The value of spontaneous alternation behavior (SAB) as a test of retention in pharmacological investigations of memory

Toxoplasma gondii infection, from predation to schizophrenia: can animal behaviour help us understand human behaviour?

We examine the role of the protozoan Toxoplasma gondii as a manipulatory parasite and question what role study of infections in its natural intermediate rodent hosts and other secondary hosts, including humans, may elucidate in terms of the epidemiology, evolution and clinical applications of infection. In particular, we focus on the potential association between T. gondii and schizophrenia. We introduce the novel term 'T. gondii-rat manipulation-schizophrenia model' and propose how future behavioural research on this model should be performed from a biological, clinical and ethically appropriate perspective.

Curcumin suppresses soluble tau dimers and corrects molecular chaperone, synaptic, and behavioral deficits in aged human tau transgenic mice

The mechanisms underlying Tau-related synaptic and cognitive deficits and the interrelationships between Tau species, their clearance pathways, and synaptic impairments remain poorly understood. To gain insight into these mechanisms, we examined these interrelationships in aged non-mutant genomic human Tau mice, with established Tau pathology and neuron loss. We also examined how these interrelationships changed with an intervention by feeding mice either a control diet or one containing the brain permeable beta-amyloid and Tau aggregate binding molecule curcumin. Transgene-dependent elevations in soluble and insoluble phospho-Tau monomer and soluble Tau dimers accompanied deficits in behavior, hippocampal excitatory synaptic markers, and molecular chaperones (heat shock proteins (HSPs)) involved in Tau degradation and microtubule stability. In human Tau mice but not control mice, HSP70, HSP70/HSP72, and HSP90 were reduced in membrane-enriched fractions but not in cytosolic fractions. The synaptic proteins PSD95 and NR2B were reduced in dendritic fields and redistributed into perikarya, corresponding to changes observed by immunoblot. Curcumin selectively suppressed levels of soluble Tau dimers, but not of insoluble and monomeric phospho-Tau, while correcting behavioral, synaptic, and HSP deficits. Treatment increased PSD95 co-immunoprecipitating with NR2B and, independent of transgene, increased HSPs implicated in Tau clearance. It elevated HSP90 and HSC70 without increasing HSP mRNAs; that is, without induction of the heat shock response. Instead curcumin differentially impacted HSP90 client kinases, reducing Fyn without reducing Akt. In summary, curcumin reduced soluble Tau and elevated HSPs involved in Tau clearance, showing that even after tangles have formed, Tau-dependent behavioral and synaptic deficits can be corrected.

Evaluation of the hematoma consequences, neurobehavioral profiles, and histopathology in a rat model of pontine hemorrhage

OBJECT

Primary pontine hemorrhage (PPH) represents approximately 7% of all intracerebral hemorrhages (ICHs) and is a clinical condition of which little is known. The aim of this study was to characterize the early brain injury, neurobehavioral outcome, and long-term histopathology in a novel preclinical rat model of PPH.

METHODS

The authors stereotactically infused collagenase (Type VII) into the ventral pontine tegmentum of the rats, in accordance with the most commonly affected clinical region. Measures of cerebrovascular permeability (brain water content, hemoglobin assay, Evans blue, collagen Type IV, ZO-1, and MMP-2 and MMP-9) and neurological deficit were quantified at 24 hours postinfusion (Experiment 1). Functional outcome was measured over a 30-day period using a vertebrobasilar scale (the modified Voetsch score), open field, wire suspension, beam balance, and inclined-plane tests (Experiment 2). Neurocognitive ability was determined at Week 3 using the rotarod (motor learning), T-maze (working memory), and water maze (spatial learning and memory) (Experiment 3), followed by histopathological analysis 1 week later (Experiment 4).

RESULTS

Stereotactic collagenase infusion caused dose-dependent elevations in hematoma volume, brain edema, neurological deficit, and blood-brain barrier rupture, while physiological variables remained stable. Functional outcomes mostly normalized by Week 3, whereas neurocognitive deficits paralleled the cystic cavitary lesion at 30 days. Obstructive hydrocephalus did not develop despite a clinically relevant 30-day mortality rate (approximately 54%).

CONCLUSIONS

These results suggest that the model can mimic several translational aspects of pontine hemorrhage in humans and can be used in the evaluation of potential preclinical therapeutic interventions.

Long-term cognitive and neurochemical effects of "bath salt" designer drugs methylone and mephedrone

INTRODUCTION/AIMS

The use of cathinone-derivative designer drugs methylone and mephedrone has increased rapidly in recent years. Our aim was to investigate the possible long-term effects of these drugs on a range of behavioral tests in mice. Further, we investigated the long-term effects of these drugs on brain neurochemistry in both rats and mice.

METHODS

We treated animals with a binge-like regimen of methylone or mephedrone (30 mg/kg, twice daily for 4 days) and, starting 2 weeks later, we performed behavioral tests of memory, anxiety and depression and measured brain levels of dopamine (DA), serotonin (5-HT), their metabolites and norepinephrine (NE). 5-HT and DA transporter (5-HTT and DAT) levels were also measured in rats by [(3)H]paroxetine and [(3)H]mazindol binding.

RESULTS

Mephedrone reduced working memory performance in the T-maze spontaneous alternation task but did not affect neurotransmitter levels aside from a 22% decrease in striatal homovanillic acid (HVA) levels in mice. Methylone had little effect on behavior or neurotransmitter levels in mice but produced a widespread depletion of 5-HT and 5-HTT levels in rats.

CONCLUSIONS

Both methylone and mephedrone appeared to have a long-term effect on either behavioral or biochemical gauges of neurotoxicity in rodents.

Role of Abca7 in mouse behaviours relevant to neurodegenerative diseases

ATP-binding cassette transporters of the subfamily A (ABCA) are responsible for the translocation of lipids including cholesterol, which is crucial for neurological function. Recent studies suggest that the ABC transporter ABCA7 may play a role in the development of brain disorders such as schizophrenia and Alzheimer’s disease. However, Abca7’s role in cognition and other behaviours has not been investigated. Therefore, we characterised homozygous Abca7 knockout mice in a battery of tests for baseline behaviours (i.e. physical exam, baseline locomotion and anxiety) and behaviours relevant to schizophrenia (i.e. prepulse inhibition and locomotor response to psychotropic drugs) and Alzheimer’s disease (i.e. cognitive domains). Knockout mice had normal motor functions and sensory abilities and performed the same as wild type-like animals in anxiety tasks. Short-term spatial memory and fear-associated learning was also intact in Abca7 knockout mice. However, male knockout mice exhibited significantly impaired novel object recognition memory. Task acquisition was unaffected in the cheeseboard task. Female mice exhibited impaired spatial reference memory. This phenomenon was more pronounced in female Abca7 null mice. Acoustic startle response, sensorimotor gating and baseline locomotion was unaltered in Abca7 knockout mice. Female knockouts showed a moderately increased motor response to MK-801 than control mice. In conclusion, Abca7 appears to play only a minor role in behavioural domains with a subtle sex-specific impact on particular cognitive domains.

Indomethacin-loaded lipid-core nanocapsules reduce the damage triggered by Aβ1-42 in Alzheimer's disease models

Neuroinflammation, characterized by the accumulation of activated microglia and reactive astrocytes, is believed to modulate the development and/or progression of Alzheimer’s disease (AD). Epidemiological studies suggesting that nonsteroidal anti-inflammatory drugs decrease the risk of developing AD have encouraged further studies elucidating the role of inflammation in AD. Nanoparticles have become an important focus of neurotherapeutic research because they are an especially effective form of drug delivery. Here, we investigate the potential protective effect of indomethacin-loaded lipid-core nanocapsules (IndOH-LNCs) against cell damage and neuroinflammation induced by amyloid beta (Aβ)1-42 in AD models. Our results show that IndOH-LNCs attenuated Aβ-induced cell death and were able to block the neuroinflammation triggered by Aβ1-42 in organotypic hippocampal cultures. Additionally, IndOH-LNC treatment was able to increase interleukin-10 release and decrease glial activation and c-jun N-terminal kinase phosphorylation. As a model of Aβ-induced neurotoxicity in vivo, animals received a single intracerebroventricular injection of Aβ1-42 (1 nmol/site), and 1 day after Aβ1-42 infusion, they were administered either free IndOH or IndOH-LNCs (1 mg/kg, intraperitoneally) for 14 days. Only the treatment with IndOH-LNCs significantly attenuated the impairment of this behavior triggered by intracerebroventricular injection of Aβ1-42. Further, treatment with IndOH-LNCs was able to block the decreased synaptophysin levels induced by Aβ1-42 and suppress glial and microglial activation. These findings might be explained by the increase of IndOH concentration in brain tissue attained using drug-loaded lipid-core NCs. All these findings support the idea that blockage of neuroinflammation triggered by Aβ is involved in the neuroprotective effects of IndOH-LNCs. These data provide strong evidence that IndOH-LNC treatment may represent a promising approach for treating AD.

Cysteamine treatment ameliorates alterations in GAD67 expression and spatial memory in heterozygous reeler mice

Brain-derived neurotrophic factor (BDNF) signalling through its receptor, TrkB is known to regulate GABAergic function and glutamic acid decarboxylase (GAD) 67 expression in neurons. Alterations in BDNF signalling have been implicated in the pathophysiology of schizophrenia and as a result, they are a potential therapeutic target. Interestingly, heterozygous reeler mice (HRM) have decreased GAD67 expression in the frontal cortex and hippocampus and they exhibit many behavioural and neurochemical abnormalities similar to schizophrenia. In this study, we evaluated the potential of cysteamine, a neuroprotective compound to improve the deficits in GAD67 expression and cognitive function in HRM. We found that cysteamine administration (150 mg/kg.d, through drinking water) for 30 d significantly ameliorated the decreases in GAD67, mature BDNF and full-length TrkB protein levels found in frontal cortex and hippocampus of HRM. A significant attenuation of the increased levels of truncated BDNF in frontal cortex and hippocampus, as well as truncated TrkB in frontal cortex of HRM was also observed following cysteamine treatment. In behavioural studies, HRM were impaired in a Y-maze spatial recognition memory task, but not in a spontaneous alternation task or a sensorimotor, prepulse inhibition (PPI) procedure. Cysteamine improved Y-maze spatial recognition in HRM to the level of wide-type controls and it improved PPI in both wild-type and HRM. Finally, mice deficient in TrkB, showed a reduced response to cysteamine in GAD67 expression suggesting that TrkB signalling plays an important role in GAD67 regulation by cysteamine.

Maternal deprivation effects on brain plasticity and recognition memory in adolescent male and female rats

Data from both human and animal studies suggest that exposure to stressful life events at neonatal stages may increase the risk of psychopathology at adulthood. In particular, early maternal deprivation, 24 h at postnatal day (pnd) 9, has been associated with persistent neurobehavioural changes similar to those present in developmental psychopathologies such as depression and schizophrenic-related disorders. Most neuropsychiatric disorders first appear during adolescence, however, the effects of MD on adolescent animals' brain and behaviour have been scarcely explored. In the present study, we aimed to investigate the emotional and cognitive consequences of MD in adolescent male and female rats, as well as possible underlying neurobiological mechanisms within frontal cortex and hippocampus. Animals were exposed to a battery of behavioural tasks, from pnd 35 to 42, to evaluate cognitive [spontaneous alternation task (SAT) and novel object test (NOT)] and anxiety-related responses [elevated plus maze (EPM)] during adolescence. Changes in neuronal and glial cells, alterations in synaptic plasticity as well as modifications in cannabinoid receptor expression were investigated in a parallel group of control and adolescent (pnd 40) male and female animals. Notably, MD induced a significant impairment in recognition memory exclusively among females. A generalized decrease in NeuN expression was found in MD animals, together with an increase in hippocampal glial fibrillar acidic protein (GFAP) expression exclusively among MD adolescent males. In addition, MD induced in the frontal cortex and hippocampus of male and female adolescent rats a significant reduction in brain derived neurotrophic factor (BDNF) and postsynaptic density (PSD95) levels, together with a decrease in synaptophysin in frontal cortex and neural cell adhesion molecule (NCAM) in hippocampus. MD induced, in animals of both sexes, a significant reduction in CB1R expression, but an increase in CB2R that was statistically significant only for the frontal cortex. Taken together, these results indicate that adolescent females are more vulnerable than males to the cognitive deficits derived from MD despite the changes in neural cells, cannabinoid receptors, as well as the reduction in neural plasticity seem to be similar in both sexes. Further investigation is needed to understand the neurobiological mechanisms underlying the sexual dimorphisms associated to the MD effects, and thus, for a better understanding of the specific sex-dependent vulnerabilities to early life stress. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Age-related changes in core body temperature and activity in triple-transgenic Alzheimer's disease (3xTgAD) mice

Alzheimer’s disease (AD) is characterised, not only by cognitive deficits and neuropathological changes, but also by several non-cognitive behavioural symptoms that can lead to a poorer quality of life. Circadian disturbances in core body temperature and physical activity are reported in AD patients, although the cause and consequences of these changes are unknown. We therefore characterised circadian patterns of body temperature and activity in male triple transgenic AD mice (3xTgAD) and non-transgenic (Non-Tg) control mice by remote radiotelemetry. At 4 months of age, daily temperature rhythms were phase advanced and by 6 months of age an increase in mean core body temperature and amplitude of temperature rhythms were observed in 3xTgAD mice. No differences in daily activity rhythms were seen in 4- to 9-month-old 3xTgAD mice, but by 10 months of age an increase in mean daily activity and the amplitude of activity profiles for 3xTgAD mice were detected. At all ages (4–10 months), 3xTgAD mice exhibited greater food intake compared with Non-Tg mice. The changes in temperature did not appear to be solely due to increased food intake and were not cyclooxygenase dependent because the temperature rise was not abolished by chronic ibuprofen treatment. No β-amyloid (Aβ) plaques or neurofibrillary tangles were noted in the hypothalamus of 3xTgAD mice, a key area involved in temperature regulation, although these pathological features were observed in the hippocampus and amygdala of 3xTgAD mice from 10 months of age. These data demonstrate age-dependent changes in core body temperature and activity in 3xTgAD mice that are present before significant AD-related neuropathology and are analogous to those observed in AD patients. The 3xTgAD mouse might therefore be an appropriate model for studying the underlying mechanisms involved in non-cognitive behavioural changes in AD.

Targeting JNK for therapeutic depletion of stem-like glioblastoma cells

Control of the stem-like tumour cell population is considered key to realizing the long-term survival of patients with glioblastoma, one of the most devastating human malignancies. To date, possible therapeutic targets and targeting methods have been described, but none has yet proven to target stem-like glioblastoma cells in the brain to the extent necessary to provide a survival benefit. Here we show that targeting JNK in vivo, the activity of which is required for the maintenance of stem-like glioblastoma cells, via transient, systemic administration of a small-molecule JNK inhibitor depletes the self-renewing and tumour-initiating populations within established tumours, inhibits tumour formation by stem-like glioblastoma cells in the brain, and provide substantial survival benefit without evidence of adverse events. Our findings not only implicate JNK in the maintenance of stem-like glioblastoma cells but also demonstrate that JNK is a viable, clinically relevant therapeutic target in the control of stem-like glioblastoma cells.

Adult-onset focal expression of mutated human tau in the hippocampus impairs spatial working memory of rats

Tauopathy in the hippocampus is one of the earliest cardinal features of Alzheimer's disease (AD), a condition characterized by progressive memory impairments. In fact, density of tau neurofibrillary tangles (NFTs) in the hippocampus strongly correlates with severity of cognitive impairments in AD. In the present study, we employed a somatic cell gene transfer technique to create a rodent model of tauopathy by injecting a recombinant adeno-associated viral vector with a mutated human tau gene (P301L) into the hippocampus of adult rats. The P301L mutation is causal for frontotemporal dementia with parkinsonism-17 (FTDP-17), but it has been used for studying memory effects characteristic of AD in transgenic mice. To ascertain if P301L-induced mnemonic deficits are persistent, animals were tested for 6 months. It was hypothesized that adult-onset, spatially restricted tau expression in the hippocampus would produce progressive spatial working memory deficits on a learned alternation task. Rats injected with the tau vector exhibited persistent impairments on the hippocampal-dependent task beginning at about 6 weeks post-transduction compared to rats injected with a green fluorescent protein vector. Histological analysis of brains for expression of human tau revealed hyperphosphorylated human tau and NFTs in the hippocampus in experimental animals only. Thus, adult-onset, vector-induced tauopathy spatially restricted to the hippocampus progressively impaired spatial working memory in rats. We conclude that the model faithfully reproduces histological and behavioral findings characteristic of dementing tauopathies. The rapid onset of sustained memory impairment establishes a preclinical model particularly suited to the development of potential tauopathy therapeutics.

Wip1 phosphatase positively modulates dendritic spine morphology and memory processes through the p38MAPK signaling pathway

Dendritic spine morphology is modulated by protein kinase p38, a mitogen-activated protein (MAPK), in the hippocampus. Protein p38MAPK is a substrate of wip1, a protein phosphatase. The role of wip1 in the central nervous system (CNS) has never been explored. Here, we report a novel function of wip1 in dendritic spine morphology and memory processes. Wip1 deficiency decreases dendritic spine size and density in pyramidal neurons of the hippocampal CA1 region. Simultaneously, impairments in object recognition tasks and contextual memory occur in wip1 deficient mice, but are reversed in wip1/p38 double mutant mice. Thus, our findings demonstrate that wip1 modulates dendritic morphology and memory processes through the p38MAPK signaling pathway. In addition to the well-characterized role of the wip1/p38MAPK in cell death and differentiation, we revealed the novel contribution of wip1 to cognition and dendritic spine morphology, which may suggest new approaches to treating neurodegenerative disorders.

Haploinsufficiency of the E3 ubiquitin ligase C-terminus of heat shock cognate 70 interacting protein (CHIP) produces specific behavioral impairments

The multifunctional E3 ubiquitin ligase CHIP is an essential interacting partner of HSP70, which together promote the proteasomal degradation of client proteins. Acute CHIP overexpression provides neuroprotection against neurotoxic mitochondrial stress, glucocorticoids, and accumulation of toxic amyloid fragments, as well as genetic mutations in other E3 ligases, which have been shown to result in familial Parkinson's disease. These studies have created a great deal of interest in understanding CHIP activity, expression and modulation. While CHIP knockout mice have the potential to provide essential insights into the molecular control of cell fate and survival, the animals have been difficult to characterize in vivo due to severe phenotypic and behavioral dysfunction, which have thus far been poorly characterized. Therefore, in the present study we conducted a battery of neurobehavioral and physiological assays of adult CHIP heterozygotic (HET) mutant mice to provide a better understanding of the functional consequence of CHIP deficiency. We found that CHIP HET mice had normal body and brain weight, body temperature, muscle tone and breathing patterns, but do have a significant elevation in baseline heart rate. Meanwhile basic behavioral screens of sensory, motor, emotional and cognitive functions were normative. We observed no alterations in performance in the elevated plus maze, light-dark preference and tail suspension assays, or two simple cognitive tasks: novel object recognition and spontaneous alternation in a Y maze. Significant deficits were found, however, when CHIP HET mice performed wire hang, inverted screen, wire maneuver, and open field tasks. Taken together, our data indicate a clear subset of behaviors that are altered at baseline in CHIP deficient animals, which will further guide whole animal studies of the effects of CHIP dysregulation on cardiac function, brain circuitry and function, and responsiveness to environmental and cellular stress.

Development of hyperactivity and anxiety responses in dopamine transporter-deficient mice

Dopamine (DA) is a catecholamine neurotransmitter that regulates many aspects of motivated behavior in animals. Extracellular DA is highly regulated by the presynaptic high-affinity dopamine transporter (DAT), and drug- or genetically induced deficiencies in DAT function result in loss of DA reuptake. Mice in which DAT expression has been ablated have been previously proposed to be a relevant model of attention deficit hyperactivity disorder and have led to mechanistic insights regarding psychostimulant drug actions. However, very little previous work has emphasized the biobehavioral development of DAT-deficient mice. We therefore examined motoric, emotional and cognitive phenotypes in preadolescent (P22-26) DAT mutant mice. Consistent with previous reports in adult DAT(-/-) mice, we observed a hyperlocomotive phenotype in preadolescent mice across multiple assays. Somewhat surprisingly, spatial working memory in a Y-maze appeared intact, suggesting that cognitive phenotypes may emerge relatively late in development following hyperdopaminergia. Anxiety levels appeared to be reduced in DAT(-/-) mice, as defined by elevated plus maze and light-dark preference assays. No significant differences were observed between wild-type and heterozygous mice, suggesting a minimal impact of DAT haploinsufficiency on neurobehavioral status. Taken together, these data for the first time establish behavioral phenotypes of DAT mutant mice during development and suggest complex developmental stage-dependent effects of DA signaling on cognitive and emotional behaviors.

The microtubule-stabilizing agent, epothilone D, reduces axonal dysfunction, neurotoxicity, cognitive deficits, and Alzheimer-like pathology in an interventional study with aged tau transgenic mice

Neurodegenerative tauopathies, such as Alzheimer's disease (AD), are characterized by insoluble deposits of hyperphosphorylated tau protein within brain neurons. Increased phosphorylation and decreased solubility has been proposed to diminish normal tau stabilization of microtubules (MTs), thereby leading to neuronal dysfunction. Earlier studies have provided evidence that small molecule MT-stabilizing drugs that are used in the treatment of cancer may have utility in the treatment of tauopathies. However, it has not been established whether treatment with a small molecule MT-stabilizing compound will provide benefit in a transgenic model with pre-existing tau pathology, as would be seen in human patients with clinical symptoms. Accordingly, we describe here an interventional study of the brain-penetrant MT-stabilizing agent, epothilone D (EpoD), in aged PS19 mice with existing tau pathology and related behavioral deficits. EpoD treatment reduced axonal dystrophy and increased axonal MT density in the aged PS19 mice, which led to improved fast axonal transport and cognitive performance. Moreover, the EpoD-treated PS19 mice had less forebrain tau pathology and increased hippocampal neuronal integrity, with no dose-limiting side effects. These data reveal that brain-penetrant MT-stabilizing drugs hold promise for the treatment of AD and related tauopathies, and that EpoD could be a candidate for clinical testing.

Over-expression of RCAN1 causes Down syndrome-like hippocampal deficits that alter learning and memory

People with Down syndrome (DS) exhibit abnormal brain structure. Alterations affecting neurotransmission and signalling pathways that govern brain function are also evident. A large number of genes are simultaneously expressed at abnormal levels in DS; therefore, it is a challenge to determine which gene(s) contribute to specific abnormalities, and then identify the key molecular pathways involved. We generated RCAN1-TG mice to study the consequences of RCAN1 over-expression and investigate the contribution of RCAN1 to the brain phenotype of DS. RCAN1-TG mice exhibit structural brain abnormalities in those areas affected in DS. The volume and number of neurons within the hippocampus is reduced and this correlates with a defect in adult neurogenesis. The density of dendritic spines on RCAN1-TG hippocampal pyramidal neurons is also reduced. Deficits in hippocampal-dependent learning and short- and long-term memory are accompanied by a failure to maintain long-term potentiation (LTP) in hippocampal slices. In response to LTP induction, we observed diminished calcium transients and decreased phosphorylation of CaMKII and ERK1/2-proteins that are essential for the maintenance of LTP and formation of memory. Our data strongly suggest that RCAN1 plays an important role in normal brain development and function and its up-regulation likely contributes to the neural deficits associated with DS.

Rodent neonatal germinal matrix hemorrhage mimics the human brain injury, neurological consequences, and post-hemorrhagic hydrocephalus

Germinal matrix hemorrhage (GMH) is the most common neurological disease of premature newborns. GMH causes neurological sequelae such as cerebral palsy, post-hemorrhagic hydrocephalus, and mental retardation. Despite this, there is no standardized animal model of spontaneous GMH using newborn rats to depict the condition. We asked whether stereotactic injection of collagenase type VII (0.3 U) into the ganglionic eminence of neonatal rats would reproduce the acute brain injury, gliosis, hydrocephalus, periventricular leukomalacia, and attendant neurological consequences found in humans. To test this hypothesis, we used our neonatal rat model of collagenase-induced GMH in P7 pups, and found that the levels of free-radical adducts (nitrotyrosine and 4-hyroxynonenal), proliferation (mammalian target of rapamycin), inflammation (COX-2), blood components (hemoglobin and thrombin), and gliosis (vitronectin and GFAP) were higher in the forebrain of GMH pups, than in controls. Neurobehavioral testing showed that pups with GMH had developmental delay, and the juvenile animals had significant cognitive and motor disability, suggesting clinical relevance of the model. There was also evidence of white-matter reduction, ventricular dilation, and brain atrophy in the GMH animals. This study highlights an instructive animal model of the neurological consequences after germinal matrix hemorrhage, with evidence of brain injuries that can be used to evaluate strategies in the prevention and treatment of post-hemorrhagic complications.

Thiamine deficiency degrades the link between spatial behavior and hippocampal synapsin I and phosphorylated synapsin I protein levels

The links between spatial behavior and hippocampal levels of synapsin I and phosphosynapsin I were assessed in normal rats and in the pyrithiamine-induced thiamine deficiency (PTD) rat model of Wernicke-Korsakoff's syndrome. Synapsin I tethers small synaptic vesicles to the actin cytoskeleton in a phosphorylation-dependent manner, is involved in neurotransmitter release and has been implicated in hippocampal-dependent learning. Positive correlations between spontaneous alternation behavior and hippocampal levels of both synapsin I and phosphorylated synapsin I were found in control rats. However, spontaneous alternation performance was impaired in PTD rats and was accompanied by a significant reduction (30%) in phosphorylated synapsin I. Furthermore, no correlations were observed between either form of synapsin I and behavior in PTD rats. These data suggest that successful spontaneous alternation performance is related to high levels of hippocampal synapsin I and phosphorylated synapsin I. These results not only support the previous findings that implicate impaired hippocampal neurotransmission in the spatial learning and memory deficits associated with thiamine deficiency, but also suggest a presynaptic mechanism.

Late effects of a perinatal exposure to a 16 PAH mixture: Increase of anxiety-related behaviours and decrease of regional brain metabolism in adult male rats

Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous pollutants originated from incomplete combustion processes. Ingestion of contaminated food is the main route of exposure for humans. These molecules are able to cross the placental barrier and are also found in breast milk. Since PAHs are neurotoxic agents, the potential adverse effects of a perinatal exposure of the developing brain is a key issue for public health especially concerning PAH mixture. In this study, female rats were exposed trough diet to a mixture of 16 PAHs, at doses of 2 μg/kg/day or 200 μg/kg/day during gestation and 1.5 μg/kg/day or 150 μg/kg/day during breast-feeding period. To assess late neurotoxic effects in male offsprings, behavioural and cognitive tests were carried out and histochemical analyses using cytochrome oxidase as a cerebral metabolism marker were performed on adult animals. Results showed that anxiety-related behaviours significantly increased in exposed animals, but there was no significant alteration of motor activity and learning and memory abilities. Several brain areas of the limbic system showed a neuronal hypometabolism in exposed animals. This work highlights that exposure to PAHs at early stages of brain development can cause later troubles on behaviour and that PAHs are able to partly alter the central nervous system metabolism on adulthood.

Thy1-hAPP(Lond/Swe+) mouse model of Alzheimer's disease displays broad behavioral deficits in sensorimotor, cognitive and social function

Alzheimer's disease (AD), the most common form of dementia, is an age-dependent progressive neurodegenerative disorder. β-amyloid, a metabolic product of the amyloid precursor protein (APP), plays an important role in the pathogenesis of AD. The Thy1-hAPP(Lond/Swe+) (line 41) transgenic mouse overexpresses human APP751 and contains the London (V717I) and Swedish (K670M/N671L) mutations. Here, we used a battery of behavioral tests to evaluate general activity, cognition, and social behavior in six-month-old male Thy1-hAPP(Lond/Swe+) mice. We found hyperactivity in a novel environment as well as significant deficits in spontaneous alternation behavior. In fear conditioning (FC), Thy1-hAPP(Lond/Swe+) mice did not display deficits in acquisition or in memory retrieval in novel context of tone-cued FC, but they showed significant memory retrieval impairment during contextual testing in an identical environment. Surprisingly, in a standard hidden platform water maze, no significant deficit was detected in mutant mice. However, a delayed-matching-to-place paradigm revealed a significant deficit in Thy1-hAPP(Lond/Swe+) mice. Lastly, in the social novelty session of a three-chamber test, Thy1-hAPP(Lond/Swe+) mice exhibited a significantly decreased interest in a novel versus a familiar stranger compared to control mice. This could possibly be explained by decreased social memory or discrimination and may parallel disturbances in social functioning in human AD patients. In conclusion, the Thy1-hAPP(Lond/Swe+) mouse model of AD displayed a behavioral phenotype that resembles, in part, the cognitive and psychiatric symptoms experienced in AD patients.

Lactate produced by glycogenolysis in astrocytes regulates memory processing

When administered either systemically or centrally, glucose is a potent enhancer of memory processes. Measures of glucose levels in extracellular fluid in the rat hippocampus during memory tests reveal that these levels are dynamic, decreasing in response to memory tasks and loads; exogenous glucose blocks these decreases and enhances memory. The present experiments test the hypothesis that glucose enhancement of memory is mediated by glycogen storage and then metabolism to lactate in astrocytes, which provide lactate to neurons as an energy substrate. Sensitive bioprobes were used to measure brain glucose and lactate levels in 1-sec samples. Extracellular glucose decreased and lactate increased while rats performed a spatial working memory task. Intrahippocampal infusions of lactate enhanced memory in this task. In addition, pharmacological inhibition of astrocytic glycogenolysis impaired memory and this impairment was reversed by administration of lactate or glucose, both of which can provide lactate to neurons in the absence of glycogenolysis. Pharmacological block of the monocarboxylate transporter responsible for lactate uptake into neurons also impaired memory and this impairment was not reversed by either glucose or lactate. These findings support the view that astrocytes regulate memory formation by controlling the provision of lactate to support neuronal functions.

Prenatal Cocaine Disrupts Serotonin Signaling-Dependent Behaviors: Implications for Sex Differences, Early Stress and Prenatal SSRI Exposure

Prenatal cocaine (PC) exposure negatively impacts the developing nervous system, including numerous changes in serotonergic signaling. Cocaine, a competitive antagonist of the serotonin transporter, similar to selective serotonin reuptake inhibitors (SSRIs), also blocks dopamine and norepinephrine transporters, leaving the direct mechanism through which cocaine disrupts the developing serotonin system unclear. In order to understand the role of the serotonin transporter in cocaine's effect on the serotonergic system, we compare reports concerning PC and prenatal antidepressant exposure and conclude that PC exposure affects many facets of serotonergic signaling (serotonin levels, receptors, transporters) and that these effects differ significantly from what is observed following prenatal SSRI exposure. Alterations in serotonergic signaling are dependent on timing of exposure, test regimens, and sex. Following PC exposure, behavioral disturbances are observed in attention, emotional behavior and stress response, aggression, social behavior, communication, and like changes in serotonergic signaling, these effects depend on sex, age and developmental exposure. Vulnerability to the effects of PC exposure can be mediated by several factors, including allelic variance in serotonergic signaling genes, being male (although fewer studies have investigated female offspring), and experiencing the adverse early environments that are commonly coincident with maternal drug use. Early environmental stress results in disruptions in serotonergic signaling analogous to those observed with PC exposure and these may interact to produce greater behavioral effects observed in children of drug-abusing mothers. We conclude that based on past evidence, future studies should put a greater emphasis on including females and monitoring environmental factors when studying the impact of PC exposure.

Nicotine reverses anhedonic-like response and cognitive impairment in the rat chronic mild stress model of depression: comparison with sertraline

Smoking rates among depressed individuals are higher than is observed in the background population, and nicotine alleviates depressive symptoms. In rodents, nicotine shows antidepressant-like effects in the forced swim and learned helplessness paradigms. Clinical depression is associated with both anhedonia and cognitive impairments. In rats, chronic mild stress (CMS) decreases voluntary sucrose intake, reflecting an anhedonic-like state, and impairs performance in the spontaneous alternation behaviour (SAB) test, suggesting impaired cognitive function. Here, we examine the effect of chronic treatment of nicotine (0.4 mg/kg/day) and sertraline (5 mg/kg/day) on CMS-induced anhedonic-like behaviour and impairment in the SAB test. Nicotine and sertraline administered individually or in combination show significant and equally efficacious reversal of the CMS-induced decrease in sucrose intake, implying there is no additive or synergistic effect of the nicotine + sertraline combination. In the SAB test, nicotine, but not sertraline or nicotine + sertraline, reversed the CMS-induced impairment. The present results show that the effect of nicotine on a CMS-induced anhedonic-like state in rats is similar to that of a standard antidepressant drug. Moreover, the data suggest that nicotine alleviates CMS-induced cognitive disturbance. A treatment strategy involving the targeting of nicotinic acetylcholine receptors may prove beneficial for emotional and cognitive disturbances associated with depression.

Analysis of sensory, motor and cognitive functions of the coloboma (C3Sn.Cg-Cm/J) mutant mouse

The coloboma mutant mouse (C3Sn.Cg-Cm/J) has been proposed as an animal model of attention-deficit hyperactivity disorder (ADHD) because of excessive locomotion in the open field, yet few studies have looked at other behavioral measures in these mice. We analyzed activity levels of male and female Cm mice and their littermate controls (C3H) in two different types of open field, as well as their hearing (acoustic startle) and sensorimotor gating (prepulse inhibition), pain responsiveness (tail flick and hot plate), motor control (balance beam), motor learning (Rotarod), hippocampal working memory (spontaneous alternation in a Y-maze) and olfactory learning and memory (conditioned odor preference). We found hyperactivity and a lack of habituation in the small and large open fields and a deficit in prepulse inhibition in these mice, as well as a learning deficit in male Cm mice in conditioned odor preference but no deficits in pain perception or spontaneous alternation. Results from the rotarod and balance beam tasks indicate that Cm mice have severe motor co-ordination and balance problems compared to their C3H littermates, suggesting that Cm mice may be a more suitable model of ataxia than ADHD.

Mouse models of genetic effects on cognition: relevance to schizophrenia

Cognitive dysfunction is a core feature of schizophrenia. Growing evidence indicates that a wide variety of genetic mutations and polymorphisms impact cognition and may thus be implicated in various aspects of this mental disorder. Despite differences between human and rodent brain structure and function, genetic mouse models have contributed critical information about brain mechanisms involved in cognitive processes. Here, we summarize discoveries of genetic modifications in mice that impact cognition. Based on functional hypotheses, gene modifications within five model systems are described: 1) dopamine (D1, D2, D3, D4, D5, DAT, COMT, MAO); 2) glutamate (GluR-A, NR1, NR2A, NR2B, GRM2, GRM3, GLAST); 3) GABA (α(5), γ(2), α(4), δGABA(A), GABA(B(1)), GAT1); 4) acetylcholine (nAChRβ2, α7, CHRM1); and 5) calcium (CaMKII-α, neurogranin, CaMKKβ, CaMKIV). We also consider other risk-associated genes for schizophrenia such as dysbindin (DTNBP1), neuregulin (NRG1), disrupted-in-schizophrenia1 (DISC1), reelin and proline dehydrogenase (PRODH). Because of the presumed importance of environmental factors, we further consider genetic modifications within the stress-sensitive systems of corticotropin-releasing factor (CRF), brain-derived neurotrophic factor (BDNF) and the endocannabinoid systems. We highlight the missing information and limitations of cognitive assays in genetically modified mice models relevant to schizophrenia pathology.

Protective effect of Zhen-Wu-Tang (ZWT) through keeping DA stable and VMAT 2/DAT mRNA in balance in rats with striatal lesions induced by MPTP

ETHNOPHARMACOLOGICAL RELEVANCE

Zhen-Wu-Tang (ZWT), the modified formulation of a classical Chinese prescription from "Treaties on Febrile Disease", was clinically employed to treat Parkinson's disease.

AIM OF THE STUDY

To investigate the neuroprotective effect of ZWT on intra-striatum injection of MPTP-induced Parkinson's disease in rats.

MATERIALS AND METHODS

The effect of ZWT on the behavioral changes (open-field test, Ladder walking, spontaneous alternation in Y maze), the dopamine transmitter systems of substantia nigra, striatum and frontal cortex of rats by HPLC-ECD, mRNA expression of tyrosine hydroxylase (TH), dopamine transporter (DAT) and vesicular monoamine transporter 2 (VMAT 2) of the above three brain regions was investigated.

RESULTS

This study showed that ZWT not only ameliorated the behavior induced by the administration of MPTP in striatum, but also increased DA in the brain, prevented the decreasing of TH and balanced the ratio of VMAT 2/DAT in mRNA level.

CONCLUSIONS

These results suggest that ZWT possesses neuroprotective and anti-parkinsonism properties.

Genetic-background modulation of core and variable autistic-like symptoms in Fmr1 knock-out mice

BACKGROUND

No animal models of autism spectrum disorders (ASD) with good construct validity are currently available; using genetic models of pathologies characterized by ASD-like deficits, but with known causes, may be therefore a promising strategy. The Fmr1-KO mouse is an example of this approach, modeling Fragile X syndrome, a well-known genetic disorder presenting ASD symptoms. The Fmr1-KO is available on different genetic backgrounds (FVB versus C57BL/6), which may explain some of the conflicting results that have been obtained with these mutants up till now.

METHODS

Fmr1 KO and their wild-type littermates on both the FVB and C57BL/6 genetic backgrounds were examined on a battery of tests modeling the clinical symptoms of ASD, including the triad of core symptoms (alterations in social interaction and communication, presence of repetitive behaviors), as well as the secondary symptoms (disturbances in sensori-motor reactivity and in circadian patterns of activity, epileptic events).

RESULTS

Fmr1-KO mice displayed autistic-like core symptoms of altered social interaction and occurrence of repetitive behaviors with additional hyperactivity. The genetic background modulated the effects of the Fmr1 deletion and it appears that the C57BL/6 background may be more suitable for further research on core autistic-like symptoms.

CONCLUSIONS

The Fmr1-mouse line does not recapitulate all of the main core and secondary ASD symptoms, but still can be useful to elucidate the neurobiological mechanisms underlying specific ASD-like endophenotypes.

Protective effect of hydrogen gas therapy after germinal matrix hemorrhage in neonatal rats

BACKGROUND

Germinal matrix hemorrhage (GMH) is a neurological disease of very low birth weight premature infants leading to post-hemorrhagic hydrocephalus, cerebral palsy, and mental retardation. Hydrogen (H2) is a potent antioxidant shown to selectively reverse cytotoxic oxygen-radical injury in the brain. This study investigated the therapeutic effect of hydrogen gas after neonatal GMH injury.

METHODS

Neonatal rats underwent stereotaxic infusion of clostridial collagenase into the right germinal matrix brain region. Cognitive function was assessed at 3 weeks, and then sensorimotor function, cerebral, cardiac and splenic growths were measured 1 week thereafter.

RESULTS

Hydrogen gas inhalation markedly suppressed mental retardation and cerebral palsy outcomes in rats at the juvenile developmental stage. The administration of H2 gas, early after neonatal GMH, also normalized the brain atrophy, splenomegaly and cardiac hypertrophy 1 month after injury.

CONCLUSION

This study supports the role of cytotoxic oxygen-radical injury in early neonatal GMH. Hydrogen gas inhalation is an effective strategy to help protect the infant brain from the post-hemorrhagic consequences of brain atrophy, mental retardation and cerebral palsy. Further studies are necessary to determine the mechanistic basis of these protective effects.

A novel preclinical model of germinal matrix hemorrhage using neonatal rats

BACKGROUND

Germinal matrix hemorrhage (GMH) is a neurological disorder associated with very low birth weight premature infants. This event can lead to post-hemorrhagic hydrocephalus, cerebral palsy, and mental retardation. This study developed a novel animal model for pre-clinical investigations.

METHODS

Neonatal rats underwent infusion of clostridial collagenase into the right germinal matrix (anterior caudate) region using stereotaxic techniques. Developmental milestones were evaluated over 10 days, cognitive function at 3 weeks, and sensorimotor function at 4 weeks after collagenase infusion. This was accomplished by anthropometric quantifications of cranial, cerebral, cardiac, and splenic growths.

RESULTS

Collagenase infusion led to delays in neonatal developmental milestones, followed by cognitive and sensorimotor dysfunctions in the juvenile animals. Cranial growth was accelerated during the first week after injury, and this was followed by significant brain atrophy, splenomegaly, and cardiac hypertrophy 3 weeks later.

CONCLUSION

This study characterized the developmental delays, mental retardation, and cerebral palsy features resembling the long-term clinical course after germinal matrix hemorrhage in premature infants. Pre-clinical testing of therapeutics in this experimental model could lead to improved patient outcomes while expanding upon the pathophysiological understanding of this disease.

Beneficial effect of hyperbaric oxygenation after neonatal germinal matrix hemorrhage

BACKGROUND

Germinal matrix hemorrhage (GMH) is a potentially devastating neurological disease of very low birth weight premature infants. This leads to post-hemorrhagic hydrocephalus, cerebral palsy, and mental retardation. Hyperbaric oxygen (HBO) treatment is a broad neuroprotectant after brain injury. This study investigated the therapeutic effect of HBO after neonatal GMH.

METHODS

Neonatal rats underwent stereotaxic infusion of clostridial collagenase into the right germinal matrix (anterior caudate) brain region. Cognitive function was assessed at 3 weeks, and then sensorimotor, cerebral, cardiac, and splenic growths were measured 1 week thereafter.

RESULTS

Hyperbaric oxygen (HBO) treatment markedly improved upon the mental retardation and cerebral palsy outcome measurements in rats at the juvenile developmental stage. The administration of HBO early after neonatal GMH also normalized brain atrophy, splenomegaly, and cardiac hypertrophy 1 month after injury.

CONCLUSION

This study supports the role of hyperbaric oxygen (HBO) treatment in the early period after neonatal GMH. HBO is an effective strategy to help protect the infant's brain from the post-hemorrhagic consequences of brain atrophy, mental retardation, and cerebral palsy. Further studies are necessary to determine the mechanistic basis of these neuroprotective effects.

Neuroprotection by melatonin after germinal matrix hemorrhage in neonatal rats

BACKGROUND

Germinal matrix hemorrhage (GMH) is a devastating neurological disorder of very low birth weight premature infants that leads to post-hemorrhagic hydrocephalus, cerebral palsy, and mental retardation. Melatonin is a potent antioxidant known to reverse free-radical mediated injury in the brain. This study investigated the effect of melatonin treatment after GMH injury.

METHODS

Clostridial collagenase was infused into the right germinal matrix region of neonatal rats with stereotaxic technique. Cognitive function, sensorimotor ability, cerebral, cardiac and splenic growths were measured in juvenile animals.

RESULTS

Systemic melatonin treatment ameliorated cognitive and sensorimotor dysfunction at the juvenile developmental stage. This hormone also normalized brain atrophy, splenomegaly, and cardiac hypertrophy consequences at 1 month after injury.

CONCLUSION

This study supports the role of free radicals in acute neonatal hemorrhagic brain injury. Melatonin is an effective antioxidant that can protect the infant's brain from the post-hemorrhagic consequences of mental retardation and cerebral palsy. Further mechanistic studies are warranted to determine the mechanisms behind these neuroprotective effects.

APP transgenic mice: their use and limitations

Alzheimer's disease is the most widespread form of dementia. Its histopathological hallmarks include vascular and extracellular β-amyloid (Aβ) deposition and intraneuronal neurofibrillary tangles (NFTs). Gradual decline of cognitive functions linked to progressive synaptic loss makes patients unable to store new information in the earlier stages of the pathology, later becoming completely dependent because they are unable to do even elementary daily life actions. Although more than a hundred years have passed since Alois Alzheimer described the first case of AD, and despite many years of intense research, there are still many crucial points to be discovered in the neuropathological pathway. The development of transgenic mouse models engineered with overexpression of the amyloid precursor protein carrying familial AD mutations has been extremely useful. Transgenic mice present the hallmarks of the pathology, and histological and behavioural examination supports the amyloid hypothesis. As in human AD, extracellular Aβ deposits surrounded by activated astrocytes and microglia are typical features, together with synaptic and cognitive defects. Although animal models have been widely used, they are still being continuously developed in order to recapitulate some missing aspects of the disease. For instance, AD therapeutic agents tested in transgenic mice gave encouraging results which, however, were very disappointing in clinical trials. Neuronal cell death and NFTs typical of AD are much harder to replicate in these mice, which thus offer a fundamental but still imperfect tool for understanding and solving dementia pathology.

Danish dementia mice suggest that loss of function and not the amyloid cascade causes synaptic plasticity and memory deficits

According to the prevailing "amyloid cascade hypothesis," genetic dementias such as Alzheimer's disease and familial Danish dementia (FDD) are caused by amyloid deposits that trigger tauopathy, neurodegeneration, and behavioral/cognitive alterations. To efficiently reproduce amyloid lesions, murine models of human dementias invariably use transgenic expression systems. However, recent FDD transgenic models showed that Danish amyloidosis does not cause memory defects, suggesting that other mechanisms cause Danish dementia. We studied an animal knock-in model of FDD (FDD(KI/+)) genetically congruous with human cases. FDD(KI/+) mice present reduced Bri2 levels, impaired synaptic plasticity and severe hippocampal memory deficits. These animals show no cerebral lesions that are reputed characteristics of human dementia, such as tangles or amyloid plaques. Bri2(+/-) mice exhibit synaptic and memory deficits similar to FDD(KI/+) mice, and memory loss of FDD(KI/+) mice is prevented by expression of WT BRI2, indicating that Danish dementia is caused by loss of BRI2 function. Together, the data suggest that clinical dementia in Danish patients occurs via a loss of function mechanism and not as a result of amyloidosis and tauopathy.

Regulation of tau pathology by the microglial fractalkine receptor

Aggregates of the hyperphosphorylated microtubule-associated protein tau (MAPT) are an invariant neuropathological feature of tauopathies. Here, we show that microglial neuroinflammation promotes MAPT phosphorylation and aggregation. First, lipopolysaccharide-induced microglial activation promotes hyperphosphorylation of endogenous mouse MAPT in nontransgenic mice that is further enhanced in mice lacking the microglial-specific fractalkine receptor (CX3CR1) and is dependent upon functional toll-like receptor 4 and interleukin-1 (IL-1) receptors. Second, humanized MAPT transgenic mice lacking CX3CR1 exhibited enhanced MAPT phosphorylation and aggregation as well as behavioral impairments that correlated with increased levels of active p38 MAPK. Third, in vitro experiments demonstrate that microglial activation elevates the level of active p38 MAPK and enhances MAPT hyperphosphorylation within neurons that can be blocked by administration of an interleukin-1 receptor antagonist and a specific p38 MAPK inhibitor. Taken together, our results suggest that CX3CR1 and IL-1/p38 MAPK may serve as novel therapeutic targets for human tauopathies.

Chronic adolescent exposure to Δ-9-tetrahydrocannabinol in COMT mutant mice: impact on psychosis-related and other phenotypes

Cannabis use confers a two-fold increase in the risk for psychosis, with adolescent use conferring even greater risk. A high-low activity catechol-O-methyltransferase (COMT) polymorphism may modulate the effects of adolescent Δ-9-tetrahydrocannabinol (THC) exposure on the risk for adult psychosis. Mice with knockout of the COMT gene were treated chronically with THC (4.0 and 8.0 mg/kg over 20 days) during either adolescence (postnatal days (PDs) 32-52) or adulthood (PDs 70-90). The effects of THC exposure were then assessed in adulthood across behavioral phenotypes relevant for psychosis: exploratory activity, spatial working memory (spontaneous and delayed alternation), object recognition memory, social interaction (sociability and social novelty preference), and anxiety (elevated plus maze). Adolescent THC administration induced a larger increase in exploratory activity, greater impairment in spatial working memory, and a stronger anti-anxiety effect in COMT knockouts than in wild types, primarily among males. No such effects of selective adolescent THC administration were evident for other behaviors. Both object recognition memory and social novelty preference were disrupted by either adolescent or adult THC administration, independent of genotype. The COMT genotype exerts specific modulation of responsivity to chronic THC administration during adolescence in terms of exploratory activity, spatial working memory, and anxiety. These findings illuminate the interaction between genes and adverse environmental exposures over a particular stage of development in the expression of the psychosis phenotype.

Characterization of the brain injury, neurobehavioral profiles, and histopathology in a rat model of cerebellar hemorrhage

Spontaneous cerebellar hemorrhage (SCH) represents approximately 10% of all intracerebral hemorrhage (ICH) and is an important clinical problem of which little is known. This study stereotaxically infused collagenase (type VII) into the deep cerebellar paramedian white matter, which corresponds to the most common clinical injury region. Measures of hemostasis (brain water, hemoglobin assay, Evans blue, collagen-IV, ZO-1, and MMP-2 and MMP-9) and neurodeficit were quantified 24 hours later (Experiment 1). Long-term functional outcomes were measured over 30 days using the ataxia scale (modified Luciani), open field, wire suspension, beam balance, and inclined plane (Experiment 2). Neurocognitive ability was assessed on the third week using the rotarod (motor learning), T maze (working memory), and water maze (spatial learning and memory) (Experiment 3), followed by a histopathological analysis 1 week later (Experiment 4). Stereotaxic collagenase infusion caused dose-dependent elevations in brain edema, neurodeficit, hematoma volume, and blood-brain barrier rupture, while physiological variables remained stable. Most functional outcomes normalized by the third week, while neurocognitive testing showed deficits parallel to the cystic-cavitary lesion at 30 days. All animals survived until sacrifice, and obstructive hydrocephalus did not develop. These results suggest that the model can generate important translational information about this subtype of ICH and could be used for future investigations of therapeutic mechanisms after cerebellar hemorrhage.

SIRT1 is essential for normal cognitive function and synaptic plasticity

Conservation of normal cognitive functions relies on the proper performance of the nervous system at the cellular and molecular level. The mammalian nicotinamide-adenine dinucleotide-dependent deacetylase SIRT1 impacts different processes potentially involved in the maintenance of brain integrity, such as chromatin remodeling, DNA repair, cell survival, and neurogenesis. Here we show that SIRT1 is expressed in neurons of the hippocampus, a key structure in learning and memory. Using a combination of behavioral and electrophysiological paradigms, we analyzed the effects of SIRT1 deficiency and overexpression on mouse learning and memory as well as on synaptic plasticity. We demonstrated that the absence of SIRT1 impaired cognitive abilities, including immediate memory, classical conditioning, and spatial learning. In addition, we found that the cognitive deficits in SIRT1 knock-out (KO) mice were associated with defects in synaptic plasticity without alterations in basal synaptic transmission or NMDA receptor function. Brains of SIRT1-KO mice exhibited normal morphology and dendritic spine structure but displayed a decrease in dendritic branching, branch length, and complexity of neuronal dendritic arbors. Also, a decrease in extracellular signal-regulated kinase 1/2 phosphorylation and altered expression of hippocampal genes involved in synaptic function, lipid metabolism, and myelination were detected in SIRT1-KO mice. In contrast, mice with high levels of SIRT1 expression in brain exhibited regular synaptic plasticity and memory. We conclude that SIRT1 is indispensable for normal learning, memory, and synaptic plasticity in mice.

A behavioural comparison of acute and chronic Delta9-tetrahydrocannabinol and cannabidiol in C57BL/6JArc mice

Cannabis contains over 70 unique compounds and its abuse is linked to an increased risk of developing schizophrenia. The behavioural profiles of the psychotropic cannabis constituent Delta9-tetrahydrocannabinol (Delta9-THC) and the non-psychotomimetic constituent cannabidiol (CBD) were investigated with a battery of behavioural tests relevant to anxiety and positive, negative and cognitive symptoms of schizophrenia. Male adult C57BL/6JArc mice were given 21 daily intraperitoneal injections of vehicle, Delta9-THC (0.3, 1, 3 or 10 mg/kg) or CBD (1, 5, 10 or 50 mg/kg). Delta9-THC produced the classic cannabinoid CB1 receptor-mediated tetrad of hypolocomotion, analgesia, catalepsy and hypothermia while CBD had modest hyperthermic effects. While sedative at this dose, Delta9-THC (10 mg/kg) produced locomotor-independent anxiogenic effects in the open-field and light-dark tests. Chronic CBD produced moderate anxiolytic-like effects in the open-field test at 50 mg/kg and in the light-dark test at a low dose (1 mg/kg). Acute and chronic Delta9-THC (10 mg/kg) decreased the startle response while CBD had no effect. Prepulse inhibition was increased by acute treatment with Delta9-THC (0.3, 3 and 10 mg/kg) or CBD (1, 5 and 50 mg/kg) and by chronic CBD (1 mg/kg). Chronic CBD (50 mg/kg) attenuated dexamphetamine (5 mg/kg)-induced hyperlocomotion, suggesting an antipsychotic-like action for this cannabinoid. Chronic Delta9-THC decreased locomotor activity before and after dexamphetamine administration suggesting functional antagonism of the locomotor stimulant effect. These data provide the first evidence of anxiolytic- and antipsychotic-like effects of chronic but not acute CBD in C57BL/6JArc mice, extending findings from acute studies in other inbred mouse strains and rats.

Long-term evaluation of granulocyte-colony stimulating factor on hypoxic-ischemic brain damage in infant rats

PURPOSE

Hypoxia-ischemia (HI), as a major cause of fetal brain damage, has long-lasting neurological implications. Therefore, therapeutic interventions that attenuate the neuropathological outcome of HI while also improving the neurofunctional outcome are of paramount clinical importance. The aim of this study was to investigate the long-term functional and protective actions of granulocyte-colony stimulating factor (G-CSF) treatment in an experimental model of cerebral HI.

METHODS

Postnatal day-7 Sprague-Dawley rats were subjected to HI surgery, which entailed ligation of the right common carotid artery followed by 2 h of hypoxia (8% O(2)). Treatment consisted of subcutaneous injection of G-CSF at 1 h after hypoxia followed by an additional one injection per day for 5 days (6 total injections) or for 10 days (11 total injections). Animals were euthanized 5 weeks post-insult for extensive evaluation of neurological deficits and assessment of brain, spleen, heart, and liver damage.

RESULTS

G-CSF treatment promoted somatic growth and prevented brain atrophy and underdevelopment of the heart. Moreover, reflexes, limb placing, muscle strength, motor coordination, short-term memory, and exploratory behavior were all significantly improved by both G-CSF dosing regimens.

CONCLUSIONS

Long-term neuroprotection afforded by G-CSF in both morphological and functional parameters after a hypoxic-ischemic event in the neonate provides a rationale for exploring clinical translation.

Impaired spatial working memory and decreased frontal cortex BDNF protein level in dopamine transporter knockout mice

Brain-derived neurotrophic factor (BDNF), one of the key brain neurotrophins, has been implicated in neuronal plasticity and memory. Recent studies document the importance of BDNF for normal long-term memory functions. However, there are few studies of the roles of BDNF in short-term memory. Dopamine is likely to play important roles in BDNF gene expression in specific brain regions, including frontal cortical regions that are implicated in short-term working memory processes that include spontaneous alternation. We have thus tested spatial working memory in dopamine transporter knockout (DAT KO) and wild-type mice. Spontaneous alternation in the Y-maze, an index of short-term spatial working memory in mice, was significantly decreased in DAT KO mice compared to wild-type mice. BDNF protein was significantly decreased in frontal cortex, though not in striatum or hippocampus, of the DAT KO mice. The data support the hypothesis that impaired spatial working memory in DAT KO mice may be related to decreased frontal cortical BDNF in these animals, and document apparent roles for BDNF in a short-term memory process.

Cyclooxygenase-2 inhibition provides lasting protection against neonatal hypoxic-ischemic brain injury

OBJECTIVE

To investigate whether inhibition of cyclooxygenase-2, a critical component of the inflammatory pathway, is neuroprotective in a neonatal rat model of cerebral hypoxia-ischemia. The development of brain inflammation largely contributes to neonatal brain injury that may lead to a lifetime of neurologic deficits.

DESIGN

Laboratory investigation.

SETTING

University research laboratory.

SUBJECTS

Postnatal day ten Sprague-Dawley rats.

INTERVENTIONS

Neonatal hypoxia-ischemia was induced by ligation of the right common carotid artery followed by 2 hrs of hypoxia (8% oxygen). The pups in treatment groups were administered 10 mg/kg (low dose) or 30 mg/kg (high dose) of a known selective cyclooxygenase-2 inhibitor (NS398). Animals were euthanized at three time points: 72 hrs, 2 wks, or 6 wks. Inflammation outcomes were assessed at 72 hrs; brain damage was assessed at 2 wks and 6 wks along with other organs (heart, spleen). Detailed neurobehavioral examination was performed at 6 wks.

MEASUREMENTS AND MAIN RESULTS

Pharmacologic inhibition of cyclooxygenase-2 markedly increased survivability within the first 72 hrs compared with untreated rats (100% vs. 72%). Low- and high-dose NS398 significantly attenuated the loss of brain and body weights observed after hypoxia-ischemia. Neurobehavioral outcomes were significantly improved in some parameters with low-dose treatment, whereas high-dose treatment consistently improved all neurologic deficits. Immunohistochemical results showed a marked decrease in macrophage, microglial, and neutrophil abundance in ipsilateral hemisphere of the NS398-treated group along with a reduction in interleukin-6 expression.

CONCLUSIONS

Selective cyclooxygenase-2 inhibition protected neonatal rats against death, progression of brain injury, growth retardation, and neurobehavioral deficits after a hypoxic-ischemic insult.

SLV330, a cannabinoid CB1 receptor antagonist, ameliorates deficits in the T-maze, object recognition and Social Recognition Tasks in rodents

Cannabinoid CB(1) receptor (CB(1)R) signaling has been suggested to play an important role in the regulation of memory and cognition. In the present study, our aim was to investigate whether the CB(1)R antagonist SLV330 (doses ranging from 0.3 to 10mg/kg, given orally, p.o.) could ameliorate impairments in distinct aspects of cognition using different disruption models in both mice and rats. Effects of SLV330 were tested on working memory deficits in the T-maze Continuous Alternation Task (T-CAT) in mice; episodic memory deficits in the Object Recognition Task (ORT) and Social Recognition Task (SRT) in rats. The acetylcholinesterase inhibitor (AChEI) donepezil (Aricept, approved for symptomatic treatment of Alzheimer's disease) and nicotine were used as reference compounds. SLV330 markedly improved aging and scopolamine-induced memory deficits in the T-CAT in mice with a lowest effective dose (LED) of 1mg/kg p.o., while reversing the cognitive dysfunction induced by the N-methyl-D-aspartate (NMDA) antagonist dizocilpine (MK-801) only at the middle dose of 3mg/kg. In the ORT, we have found that combined administration of subthreshold doses of SLV330 (1mg/kg, p.o.) and the AChEI donepezil (0.1mg/kg, p.o.), that had no discernable effects on performance when given alone, enhanced memory performance in Wistar rats with deficits induced by the muscarinic antagonist scopolamine, suggestive of additive synergistic effects of SLV330 and donepezil on cognitive impairment. Finally, SLV330 was found to have cognition enhancing properties in a time delay paradigm in the SRT at a LED dose of 3mg/kg (p.o.). In conclusion, the CB(1)R antagonist SLV330 was found to clearly improve memory in several preclinical models for cognitive impairment.

Molecular basis of pharmacotherapies for cognition in Down syndrome

Intellectual disability in Down syndrome (DS) ranges from low normal to severely impaired and has a significant impact on the quality-of-life of the individuals affected and their families. Because the incidence of DS remains at approximately 1 in 700 live births and the lifespan is now >50 years, development of pharmacotherapies for cognitive deficits is an important goal. DS is due to an extra copy of human chromosome 21 and has often been considered too complex a genetic abnormality to be amenable to intervention. However, recent successes in rescuing learning/memory impairments in a mouse model of DS suggest that this negative outlook may not be justified. In this contribution, we first review the DS phenotype, chromosome 21 gene content and mouse models. We then discuss recent successes and the remaining challenges in the identification of targets for and preclinical evaluation of potential therapeutics.