From Mouse to Man: N-Methyl-d-Aspartic Acid Receptor Activation as a Promising Pharmacotherapeutic Strategy for Autism Spectrum Disorders

The BALB/c mouse displays hypersensitivity to behavioral effects of MK-801 (dizocilpine), a noncompetitive N-methyl-d-aspartic acid (NMDA) receptor "open-channel" blocker, and shows both no preference for an enclosed stimulus mouse over an inanimate object and reduced social interaction with a freely behaving stimulus mouse. NMDA receptor agonist interventions improved measures of social preference and social interaction of the BALB/c mouse model of autism spectrum disorder (ASD). A "proof of principle/proof of concept" translational 10-week clinical trial with 8-week of active medication administration was conducted comparing 20 DSM-IV-TR-diagnosed older adolescent/young adult patients with ASD randomized to once-weekly pulsed administration (50 mg/d) versus daily administration of d-cycloserine (50 mg/d). The results showed that d-cycloserine, a partial glycine agonist, was well tolerated, the 2 dosing strategies did not differ, and improvement was noted on the "lethargy/social withdrawal" and "stereotypic behavior" subscales of the Aberrant Behavior Checklist. NMDA receptor activation contributes to the regulation of mTOR signaling, a pathologic point of convergence in several monogenic syndromic forms of ASD. Furthermore, both NMDA receptor hypofunction and imbalance between NMDA receptor activation mediated by GluN2B and GluN2A-containing NMDA receptors occur as "downstream" consequences of several genetically unrelated abnormalities associated with ASD. NMDA receptor-subtype selective "positive allosteric modulators (PAMs)" are particularly appealing medication candidates for future translational trials.

Targeted NMDA Receptor Interventions for Autism: Developmentally Determined Expression of GluN2B and GluN2A-Containing Receptors and Balanced Allosteric Modulatory Approaches

Various ASD risk alleles have been associated with impairment of NMDA receptor activation (i.e., NMDA Receptor Hypofunction) and/or disturbance of the careful balance between activation mediated by GluN2B-subtype and GluN2A-subtype-containing NMDA receptors. Importantly, although these various risk alleles affect NMDA receptor activation through different mechanisms, they share the pathogenic consequences of causing disturbance of highly regulated NMDA receptor activation. Disturbances of NMDA receptor activation due to sequence variants, protein termination variants and copy number variants are often cell-specific and regionally selective. Thus, translational therapeutic NMDA receptor agonist interventions, which may require chronic administration, must have specificity, selectivity and facilitate NMDA receptor activation in a manner that is physiologic (i.e., mimicking that of endogenously released glutamate and glycine/D-serine released in response to salient and relevant socio-cognitive provocations within discrete neural circuits). Importantly, knockout mice with absent expression and mice with haploinsufficient expression of the deleterious genes often serve as good models to test the potential efficacy of promising pharmacotherapeutic strategies. The Review considers diverse examples of “illness” genes, their pathogenic effects on NMDA receptor activation and, when available, results of studies of impaired sociability in mouse models, including “proof of principle/proof of concept” experiments exploring NMDA receptor agonist interventions and the development of promising positive allosteric modulators (PAMs), which serve as support and models for developing an inventory of PAMs and negative allosteric modulators (NAMs) for translational therapeutic intervention. Conceivably, selective PAMs and NAMs either alone or in combination will be administered to patients guided by their genotype in order to potentiate and/or restore disrupted balance between activation mediated by GluN2B-subtype and GluN2A-subtype containing NMDA receptors.

Psychotropic medication use for adults and older adults with intellectual disability; selective review, recommendations and future directions

A growing expert consensus has emerged to guide prescribing behavior and monitoring of psychotropic medications in adults and older adults with intellectual disability (ID). However, there is little empirically-derived evidence to inform physician selection of specific categories of psychotropic medication for treatment of "challenging" behaviors in this vulnerable population (such as aggression to self, others and objects; self-injurious behaviors; repetitive stereotypic behaviors; and hyperactivity). Difficulties with application of formal definitional diagnostic criteria and reliable assignment of psychiatric diagnoses to adults with ID, which is often difficult due to their poor communication skills, contribute to confusion and uncertainty surrounding medication selection. Long-term administration of antipsychotic medications are commonly prescribed for challenging behaviors in spite of their questionable long-term efficacy, leading some to suggest that their "episodic" short-term administration for imminent dangerousness to self and others or when difficult-to-find residential placements are threatened is preferred to their long-term administration. Further, literature supports engagement of interdisciplinary treatment teams to seek causes for challenging behaviors, formulate non-pharmacological psychosocial and behavioral plans for their amelioration and, if medications are initiated, convene regular medication monitoring to identify "drug-related problems". Medication monitoring is important because medication-related adverse events cause or contribute to challenging behaviors, which can sometimes be improved by dose reduction, medication discontinuation and/or elimination of polypharmacy and co-pharmacy. Importantly, medications themselves may interfere with self-reported measures of Quality of Life. The data clearly highlight the need for well-designed randomized controlled clinical trials in samples that are homogeneous with respect to severity of ID and residential setting; moreover, they should include a wider variety of clinical and safety outcome measures. Preclinical studies have suggested novel pharmacological strategies to prevent progressive worsening of adaptive function in adults with Down syndrome in particular, and improvement of cognition in adults with ID in general, irrespective of the etiopathogenesis of the ID. Translational clinical trials to address pathogenic mechanisms of ID, as well as challenging behaviors, are anticipated but raise societal issues pertaining to protection of this vulnerable population enrolling in clinical trials and prioritization of urgent therapeutic targets (e.g., amelioration of challenging behaviors versus improving or preserving intellectual functioning).

Glycine transporter type 1 (GlyT1) inhibition improves conspecific-provoked immobility in BALB/c mice: Analysis of corticosterone response and glucocorticoid gene expression in cortex and hippocampus

Stress reactivity and glucocorticoid signaling alterations are reported in mouse models of autism spectrum disorder (ASD). BALB/c mice display decreased locomotor activity in the presence of stimulus mice and spend less time exploring enclosed stimulus mice; this mouse strain has been validated as an ASD model. VU0410120, a glycine type 1 transporter (GlyT1) inhibitor, improved sociability in BALB/c mice, consistent with data that NMDA Receptor (NMDAR) activation regulates sociability, and the endogenous tone of NMDAR-mediated neurotransmission is altered in this strain. Effects of a prosocial dose of VU0410120 on conspecific-provoked immobility, and relationships between conspecific-provoked immobility and corticosterone response were explored. VU0410120-treated BALB/c mice showed reduced immobility in the presence of conspecifics and increased the conspecific-provoked corticosterone response. However, the intensity of conspecific-provoked immobility in VU0410120-treated BALB/c mice did not differ as a function of corticosterone response. Expression profiles of 88 glucocorticoid signaling associated genes within frontal cortex and hippocampus were examined. BALB/c mice resistant to prosocial effects of VU0410120 had increased mRNA expression of Ddit4, a negative regulator of mTOR signaling. Dysregulated mTOR signaling activity is a convergent finding in several monogenic syndromic forms of ASD. Prosocial effects of VU0410120 in the BALB/c strain may be related to regulatory influences of NMDAR-activation on mTOR signaling activity. Because corticosterone response is a marker of social stress, the current data suggest that the stressfulness of a social encounter alone may not be the sole determinant of increased immobility in BALB/c mice; this strain may also display an element of social disinterest.

An Evolving Therapeutic Rationale for Targeting the α7 Nicotinic Acetylcholine Receptor in Autism Spectrum Disorder

Abnormalities of cholinergic nuclei, cholinergic projections, and cholinergic receptors, as well as abnormalities of growth factors involved in the maturation and maintenance of cholinergic neurons, have been described in postmortem brains of persons with autism spectrum disorder (ASD). Further, microdeletions of the 15q13.3 locus that encompasses CHRNA7, the gene coding the α₇ nicotinic acetylcholine receptor (α₇ nAChR), are associated with a spectrum of neurodevelopmental disorders, including ASD. The heterozygous 15q13.3 microdeletion syndrome suggests that diminished or impaired transduction of the acetylcholine (ACh) signal by the α₇ nAChR can be a pathogenic mechanism of ASD. The α₇ nAChR has a role in regulating the firing and function of parvalbumin (PV)-expressing GABAergic projections, which synchronize the oscillatory output of assemblies of pyramidal neurons onto which they project. Synchronous oscillatory output is an electrophysiological substrate for higher executive functions, such as working memory, and functional connectivity between discrete anatomic areas of the brain. The α₇ nAChR regulates PV expression and works cooperatively with the co-expressed NMDA receptor in subpopulations of GABAergic interneurons in mouse models of ASD. An evolving literature supports therapeutic exploration of selectively targeted cholinergic interventions for the treatment of ASD, especially compounds that target the α₇ nAChR subtype. Importantly, development and availability of high-affinity, brain-penetrable, α₇ nAChR-selective agonists, partial agonists, allosteric agonists, and positive allosteric modulators (PAMs) should facilitate "proof-of-principle/concept" clinical trials. nAChRs are pentameric allosteric proteins that function as ligand-gated ion channel receptors constructed from five constituent polypeptide subunits, all of which share a common structural motif. Importantly, in addition to α₇ nAChR-gated Ca²⁺ conductance causing membrane depolarization, there are emerging data consistent with possible metabotropic functions of this ionotropic receptor. The ability of α₇-selective type II PAMs to "destabilize" the desensitized state and promote ion channel opening may afford them therapeutic advantages over orthosteric agonists. The current chapter reviews historic and recent literature supporting selective therapeutic targeting of the α₇ nAChR in persons affected with ASD.

Understanding facial expressivity in autism spectrum disorder: An inside out review of the biological basis and clinical implications

Deficits in decoding and understanding facially expressed emotions occur commonly in persons with autism spectrum disorder (ASD), which contribute to the impairment of social communication that serves as one of its core diagnostic criteria. Research suggests that abnormalities of visual scanning of the face, activation of key nodes within the "social brain" by facially expressed emotions, functional connectivity within and between nodes of the "social brain", and transduction of specific neurotransmitter/neuromodulatory signals contribute to the pathogenesis of these deficits in at least some persons with ASD. Importantly, the etiologies of these deficits are heterogeneous and include genetic, immunologic, and inflammatory mechanisms, as well as in utero exposures to drugs and toxins. The manifestation and severity of these deficits can also be influenced by developmental age, IQ and genetic background. Consistent with the goals of the Special Issue, the current Review is intended to familiarize the readership with several of the leading neurobiological mechanisms proposed to underlie these deficits in decoding facially expressed emotions and stimulate interest in translational preclinical and clinical investigations, whose ultimate purpose is to attenuate their severity and, thereby, improve functional outcomes of persons with ASD.

Age-dependent effects on social interaction of NMDA GluN2A receptor subtype-selective antagonism

NMDA receptor-mediated neurotransmission is implicated in the regulation of normal sociability in mice. The heterotetrameric NMDA receptor is composed of two obligatory GluN1 and either two "modulatory" GluN2A or GluN2B receptor subunits. GluN2A and GluN2B-containing receptors differ in terms of their developmental expression, distribution between synaptic and extrasynaptic locations, and channel kinetic properties, among other differences. Because age-dependent differences in disruptive effects of GluN2A and GluN2B subtype-selective antagonists on sociability and locomotor activity have been reported in rats, the current investigation explored age-dependent effects of PEAQX, a GluN2A subtype-selective antagonist, on sociability, stereotypic behaviors emerging during social interaction, and spatial working memory in 4- and 8-week old male Swiss Webster mice. The data implicate an age-dependent contribution of GluN2A-containing NMDA receptors to the regulation of normal social interaction in mice. Specifically, at a dose of PEAQX devoid of any effect on locomotor activity and mouse rotarod performance, the social interaction of 8-week old mice was disrupted without any effect on the social salience of a stimulus mouse. Moreover, PEAQX attenuated stereotypic behavior emerging during social interaction in 4- and 8-week old mice. However, PEAQX had no effect on spontaneous alternations, a measure of spatial working memory, suggesting that neural circuits mediating sociability and spatial working memory may be discrete and dissociable from each other. Also, the data suggest that the regulation of stereotypic behaviors and sociability may occur independently of each other. Because expression of GluN2A-containing NMDA receptors occurs at a later developmental stage, they may be more involved in mediating the pathogenesis of ASDs in patients with histories of "regression" after a period of normal development than GluN2B receptors.

Experimental Assessment of Mouse Sociability Using an Automated Image Processing Approach

Mouse is the preferred model organism for testing drugs designed to increase sociability. We present a method to quantify mouse sociability in which the test mouse is placed in a standardized apparatus and relevant behaviors are assessed in three different sessions (called session I, II, and III). The apparatus has three compartments (see Figure 1), the left and right compartments contain an inverted cup which can house a mouse (called "stimulus mouse"). In session I, the test mouse is placed in the cage and its mobility is characterized by the number of transitions made between compartments. In session II, a stimulus mouse is placed under one of the inverted cups and the sociability of the test mouse is quantified by the amounts of time it spends near the cup containing the enclosed stimulus mouse vs. the empty inverted cup. In session III, the inverted cups are removed and both mice interact freely. The sociability of the test mouse in session III is quantified by the number of social approaches it makes toward the stimulus mouse and by the number of times it avoids a social approach by the stimulus mouse. The automated evaluation of the movie detects the nose of the test mouse, which allows the determination of all described sociability measures in session I and II (in session III, approaches are identified automatically but classified manually). To find the nose, the image of an empty cage is digitally subtracted from each frame of the movie and the resulting image is binarized to identify the mouse pixels. The mouse tail is automatically removed and the two most distant points of the remaining mouse are determined; these are close to nose and base of tail. By analyzing the motion of the mouse and using continuity arguments, the nose is identified. Figure 1. Assessment of Sociability During 3 sessions. Session I (top): Acclimation of test mouse to the cage. Session II (middle): Test mouse moving freely in the cage while the stimulus mouse is enclosed in an inverted cup. Session III (bottom): Both test mouse and stimulus mouse are allowed to move freely and interact with each other.

Characterization of gait and olfactory behaviors in the Balb/c mouse model of autism spectrum disorders

Abnormalities of gait and olfaction have been reported in persons with autism spectrum disorders (ASDs), which could reflect involvement of the cerebellum and nodes related to olfaction (e.g., olfactory bulb and ventral temporal olfactory cortex) in neural circuits subserving social, cognitive, and motor domains of psychopathology in these disorders. We hypothesized that the Balb/c mouse model of ASD would express "abnormalities" of gait and olfaction, relative to the Swiss Webster comparator strain. Contrary to expectation, Balb/c and Swiss Webster mice did not differ in terms of quantitative measurements of gait and mouse rotarod behavior, and Balb/c mice displayed a shorter latency to approach an unscented cotton swab, suggesting that there was no disturbance of its locomotor behavior. However, Balb/c mice showed significant inhibition of locomotor activity in the presence of floral scents, including novel and familiar floral scents, and a socially salient odor (i.e., concentrated mouse urine); the inhibitory effect on the locomotor behavior of the Balb/c mouse was especially pronounced with the salient social odor. Unlike the Swiss Webster strain, mouse urine lacks social salience for the Balb/c mouse strain, a model of ASD, which does not appear to be an artifact of diminished olfactory sensitivity or impaired locomotion.

A trial of d-cycloserine to treat the social deficit in older adolescents and young adults with autism spectrum disorders

Autism spectrum disorders are difficult for older adolescents and young adults as impaired social communication affects the transition to adult life. d-Cycloserine, a partial glycine agonist at the N-methyl-d-aspartic acid receptor, was tested in a double-blind randomized trial in 20 older adolescents and young adults with autism spectrum disorders using two dosing strategies (50 mg daily versus 50 mg weekly) for 8 weeks with a 2-week follow-up after discontinuation. d-Cycloserine caused statistically and clinically significant improvement with no differentiation between dosing strategies on the Social Responsiveness Scale and the Aberrant Behavior Checklist before and after d-cycloserine administration.

The 15q13.3 deletion syndrome: Deficient α(7)-containing nicotinic acetylcholine receptor-mediated neurotransmission in the pathogenesis of neurodevelopmental disorders

Array comparative genomic hybridization (array CGH) has led to the identification of microdeletions of the proximal region of chromosome 15q between breakpoints (BP) 3 or BP4 and BP5 encompassing CHRNA7, the gene encoding the α7-nicotinic acetylcholine receptor (α7nAChR) subunit. Phenotypic manifestations of persons with these microdeletions are variable and some heterozygous carriers are seemingly unaffected, consistent with their variable expressivity and incomplete penetrance. Nonetheless, the 15q13.3 deletion syndrome is associated with several neuropsychiatric disorders, including idiopathic generalized epilepsy, intellectual disability, autism spectrum disorders (ASDs) and schizophrenia. Haploinsufficient expression of CHRNA7 in this syndrome has highlighted important roles the α7nAChR plays in the developing brain and normal processes of attention, cognition, memory and behavior throughout life. Importantly, the existence of the 15q13.3 deletion syndrome contributes to an emerging literature supporting clinical trials therapeutically targeting the α7nAChR in disorders such as ASDs and schizophrenia, including the larger population of patients with no evidence of haploinsufficient expression of CHRNA7. Translational clinical trials will be facilitated by the existence of positive allosteric modulators (PAMs) of the α7nAChR that act at sites on the receptor distinct from the orthosteric site that binds acetylcholine and choline, the receptor's endogenous ligands. PAMs lack intrinsic efficacy by themselves, but act where and when the endogenous ligands are released in response to relevant social and cognitive provocations to increase the likelihood they will result in α7nAChR ion channel activation.

NMDA agonists for autism spectrum disorders: progress and possibilities

Transgenic mice with NMDA-receptor (NMDAR) hypofunction display impaired sociability (i.e., diminished preference for exploring conspecifics), supporting a critical role for the NMDAR in regulation of sociability. The endogenous tone of NMDAR-mediated neurotransmission is altered in the Balb/c mouse model of autism spectrum disorders; thus, the effects of targeting the NMDAR in Balb/c mice on sociability, cognition and stereotypic behavior were explored. Positive effects of this pharmacotherapeutic strategy were observed in Balb/c and other relevant mouse strains displaying impaired sociability. Furthermore, in a preliminary translational clinical trial, D-cycloserine, a partial glycineB site agonist, improved sociability and diminished stereotypies in a sample of adolescents and young adults with autism spectrum disorders. The data encourage pharmacotherapeutic targeting of the NMDAR.

NMDA receptor activation regulates sociability by its effect on mTOR signaling activity

Tuberous Sclerosis Complex is one example of a syndromic form of autism spectrum disorder associated with disinhibited activity of mTORC1 in neurons (e.g., cerebellar Purkinje cells). mTORC1 is a complex protein possessing serine/threonine kinase activity and a key downstream molecule in a signaling cascade beginning at the cell surface with the transduction of neurotransmitters (e.g., glutamate and acetylcholine) and nerve growth factors (e.g., Brain-Derived Neurotrophic Factor). Interestingly, the severity of the intellectual disability in Tuberous Sclerosis Complex may relate more to this metabolic disturbance (i.e., overactivity of mTOR signaling) than the density of cortical tubers. Several recent reports showed that rapamycin, an inhibitor of mTORC1, improved sociability and other symptoms in mouse models of Tuberous Sclerosis Complex and autism spectrum disorder, consistent with mTORC1 overactivity playing an important pathogenic role. NMDA receptor activation may also dampen mTORC1 activity by at least two possible mechanisms: regulating intraneuronal accumulation of arginine and the phosphorylation status of a specific extracellular signal regulating kinase (i.e., ERK1/2), both of which are "drivers" of mTORC1 activity. Conceivably, the prosocial effects of targeting the NMDA receptor with agonists in mouse models of autism spectrum disorders result from their ability to dampen mTORC1 activity in neurons. Strategies for dampening mTORC1 overactivity by NMDA receptor activation may be preferred to its direct inhibition in chronic neurodevelopmental disorders, such as autism spectrum disorders.

Safety of paliperidone extended-release in patients with schizophrenia or schizoaffective disorder and hepatic disease

BACKGROUND/PURPOSE

Patients with schizophrenia often suffer from comorbid hepatic disease. This multicenter, open-label, single-arm, crossover study evaluated the safety and efficacy of paliperidone extended-release (ER) in patients with schizophrenia or schizoaffective disorder and hepatic disease.

METHODS

The study comprised a screening period, followed by 9 weeks' open-label treatment, divided into 2 phases. Phase 1 (4 weeks) was a continuation of usual antipsychotic treatment (UAT); phase 2 (5 weeks) consisted of a 1-week cross-titration from UAT to flexibly dosed paliperidone ER (3-12 mg/d), followed by 4 weeks of paliperidone ER alone. Treatment-emergent adverse events (TEAEs), including those considered more relevant to antipsychotic treatment (prespecified adverse events [AEs]), were analyzed.

RESULTS

Although more subjects reported TEAEs during the paliperidone ER alone period than during the UAT period, no significant differences occurred in prespecified AE rates. No new safety signals were detected, and minimal shifts in liver function test values were observed. Improvements in psychiatric symptoms and functioning were observed after 4 weeks' paliperidone ER treatment.

CONCLUSIONS

This study suggests that paliperidone ER is well tolerated in patients with schizophrenia or schizoaffective disorder and hepatic disease. To the best of our knowledge, this is the largest prospective study to date in this population.

Targeting the α7 nicotinic acetylcholine receptor to prevent progressive dementia and improve cognition in adults with Down's syndrome

As persons with Down's syndrome (DS) age into the third decade and beyond, they develop Alzheimer's disease (AD)-like histopathological changes in brain and may manifest progressive worsening of adaptive functions. Increasingly, persons with DS have near-normal to normal life spans; thus, it has become a therapeutic imperative to preserve adaptive functions and ability to live as independently as possible in the least restrictive environment throughout adulthood. Data suggest that these histopathological changes and worsening adaptive functions result, at least in part, from the binding of the amyloidogenic Aβ1-42 peptide to α7 nicotinic acetylcholine receptors (α7nAChRs) on the surface of neurons, which can lead to the internalization of the tightly-bound complex and cell lysis. Pharmacotherapeutic targeting of the α7nAChR may inhibit the creation of the Aβ1-42-α7nAChR complex, which has been observed both intraneuronally and as a component of the amyloid plaque seen in AD. Additionally, selective α7nAChR agonists may improve memory and cognition independently of their potential ability to attenuate the cytotoxicity of Aβ1-42 and retard the deposition of amyloid plaques in adults with DS. However, there are conflicting data supporting an antagonist strategy to improve cognition in the presence of elevated levels of Aβ amyloidogenic peptides, as well as to prevent emergence of pyramidal neuron hyperexcitability. A major challenge to the implementation of clinical trials of targeted α7nAChR interventions in adults with DS will be the ability to detect medication-induced changes in cognition in the context of intellectual disability. The Review will consider some of the current evidence supporting both the role of the Aβ1-42-α7nAChR complex in the pathogenesis of the AD-like histopathology in adult persons with DS, and pharmacotherapeutic interventions with α7nAChR agonists.

A trial of D-cycloserine to treat stereotypies in older adolescents and young adults with autism spectrum disorder

OBJECTIVES

Autism spectrum disorders (ASDs) have core impairments in social communication as well as the presence of repetitive, stereotypic behaviors and restricted interests. Older adolescents and young adults are particularly impacted by these deficits. Preclinical data implicate glutamatergic dysfunction in the pathophysiology of ASDs. D-Cycloserine (DCS), a partial glycineB agonist at the N-methyl-D-aspartic acid receptor site, has been shown to improve sociability in mouse models and a small human study. The sensitivity of the obligatory glycineB co-agonist binding site may change with daily administration of DCS as a result of agonist-induced desensitization. The efficacy of a "pulsed" once-weekly administration versus "daily" administration of DCS was compared.

METHODS

Males and females, ages 14 to 25 years, with a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Text Revision diagnosis of an ASD were enrolled in a double-blind, randomized 10-week trial consisting of 8 weeks of active drug with either weekly or daily administration of 50 mg of DCS followed by a 2-week follow-up visit.

RESULTS

For the purposes of this study, no statistical or clinical differences existed between the 2 dosage groups on the Aberrant Behavior Checklist subscale 3, which measures stereotypies/repetitive movements. When combining groups, a statistically significant decrease of 37% was found from baseline to week 8 when study drug was completed using a linear mixed effects model (P = 0.003).

CONCLUSIONS

D-Cycloserine was shown to be effective in improving stereotypic symptoms in older adolescents and young adults with ASDs measured by the Aberrant Behavior Checklist subscale 3. In addition, DCS was safe and well tolerated.

NMDA receptors on the surface of cancer cells: target for chemotherapy?

The mammalian target of rapamycin (mTOR), a serine/threonine kinase, is a therapeutic target for many types of cancers. NMDA receptors regulate mTOR signalling activity; their inappropriate expression on several human cancer cell lines represents a potential therapeutic avenue to control dysregulated growth, division and invasiveness. Targeting these receptors with selective ligands (e.g., glycineB site ligands) may be a less toxic and more tolerable approach than administering compounds acting at the mTORC1 complex itself, such as rapamycin and its derivatives. Thus, testing glycineB site ligands in relevant in vitro and in vivo paradigms with established human cancer cells that express NMDA receptors on their surface could provide proofs of concept/principle that would encourage exploration of these and other "non-toxic" strategies. Interestingly, in some cancer models that express NMDA receptors on their surface, NMDA receptor antagonists, such as MK-801 (dizocilpine), were shown to possess anti-proliferative and anti-invasive effects, which conflict with hypotheses about promoting NMDA receptor activation as a cancer chemotherapeutic strategy. Whether NMDA receptor activation or antagonism is associated with anti-proliferative and anti-invasive effects may reflect differences between cancer cell lines in terms of the proteins associated with the NMDA receptors on their cell surfaces, which, in turn, could lead to different "downstream" effects on cascades of intracellular phosphorylations. Irrespective of whether activation or antagonism is associated with anti-proliferative and anti-invasive effects for specific types of cancer, data are emerging that support exploration of targeting NMDA receptors expressed on the surface of cancer cells as a therapeutic strategy.

Rapamycin improves sociability in the BTBR T(+)Itpr3(tf)/J mouse model of autism spectrum disorders

Overactivation of the mammalian target of rapamycin (mTOR) has been implicated in the pathogenesis of syndromic forms of autism spectrum disorders (ASDs), such as tuberous sclerosis complex, neurofibromatosis 1, and fragile X syndrome. Administration of mTORC1 (mTOR complex 1) inhibitors (e.g. rapamycin) in syndromic mouse models of ASDs improved behavior, cognition, and neuropathology. However, since only a minority of ASDs are due to the effects of single genes (∼10%), there is a need to explore inhibition of mTOR activity in mouse models that may be more relevant to the majority of nonsyndromic presentations, such as the genetically inbred BTBR T(+)Itpr3(tf)/J (BTBR) mouse model of ASDs. BTBR mice have social impairment and exhibit increased stereotypic behavior. In prior work, d-cycloserine, a partial glycineB site agonist that targets the N-methyl-d-aspartate (NMDA) receptor, was shown to improve sociability in both Balb/c and BTBR mouse models of ASDs. Importantly, NMDA receptor activation regulates mTOR signaling activity. The current study investigated the ability of rapamycin (10mg/kg, i.p.×four days), an mTORC1 inhibitor, to improve sociability and stereotypic behavior in BTBR mice. Using a standard paradigm to assess mouse social behavior, rapamycin improved several measures of sociability in the BTBR mouse, suggesting that mTOR overactivation represents a therapeutic target that mediates or contributes to impaired sociability in the BTBR mouse model of ASDs. Interestingly, there was no effect of rapamycin on stereotypic behaviors in this mouse model.

Clinical outcomes of mild isolated cerebral ventriculomegaly in the presence of other neurodevelopmental risk factors

OBJECTIVES

The purpose of this study was to evaluate neuropsychological test data in school-aged children whose fetal sonograms revealed mild isolated cerebral ventriculomegaly without asymmetry of the lateral ventricles.

METHODS

Nine of 52 children 6 years and older with sonographic evidence of mild isolated cerebral ventriculomegaly without asymmetry of the lateral ventricles were able to be recruited for follow-up school-aged neuropsychological testing. The children received a half-day battery of neuropsychological tests, including the Wechsler Abbreviated Scales of Intelligence; Beery-Buktenica Developmental Test of Visual Motor Integration, Fifth Edition; Wide Range Achievement Test, Fourth Edition; and Integrated Visual and Auditory Continuous Performance Test. Parents completed the Conners 3 Parent Short Form and the Personality Inventory for Children, Second Edition.

RESULTS

In this small group, other risk factors for neurodevelopmental disorders were often present, including preterm birth, perinatal hypoxia, and a family history of psychiatric disease or substance abuse. Within this sample, the proportion of children with a pattern of test results showing poorer nonverbal intelligence than verbal intelligence scores and poorer math than reading performance, as well as meeting criteria for a diagnosis of attention deficit/hyperactivity disorder, was higher than the basal rates of these problems among children in general.

CONCLUSIONS

Particularly given the complexity of various factors affecting neurodevelopment, follow-up neuropsychological evaluation is warranted in children with sonographic evidence of mild isolated cerebral ventriculomegaly without asymmetry of the lateral ventricle (eg, in the context of poor school performance).

Targeting alpha-7 nicotinic neurotransmission in schizophrenia: a novel agonist strategy

Alpha7 nicotinic acetylcholine receptor (α7 nAChR) agonists may be valuable treatments for negative symptoms and cognitive impairment in schizophrenia. Unfortunately, chronic exposure to an agonist may reduce the receptor's sensitivity. Therefore, we combined CDP-choline, a dietary source of the direct agonist choline, with galantamine, a positive allosteric modulator (PAM) of nicotinic acetylcholine receptors, to improve the efficiency of transducing the choline signal and, possibly, preserve the receptor in a sensitive state. We conducted a single-site, double-blind randomized clinical trial comparing galantamine/CDP-choline to placebos in schizophrenia patients with negative symptoms who were receiving second generation antipsychotics. Forty-three subjects received galantamine and CDP-choline or matching placebos for 16weeks. The primary outcome measure was the 5-item Marder negative-symptoms factor of the Positive and Negative Syndrome Scale (PANSS). Cognition and functioning were also assessed. Trial completion was high; 79%. There was no significant treatment effect on negative symptoms, other PANSS symptom factors, or the MATRICS Cognitive Consensus Battery. There were significant treatment effects in overall functioning and a test of free verbal recall. Three subjects discontinued treatment in the active treatment group for gastro-intestinal adverse events (AE). The most common AE for galantamine/CDP-choline was abdominal pain; for placebo it was headache and sweating. Although there was no significant treatment effect on negative symptoms, the direction of effect mirrored the effects on a cognitive measure and overall functioning. Further study of α7 nAChR agonist/PAMs is warranted in larger studies that will have greater power.

D-Cycloserine improves sociability in the BTBR T+ Itpr3tf/J mouse model of autism spectrum disorders with altered Ras/Raf/ERK1/2 signaling

The genetically inbred BTBR T+ Itpr3tf/J (BTBR) mouse is a proposed model of autism spectrum disorders (ASDs). Similar to several syndromic forms of ASDs, mTOR activity may be enhanced in this mouse strain as a result of increased Ras signaling. Recently, D-cycloserine, a partial glycineB site agonist that targets the NMDA receptor, was shown to improve the sociability of the Balb/c mouse strain, another proposed genetically inbred model of ASDs. NMDA receptor activation is an important regulator of mTOR signaling activity. Given the ability of D-cycloserine to improve the sociability of the Balb/c mouse strain and the regulatory role of the NMDA receptor in mTOR signaling, we wondered if D-cycloserine would improve the impaired sociability of the BTBR mouse strain. D-Cycloserine (320 mg/kg, ip) improved measures of sociability in a standard sociability paradigm and spontaneous grooming that emerged during social interaction with an ICR stimulus mouse in the BTBR strain; however, similar effects were observed in the Swiss Webster comparator strain, raising questions about their strain-selectivity. Importantly, the profile of D-cycloserine's effects on both measures of sociability and stereotypies is consistent with that of a desired medication for ASDs; specifically, a desired medication would not improve sociability at the expense of worsening stereotypic behaviors or vice versa.

Neural basis of implicit memory for socio-emotional information in schizophrenia

Individuals with schizophrenia are impaired in processing social signals such as facial expressions of emotion. Perceiving facial expressions is a complex process that depends on a distributed neural network of regions involved in affective, cognitive, and visual processing. We examined repetition priming, a non-conscious form of perceptual learning, to explore the visual-perceptual processes associated with perceiving facial expression in people with schizophrenia. Functional magnetic resonance imaging (fMRI) was also employed to probe the sensitivity of face-responsive regions in the ventral pathway to the repetition of stimuli. Subjects viewed blocks of novel and repeated faces displaying fear expressions and neutral expressions and identified each face as male or female. Gender decisions were faster for repeated encoding relative to initial encoding of faces, indicating significant priming for facial expressions. Priming was normal in schizophrenia patients, but, as expected, recognition memory for the expressions was impaired. Neuroimaging findings showed that priming-related activation for patients was reduced in the left fusiform gyrus, relative to controls, regardless of facial expression. The findings suggest that schizophrenia patients have altered neural sensitivity in regions of the ventral visual processing stream that underlie early perceptual learning of objects and faces.

D-cycloserine improves sociability and spontaneous stereotypic behaviors in 4-week old mice

Balb/c mice are a model of impaired sociability and social motivation relevant to autism spectrum disorders (ASDs). Impaired sociability of 8-week old Balb/c mice is attenuated by agonists of the glycine(B) site on the NMDA receptor, such as d-cycloserine. Although ASDs are often recognized in toddlerhood, there is interest in earlier identification (e.g., before 6 months) and disease-modifying interventions to improve functional outcomes. Thus, we wondered if d-cycloserine could improve sociability in 4-week old Balb/c mice, similar to its effects in 8-week old mice. d-Cycloserine improved measures of impaired sociability in 4-week old (i.e., one-week post-weanling) Balb/c mice. Moreover, because stereotypies can compete with the salience of social stimuli, we compared Balb/c and Swiss Webster mice on several spontaneous stereotypic behaviors emerging during social interaction with a social stimulus mouse. Interestingly, similar to 8-week old mice, spontaneous stereotypic behaviors during social interaction were more intense in the 4-week old Swiss Webster mice; furthermore, d-cycloserine reduced their intensity. Thus, d-cycloserine improves both sociability and stereotypic behaviors, but these effects may lack strain-selectivity. A prosocial effect of d-cycloserine was observed at a dose as low as 32.0mg/kg in Balb/c mice. d-cycloserine has the therapeutic properties of a desired medication for ASDs; specifically, a medication should not improve stereotypic behaviors at the expense of worsening sociability and vice versa. The data suggest that targeting the NMDA receptor can have promising therapeutic effects on two prominent domains of psychopathology in ASDs: impaired sociability and spontaneous stereotypic behaviors.

Genetically inbred Balb/c mice differ from outbred Swiss Webster mice on discrete measures of sociability: relevance to a genetic mouse model of autism spectrum disorders

The Balb/c mouse is proposed as a model of human disorders with prominent deficits of sociability, such as autism spectrum disorders (ASDs) that may involve pathophysiological disruption of NMDA receptor-mediated neurotransmission. A standard procedure was used to measure sociability in 8-week-old male genetically inbred Balb/c and outbred Swiss Webster mice. Moreover, because impaired sociability may influence the social behavior of stimulus mice, we also measured the proportion of total episodes of social approach made by the stimulus mouse while test and stimulus mice were allowed to interact freely. Three raters with good inter-rater agreement evaluated operationally defined measures of sociability chosen because of their descriptive similarity to deficits of social behavior reported in persons with ASDs. The data support previous reports that the Balb/c mouse is a genetic mouse model of impaired sociability. The data also show that the behavior of the social stimulus mouse is influenced by the impaired sociability of the Balb/c strain. Interestingly, operationally defined measures of sociability did not necessarily correlate with each other within mouse strain and the profile of correlated measures differed between strains. Finally, "stereotypic" behaviors (i.e. rearing, grooming and wall climbing) recorded during the session of free interaction between the test and social stimulus mice were more intensely displayed by Swiss Webster than Balb/c mice, suggesting that the domains of sociability and "restricted repetitive and stereotyped patterns of behavior" are independent of each other in the Balb/c strain.

Complex effects of mGluR5 antagonism on sociability and stereotypic behaviors in mice: possible implications for the pharmacotherapy of autism spectrum disorders

Balb/c mice display deficits of sociability; for example, they show reduced locomotor activity in the presence of an enclosed or freely-moving social stimulus mouse. Transgenic mice with defective or diminished expression of NMDA receptors manifest impaired sociability, while a partial and full agonist of the obligatory glycine co-agonist binding site on the NMDA receptor improved sociability in the Balb/c mouse strain. Because 2-methyl-6-(phenylethynyl)-pyridine (MPEP), an antagonist of the mGluR5 metabotropic glutamate receptor (mGluR), reduced self-grooming behavior in BTBR T+tfJ (BTBR) mice, another inbred genetic mouse model of autism spectrum disorders (ASDs), and mGluR5 antagonism is emerging as an experimental treatment for the 'fragile X syndrome," which has a high prevalence of co-morbid ASDs, we examined the effects of MPEP on sociability and stereotypic behaviors in Balb/c and Swiss Webster mice in a standard paradigm. MPEP had complex effects on sociability, impairing some measures of sociability in both strains, while it reduced the intensity of some spontaneous measures of stereotypic behaviors emerging during free social interaction in Swiss Webster mice. Conceivably, mGluR5 antagonism exacerbates diminished endogenous tone of NMDA receptor-mediated neurotransmission in neural circuits relevant to at least some measures of sociability in Balb/c mice; the mGluR5 receptor contributes to regulation of the phosphorylation status of the NMDA receptor. In any event, although stereotypies are an important therapeutic target in ASDs, medication strategies to attenuate their severity via antagonism of mGluR5 receptors must be pursued cautiously because of their potential to worsen at least some measures of sociability.

Selective mGluR5 antagonism attenuates the stress-induced reduction of MK-801's antiseizure potency in the genetically inbred Balb/c mouse

The ability of MK-801 (dizocilpine), a noncompetitive N-methyl D-aspartate (NMDA) antagonist, to antagonize electrical seizures is reduced in stressed mice. Stress-associated alterations in seizure susceptibility and diminished efficacy of antiseizure medications in humans have been reported [Joëls, 2009; Haut et al., 2007; Moshe et al., 2008]; thus, these experimental observations implicate altered endogenous tone of NMDA receptor-mediated neurotransmission in clinically adverse effects of stress on seizure proneness and treatment. The current exploratory experiment examined the effect of 2-methyl-6-(phenylethynyl)-pyridine (MPEP), an antagonist of mGluR5, administered prior to stress on the stress-induced reduction of MK-801's antiseizure effect in Swiss-Webster and Balb/c mice; the Balb/c mouse is behaviorally hypersensitive to MK-801. Interestingly, the data suggest that MPEP can attenuate the severity of the stress-induced reduction of MK-801's antiseizure effect in the Balb/c strain. Thus, mGluR5 could serve as a target for strategies for adjuvant treatment of seizures exacerbated by stress.

D-Cycloserine enhances social exploration in the Balb/c mouse

Inbred Balb/c mice show deficits of sociability. The endogenous tone of NMDA receptor-mediated neurotransmission is altered in Balb/c mice, which may explain the beneficial effect of D-cycloserine on impaired sociability. In the current study, Balb/c mice spent more time than the Swiss Webster comparator strain in the open arms of an elevated plus maze (EPM), suggesting that they are not more anxious or fearful in the absence of a social stimulus mouse. Moreover, Balb/c and Swiss Webster mice did not differ in the amount of time they spent exploring an inanimate object in an open field. Differences in exploratory activity between strains emerged only when a salient social stimulus mouse was enclosed in the open field. D-Cycloserine increased the amount of time Balb/c mice spent exploring the enclosed stimulus mouse to levels observed in vehicle-treated Swiss Webster mice. Finally, irrespective of strain, D-cycloserine increased exploratory activity as measured in open arm entries in the EPM, when no enclosed stimulus mouse was present. The data show that mouse strain influences D-cycloserine's effect on exploration in the presence of a salient social stimulus mouse. In the absence of an enclosed stimulus mouse, D-cycloserine increased open arm entries significantly in both the sociability-impaired Balb/c and comparator Swiss Webster strains. Thus, D-cycloserine positively affects exploratory activity in general, but strain differences emerge when the stimulus eliciting exploration is a salient social stimulus mouse versus an inanimate object. Further, the sociability deficit of the Balb/c mouse is not an epiphenomenon of increased generalized anxiety.

Attention to gaze and emotion in schizophrenia

OBJECTIVE

Individuals with schizophrenia have difficulty interpreting social and emotional cues such as facial expression, gaze direction, body position, and voice intonation. Nonverbal cues are powerful social signals but are often processed implicitly, outside the focus of attention. The aim of this research was to assess implicit processing of social cues in individuals with schizophrenia.

METHOD

Patients with schizophrenia or schizoaffective disorder and matched controls performed a primary task of word classification with social cues in the background. Participants were asked to classify target words (LEFT/RIGHT) by pressing a key that corresponded to the word, in the context of facial expressions with eye gaze averted to the left or right.

RESULTS

Although facial expression and gaze direction were irrelevant to the task, these facial cues influenced word classification performance. Participants were slower to classify target words (e.g., LEFT) that were incongruent to gaze direction (e.g., eyes averted to the right) compared to target words (e.g., LEFT) that were congruent to gaze direction (e.g., eyes averted to the left), but this only occurred for expressions of fear. This pattern did not differ for patients and controls.

CONCLUSION

The results showed that threat-related signals capture the attention of individuals with schizophrenia. These data suggest that implicit processing of eye gaze and fearful expressions is intact in schizophrenia.

D-serine improves dimensions of the sociability deficit of the genetically-inbred Balb/c mouse strain

The Balb/c mouse strain shows quantitative deficits of sociability and is behaviorally-hypersensitive to MK-801 (dizocilpine), a noncompetitive NMDA receptor antagonist. D-Serine (560mg/kg, intraperitoneally), a full agonist for the obligatory glycine co-agonist binding site on the NMDA receptor, increased the amount of time Balb/c mice spend in a compartment containing the enclosed social stimulus mouse and the amount of time Balb/c mice spend exploring (sniffing) an inverted cup containing the enclosed social stimulus mouse in a standard sociability apparatus. These effects of D-serine on the impaired sociability of the Balb/c mouse strain were not due to a "nonspecific" effect on locomotor activity; importantly, the locomotor activity of the Balb/c mouse strain decreases in the presence of an enclosed or freely-moving social stimulus mouse. The data suggest that dimensions of the impaired sociability of the Balb/c mouse strain may be improved by targeted NMDA receptor agonist interventions.

D-Cycloserine improves the impaired sociability of the Balb/c mouse

The genetically inbred Balb/c mouse strain shows evidence of impaired sociability in a standard paradigm. For example, relative to 8-week-old male outbred Swiss-Webster mice, 8 week-old male Balb/c mice spend less time sniffing and in the vicinity of an enclosed 4 week-old male ICR stimulus mouse and, when allowed to interact freely with the stimulus mouse for five minutes, make fewer discrete episodes of social approach and show suppression of locomotor activity. We explored the effect of D-cycloserine (320mg/kg, intraperitoneally), a partial glycine agonist that binds to the obligatory co-agonist glycine binding site on the NMDA receptor, on the sociability of the Balb/c and Swiss-Webster mouse strains in a standard paradigm. The results show that treatment with D-cycloserine increased the locomotor activity of the Balb/c mouse strain in the presence of an enclosed social stimulus mouse and when these mice were allowed to interact freely with each other. Also, D-cycloserine increased the number of discrete episodes of social approach when Balb/c mice were allowed to interact freely with social stimulus mice. However, D-cycloserine had similar effects on measures of sociability in the Swiss-Webster mouse, raising the possibility that the positive effects on the sociability of the Balb/c mouse strain may be mediated by indirect effects on locomotion, arousal, and anxiety.

Locomotor activity of the genetically inbred Balb/c mouse strain is suppressed by a socially salient stimulus

The genetically inbred Balb/c mouse strain shows behavioral hypersensitivity to MK-801 (dizocilpine), a noncompetitive NMDA receptor antagonist. In the current study, the locomotor activity of male Balb/c mice was more severely reduced in the presence of a "stimulus" mouse, compared with the outbred Swiss-Webster mouse strain; reduced locomotor activity of the Balb/c mouse was observed when the stimulus mouse was enclosed and when the two mice were allowed to interact freely. The Balb/c mouse strain with altered endogenous tone of NMDA receptor-mediated neurotransmission may lend itself to the identification of candidate compounds targeting impaired sociability, an important dimension of psychopathology in schizophrenia and autism spectrum disorders (ASDs). Reduced locomotor activity in the presence of a stimulus mouse is a sensitive behavioral outcome measure of impaired sociability.

Does subtle disturbance of neuronal migration contribute to schizophrenia and other neurodevelopmental disorders? Potential genetic mechanisms with possible treatment implications

Pathways associated with genes that regulate neuronal migration by influencing the function of microtubules in the developing fetal brain may be interfered with as part of the "first-hit" of schizophrenia. In the fully-developed brain, these same pathways that impact microtubule function mediate at least some aspects of experience-dependent plasticity, which may also be impaired in schizophrenia. Whereas severe presentations of "lissencephaly" are associated with mutations and deletions of DISC1, LIS1 and the gene for the very low-density lipoprotein receptor, genetic variations of these loci are good candidate schizophrenia genes. Importantly, in the fully-developed brain, there is a possibility that at least some of the consequences of these disturbed genetic pathways that adversely affect microtubule function may be "bypassed" or mitigated.

NMDA NR2B subtype-selective receptor antagonists fail to antagonize electrically-precipitated seizures and elicit popping in mice

NR2B-subtype-selective antagonists differ from MK-801, a nonselective NMDA receptor antagonist. MK-801 antagonizes electrical seizures at doses as low as 0.1 to 0.18mg/kg and elicits popping at doses as low as 0.5mg/kg, whereas ifenprodil and Ro 8-4304 were unable to do so at the doses tested. Ro 25-6981, however, was able to antagonize electrically-precipitated tonic hindlimb extension at 100mg/kg, but was not able to elicit popping behavior at this dose.

Regulation of intermittent oscillatory activity of pyramidal cell neurons by GABA inhibitory interneurons is impaired in schizophrenia: rationale for pharmacotherapeutic GABAergic interventions

GABA, the major inhibitory neurotransmitter in the brain, is synthesized from L-glutamate and packaged within a family of highly differentiated inhibitory interneurons. Individual GABA inhibitory interneurons in the frontal cortex can make terminal synaptic connections with more than 200 distinct pyramidal neurons, the principal output neuron. Moreover, the sites of these synaptic connections include shafts of dendritic spines, soma, dendritic branches, and initial axon segments. The phasic activity of GABAergic neurons regulate intermittent oscillations of assemblies of pyramidal cell neurons, which are critical for many higher cortical functions such as working memory. Potentially, there are several viable pharmacotherapeutic strategies for facilitating GABAergic neurotransmission. A major research question is whether tonically-administered, selective GABAergic therapeutic interventions can mimic and correct disruptions of the intermittent oscillatory activity of assemblies of cortical pyramidal cell neurons.

Genetically inbred Balb/C mice are more sensitive to an effect of flurazepam and more resistant to an effect of stress than a genetically outbred mouse strain

The inbred Balb/c mouse strain was more sensitive than the outbred NIH Swiss mouse to flurazepam's ability to antagonize electrically precipitated seizures. In prior work, a reduction in flurazepam's antiseizure efficacy was not observed 24h after forcing Balb/c mice to swim for up to 10 min in ambient temperature water. Thus, we wondered if a stress-induced reduction would be observed after forcing mice to swim for up to 10 min in cold (6 degrees C) water, a more severe stress. The current data show that 24 h after exposure to this stress, the ability of flurazepam to raise the threshold voltage for the elicitation of tonic hindlimb extension in the Balb/c mouse strain was reduced. The genetically inbred Balb/c mouse strain is emerging as an interesting animal model in which to study interactions of stress and genetic factors that affect endogenous neurotransmission mediated by l-glutamate and GABA at the NMDA and GABA(A) receptor complexes, respectively.

An epigenetic intervention interacts with genetic strain differences to modulate the stress-induced reduction of flurazepam's antiseizure efficacy in the mouse

Stress induces changes in the endogenous tone of both GABA and NMDA receptor-mediated neurotransmission in the intact mouse. Because changes are observed 24 h after stress, epigenetically-regulated alterations in gene expression may mediate these effects. In earlier work, sodium butyrate, a centrally-active histone deacetylase inhibitor that promotes gene expression, was shown to modulate the stress-induced reduction of the ability of MK-801 (dizocilpine), a noncompetitive NMDA receptor antagonist, to antagonize electrically-precipitated seizures. In the current study, we extended this work to look at sodium butyrate's modulatory effect on stress-induced changes in the antiseizure efficacy of flurazepam, a benzodiazepine receptor agonist, in two strains of mice. Epigenetic mechanisms, genetic strain differences and a standard stress interacted to alter flurazepam's antiseizure efficacy. These data support examination and development of epigenetic treatment strategies.

Recognition memory probes affect what is remembered in schizophrenia

Cognitive psychology offers tools to localize the memory processes most vulnerable to disruption in schizophrenia and to identify how patients with schizophrenia best remember. In this research, we used the University of Southern California Repeatable Episodic Memory Test (USC-REMT; Parker, E.S., Landau, S.M., Whipple, S.C., Schwartz, B.L., 2004. Aging, recall, and recognition: A study on the sensitivity of the University of Southern California Repeatable Episodic Memory Test (USC-REMT). Journal of Clinical and Experimental Neuropsychology 26(3), 428-440.) to examine how two different recognition memory probes affect memory performance in patients with schizophrenia and matched controls. Patients with schizophrenia studied equivalent word lists and were tested by yes-no recognition and forced-choice recognition following identical encoding and storage conditions. Compared with controls, patients with schizophrenia were particularly impaired when tested by yes-no recognition relative to forced-choice recognition. Patients had greatest deficits on hits in yes-no recognition but did not exhibit elevated false alarms. The data point to the importance of retrieval processes in schizophrenia, and highlight the need for further research on ways to help patients with schizophrenia access what they have learned.

Expression of NR1, NR2A and NR2B NMDA receptor subunits is not altered in the genetically-inbred Balb/c mouse strain with heightened behavioral sensitivity to MK-801, a noncompetitive NMDA receptor antagonist

The genetically-inbred Balb/c mouse strain shows heightened sensitivity to the ability of MK-801 (dizocilpine), a noncompetitive NMDA receptor antagonist, to raise the threshold voltage necessary to precipitate tonic hindlimb extension and elicit irregular episodes of intense jumping behavior (referred to as "popping"), relative to other inbred mouse strains and the outbred NIH Swiss mouse. Moreover, an allosteric modulatory effect of sarcosine, a glycine reuptake inhibitor, on MK-801's antagonism of electrically precipitated seizures was detected 24 h after Balb/c mice were forced to swim in cold water for up to 10 min; this was not observed in unstressed Balb/c mice or stressed or unstressed NIH Swiss mice. Phencyclidine (PCP), a noncompetitive NMDA receptor antagonist that binds to the same hydrophobic channel domain as MK-801, precipitates a schizophreniform psychosis in susceptible individuals that shares descriptive similarities with schizophrenia. This observation has led to the hypothesis that NMDA receptor hypofunction (NRH) is involved in the pathophysiology of schizophrenia and the testing of pharmacotherapeutic strategies to facilitate NMDA receptor-mediated neurotransmission in patients with this disorder (e.g., glycine reuptake inhibitors). The heightened behavioral sensitivity of the Balb/c mouse to MK-801 suggests that this mouse strain may be a useful model to study "psychosis-proneness" and screen for positive allosteric modulators of NMDA receptor-mediated neurotransmission. Conceivably, strain differences in the pharmacology of the NMDA receptor are due to differences in the relative expression of individual NMDA receptor subunits to each other (i.e., combinatorial regulation). The current study compared the normal protein expression patterns of six of the eight identified splice variant isoforms of the NR1 NMDA receptor subunit, and NR2A and NR2B subunits in the hippocampus and cerebral cortex of Balb/c and NIH Swiss mice. The heightened behavioral sensitivity of the Balb/c genetically-inbred mouse strain to MK-801, compared to the outbred NIH Swiss mouse strain, does not appear to result from relative alterations of expression of these NMDA receptor protein subunits that were examined.

Sodium butyrate, an epigenetic interventional strategy, attenuates a stress-induced alteration of MK-801's pharmacologic action

Twenty-four hours after mice are exposed to a single session of forced swimming in cold water, the ability of MK-801 (dizocilpine), a noncompetitive NMDA receptor antagonist, to antagonize electrically precipitated seizures is reduced. Conceivably, this reduction in MK-801's antiseizure efficacy reflects a stress-induced alteration in NMDA receptor-mediated neurotransmission due to changes in gene expression 24 h after a single stress. Recently, epigenetic interventional strategies impacting expression of genes whose regulation is controlled by the acetylation status of histone proteins in the nucleosome, an octomeric complex of histone proteins and promoter regions of double-stranded DNA, have been tested in preclinical models of various neuropsychiatric disorders, including Huntington disease and major depression. These strategies have been studied extensively in cancer biology. In the current investigation, the severity of the stress-induced reduction of MK-801's ability to raise the threshold voltage for the elicitation of tonic hindlimb extension was reduced when sodium butyrate (1.5 g/kg, ip) was administered around the time of stress. Prior research showed that this dose of sodium butyrate reliably increased the acetylation status of H3 and H4 histone proteins in the hippocampus and cerebral cortex of mice. Thus, the attenuation of the stress-induced reduction of MK-801's antiseizure efficacy may be due to the increased acetylation of histone proteins in the nucleosomal core and promotion of gene expression. These data encourage development of epigenetic strategies to prevent some of the deleterious consequences of stress.

Effects of CDP-choline and the combination of CDP-choline and galantamine differ in an animal model of schizophrenia: development of a selective alpha7 nicotinic acetylcholine receptor agonist strategy

The regionally selective reduction of expression of the alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) in schizophrenia underlies impaired sensory inhibition, a possible endophenotype of the disorder. This ligand-gated ion channel receptor has been proposed as a pharmacotherapeutic target in schizophrenia. The current study examined the effect of CDP-choline alone and the combination of CDP-choline and galantamine, administered acutely and once-daily for five consecutive days, in an animal model of NMDA receptor hypofunction that is relevant to schizophrenia. The results support the allosteric modulatory influence of galantamine on CDP-choline; however, individual doses of CDP-choline and galantamine must be carefully titrated in order to achieve optimal levels of alpha7 nAChR "agonism" that may be necessary for the desired therapeutic effect.

Phencyclidine and dizocilpine induced behaviors reduced by N-acetylaspartylglutamate peptidase inhibition via metabotropic glutamate receptors

BACKGROUND

N-methyl-D-aspartate (NMDA) receptor open channel blockers phencyclidine (PCP) and dizocilpine (MK-801) elicit schizophrenia-like symptoms in humans and in animal models. Group II metabotropic glutamate receptor agonists reverse the behavioral effects of PCP and MK-801 in animal models. N-acetylaspartylglutamate (NAAG), the third most prevalent neurotransmitter in the mammalian nervous system, is a selective group II metabotropic glutamate receptor agonist. We previously reported that ZJ43, a potent inhibitor of the enzymes that inactivate synaptically released NAAG, reduced motor and stereotypic effects of PCP in the rat.

METHODS

To confirm the efficacy of NAAG peptidase inhibition in decreasing motor behaviors induced by PCP and MK-801, ZJ43 was tested in additional schizophrenia models.

RESULTS

ZJ43 reduced MK-801-induced motor activation in a mouse model that has been used to characterize the efficacy of a wide range of pharmacotherapies for this human disorder. In a second mouse strain, the peptidase inhibitor reduced PCP-induced stereotypic movements. ZJ43 also reduced PCP-induced negative symptoms in a resident-intruder assay. The group II metabotropic glutamate receptor antagonist, LY341495, blocked the effect of NAAG peptidase inhibition in these mouse models of positive and negative PCP- and MK-801-induced behaviors. Additionally, LY341495 alone increased some PCP-induced behaviors suggesting that normal levels of NAAG act to moderate the effect of PCP via a group II mGluR.

CONCLUSIONS

These data support the proposal that NAAG peptidase inhibition and elevation of synaptic NAAG levels represent a new therapeutic approach to treating the positive and negative symptoms of schizophrenia that are modeled by open channel NMDA receptor antagonists.

Mitochondrial myopathy complicated by eating disorder: a case report highlighting the potential interaction of genetic, metabolic, and psychodynamic factors

A case is presented of a 56-year-old woman with a history of an eating disorder that preceded recognition of a mitochondrial myopathy. The possibility exists that her eating disorder was causally related to a more fundamental defect in mitochondrial oxidative metabolism. This case report highlights the phenotypic variability of mitochondrial myopathies. An increased risk of eating disorder may be associated with drugs that interfere with mitochondrial oxidative respiration.

Rare neurodevelopmental abnormalities of sarcosinemia may involve glycinergic stimulation of a primed N-methyl-d-aspartate receptor

Sarcosinemia is a relatively rare autosomal recessive disorder that has a varied phenotypic presentation; rarely, it is associated with neurodevelopmental and neurological abnormalities. Sarcosine is a key intermediate in 1-carbon metabolism, and its elevation in blood and urine could reflect a deficient pool size of activated 1-carbon units. Sarcosine is also an inhibitor of an important glycine transporter in brain and is under clinical investigation as a glycinergic intervention for conditions with presumed N-methyl-d-aspartate (NMDA) receptor hypofunction, such as schizophrenia. Preclinical research with a mouse model that is used to study pharmacological modulation of endogenous NMDA receptor-mediated tone may clarify, at least in some instances, varied phenotypic presentations of sarcosinemia that are often clinically benign. Sarcosine's effectiveness as a glycinergic agonist intervention for NMDA receptor hypofunction depends on an interaction between genetic background and a stressful environmental insult. Thus, neurodevelopmental and neurological abnormalities may manifest rarely in sarcosinemia in the context of relatively unique genetic factors and fetal insult or stress.

Exogenously administered D-serine failed to potentiate the ability of MK-801 to antagonize electrically precipitated seizures in nonhandled control and stressed mice

NMDA receptor hypofunction (NRH) has been implicated in the pathophysiology of schizophrenia because of the ability of phencyclidine (PCP), a noncompetitive NMDA receptor antagonist, to precipitate a schizophreniform psychosis. The possible role that NRH plays in the pathophysiology of schizophrenia stimulated characterization of behaviors elicited by PCP and its analogues. For example, MK-801 (dizocilpine), a noncompetitive NMDA receptor antagonist that binds with higher affinity to the same hydrophobic channel domain as PCP, raises the threshold voltage required for the electrical precipitation of tonic hindlimb extension in mice. This ability of MK-801 is significantly reduced following stress. We showed that an exogenously administered glycine prodrug (i.e., milacemide) was able to potentiate MK-801's antiseizure efficacy in unstressed mice and restore MK-801's antiseizure efficacy in stressed animals. d-Serine may serve as an endogenous agonist for the obligatory glycine co-agonist site on the NMDA receptor complex. Orally administered d-serine has been studied clinically as an adjuvant therapeutic intervention in schizophrenia. Thus, we were surprised at its inability to potentiate MK-801's antiseizure efficacy in either control or stressed animals. These data do not support the development of d-serine as a viable therapeutic intervention for schizophrenia and, possibly, other disorders.

Dysregulation of tau phosphorylation is a hypothesized point of convergence in the pathogenesis of alzheimer's disease, frontotemporal dementia and schizophrenia with therapeutic implications

Two members of the family of low-density lipoprotein receptors (i.e., very low-density lipoprotein [VLDL] receptor and apolipoprotein E [apoE] type 2 receptor) are expressed in brain, where they bind and transduce reelin, a secreted glycoprotein that shares structural analogies with extracellular matrix proteins. In the developing fetal brain, reelin-signal transduction is critical for the correct positioning of neurons and the formation of appropriate synaptic connections, whereas in the mature brain, reelin participates in the mediation of experience-dependent synaptic plasticity. An important "downstream" consequence of the reelin-signal transduction cascade is inhibition of the phosphorylation of tau, a protein that regulates microtubule assembly and stability. Importantly, hyperphosphorylated tau comprises the paired helical filament, whose pathological deposition as neurofibrillary tangles is implicated in Alzheimer's disease; hyperphosphorylated tau is also implicated in the pathogenesis of other neurodegenerative disorders. Isoforms of apoE may affect the binding of reelin to its cell surface receptors and, thereby, influence tau phosphorylation, whereas insulin, insulin-like growth factor-1, and the lithium ion have actions within the cell at the level of the specific tyrosine kinases involved in the phosphorylation of tau. These data support the exploration of pharmacotherapeutic interventions designed to prevent or reduce the burden of hyperphosphorylated tau. Impaired reelin-signal transduction due to an actual deficiency of reelin expression may occur in at least some patients with psychotic disorders, especially schizophrenia; conceivably, hyperphosphorylation of tau would result from deficient transduction of reelin in schizophrenia. Schizophrenia has been conceptualized as a neurodevelopmental disorder of impaired synaptic "connectivity", whose consequence does not become fully apparent until late adolescence or early adulthood. In summary, hyperphosphorylation of tau may be an underlying point of pathological convergence for several neuropsychiatric disorders, and prevention of tau hyperphosphorylation may be an important therapeutic target.

Imitation of facial expressions in schizophrenia

Diminished facial expressivity is a common feature of schizophrenia that interferes with effective interpersonal communication. This study was designed to determine if real-time visual feedback improved the ability of patients with schizophrenia to imitate and produce modeled facial expressions. Twenty patients with schizophrenia and 10 controls viewed static images of facial expressions and were asked to imitate them. Half of the images were imitated with the use of a mirror and half were imitated without the use of a mirror. In addition, we examined whether practice in imitating and producing expressions improved the ability of participants to generate facial expressions on their own, without the aid of a model or mirror. Participants' facial expressions were photographed with a digital camera and each was rated for accuracy in producing characteristic facial expressions. Patients with schizophrenia were less accurate in imitating and producing facial expressions than controls, and real-time visual feedback did not improve accuracy in either group. Preliminary findings suggest that exposure to model expressions and practice in generating these expressions can improve the accuracy of certain posed expressions in schizophrenia.

Faulty regulation of tau phosphorylation by the reelin signal transduction pathway is a potential mechanism of pathogenesis and therapeutic target in Alzheimer's disease

Hyperphosphorylated tau protein is the basic structural component of the neurofibrillary tangle, a histopathological hallmark of Alzheimer's disease. The formation of hyperphosphorylated tau protein may impair learning and the synaptic plasticity of neurons. Tau is a protein that is associated with and stabilizes microtubules; hyperphosphorylated tau protein is unable to perform this stabilization function. The transduction of reelin, a protein that is crucial to neuronal migration and the formation of synaptic connections in the fetal brain, may have an equally important role in regulating at least some forms of learning and synaptic plasticity in the fully developed mature brain. Reelin transduction is mediated by receptors in the brain that are members of the superfamily of low-density lipoprotein receptors. An important downstream target of reelin signal transduction appears to be inhibition of an enzyme involved in the regulation of tau phosphorylation. The faulty transduction of the reelin signal may be a pathological mechanism leading to hyperphosphorylation of tau protein. Ultimately, inhibition of tau phosphorylation may be an important therapeutic target in Alzheimer's disease and other neuropsychiatric disorders.

Modulatory effects of d-serine and sarcosine on NMDA receptor-mediated neurotransmission are apparent after stress in the genetically inbred BALB/c mouse strain

Abnormalities of NMDA receptor-mediated neurotransmission are involved in the pathophysiology of schizophrenia, Alzheimer's disease, substance abuse and seizure disorders. The NMDA receptor is implicated in schizophrenia because phencyclidine (PCP), a noncompetitive NMDA receptor antagonist, binds to a hydrophobic domain within the channel, precipitating a schizophreniform psychosis in susceptible persons. Pharmacological, environmental, and genetic variables alter NMDA receptor-mediated neurotransmission. Inbred mouse strains differ in their sensitivity to some of the behavioral effects of MK-801 (dizocilpine), a PCP analogue. The NMDA receptor complex in the BALB/c strain could reflect a unique stoichiometric combination of receptor subunits resulting in a higher proportion of the channels in the open configuration, a higher affinity of MK-801 for its hydrophobic channel domain, and/or a combination of the above. The BALB/c mouse strain, "stressed" mice, and behavioral consequences of MK-801 administration represent models of altered glutamatergic neural transmission. We were interested in examining the effect of stress on the modulatory properties of d-serine and sarcosine. d-Serine is a naturally occurring glycine agonist that modulates the ability of l-glutamate to influence the opening of the NMDA receptor-associated ionophore, and sarcosine is a naturally occurring glycine reuptake inhibitor. The data suggest that 24h after stress, d-serine and sarcosine interact synergistically to reduce MK-801's ability to antagonize electrically precipitated tonic hindlimb extension. Under conditions of stress, modulatory effects of d-serine and sarcosine on the antiseizure effect of MK-801 are observed that are not apparent in the nonstress condition. The results could be relevant to the development of glycinergic interventions for the treatment of neuropsychiatric disorders.