Olanzapine attenuates the okadaic acid-induced spatial memory impairment and hippocampal cell death in rats

Microbial Interactions between Marine Microalgae and Fungi: From Chemical Ecology to Biotechnological Possible Applications

Chemical interactions have been shown to regulate several marine life processes, including selection of food sources, defense, behavior, predation, and mate recognition. These chemical communication signals have effects not only at the individual scale, but also at population and community levels. This review focuses on chemical interactions between marine fungi and microalgae, summarizing studies on compounds synthetized when they are cultured together. In the current study, we also highlight possible biotechnological outcomes of the synthetized metabolites, mainly for human health applications. In addition, we discuss applications for bio-flocculation and bioremediation. Finally, we point out the necessity of further investigating microalgae-fungi chemical interactions because it is a field still less explored compared to microalga-bacteria communication and, considering the promising results obtained until now, it is worthy of further research for scientific advancement in both ecology and biotechnology fields.

Phytoplankton Toxins and Their Potential Therapeutic Applications: A Journey toward the Quest for Potent Pharmaceuticals

Phytoplankton are prominent organisms that contain numerous bioactive substances and secondary metabolites, including toxins, which can be valuable to pharmaceutical, nutraceutical, and biotechnological industries. Studies on toxins produced by phytoplankton such as cyanobacteria, diatoms, and dinoflagellates have become more prevalent in recent years and have sparked much interest in this field of research. Because of their richness and complexity, they have great potential as medicinal remedies and biological exploratory probes. Unfortunately, such toxins are still at the preclinical and clinical stages of development. Phytoplankton toxins are harmful to other organisms and are hazardous to animals and human health. However, they may be effective as therapeutic pharmacological agents for numerous disorders, including dyslipidemia, obesity, cancer, diabetes, and hypertension. In this review, we have focused on the properties of different toxins produced by phytoplankton, as well as their beneficial effects and potential biomedical applications. The anticancer properties exhibited by phytoplankton toxins are mainly attributed to their apoptotic effects. As a result, phytoplankton toxins are a promising strategy for avoiding postponement or cancer treatment. Moreover, they also displayed promising applications in other ailments and diseases such as Alzheimer’s disease, diabetes, AIDS, fungal, bacterial, schizophrenia, inflammation, allergy, osteoporosis, asthma, and pain. Preclinical and clinical applications of phytoplankton toxins, as well as future directions of their enhanced nano-formulations for improved clinical efficacy, have also been reviewed.

Hepatoprotective effect of trypsin/chymotrypsin against olanzapine-induced non-alcoholic steatohepatitis in rats

Metabolic side effects of atypical antipsychotics are an important cause of deterioration of cognitive function and failure of drug adherence. The antifatty effect trypsin/chymotrypsin (T/C) and their mechanisms of action remain unclear. To investigate possible therapeutic effect of T/C in rat model of chronic olanzapine (OLZ) - induced hepatic steatosis. Twenty rats were divided into two groups: control (C), given distilled water, and O, given 1 mg/kg of OLZ orally daily for 7 weeks. Then, both groups were given T/C 3 enzyme activity unit (EAU)/kg orally as an add-on treatment daily for the next 5 weeks and were named T/C or T/C+O groups. Rat performance in radial arm water maze was tested twice before and after T/C treatment. We measured liver enzymes, alpha-1 antitrypsin, albumin, total protein, direct and total bilirubin, inflammatory cytokines, and lipoprotein serum levels. Liver samples were collected for histopathology and Ki67 expression. The T/C add-on caused significant reduction in OLZ-induced elevation of alanine transaminase (ALT; P < 0.01), aspartate transaminase (AST; P < 0.001), alkaline phosphatase (ALP; P < 0.05), total cholesterol (Tc; P < 0.01), low-density lipoproteins (LDL-c; P < 0.05), steatosis score (P < 0.001), hepatocyte necrosis (P < 0.01), and significantly increased Ki67 expression (P < 0.01). The T/C add-on to OLZ provided protection against hepatic steatosis, elevated enzymes, and disturbed lipid profile and increased Ki67 without disturbing memory function.

Olanzapine attenuates postoperative cognitive dysfunction in adult rats

Background

Postoperative cognitive dysfunction (POCD) is associated with poor quality of life and difficulty working. Its impact may be greater in middle-aged patients than in elderly patients. Neuroinflammation is reported to be a main cause of POCD. Olanzapine has been reported to improve learning and memory functions. We therefore investigated olanzapine's effectiveness and mechanisms in an adult rat POCD model.

Methods

Six-month-old rats underwent laparotomy and lipopolysaccharide (LPS group) or LPS + olanzapine (OLA group) intraperitoneal injection or anesthesia alone (CON group) 1 week after a Barnes maze training session. A Barnes maze test trial was then conducted the day after surgery or anesthesia. The microglial activity in the hippocampus and cytokine levels were measured by Iba1 staining and enzyme-linked immunosorbent assay, respectively.

Results

The OLA group had significantly higher success rates of Barnes maze trial than the LPS group. The success rate in time of the OLA group was inferior to that of the CON group. On the other hand, the success rate in distance of the OLA group was similar to that of the CON group. Iba1 staining areas in the LPS and OLA groups were larger than that in the CON group; however, the staining area in the OLA group was smaller than that of the LPS group. Plasma interleukin-1β concentration in the LPS and OLA groups was significantly higher than that in the CON group; however, there was no significant difference between the LPS and OLA groups.

Conclusion

Olanzapine attenuated both spatial cognitive dysfunction and microglial activity of the hippocampus, which were induced by surgery and LPS injection. These effects were unrelated to inflammatory cytokine concentrations in plasma and hippocampus.

Pro-cognitive effect of 1MeTIQ on recognition memory in the ketamine model of schizophrenia in rats: the behavioural and neurochemical effects

RATIONALE

Schizophrenia is a mental illness which is characterised by positive and negative symptoms and by cognitive impairments. While the major prevailing hypothesis is that altered dopaminergic and/or glutamatergic transmission contributes to this disease, there is evidence that the noradrenergic system also plays a role in its major symptoms.

OBJECTIVES

In the present paper, we investigated the pro-cognitive effect of 1-methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ) an endogenous neuroprotective compound, on ketamine-modelled schizophrenia in rats.

METHODS

We used an antagonist of NMDA receptors (ketamine) to model memory deficit symptoms in rats. Using the novel object recognition (NOR) test, we investigated the pro-cognitive effect of 1MeTIQ. Additionally, olanzapine, an atypical antipsychotic drug, was used as a standard to compare the pro-cognitive effects of the substances. In vivo microdialysis studies allowed us to verify the changes in the release of monoamines and their metabolites in the rat striatum.

RESULTS

Our study demonstrated that 1MeTIQ, similarly to olanzapine, exhibits a pro-cognitive effect in NOR test and enhances memory disturbed by ketamine treatment. Additionally, in vivo microdialysis studies have shown that ketamine powerfully increased noradrenaline release in the rat striatum, while 1MeTIQ and olanzapine completely antagonised this neurochemical effect.

CONCLUSIONS

1MeTIQ, as a possible pro-cognitive drug, in contrast to olanzapine, expresses beneficial neuroprotective activity in the brain, increasing concentration of the extraneuronal dopamine metabolite, 3-methoxytyramine (3-MT), which plays an important physiological role in the brain as an inhibitory regulator of catecholaminergic activity. Moreover, we first demonstrated the essential role of noradrenaline release in memory disturbances observed in the ketamine-model of schizophrenia, and its possible participation in negative symptoms of the schizophrenia.

Clozapine increased c-Fos protein expression in several brain subregions of socially isolated rats

Chronic social stress and/or pharmacological treatments differentially modulate the expression of c-Fos, a marker of neuronal activity, in subregions of the rat brain. Here, we examined the effect of the atypical antipsychotic Clozapine (Clz) (20 mg/kg/day for 3 weeks) on the neuronal activation pattern of c-Fos protein expression in stress-relevant brain subregions of adult male Wistar rats exposed to chronic social isolation (CSIS: 3 weeks), an animal model of depression and schizophrenia, and controls. The protein expression of c-Fos was also used to map neuronal populations in brain subregions activated by CSIS alone. Subregions which showed significantly increased c-Fos protein expression following CSIS included the retrosplenial cortex (RSC), (subregions:RSC granular cortex, c region (RSGc) and dysgranular (RSD)), dentate gyrus, dorsal (DGd), paraventricular thalamic nucleus, posterior part (PVP), lateral (LA)/basolateral (BL) complex of amygdala, caudate putamen (CPu) and accumbens nucleus, shell (AcbSh). Increases in c-Fos protein expression in the RSGc, RSD, DGd, PVP, LA/BL complex of amygdala and striatum (CPu, Acb Core (AcbC) and AcbSh) following Clz treatment in controls were found. Clz applied simultaneously with CSIS modulated neuronal activity in CPu, AcbC and AcbSh subregions compared to CSIS alone, increasing c-Fos protein expression. Furthermore, Clz revealed synergistic effects with CSIS in the CA1d and PVP. These identified neural circuits reflect brain subregions activated following CSIS and/or Clz administration. These data further contribute to the understanding of the effectiveness of Clz in the modulation of brain subregion activation in response to CSIS.

Microalgae metabolites: A rich source for food and medicine

Microalgae are one of the important components in food chains of aquatic ecosystems and have been used for human consumption as food and as medicines. The wide diversity of compounds synthesized from different metabolic pathways of fresh and marine water algae provide promising sources of fatty acids, steroids, carotenoids, polysaccharides, lectins, mycosporine-like amino acids, halogenated compounds, polyketides, toxins, agar agar, alginic acid and carrageenan. This review discusses microalgae used to produce biological substances and its economic importance in food science, the pharmaceutical industry and public health.

The Marine Dinoflagellate Alexandrium andersoni Induces Cell Death in Lung and Colorectal Tumor Cell Lines

Dinoflagellates are one of the most important components in marine phytoplankton, second only to diatoms as primary producers. Dinoflagellates have also been reported to produce bioactive secondary metabolites such as polyethers and macrolides with potential applications as pharmaceuticals. Here, we tested the effect of the organic extract and its related enriched extracts from solid-phase extraction (SPE) of a strain of the dinoflagellate Alexandrium andersoni. We found that the SPE extracts induced high cytotoxicity towards two cancer cell lines (A549 lung cancer and HT29 colorectal cancer) without affecting normal cell viability. The SPE extracts activated two different cell death pathways in the two tumor cell lines at the gene expression level, with the involvement of the major mediators of the tumor necrosis factor (TNF) cell signaling cascade. In HT29 cells, in addition to TNF activation, a death signaling pathway in response to DNA damage was also induced. This is an interesting finding since the HT29 cell line is highly aggressive since it is p53 gene-defect and this DNA instability renders this type of cancer very resistant towards all chemotherapeutic agents. Another significant result is that two distinct chemical fractions were selectively able to induce different and specific responses on the two different tumor cells treated.

Biotechnological and Pharmacological Applications of Biotoxins and Other Bioactive Molecules from Dinoflagellates

The long-lasting interest in bioactive molecules (namely toxins) produced by (microalga) dinoflagellates has risen in recent years. Exhibiting wide diversity and complexity, said compounds are well-recognized for their biological features, with great potential for use as pharmaceutical therapies and biological research probes. Unfortunately, provision of those compounds is still far from sufficient, especially in view of an increasing demand for preclinical testing. Despite the difficulties to establish dinoflagellate cultures and obtain reasonable productivities of such compounds, intensive research has permitted a number of advances in the field. This paper accordingly reviews the characteristics of some of the most important biotoxins (and other bioactive substances) produced by dinoflagellates. It also presents and discusses (to some length) the main advances pertaining to dinoflagellate production, from bench to large scale-with an emphasis on material published since the latest review available on the subject. Such advances encompass improvements in nutrient formulation and light supply as major operational conditions; they have permitted adaptation of classical designs, and aided the development of novel configurations for dinoflagellate growth-even though shearing-related issues remain a major challenge.

Polymeric alkylpyridinium salts permit intracellular delivery of human Tau in rat hippocampal neurons: requirement of Tau phosphorylation for functional deficits

Patients suffering from tauopathies including frontotemporal dementia (FTD) and Alzheimer's disease (AD) present with intra-neuronal aggregation of microtubule-associated protein Tau. During the disease process, Tau undergoes excessive phosphorylation, dissociates from microtubules and aggregates into insoluble neurofibrillary tangles (NFTs), accumulating in the soma. While many aspects of the disease pathology have been replicated in transgenic mouse models, a region-specific non-transgenic expression model is missing. Complementing existing models, we here report a novel region-specific approach to modelling Tau pathology. Local co-administration of the pore-former polymeric 1,3-alkylpyridinium salts (Poly-APS) extracted from marine sponges, and synthetic full-length 4R recombinant human Tau (hTau) was performed in vitro and in vivo. At low doses, Poly-APS was non-toxic and cultured cells exposed to Poly-APS (0.5 µg/ml) and hTau (1 µg/ml; ~22 µM) had normal input resistance, resting-state membrane potentials and Ca(2+) transients induced either by glutamate or KCl, as did cells exposed to a low concentration of the phosphatase inhibitor Okadaic acid (OA; 1 nM, 24 h). Combined hTau loading and phosphatase inhibition resulted in a collapse of the membrane potential, suppressed excitation and diminished glutamate and KCl-stimulated Ca(2+) transients. Stereotaxic infusions of Poly-APS (0.005 µg/ml) and hTau (1 µg/ml) bilaterally into the dorsal hippocampus at multiple sites resulted in hTau loading of neurons in rats. A separate cohort received an additional 7-day minipump infusion of OA (1.2 nM) intrahippocampally. When tested 2 weeks after surgery, rats treated with Poly-APS+hTau+OA presented with subtle learning deficits, but were also impaired in cognitive flexibility and recall. Hippocampal plasticity recorded from slices ex vivo was diminished in Poly-APS+hTau+OA subjects, but not in other treatment groups. Histological sections confirmed the intracellular accumulation of hTau in CA1 pyramidal cells and along their processes; phosphorylated Tau was present only within somata. This study demonstrates that cognitive, physiological and pathological symptoms reminiscent of tauopathies can be induced following non-mutant hTau delivery into CA1 in rats, but functional consequences hinge on increased Tau phosphorylation. Collectively, these data validate a novel model of locally infused recombinant hTau protein as an inducer of Tau pathology in the hippocampus of normal rats; future studies will provide insights into the pathological spread and maturation of Tau pathology.

Green tea polyphenols protect against okadaic acid-induced acute learning and memory impairments in rats

OBJECTIVE

Green tea polyphenols (GTPs) are now being considered possible protective agents in neurodegenerative diseases such as Alzheimer's disease (AD). Previous studies suggested that GTPs could inhibit amyloid fibril formation and protect neurons from toxicity induced by β-amyloid. However, whether GTPs can ameliorate learning and memory impairments and also reduce tau hyperphosphorylation induced by okadaic acid (OA) in rats remains unclear. The aim of this study was to determine if GTPs have neuroprotection against OA-induced neurotoxicity.

METHODS

In this work, rats were pretreated with GTPs by intragastric administration for 4 wk. Then OA was microinjected into the right dorsal hippocampus. Morris water maze tests were used to test the ethologic changes in all groups, and tau protein hyperphosphorylation was detected both in vivo and in vitro.

RESULTS

The ethologic test indicated that the staying time and swimming distance in the target quadrant were significantly decreased after OA treatment, whereas rats pretreated with GTPs stayed longer in the target quadrant. Methyl thiazolyl tetrazolium assay and lactate dehydrogenase leakage showed that GTPs greatly ameliorated primary hippocampal neurons damage induced by OA. Furthermore, reduced hyperphosphorylated tau protein was detected with GTPs pretreatment.

CONCLUSION

Taken together, our results suggest that GTPs have neuroprotection against OA-induced neurotoxicity.

Is protein phosphatase inhibition responsible for the toxic effects of okadaic Acid in animals?

Okadaic acid (OA) and its derivatives, which are produced by dinoflagellates of the genera Prorocentrum and Dinophysis, are responsible for diarrhetic shellfish poisoning in humans. In laboratory animals, these toxins cause epithelial damage and fluid accumulation in the gastrointestinal tract, and at high doses, they cause death. These substances have also been shown to be tumour promoters, and when injected into the brains of rodents, OA induces neuronal damage reminiscent of that seen in Alzheimer’s disease. OA and certain of its derivatives are potent inhibitors of protein phosphatases, which play many roles in cellular metabolism. In 1990, it was suggested that inhibition of these enzymes was responsible for the diarrhetic effect of these toxins. It is now repeatedly stated in the literature that protein phosphatase inhibition is not only responsible for the intestinal effects of OA and derivatives, but also for their acute toxic effects, their tumour promoting activity and their neuronal toxicity. In the present review, the evidence for the involvement of protein phosphatase inhibition in the induction of the toxic effects of OA and its derivatives is examined, with the conclusion that the mechanism of toxicity of these substances requires re-evaluation.

The role of protein phosphorylation in the gustatory cortex and amygdala during taste learning

Protein phosphorylation and dephosphorylation form a major post-translation mechanism that enables a given cell to respond to ever-changing internal and external environments. Neurons, similarly to any other cells, use protein phosphorylation/dephosphorylation to maintain an internal homeostasis, but they also use it for updating the state of synaptic and intrinsic properties, following activation by neurotransmitters and growth factors. In the present review we focus on the roles of several families of kinases, phosphatases, and other synaptic-plasticity-related proteins, which activate membrane receptors and various intracellular signals to promote transcription, translation and protein degradation, and to regulate the appropriate cellular proteomes required for taste memory acquisition, consolidation and maintenance. Attention is especially focused on the protein phosphorylation state in two forebrain areas that are necessary for taste-memory learning and retrieval: the insular cortex and the amygdala. The various temporal phases of taste learning require the activation of appropriate waves of biochemical signals. These include: extracellular signal regulated kinase I and II (ERKI/II) signal transduction pathways; Ca(2+)-dependent pathways; tyrosine kinase/phosphatase-dependent pathways; brain-derived neurotrophicfactor (BDNF)-dependent pathways; cAMP-responsive element bindingprotein (CREB); and translation-regulation factors, such as initiation and elongation factors, and the mammalian target of rapamycin (mTOR). Interestingly, coding of hedonic and aversive taste information in the forebrain requires activation of different signal transduction pathways.

WITHDRAWN: Effects of traditional Chinese medicine Fuzhisan on PP1 expression in the hippocampus of SAMP8 mice

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An okadaic acid-induced model of tauopathy and cognitive deficiency

Alzheimer's disease (AD) is a progressive neurodegenerative disease that causes cognitive and behavioral deterioration in the elderly. Neurofibrillary tangles (NFTs) are one of the pathological hallmarks of AD that has been shown to correlate positively with the severity of dementia in the neocortex of AD patients. In an attempt to characterize an in vivo AD tauopathy model, okadaic acid (OA), a protein phosphatase inhibitor, was microinfused into the right lateral dorsal hippocampus area of ovariectomized adult rat. Cognitive deficiency was seen in OA-treated rats without a change in motor function. Both silver staining and immunohistochemistry staining revealed that OA treatment induces NFTs-like conformational changes in both the cortex and hippocampus. Phosphorylated tau as well as cyclin-dependent kinase 5 (cdk5) and its coactivator, p25, were significantly increased in these regions of the brain. Oxidative stress was also increased with OA treatment as measured by protein carbonylation and lipid peroxidation. These data suggest that the unilateral microinfusion of OA into the dorsal hippocampus causes cognitive deficiency, NFTs-like pathological changes, and oxidative stress as seen in AD pathology via tau hyperphosphorylation caused by inhibition of protein phosphatases.

Intra-amygdalar okadaic acid enhances conditioned taste aversion learning and CREB phosphorylation in rats

Protein phosphatases (PPs) regulate many substrates implicated in learning and memory. Conditioned taste aversion (CTA) learning, in which animals associate a novel taste paired with a toxin and subsequently avoid the taste, is dependent on several serine/threonine phosphatase substrates and the PP1-binding protein spinophilin. In order to examine the effects of PP1/2A blockade on CTA acquisition and extinction, rats received bilateral infusions of okadaic acid (OA) (100nM, 1microl/hemisphere) or vehicle (0.15M NaCl) into the amygdala either 5min prior to, or 5min after, a single pairing of sodium saccharin (0.125%, 10-min access) and LiCl or NaCl (0.15M, 3ml/kg i.p.). Two-bottle, 24-h preference tests were conducted for 13days to measure CTA expression and extinction. Rats conditioned with saccharin and LiCl showed a decreased preference for saccharin, and OA administered before (but not after) the pairing of saccharin and LiCl resulted in a significantly stronger CTA that did not extinguish over 13days. The enhancement of the CTA was not due to aversive effects of OA, because rats given OA and a pairing of saccharin and NaCl did not acquire a CTA. Finally, OA administration increased levels of phosphorylated CREB immunoreactivity following a CTA trial. Together, these results suggest a critical role for PP1/2A during normal CTA learning. Because CTA learning was enhanced only when OA was given prior to conditioning, phosphatase activity may be a constraint on learning during the taste-toxin interval but not during acquisition and consolidation processes that occur after toxin administration.

Roles of astrocytes and microglia in seizure-induced aberrant neurogenesis in the hippocampus of adult rats

Recent evidence showed that epileptic seizures increase hippocampal neurogenesis in the adult rat, but prolonged seizures result in the aberrant hippocampal neurogenesis that often leads to a recurrent excitatory circuitry and thus contributes to epileptogenesis. However, the mechanism underlying the aberrant neurogenesis after prolonged seizures remains largely unclear. In this study, we examined the role of activated astrocytes and microglia in the aberrant hippocampal neurogenesis induced by status epilepticus. Using a lithium-pilocarpine model to mimic human temporal lobe epilepsy, we found that status epilepticus induced a prominent activation of astrocytes and microglia in the dentate gyrus 3, 7, 14, and 20 days after the initial seizures. Then, we injected fluorocitrate stereotaxicly into the dentate hilus to inhibit astrocytic metabolism and found that fluorocitrate failed to prevent the seizure-induced formation of ectopic hilar basal dendrites but instead promoted the degeneration of dentate granule cells after seizures. In contrast, a selective inhibitor of microglia activation, minocycline, inhibited the aberrant migration of newborn neurons at 14 days after status epilepticus. Furthermore, with stereotaxic injection of lipopolysaccharide into the intact dentate hilus to activate local microglia, we found that lipopolysaccharide promoted the development of ectopic hilar basal dendrites in the hippocampus. These results indicate that the activated microglia in the epileptic hilus may guide the aberrant migration of newborn neurons and that minocycline could be a potential drug to impede seizure-induced aberrant migration of newborn neurons.

Effect of second-generation antipsychotics on cognition: current issues and future challenges

Generalized cognitive impairments are stable deficits linked to schizophrenia and key factors associated with functional disability in the disorder. Preclinical data suggest that second-generation antipsychotics could potentially reduce cognitive impairments; however, recent large clinical trials indicate only modest cognitive benefits relative to first-generation antipsychotics. This might reflect a limited drug effect in humans, a differential drug effect due to brain alterations associated with schizophrenia, or limited sensitivity of the neuropsychological tests for evaluating cognitive outcomes. New adjunctive procognitive drugs may be needed to achieve robust cognitive and functional improvement. Drug discovery may benefit from greater utilization of translational neurocognitive biomarkers to bridge preclinical and clinical proof-of-concept studies, to optimize assay sensitivity, enhance cost efficiency, and speed progress in drug development.

Okadaic acid (ICV) induced memory impairment in rats: a suitable experimental model to test anti-dementia activity

Okadaic acid (OKA) is a potent and selective inhibitor of protein phosphatases, PP2A and PP1. In the present study, we evaluated effect of intracerebroventricular (ICV) bilateral injection of OKA (100 and 200 ng) on memory function and oxidative stress in rats. ICV injection of OKA (200 ng) produced memory impairment as evidenced by no significant decrease in latency time to reach the hidden platform in water maze test. It produced increase in malondialdehyde (MDA), nitrite level, reactive oxygen species (ROS) generation, mitochondrial calcium ion [Ca(2)](i) level and decreased glutathione (GSH) level in rat brain areas, indicating oxidative stress. Furthermore, we evaluated the effect of anti-dementia drugs memantine, a NMDA antagonist, and donepezil, a cholinesterase inhibitor, on OKA ICV induced memory impairment. Administration of memantine (10 mg/kg, p.o.) and donepezil (5 mg/kg, p.o.) for 13 days starting from the OKA injection improved performance in memory tests and also significantly restored GSH, MDA, nitrite levels, ROS generation and [Ca(2+)](i) level. This study demonstrates that the clinically used anti-dementic drugs are effective in OKA induced free radical generation and memory impairment in rats. Thus, OKA ICV induced memory impairment in rat appeared as a useful test model to screen anti-dementia drugs.

Neuroprotective effect of atypical antipsychotics in cognitive and non-cognitive behavioral impairment in animal models

Antipsychotic drugs are divided into two groups: typical and atypical. Recent clinical studies show atypical antipsychotics have advantages over typical antipsychotics in a wide variety of neuropsychiatric conditions, in terms of greater efficacy for positive and negative symptoms, beneficial effects on cognitive functioning, and fewer extra pyramidal side effects in treating schizophrenia. As such, atypical antipsychotics may be effective in the treatment of depressive symptoms associated with psychotic and mood disorders, posttraumatic stress disorder and psychosis in Alzheimer disease. In this paper, we describe the effects and potential neurochemical mechanisms of action of atypical antipsychotics in several animal models showing memory impairments and/or non-cognitive behavioral changes. The data provide new insights into the mechanisms of action of atypical antipsychotics that may broaden their clinical applications.

Antipsychotic drugs: comparison in animal models of efficacy, neurotransmitter regulation, and neuroprotection

Various lines of evidence indicate the presence of progressive pathophysiological processes occurring within the brains of patients with schizophrenia. By modulating chemical neurotransmission, antipsychotic drugs may influence a variety of functions regulating neuronal resilience and viability and have the potential for neuroprotection. This article reviews the current literature describing preclinical and clinical studies that evaluate the efficacy of antipsychotic drugs, their mechanism of action and the potential of first- and second-generation antipsychotic drugs to exert effects on cellular processes that may be neuroprotective in schizophrenia. The evidence to date suggests that although all antipsychotic drugs have the ability to reduce psychotic symptoms via D(2) receptor antagonism, some antipsychotics may differ in other pharmacological properties and their capacities to mitigate and possibly reverse cellular processes that may underlie the pathophysiology of schizophrenia.

Biotechnological significance of toxic marine dinoflagellates

Dinoflagellates are microalgae that are associated with the production of many marine toxins. These toxins poison fish, other wildlife and humans. Dinoflagellate-associated human poisonings include paralytic shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning, and ciguatera fish poisoning. Dinoflagellate toxins and bioactives are of increasing interest because of their commercial impact, influence on safety of seafood, and potential medical and other applications. This review discusses biotechnological methods of identifying toxic dinoflagellates and detecting their toxins. Potential applications of the toxins are discussed. A lack of sufficient quantities of toxins for investigational purposes remains a significant limitation. Producing quantities of dinoflagellate bioactives requires an ability to mass culture them. Considerations relating to bioreactor culture of generally fragile and slow-growing dinoflagellates are discussed. Production and processing of dinoflagellates to extract bioactives, require attention to biosafety considerations as outlined in this review.

The effects of chronic administration of quetiapine on the methamphetamine-induced recognition memory impairment and dopaminergic terminal deficit in rats

Previous studies have suggested that quetiapine, a new atypical antipsychotic drug, may have beneficial effects on cognitive impairment and be a neuroprotectant in treating neurodegenerative diseases. In the present study, we investigated the therapeutic effects of chronic administration of quetiapine on methamphetamine (METH)-induced recognition memory impairment and dopaminergic terminal neurotoxicity in rats. Rats were pretreated with METH (5 mg/kg; s.c.) four times at 2-h intervals while their body temperature was monitored. Fifteen minutes after the last METH injection, rats were administered quetiapine (10 mg/kg/day; i.p.) for 28 days. One day after the last quetiapine injection, rats were trained and tested on an object recognition task on days 29 and 30. Finally, on day 31, rats were sacrificed for immunohistochemistry, 1 day after the object recognition task. METH induced hyperthermia, recognition memory impairment and a decrease of tyrosine hydroxylase immunoreactivity in the caudate putamen (CPu) of striatum. Quetiapine attenuated the METH-induced hyperthermia. Furthermore, chronic post-treatment of quetiapine reversed the METH-induced memory impairment and dopaminergic terminal deficit. These findings suggest that quetiapine may have therapeutic effects in the treatment of cognitive impairment and neurodegeneration induced by METH.

Haloperidol and atypical antipsychotics share a same action of decreasing P75NTR mRNA levels in PC12 cells

P75(NTR) is a common neurotrophin receptor which binds all neurotrophins with similar affinities and has been shown to be capable of mediating programmed cell death. In this study, we investigated effects of the antipsychotic drugs (APDs) haloperidol, clozapine, quetiapine, and risperidone on p75(NTR) mRNA levels in PC12 cells. Haloperidol is a prototype of typical APDs, and the other three drugs are atypical APDs, which are effective in reducing negative symptoms and cognitive deficits of schizophrenia, cause less side effects, and are more tolerable compared to haloperidol. PC12 cells were cultured with various concentrations of haloperidol, clozapine, quetiapine, or risperidone, in their media. After culture for 48h, the cell viabilities and p75(NTR) mRNA levels were measured. It was shown that both haloperidol and the atypical APDs used in this study deceased p75(NTR) mRNA levels in PC12 cells in a dose dependent manner, while not affecting cell viabilities. In further experiments, doses that produced significant/greatest effects were chosen and provided in the culture media for various periods. Decreases in p75(NTR) mRNA levels were observed in cultures treated for 12h with quetiapine, 24h with clozapine or risperidone, or for 48h with haloperidol. These results suggest that both haloperidol and atypical APDs have the same action of decreasing p75(NTR) mRNA levels in PC12 cells. Although the underlying molecular mechanism of this action remains to be elucidated, this finding is particularly relevant given the neurodevelopmental deficits associated with schizophrenia and important roles of p75(NTR) in mediating cell death.

The effects of chronic administration of quetiapine on the phencyclidine-induced reference memory impairment and decrease of Bcl-XL/Bax ratio in the posterior cingulate cortex in rats

Quetiapine, a new atypical antipsychotic drug, effectively alleviates positive and negative symptoms, as well as cognitive impairment that may be caused by neurodegeneration, in schizophrenia patients. Earlier in vivo and in vitro studies have demonstrated that quetiapine may be a neuroprotectant. The present study was designed to examine the beneficial effects of quetiapine on the possible cognitive impairment and changes of brain apoptotic regulation proteins induced by phencyclidine (PCP) in rats. Rats were treated with quetiapine (10 mg/kg/day; intraperitoneal (i.p.)) or vehicle for 16 days. On day 14, 1 h after the administration of quetiapine, the rats were given PCP (50 mg/kg; subcutaneous (s.c.)) or vehicle. Then quetiapine was administrated for an additional 2 days. One day after the last quetiapine injection (3 days after the PCP injection), the rats were trained on a spatial memory task in a radial arm maze. After the behavioural test, the rats were decapitated for Western blot analysis. PCP induced reference memory impairment, and a decrease of the ratio of an anti-apoptotic Bcl-2 family member (Bcl-XL) to a pro-apoptotic analogue (Bax) in the posterior cingulate cortex. Chronic administration of quetiapine counteracted the PCP-induced reference memory impairment and decrease of Bcl-XL/Bax ratio in the posterior cingulate cortex. These results suggest that quetiapine may have ameliorating effects on the cognitive impairment and brain apoptotic processes induced by PCP.