Characterizing mood disorders in the AFFECT study: a large, longitudinal, and phenotypically rich genetic cohort in the US.

There has recently been marked progress in identifying genetic risk factors for major depression (MD) and bipolar disorder (BD); however, few systematic efforts have been made to elucidate heterogeneity that exists within and across these diagnostic taxa. The Affective disorders, Environment, and Cognitive Trait (AFFECT) study presents an opportunity to identify and associate the structure of cognition and symptom-level domains across the mood disorder spectrum in a prospective study from a diverse US population.Participants were recruited from the 23andMe, Inc research participant database and through social media; self-reported diagnosis of MD or BD by a medical professional and medication status data were used to enrich for mood-disorder cases. Remote assessments were used to acquire an extensive range of phenotypes, including mood state, transdiagnostic symptom severity, task-based measures of cognition, environmental exposures, personality traits. In this paper we describe the study design, and the demographic and clinical characteristics of the cohort. In addition we report genetic ancestry, SNP heritability, and genetic correlations with other large cohorts of mood disorders.A total of 48,467 participants were enrolled: 14,768 with MD, 9864 with BD, and 23,835 controls. Upon enrollment, 47% of participants with MD and 27% with BD indicated being in an active mood episode. Cases reported early ages of onset (mean = 13.2 and 14.3 years for MD and BD, respectively), and high levels of recurrence (78.6% and 84.9% with >5 episodes), psychotherapy, and psychotropic medication use. SNP heritability on the liability scale for the ascertained MD participants (0.19-0.21) was consistent with the high level of disease severity in this cohort, while BD heritability estimates (0.16-0.22) were comparable to reports in other large scale genomic studies of mood disorders. Genetic correlations between the AFFECT cohort and other large-scale cohorts were high for MD but not for BD. By incorporating transdiagnostic symptom assessments, repeated measures, and genomic data, the AFFECT study represents a unique resource for dissecting the structure of mood disorders across multiple levels of analysis. In addition, the fully remote nature of the study provides valuable insights for future virtual and decentralized clinical trials within mood disorders.

Modulation of thalamo-cortical activity by the NMDA receptor antagonists ketamine and phencyclidine in the awake freely-moving rat.

Non-competitive N-methyl-d-aspartate receptor antagonists mimic schizophrenia symptoms and produce immediate and persistent antidepressant effects. We investigated the effects of ketamine and phencyclidine (PCP) on thalamo-cortical network activity in awake, freely-moving male Wistar rats to gain new insight into the neuronal populations and brain circuits involved in the effects of NMDA-R antagonists. Single unit and local field potential (LFP) recordings were conducted in mediodorsal/centromedial thalamus and in medial prefrontal cortex (mPFC) using microelectrode arrays. Ketamine and PCP moderately increased the discharge rates of principal neurons in both areas while not attenuating the discharge of mPFC GABAergic interneurons. They also strongly affected LFP activity, reducing beta power and increasing that of gamma and high-frequency oscillation bands. These effects were short-lasting following the rapid pharmacokinetic profile of the drugs, and consequently were not present at 24 h after ketamine administration. The temporal profile of both drugs was remarkably different, with ketamine effects peaking earlier than PCP effects. Although this study is compatible with the glutamate hypothesis for fast-acting antidepressant action, it does not support a local disinhibition mechanism as the source for the increased pyramidal neuron activity in mPFC. The short-lasting increase in thalamo-cortical activity is likely associated with the rapid psychotomimetic action of both agents but could also be part of a cascade of events ultimately leading to the persistent antidepressant effects of ketamine. Changes in spectral contents of high-frequency bands by the drugs show potential as translational biomarkers for target engagement of NMDA-R modulators.

Comparison of quantitative trait loci methods: Total expression and allelic imbalance method in brain RNA-seq.

BACKGROUND: Of the 108 Schizophrenia (SZ) risk-loci discovered through genome-wide association studies (GWAS), 96 are not altering the sequence of any protein. Evidence linking non-coding risk-SNPs and genes may be established using expression quantitative trait loci (eQTL). However, other approaches such allelic expression quantitative trait loci (aeQTL) also may be of use. METHODS: We applied both the eQTL and aeQTL analysis to a biobank of deeply sequenced RNA from 680 dorso-lateral pre-frontal cortex (DLPFC) samples. For each of 340 genes proximal to the SZ risk-SNPs, we asked how much SNP-genotype affected total expression (eQTL), as well as how much the expression ratio between the two alleles differed from 1:1 as a consequence of the risk-SNP genotype (aeQTL). RESULTS: We analyzed overlap with comparable eQTL-findings: 16 of the 30 risk-SNPs known to have gene-level eQTL also had gene-level aeQTL effects. 6 of 21 risk-SNPs with known splice-eQTL had exon-aeQTL effects. 12 novel potential risk genes were identified with the aeQTL approach, while 55 tested SNP-pairs were found as eQTL but not aeQTL. Of the tested 108 loci we could find at least one gene to be associated with 21 of the risk-SNPs using gene-level aeQTL, and with an additional 18 risk-SNPs using exon-level aeQTL. CONCLUSION: Our results suggest that the aeQTL strategy complements the eQTL approach to susceptibility gene identification.

Temporally dissociable effects of ketamine on neuronal discharge and gamma oscillations in rat thalamo-cortical networks.

BACKGROUND: Sub-anesthetic doses of the non-competitive N-methyl-d-aspartate receptor (NMDA-R) antagonist ketamine evoke transient psychotomimetic effects, followed by persistent antidepressant effects in treatment-resistant depressed patients and rodents through still poorly understood mechanisms. Since phencyclidine (PCP) disinhibits thalamo-cortical networks by blocking NMDA-Rs on GABAergic neurons of the reticular thalamic nucleus (RtN), we examined ketamine's actions in the same areas. METHODS: Single units and local field potentials were recorded in chloral hydrate anesthetized male Wistar rats. The effects of cumulative ketamine doses (0.25-5 mg/kg, i.v.) on neuronal discharge and oscillatory activity were examined in RtN, mediodorsal and centromedial (MD/CM) thalamic nuclei, and layer VI of the medial prefrontal cortex (mPFC). RESULTS: Ketamine (1, 2 and 5 mg/kg, i.v.) significantly decreased the discharge of MD/CM, RtN and layer VI mPFC pyramidal neurons. Simultaneously, ketamine decreased the power of low frequency oscillations in all areas examined and increased gamma oscillations in mPFC and MD/CM. Lower ketamine doses (0.25 and 0.5 mg/kg, i.v.) were ineffective. CONCLUSIONS: As observed for PCP, ketamine markedly inhibited the activity of RtN neurons. However, unlike PCP, this effect did not translate into a disinhibition of MD/CM and mPFC excitatory neurons, possibly due to a more potent and simultaneous blockade of NMDA-Rs by ketamine in MD/CM and mPFC neurons. Hence, the present in vivo results show that ketamine evokes an early transient inhibition of neuronal discharge in thalamo-cortical networks, following its rapid pharmacokinetics, which is likely associated to its psychotomimetic effects. The prolonged increase in gamma oscillations may underlie its antidepressant action.

Therapeutic endocannabinoid augmentation for mood and anxiety disorders: comparative profiling of FAAH, MAGL and dual inhibitors.

Recent studies have demonstrated anxiolytic potential of pharmacological endocannabinoid (eCB) augmentation approaches in a variety of preclinical models. Pharmacological inhibition of endocannabinoid-degrading enzymes, such as fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), elicit promising anxiolytic effects in rodent models with limited adverse behavioral effects, however, the efficacy of dual FAAH/MAGL inhibition has not been investigated. In the present study, we compared the effects of FAAH (PF-3845), MAGL (JZL184) and dual FAAH/MAGL (JZL195) inhibitors on (1) anxiety-like behaviors under non-stressed and stressed conditions, (2) locomotor activity and body temperature, (3) lipid levels in the brain and (4) cognitive functions. Behavioral analysis showed that PF-3845 or JZL184, but not JZL195, was able to prevent restraint stress-induced anxiety in the light-dark box assay when administered before stress exposure. Moreover, JZL195 treatment was not able to reverse foot shock-induced anxiety-like behavior in the elevated zero maze or light-dark box. JZL195, but not PF-3845 or JZL184, decreased body temperature and increased anxiety-like behavior in the open-field test. Overall, JZL195 did not show anxiolytic efficacy and the effects of JZL184 were more robust than that of PF-3845 in the models examined. These results showed that increasing either endogenous AEA or 2-AG separately produces anti-anxiety effects under stressful conditions but the same effects are not obtained from simultaneously increasing both AEA and 2-AG.

Functional Redundancy Between Canonical Endocannabinoid Signaling Systems in the Modulation of Anxiety.

BACKGROUND: Increasing the available repertoire of effective treatments for mood and anxiety disorders represents a critical unmet need. Pharmacological augmentation of endogenous cannabinoid (eCB) signaling has been suggested to represent a novel approach to the treatment of anxiety disorders; however, the functional interactions between two canonical eCB pathways mediated via anandamide (N-arachidonylethanolamine [AEA]) and 2-arachidonoylglycerol (2-AG) in the regulation of anxiety are not well understood. METHODS: We utilized pharmacological augmentation and depletion combined with behavioral and electrophysiological approaches to probe the role of 2-AG signaling in the modulation of stress-induced anxiety and the functional redundancy between AEA and 2-AG signaling in the modulation of anxiety-like behaviors in mice. RESULTS: Selective 2-AG augmentation reduced anxiety in the light/dark box assay and prevented stress-induced increases in anxiety associated with limbic AEA deficiency. In contrast, acute 2-AG depletion increased anxiety-like behaviors, which was normalized by selective pharmacological augmentation of AEA signaling and via direct cannabinoid receptor 1 stimulation with Δ9-tetrahydrocannabinol. Electrophysiological studies revealed 2-AG modulation of amygdala glutamatergic transmission as a key synaptic correlate of the anxiolytic effects of 2-AG augmentation. CONCLUSIONS: Although AEA and 2-AG likely subserve distinct physiological roles, a pharmacological and functional redundancy between these canonical eCB signaling pathways exists in the modulation of anxiety-like behaviors. These data support development of eCB-based treatment approaches for mood and anxiety disorders and suggest a potentially wider therapeutic overlap between AEA and 2-AG augmentation approaches than was previously appreciated.

The subchronic phencyclidine rat model: relevance for the assessment of novel therapeutics for cognitive impairment associated with schizophrenia.

RATIONALE: Current treatments for schizophrenia have modest, if any, efficacy on cognitive dysfunction, creating a need for novel therapies. Their development requires predictive animal models. The N-methyl-D-aspartate (NMDA) hypothesis of schizophrenia indicates the use of NMDA antagonists, like subchronic phencyclidine (scPCP) to model cognitive dysfunction in adult animals. OBJECTIVES: The objective of this study was to assess the scPCP model by (1) reviewing published findings of scPCP-induced neurochemical changes and effects on cognitive tasks in adult rats and (2) comparing findings from a multi-site study to determine scPCP effects on standard and touchscreen cognitive tasks. METHODS: Across four research sites, the effects of scPCP (typically 5 mg/kg twice daily for 7 days, followed by at least 7-day washout) in adult male Lister Hooded rats were studied on novel object recognition (NOR) with 1-h delay, acquisition and reversal learning in Morris water maze and touchscreen-based visual discrimination. RESULTS: Literature findings showed that scPCP impaired attentional set-shifting (ASST) and NOR in several labs and induced a variety of neurochemical changes across different labs. In the multi-site study, scPCP impaired NOR, but not acquisition or reversal learning in touchscreen or water maze. Yet, this treatment regimen induced locomotor hypersensitivity to acute PCP until 13-week post-cessation. CONCLUSIONS: The multi-site study confirmed that scPCP impaired NOR and ASST only and demonstrated the reproducibility and usefulness of the touchscreen approach. Our recommendation, prior to testing novel therapeutics in the scPCP model, is to be aware that further work is required to understand the neurochemical changes and specificity of the cognitive deficits.

Aberrant Wnt signaling pathway in medial temporal lobe structures of Alzheimer's disease.

Cognitive decline is a cardinal feature of Alzheimer's disease (AD) predominantly linked to synaptic failure, disrupted network connectivity and neurodegeneration. A large body of evidence associates the Wnt pathway with synaptic modulation and cognitive processes, suggesting a potential role for aberrant Wnt signaling in cognitive impairment. In fact, altered expression of key Wnt pathway components has been found in brains of AD patients as well as AD animal models supporting a deregulated pathway in AD. The evidence for deregulated Wnt signaling in AD, however, remains sparse and focused on isolated Wnt pathway components. Here, we provide the first comprehensive pathway-focused evaluation of the Wnt pathway in the entorhinal cortex and hippocampus of AD brains. Our data demonstrate altered Wnt pathway gene expression at all levels of the pathway in both medial temporal lobe regions with the hippocampus exhibiting most pronounced changes. Furthermore, the Wnt pathway constituents Wnt7b and Tcf7l1/Tcf3 showed overlapping gene expression alterations across both medial temporal lobe structures, while ß-catenin was inversely expressed between brain regions. We also identified total protein alterations of the intracellular Wnt pathway signaling components ß-catenin, Gsk3ß and Tcf7l1/Tcf3 and the phosphorylation state of ß-catenin and Gsk3ß in the hippocampus suggestive of a link between AD and aberrant canonical activity. Alterations in Gsk3ß co-appeared with hippocampal kinase-targeted hyperphosphorylation at specific tau epitope in soluble pretangles and prominent tau aggregation exclusively in insoluble neurofibrillary tangles of AD subjects. The Wnt pathway-focused approach confirms altered Wnt signaling in the neurodegenerative AD brain and highlights the potential role of the pathway as a therapeutic target for the treatment of patients.

Vortioxetine disinhibits pyramidal cell function and enhances synaptic plasticity in the rat hippocampus.

Vortioxetine, a novel antidepressant with multimodal action, is a serotonin (5-HT)3, 5-HT7 and 5-HT1D receptor antagonist, a 5-HT1B receptor partial agonist, a 5-HT1A receptor agonist and a 5-HT transporter (SERT) inhibitor. Vortioxetine has been shown to improve cognitive performance in several preclinical rat models and in patients with major depressive disorder. Here we investigated the mechanistic basis for these effects by studying the effect of vortioxetine on synaptic transmission, long-term potentiation (LTP), a cellular correlate of learning and memory, and theta oscillations in the rat hippocampus and frontal cortex. Vortioxetine was found to prevent the 5-HT-induced increase in inhibitory post-synaptic potentials recorded from CA1 pyramidal cells, most likely by 5-HT3 receptor antagonism. Vortioxetine also enhanced LTP in the CA1 region of the hippocampus. Finally, vortioxetine increased fronto-cortical theta power during active wake in whole animal electroencephalographic recordings. In comparison, the selective SERT inhibitor escitalopram showed no effect on any of these measures. Taken together, our results indicate that vortioxetine can increase pyramidal cell output, which leads to enhanced synaptic plasticity in the hippocampus. Given the central role of the hippocampus in cognition, these findings may provide a cellular correlate to the observed preclinical and clinical cognition-enhancing effects of vortioxetine.

PCP-induced deficits in murine nest building activity: employment of an ethological rodent behavior to mimic negative-like symptoms of schizophrenia.

Schizophrenia is a severe psychiatric disorder characterized by three symptom domains, positive (hallucinations, obsession), negative (social withdrawal, apathy, self-neglect) and cognitive (impairment in attention, memory and executive function). Whereas current medication ameliorates positive symptomatology, negative symptoms as well as cognitive dysfunctions remain untreated. The development of improved therapies for negative symptoms has proven particularly difficult, in part due to the inability of mimicking these in rodents. Here, we address the predictive validity of combining an ethologically well preserved behavior in rodents, namely nest building activity, with an established animal model of schizophrenia, the sub-chronic PCP model, for negative symptoms. Decline in rodent nesting activity has been suggested to mirror domains of negative symptoms of schizophrenia, including social withdrawal, anhedonia and self-neglect, whereas repeated treatment with the NMDAR antagonist PCP induces and exacerbates schizophrenia-like symptoms in rodents and human subjects. Using a back-translational approach of pharmacological validation, we tested the effects of two agents targeting the nicotinic α7 receptor (EVP-6124 and TC-5619) that were reported to exert some beneficial effect on negative symptoms in schizophrenic patients. Sub-chronic PCP treatment resulted in a significant nest building deficit in mice and treatment with EVP-6124 and TC-5619 reversed this PCP-induced deficit. In contrast, the atypical antipsychotic drug risperidone remained ineffective in this assay. In addition, EVP-6124, TC-5619 and risperidone were tested in the Social Interaction Test (SIT), an assay suggested to address negative-like symptoms. Results obtained in SIT were comparable to results in the nest building test (NEST). Based on these findings, we propose nest building in combination with the sub-chronic PCP model as a novel approach to assess negative-like symptoms of schizophrenia in rodents.

In vitro and in vivo characterisation of Lu AF64280, a novel, brain penetrant phosphodiesterase (PDE) 2A inhibitor: potential relevance to cognitive deficits in schizophrenia.

Here, we present the pharmacological characterisation of Lu AF64280, a novel, selective, brain penetrant phosphodiesterase (PDE) 2A inhibitor, in in vitro/in vivo assays indicative of PDE2A inhibition, and in vivo models/assays relevant to cognitive processing or antipsychotic-like activity. The in vitro selectivity of Lu AF64280 was determined against a panel of PDE enzymes and 3',5'-cyclic guanosine monophosphate (cGMP) levels in the hippocampus were determined using in vivo microdialysis. Lu AF64280 potently inhibited hPDE2A (Ki = 20 nM), 50-fold above moderate inhibition of both hPDE9A (Ki = 1,000 nM) and hPDE10A (Ki = 1,800 nM), and displayed a >250-fold selectivity over all other full-length human recombinant PDE family members (Ki above 5,000 nM). Lu AF64280 (20 mg/kg) significantly increased cGMP levels in the hippocampus (p < 0.01 versus vehicle-treated mice), attenuated sub-chronic phencyclidine-induced deficits in novel object exploration in rats (10 mg/kg, p < 0.001 versus vehicle-treated), blocked early postnatal phencyclidine-induced deficits in the intradimensional/extradimensional shift task in rats (1 and 10 mg/kg, p < 0.001 versus vehicle-treated) and attenuated spontaneous P20-N40 auditory gating deficits in DBA/2 mice (20 mg/kg, p < 0.05 versus vehicle-treated). In contrast, Lu AF64280 failed to attenuate phencyclidine-induced hyperactivity in mice, and was devoid of antipsychotic-like activity in the conditioned avoidance response paradigm in rats, at any dose tested. Lu AF64280 represents a novel tool compound for selective PDE2A inhibition that substantiates a critical role of this enzyme in cognitive processes under normal and pathological conditions.

Impaired hippocampal acetylcholine release parallels spatial memory deficits in Tg2576 mice subjected to basal forebrain cholinergic degeneration.

The Alzheimer's disease (AD) mouse model Tg2576 overexpresses an AD associated mutant variant of human APP and accumulates amyloid beta (Aß) in an age-dependent manner. Using the selective cholinergic immunotoxin mu p75-saporin (SAP), we induced a partial basal forebrain cholinergic degeneration (BFCD) in 3 months old male Tg2576 mice to co-express cholinergic degeneration with Aß overexpression as these characteristics constitutes key hallmarks of AD. At 9 months, SAP lesioned Tg2576 mice were cognitively impaired in two spatial paradigms addressing working memory and mid to long-term memory. Conversely, there was no deterioration of cognitive functioning in sham lesioned Tg2576 mice or wild type littermates (wt) receiving the immunotoxin. At 10 months of age, release of acetylcholine (ACh) was addressed by microdialysis in conscious mice. Scopolamine-induced increases in hippocampal ACh efflux was significantly reduced in SAP lesioned Tg2576 mice compared to sham lesioned Tg2576 mice. Intriguingly, there was no significant difference in ACh efflux between wt treatment groups. Following SAP treatment, choline acetyltransferase activity was reduced in the hippocampus and frontal cortex and the reduction was comparable between groups. Our results suggest that partial BFCD acts collectively with increased levels of Aß to induce cognitive decline and to compromise cholinergic release. Tg2576 mice with BFCD may constitute a new and suitable AD mouse model to study the interrelations between cholinergic deficits and amsyloid deposition.

Expression of presynaptic markers in a neurodevelopmental animal model with relevance to schizophrenia.

Administration of N-methyl-D-aspartate receptor antagonist phencyclidine (PCP) to rat pups at postnatal day (PND) 7, 9, and 11 [neonatal PCP (neoPCP) model] induces cognitive deficits similar to those observed in schizophrenia. Expression of presynaptic SNARE protein, synaptosomal-associated protein of 25 kDa (Snap25), has been shown to be downregulated in postmortem brains from patients with schizophrenia. The present study was designed to investigate the long-term effects of neoPCP administration on expression of presynaptic markers altered in schizophrenia. Using radioactive in-situ hybridization, the expression of Snap25 was measured in the prefrontal cortex and the hippocampal formation (CA1, CA3, CA4, and dentate gyrus) at PND 29 and 80 in neoPCP and control rats. As a secondary presynaptic marker, the expressional level of synaptophysin was also measured in the same areas. Stereological estimation of the number of neurons and volume was used to exclude potential bias in cell numbers. A significant reduction in the expression of Snap25 in the hippocampal CA4 region was observed in adult neoPCP rats (PND 80, P<0.01), but not in preadolescent rats (PND 29), indicating a late developmental manifestation of a presynaptic pathology. The number of neurons and volume of the CA4 region showed no change in PCP rats compared with the controls. Furthermore, expression of another presynaptic marker, synaptophysin, remained unaffected by the PCP treatment. These findings indicate that perinatal PCP injections induce a delayed presynaptic impact on the vesicle fusion machinery in a brain region important for cognitive processes.

A schizophrenia rat model induced by early postnatal phencyclidine treatment and characterized by Magnetic Resonance Imaging.

Better animal models are needed to aid the development of new medications to alleviate the cognitive deficits associated with schizophrenia. Growing evidence suggests neurodevelopmental insults and disturbances in NMDA receptor (NMDAR) signaling to be involved in the schizophrenia etiology. Acute administration of phencyclidine (PCP) induces schizophrenia-like symptoms in healthy volunteers and exacerbates symptoms in patients with schizophrenia. In this study, pharmacological Magnetic Resonance Imaging (phMRI) was used to evaluate if rats treated with 20mg/kg PCP on postnatal days 7, 9, and 11 (neoPCP), compared to saline (neoVeh), were hypersensitive to acute PCP administration in adulthood (acutePCP). Intravenous administration of 0.5mg/kg acutePCP produced robust and sustained relative cerebral blood volume (rCBV) increase in discrete frontal, neocortical, hippocampal, thalamic, and limbic brain structures in both neoPCP:acutePCP and neoVeh:acutePCP rats compared to acute saline treatment (Vehicle control group). AcutePCP injection significantly increased the rCBV response in the medial prefrontal cortex and nucleus accumbens compared to the Vehicle control group, without distinguishing neoPCP and neoVeh animals. However, at late time points (25-33min post acutePCP injection), neoPCP animals showed significantly higher rCBV values compared to the Vehicle control group, suggesting an altered sensitivity toward NMDAR blockade in adult rats subjected to this neurodevelopmental procedure. In combination with the observed cognitive deficits revealed in this animal model, the present findings indicate that altered NMDAR signaling might underlie the symptomatic changes seen in schizophrenia, adding to the construct and face validity of this model.

Vortioxetine (Lu AA21004), a novel multimodal antidepressant, enhances memory in rats.

The serotonergic system plays an important role in cognitive functions via various 5-HT receptors. Vortioxetine (Lu AA21004) in development as a novel multimodal antidepressant is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, a 5-HT1B receptor partial agonist, a 5-HT1A receptor agonist and a 5-HT transporter (5-HTT) inhibitor in vitro. Preclinical studies suggest that 5-HT3 and 5-HT7 receptor antagonism as well as 5-HT1A receptor agonism may have a positive impact on cognitive functions including memory. Thus vortioxetine may potentially enhance memory. We investigated preclinical effects of vortioxetine (1-10mg/kg administered subcutaneously [s.c.]) on memory in behavioral tests, and on cortical neurotransmitter levels considered important in rat memory function. Contextual fear conditioning and novel object recognition tests were applied to assess memory in rats. Microdialysis studies were conducted to measure extracellular neurotransmitter levels in the rat medial prefrontal cortex. Vortioxetine administered 1h before or immediately after acquisition of contextual fear conditioning led to an increase in freezing time during the retention test. This mnemonic effect was not related to changes in pain sensitivity as measured in the hotplate test. Rats treated with vortioxetine 1h before training spent more time exploring the novel object in the novel object recognition test. In microdialysis studies of the rat medial prefrontal cortex, vortioxetine increased extracellular levels of acetylcholine and histamine. In conclusion, vortioxetine enhanced contextual and episodic memory in rat behavioral models. Further demonstration of its potential effect on memory functions in clinical settings is warranted.

Design, synthesis, and pharmacological characterization of N- and O-substituted 5,6,7,8-tetrahydro-4H-isoxazolo[4,5-d]azepin-3-ol analogues: novel 5-HT(2A)/5-HT(2C) receptor agonists with pro-cognitive properties.

The isoxazol-3-one tautomer of the bicyclic isoxazole, 5,6,7,8-tetrahydro-4H-isoxazolo[4,5-d]azepin-3-ol (THAZ), has previously been shown to be a weak GABA(A) and glycine receptor antagonist. In the present study, the potential in this scaffold has been explored through the synthesis and pharmacological characterization of a series of N- and O-substituted THAZ analogues. The analogues N-Bn-THAZ (3d) and O-Bn-THAZ (4d) were found to be potent agonists of the human 5-HT(2A) and 5-HT(2C) receptors. Judging from an elaborate pharmacological profiling at numerous other CNS targets, the 3d analogue appears to be selective for the two receptors. Administration of 3d substantially improved the cognitive performance of mice in a place recognition Y-maze model, an effect fully reversible by coadministration of the selective 5-HT(2C) antagonist SB242084. In conclusion, as novel bioavailable cognitive enhancers that most likely mediate their effects through 5-HT(2A) and/or 5-HT(2C) receptors, the isoxazoles 3d and 4d constitute interesting leads for further medicinal chemistry development.

Differential expression of parvalbumin in neonatal phencyclidine-treated rats and socially isolated rats.

Decreased parvalbumin expression is a hallmark of the pathophysiology of schizophrenia and has been associated with abnormal cognitive processing and decreased network specificity. It is not known whether this decrease is due to reduced expression of the parvalbumin protein or degeneration of parvalbumin-positive interneurons (PV(+) interneurons). In this study, we examined PV(+) expression in two rat models of cognitive dysfunction in schizophrenia: the environmental social isolation (SI) and pharmacological neonatal phencyclidine (neoPCP) models. Using a stereological method, the optical fractionator, we counted neurons, PV(+) interneurons, and glial cells in the medial prefrontal cortex (mPFC) and hippocampus (HPC). In addition, we quantified the mRNA level of parvalbumin in the mPFC. There was a statistically significant reduction in the number of PV(+) interneurons (p = 0.021) and glial cells (p = 0.024) in the mPFC of neonatal phencyclidine rats, but not in SI rats. We observed no alterations in the total number of neurons, hippocampal PV(+) interneurons, parvalbumin mRNA expression or volume of the mPFC or HPC in the two models. Thus, as the total number of neurons remains unchanged following phencyclidine (PCP) treatment, we suggest that the decreased number of counted PV(+) interneurons represents a reduced parvalbumin protein expression below immunohistochemical detection limit rather than a true cell loss. Furthermore, these results indicate that the effect of neonatal PCP treatment is not limited to neuronal populations.

Cholinergic degeneration is associated with increased plaque deposition and cognitive impairment in APPswe/PS1dE9 mice.

Cholinergic dysfunction and deposition of plaques containing amyloid ß-peptides (Aß) are two of the characteristics of Alzheimer's disease. Here, we combine APPswe/PS1dE9 (APP/PS1) mice with the cholinergic immunotoxin mu p75-saporin (SAP) to integrate partial basal forebrain cholinergic degeneration and the neuropathology of APP/PS1 mice. By 6 months of age, APP/PS1 mice and wild type littermates (Wt) received intracerebroventricular injection of 0.6 µg SAP (lesion) or PBS (sham). Two months following surgery, APP/PS1 mice treated with SAP were significantly impaired compared to sham treated APP/PS1 mice in a behavioural paradigm addressing working memory. Conversely, the performance of Wt mice was unaffected by SAP treatment. Choline acetyltransferase activity was reduced in the hippocampus and frontal cortex following SAP treatment. The selective effect of a mild SAP lesion in APP/PS1 mice was not due to a more extensive cholinergic degeneration since the reduction in choline acetyltransferase activity was similar following SAP treatment in APP/PS1 mice and Wt. Interestingly, plaque load was significantly increased in SAP treated APP/PS1 mice relative to sham lesioned APP/PS1 mice. Additionally, APP/PS1 mice treated with SAP showed a tendency towards an increased level of soluble and insoluble Aß1-40 and Aß1-42 measured in brain tissue homogenate. Our results suggest that the combination of cholinergic degeneration and Aß overexpression in the APP/PS1 mouse model results in cognitive decline and accelerated plaque burden. SAP treated APP/PS1 mice might thus constitute an improved model of Alzheimer's disease-like neuropathology and cognitive deficits compared to the conventional APP/PS1 model without selective removal of basal forebrain cholinergic neurons.

NMDA receptors, cognition and schizophrenia--testing the validity of the NMDA receptor hypofunction hypothesis.

Cognitive dysfunction is core to schizophrenia, and remains poorly treated by existing therapies. A prominent hypothesis suggests that many symptoms arise from N-methyl-d-aspartate receptor (NMDAR) hypofunction. Subsequently, there has emerged a widespread use of many preclinical and clinical NMDAR antagonist models in the search for novel treatments. Clinically, ketamine is broadly purported to induce cognitive symptoms similar to those of schizophrenia. Preclinically, acute, subchronic and neonatal NMDAR antagonist administration models are all utilised in this context, as well as NMDAR transgenic animals. In this review, key strengths and weaknesses of each of these approaches are described with regard to their ability to recapitulate the deficits seen in patients. Given the breadth of literature and vogue for research in this topic, instances of NMDAR antagonist effects in the desired domains can readily be found preclinically. However, it is surprisingly difficult to identify any single aspect of cognitive function that possesses complete translational integrity. That is, there does not seem to be an NMDAR antagonist regimen proven to engage NMDARs equivalently in humans and animals that reliably produces the same cognitive effects in each species. This is likely due to the diverse range of techniques and models used by preclinical researchers, a paucity of research describing pharmacokinetic-pharmacodynamic relationships of NMDAR antagonist regimens, little capability to measure target engagement, and the lack of harmonized procedures between preclinical and clinical studies. Realizing the potential of the NMDAR hypofunction hypothesis to model cognitive impairment in schizophrenia will require some of these issues to be addressed.

Can small molecules provide truly effective enhancement of cognition? Current achievements and future directions.

INTRODUCTION: The prevalence of age-related diseases that implicate a deterioration of cognitive abilities is increasing. Moreover, cognitive decline occurs in numerous CNS disorders affecting patients at younger ages as well, resulting in reduced functional ability and quality of life. Despite the existence of few medications treating cognition, the need for efficacious treatment options to alleviate, halt or even prevent cognitive decline is generally unmet to date. Consequently, extensive research efforts are undertaken to identify medications that can effectively enhance cognition. AREAS COVERED: This review covers ongoing clinical trials for cognition and reflects on efforts undertaken to increase the success rates of procognitive drug treatment. The review discusses ways to optimize the drug development process for cognition enhancing agents at the preclinical to clinical interface and provides concrete examples. EXPERT OPINION: The existing efficacy readouts addressing cognition in preclinical research offer little translational validity to the clinical situation. In order to identify truly efficacious drug candidates, biomarkers need to be developed that directly address conserved mechanisms underlying cognitive performances. To this end, technologies such as neuroimaging or electroencephalography constitute promising entry points for identifying both the cognitive domain and the patient population most responsive to drug treatment.