and social aggregation of animals in response to a potential aquatic predator (Geophagus brasiliensis). An increased frequency of erythrocyte nuclear abnormalities was also observed in animals exposed to SARS-CoV-2. Furthermore, our data suggest that such changes were associated with a redox imbalance [↑ROS (reactive oxygen species), ↑H2O2 (hydrogen peroxide), ↓SOD (superoxide dismutase), and ↓CAT (catalase)], cholinesterasic effect [↑AChE (acetylcholinesterase) activity], as well as the induction of an inflammatory immune response [↑NO (nitric oxide), ↑IFN-γ (interferon-gamma), and ↓IL-10 (interleukin-10)]. For some biomarkers, we noticed that the response of the animals to the treatments was not concentration-dependent. However, principal component analysis (PCA) and the "Integrated Biomarker Response" index (IBRv2) indicated a more prominent ecotoxicity of SARS-CoV-2 at 2.226 pg/L. Therefore, our study advances knowledge about the ecotoxicological potential of SARS-CoV-2 and reinforces the presumption that the COVID-19 pandemic has negative implications beyond its economic, social, and public health impacts.

Pretreatment with Carpolobia lutea ethanol extract prevents schizophrenia-like behavior in mice models of psychosis

ETHNOPHARMACOLOGICAL RELEVANCE

Carpolobia lutea decoction is widely used as a phytotherapeutic against central nervous system-related disorders including insomnia, migraine headache, and mental illness in West and Central Tropical Africa.

AIM

This study was designed to investigate the antipsychotic activity of Carpolobia lutea (EECL) in mice models of psychosis.

METHODS

Male Swiss mice (n = 5/group) were given EECL (100, 200, 400, and 800 mg/kg), haloperidol (1 mg/kg), clozapine (5 mg/kg) and vehicle (10 mL/kg) orally before amphetamine (5 mg/kg)-induced hyperlocomotion and stereotypy, apomorphine (2 mg/kg)-induced stereotypy, or ketamine (10, 30, and 100 mg/kg)-induced hyperlocomotion, enhancement of immobility and cognitive impairment.

RESULTS

EECL (200, 400, and 800 mg/kg) prevented amphetamine- and apomorphine-induced stereotypies, as well as reduced hyperlocomotion induced by amphetamine and ketamine, all of which are predictors of positive symptoms. Regardless of the dose administered, EECL prevented the index of negative symptoms induced by ketamine. Furthermore, higher doses of EECL (400 and 800 mg/kg) also prevented ketamine-induced cognitive impairment, a behavioral phenotype of cognitive symptoms.

CONCLUSION

Pretreatment with EECL demonstrated antipsychotic activity in mice, preventing amphetamine-, apomorphine-, and ketamine-induced schizophrenia-like symptoms, with 800 mg/kg being the most effective dose.

Virgin coconut oil abrogates depression-associated cognitive deficits by modulating hippocampal antioxidant balance, GABAergic and glutamatergic receptors in mice

OBJECTIVES

GABA and glutamate neurotransmission play critical roles in both the neurobiology of depression and cognition; and Virgin coconut oil (VCO) is reported to support brain health. The present study investigated the effect of VCO on depression-associated cognitive deficits in mice.

METHODS

Thirty male mice divided into five groups were either exposed to chronic unpredicted mild stress (CUMS) protocol for 28 days or pre-treated with 3 mL/kg b. wt. of VCO for 21 days or post-treated with 3 mL/kg b. wt. of VCO for 21 days following 28 days of CUMS exposure. Mice were subjected to behavioural assessments for depressive-like behaviours and short-term memory, and thereafter euthanised. Hippocampal tissue was dissected from the harvested whole brain for biochemical and immunohistochemical evaluations.

RESULTS

Our results showed that CUMS exposure produced depressive-like behaviours, cognitive deficits and altered hippocampal redox balance. However, treatment with VCO abrogated depression-associated cognitive impairment, and enhanced hippocampal antioxidant concentration. Furthermore, immunohistochemical evaluation revealed significant improvement in GABA_A and mGluR1a immunoreactivity following treatment with VCO in the depressed mice.

CONCLUSIONS

Therefore, findings from this study support the dietary application of VCO to enhance neural resilience in patients with depression and related disorders.

(R,S)-ketamine and (2R,6R)-hydroxynorketamine differentially affect memory as a function of dosing frequency

A single subanesthetic infusion of ketamine can rapidly alleviate symptoms of treatment-resistant major depression. Since repeated administration is required to sustain symptom remission, it is important to characterize the potential untoward effects of prolonged ketamine exposure. While studies suggest that ketamine can alter cognitive function, it is unclear to what extent these effects are modulated by the frequency or chronicity of treatment. To test this, male and female adolescent (postnatal day [PD] 35) and adult (PD 60) BALB/c mice were treated for four consecutive weeks, either daily or thrice-weekly, with (R,S)-ketamine (30 mg/kg, intraperitoneal) or its biologically active metabolite, (2R,6R)-hydroxynorketamine (HNK; 30 mg/kg, intraperitoneal). Following drug cessation, memory performance was assessed in three operationally distinct tasks: (1) novel object recognition to assess explicit memory, (2) Y-maze to assess working memory, and (3) passive avoidance to assess implicit memory. While drug exposure did not influence working memory performance, thrice-weekly ketamine and daily (2R,6R)-HNK led to explicit memory impairment in novel object recognition independent of sex or age of exposure. Daily (2R,6R)-HNK impaired implicit memory in the passive-avoidance task whereas thrice-weekly (2R,6R)-HNK tended to improve it. These differential effects on explicit and implicit memory possibly reflect the unique mechanisms by which ketamine and (2R,6R)-HNK alter the functional integrity of neural circuits that subserve these distinct cognitive domains, a topic of clinical and mechanistic relevance to their antidepressant actions. Our findings also provide additional support for the importance of dosing frequency in establishing the cognitive effects of repeated ketamine exposure.

Schizophrenia-like behavior is not altered by melatonin supplementation in rodents

An emerging area in schizophrenia research focuses on the impact of immunomodulatory drugs such as melatonin, which have played important roles in many biological systems and functions, and appears to be promising. The objective was to evaluate the effect of melatonin on behavioral parameters in an animal model of schizophrenia. For this, Wistar rats were divided and used in two different protocols. In the prevention protocol, the animals received 1 or 10mg/kg of melatonin or water for 14 days, and between the 8th and 14th day they received ketamine or saline. In the reversal protocol, the opposite occurred. On the 14th day, the animals underwent behavioral tests: locomotor activity and prepulse inhibition task. In both protocols, the results revealed that ketamine had effects on locomotor activity and prepulse inhibition, confirming the validity of ketamine construction as a good animal model of schizophrenia. However, at least at the doses used, melatonin was not able to reverse/prevent ketamine damage. More studies are necessary to evaluate the role of melatonin as an adjuvant treatment in psychiatric disorders.

Dietary zinc supplement militates against ketamine-induced behaviours by age-dependent modulation of oxidative stress and acetylcholinesterase activity in mice

BACKGROUND

The potential differential modulatory effects of zinc-supplemented diet on ketamine-induced changes in behaviours, brain oxidative stress, acetylcholinesterase activity, and zinc (ZN) levels were examined in prepubertal and aged mice.

METHODS

Aged and prepubertal mice were divided into 2 groups consisting of 80 aged and 80 prepubertal mice, each having 8 treatment groups of 10 animals each. The treatment groups are: vehicle control group (fed standard diet and given intraperitoneal {ip} normal saline), three groups fed ZN-supplemented diet (at 25, 50 and 100 mg/kg of feed) and given ip normal saline, ketamine control group (fed standard diet and given ip ketamine), and finally another three groups fed ZN-supplemented diet (at 25, 50 and 100 mg/kg of feed) and given ip ketamine. Intraperitoneal normal saline (at 2 ml/kg/day) or ketamine (at 30 mg/kg/day) were administered during the last 10 days of study. On day 60, animals were exposed to the open-field, Y-maze, radial-arm maze, and elevated plus maze following which they were euthanised; blood and brain homogenate were used for assessment of biochemical parameters.

RESULTS

Zinc supplementation was associated with an increase in food intake and body weight (in both age groups), a reduction in ketamine-induced increase in locomotion, rearing and grooming, and significantly higher working-memory scores (compared to ketamine control). Also, there was a decrease in anxiety-related behaviours, enhanced antioxidant status, reduced lipid peroxidation, and reduced acetylcholinesterase activity.

CONCLUSION

In conclusion, dietary ZN supplementation was associated with variable degrees of prevention of ketamine-induced changes, depending on the age of animals.

Blackberry extract improves behavioral and neurochemical dysfunctions in a ketamine-induced rat model of mania

Bipolar disorder is a chronic mood disorder characterized by episodes of mania and depression. The aim of this study was to investigate the effects of blackberry extract on behavioral parameters, oxidative stress and inflammatory markers in a ketamine-induced model of mania. Animals were pretreated with extract (200 mg/kg, once a day for 14 days), lithium chloride (45 mg/kg, twice a day for 14 days), or vehicle. Between the 8th and 14th days, the animals received an injection of ketamine (25 mg/kg) or vehicle. On the 15th day, thirty minutes after ketamine administration, the animals' locomotion was assessed using open-field apparatus. After the experiments, the animals were euthanized and cerebral structures were removed for neurochemical analyses. The results showed that ketamine treatment induced hyperlocomotion and oxidative damage in the cerebral cortex, hippocampus and striatum. In contrast, pretreatment with the extract or lithium was able to prevent hyperlocomotion and oxidative damage in the cerebral cortex, hippocampus, and striatum. In addition, IL-6 and IL-10 levels were increased by ketamine, while the extract prevented these effects in the cerebral cortex. Pretreatment with the extract was also effective in decreasing IL-6 and increasing the level of IL-10 in the striatum. In summary, our findings suggest that blackberry consumption could help prevent or reduce manic episodes, since this extract have demonstrated neuroprotective properties as well as antioxidant and anti-inflammatory effects in the ketamine-induced mania model.

Antioxidants Reverse the Changes in the Cholinergic System Caused by L-Tyrosine Administration in Rats

Tyrosinemia type II is an inborn error of metabolism caused by a deficiency in the activity of the enzyme tyrosine aminotransferase, leading to tyrosine accumulation in the body. Although the mechanisms involved are still poorly understood, several studies have showed that higher levels of tyrosine are related to oxidative stress and therefore may affect the cholinergic system. Thus, the aim of this study was to investigate the effects of chronic administration of L-tyrosine on choline acetyltransferase activity (ChAT) and acetylcholinesterase (AChE) in the brain of rats. Moreover, we also examined the effects of one antioxidant treatment (N-acetylcysteine (NAC) + deferoxamine (DFX)) on cholinergic system. Our results showed that the chronic administration of L-tyrosine decreases the ChAT activity in the cerebral cortex, while the AChE activity was increased in the hippocampus, striatum, and cerebral cortex. Moreover, we found that the antioxidant treatment was able to prevent the decrease in the ChAT activity in the cerebral cortex. However, the increase in AChE activity induced by L-tyrosine was partially prevented the in the hippocampus and striatum, but not in the cerebral cortex. Our results also showed no differences in the aversive and spatial memory after chronic administration of L-tyrosine. In conclusion, the results of this study demonstrated an increase in AChE activity in the hippocampus, striatum, and cerebral cortex and an increase of ChAT in the cerebral cortex, without cognitive impairment. Furthermore, the alterations in the cholinergic system were partially prevented by the co-administration of NAC and DFX. Thus, the restored central cholinergic system by antioxidant treatment further supports the view that oxidative stress may be involved in the pathophysiology of tyrosinemia type II.

Enhanced memory in Wistar rats by virgin coconut oil is associated with increased antioxidative, cholinergic activities and reduced oxidative stress

CONTEXT

Virgin coconut oil (VCO) has been reported to possess antioxidative, anti-inflammatory and anti-stress properties.

OBJECTIVE

Capitalizing on these therapeutic effects, this study investigated for the first time the potential of VCO on memory improvement in vivo.

MATERIALS AND METHODS

Thirty male Wistar rats (7-8 weeks old) were randomly assigned to five groups (n = six per group). Treatment groups were administered with 1, 5 and 10 g/kg VCO for 31 days by oral gavages. The cognitive function of treated-rats were assessed using the Morris Water Maze Test. Brains were removed, homogenized and subjected to biochemical analyses of acetylcholine (ACh) and acetylcholinesterase (AChE), antioxidants [superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GPx) and glutathione reductase (GRx)], lipid peroxidase [malondialdehyde (MDA)] as well as nitric oxide (NO). α-Tocopherol (αT; 150 mg/kg) was also included for comparison purposes.

RESULTS

VCO-fed Wistar rats exhibited significant (p < 0.05) improvement of cognitive functions [reduced escape latency (≥ 1.8 s), reduced escape distance (≥ 0.3 m) and increased total time spent on platform (≥ 1 s)]. The findings were accompanied by elevation of ACh (15%), SOD (8%), CAT (≥ 54%), GSH (≥ 20%) and GPx (≥ 12%) and reduction of AChE (≥17%), MDA (> 33%) and NO (≥ 34%). Overall, memory improvement by VCO was comparable to αT.

DISCUSSION AND CONCLUSION

VCO has the potential to be used as a memory enhancer, the effect of which was mediated, at least in part, through enhanced cholinergic activity, increased antioxidants level and reduced oxidative stress.

Ketamine: differential neurophysiological dynamics in functional networks in the rat brain

Recently, the N-methyl-d-aspartate-receptor (NMDAR) antagonist ketamine has emerged as a fast-onset mechanism to achieve antidepressant activity, whereas its psychomimetic, dissociative and amnestic effects have been well documented to pharmacologically model schizophrenia features in rodents. Sleep-wake architecture, neuronal oscillations and network connectivity are key mechanisms supporting brain plasticity and cognition, which are disrupted in mood disorders such as depression and schizophrenia. In rats, we investigated the dynamic effects of acute and chronic subcutaneous administration of ketamine (2.5, 5 and 10 mg kg-1) on sleep-wake cycle, multichannels network interactions assessed by coherence and phase-amplitude cross-frequency coupling, locomotor activity (LMA), cognitive information processing as reflected by the mismatch negativity-like (MMN) component of event-related brain potentials (ERPs). Acute ketamine elicited a short, lasting inhibition of rapid eye movement (REM) sleep, increased coherence in higher gamma frequency oscillations independent of LMA, altered theta-gamma phase-amplitude coupling, increased MMN peak-amplitude response and evoked higher gamma oscillations. In contrast, chronic ketamine reduced large-scale communication among cortical regions by decreasing oscillations and coherent activity in the gamma frequency range, shifted networks activity towards slow alpha rhythm, decreased MMN peak response and enhanced aberrant higher gamma neuronal network oscillations. Altogether, our data show that acute and chronic ketamine elicited differential changes in network connectivity, ERPs and event-related oscillations (EROs), supporting possible underlying alterations in NMDAR-GABAergic signaling. The findings underscore the relevance of intermittent dosing of ketamine to accurately maintain the functional integrity of neuronal networks for long-term plastic changes and therapeutic effect.

Increased risk of developing schizophrenia in animals exposed to cigarette smoke during the gestational period

Cigarette smoking during the prenatal period has been investigated as a causative factor of obstetric abnormalities, which lead to cognitive and behavioural changes associated with schizophrenia. The aim of this study was to investigate behaviour and AChE activity in brain structures in adult rats exposed to cigarette smoke during the prenatal period. Pregnant rats were divided into non-PCSE (non-prenatal cigarette smoke exposure) and PCSE (prenatal cigarette smoke exposure) groups. On post-natal day 60, the rats received saline or ketamine for 7days and were subjected to behavioural tasks. In the locomotor activity task, the non-PCSE+ketamine and PCSE+ketamine groups exhibited increased locomotor activity compared with the saline group. In the social interaction task, the non-PCSE+ketamine and PCSE+ketamine groups exhibited an increased latency compared with the control groups. However, the PCSE+ketamine group exhibited a decreased latency compared with the non-PCSE+ketamine group, which indicates that the cigarette exposure appeared to decrease, the social deficits generated by ketamine. In the inhibitory avoidance task, the non-PCSE+ketamine, PCSE, and PCSE+ketamine groups exhibited impairments in working memory, short-term memory, and long-term memory. In the pre-pulse inhibition (PPI) test, cigarette smoke associated with ketamine resulted in impaired PPI in 3 pre-pulse (PP) intensity groups compared with the control groups. In the biochemical analysis, the AChE activity in brain structures increased in the ketamine groups; however, the PCSE+ketamine group exhibited an exacerbated effect in all brain structures. The present study indicates that exposure to cigarette smoke during the prenatal period may affect behaviour and cerebral cholinergic structures during adulthood.

A heuristic model for working memory deficit in schizophrenia

BACKGROUND

The life of schizophrenia patients is severely affected by deficits in working memory. In various brain regions, the reciprocal interactions between excitatory glutamatergic neurons and inhibitory GABAergic neurons are crucial. Other neurotransmitters, in particular dopamine, serotonin, acetylcholine, and norepinephrine, modulate the local balance between glutamate and GABA and therefore regulate the function of brain regions. Persistent alterations in the balances between the neurotransmitters can result in working memory deficits.

METHODS

Here we present a heuristic computational model that accounts for interactions among neurotransmitters across various brain regions. The model is based on the concept of a neurochemical interaction matrix at the biochemical level and combines this matrix with a mobile model representing physiological dynamic balances among neurotransmitter systems associated with working memory.

RESULTS

The comparison of clinical and simulation results demonstrates that the model output is qualitatively very consistent with the available data. In addition, the model captured how perturbations migrated through different neurotransmitters and brain regions. Results showed that chronic administration of ketamine can cause a variety of imbalances, and application of an antagonist of the D2 receptor in PFC can also induce imbalances but in a very different manner.

CONCLUSIONS

The heuristic computational model permits a variety of assessments of genetic, biochemical, and pharmacological perturbations and serves as an intuitive tool for explaining clinical and biological observations.

GENERAL SIGNIFICANCE

The heuristic model is more intuitive than biophysically detailed models. It can serve as an important tool for interdisciplinary communication and even for psychiatric education of patients and relatives. This article is part of a Special Issue entitled "System Genetics" Guest Editor: Dr. Yudong Cai and Dr. Tao Huang.