Behavioural abnormalities in male mice lacking neuronal nitric oxide synthase

Nitric oxide-signalling affects panic-like defensive behaviour and defensive antinociception neuromodulation in the prelimbic cerebral cortex

RATIONALE

The prelimbic division (PrL) of the medial prefrontal cortex (mPFC) is a key structure in panic.

OBJECTIVES

To evaluate the role of nitric oxide (NO) in defensive behaviour and antinociception.

METHODS

Either Nω-propyl-L-arginine (NPLA) or Carboxy-PTIO was microinjected in the PrL cortex, followed by hypothalamic treatment with bicuculline. The exploratory behaviours, defensive reactions and defensive antinociception were recorded. Encephalic c-Fos protein was immunolabelled after escape behaviour.

RESULTS

NPLA (an inhibition of nNOs) decreased panic-like responses and innate fear-induced antinociception. The c-PTIO (a membrane-impermeable NO scavenger) decreased the escape behaviour. PrL cortex pre-treatment with c-PTIO at all doses decreased defensive antinociception. c-Fos protein was labelled in neocortical areas, limbic system, and mesencephalic structures.

CONCLUSION

The NPLA and c-PTIO in the PrL/mPFC decreased the escape behaviour and defensive antinociception organised by medial hypothalamic nuclei. The oriented escape behaviour recruits neocortical areas, limbic system, and mesencephalic structures. These findings suggest that the organisation of defensive antinociception recruits NO-signalling mechanisms within the PrL cortex. Furthermore, the present findings also support the role of NO as a retrograde messenger in the PrL cortex during panic-like emotional reactions.

Association of impulsive behavior and cerebrospinal fluid/plasma oxidation and antioxidation ratio in Chinese men

OBJECTIVES

Impulsive behavior is the precursor of many psychiatric and neurological conditions. High levels of impulsive behavior will increase health risk behavior and related injuries. Impulsive behavior is produced and regulated by central and peripheral biological factors, and oxidative stress (OS) can aggravate it. However, previous studies only showed that impulsive behavior was related to the level of the peripheral OS. Therefore, this study aims to clarify the relationship between OS and impulsive behavior in the brain and peripheral blood.

METHODS

We recruited 64 Chinese men. We measured superoxide dismutase (SOD) (including copper, zinc and manganese) and nitric oxide synthase (NOS) (including total, inducible and constitutive) in cerebrospinal fluid (CSF) and plasma. The Barratt Impulsiveness Scale version 11 (BIS-11) was used to evaluate impulsive behavior. The relationship between OS and impulsive behavior was evaluated by partial correlation analysis and stepwise multiple regression analysis.

RESULTS

Partial correlation analysis showed that the ratio of total NOS-to-MnSOD and iNOS-to-MnSOD in CSF were negatively correlated with the BIS-11 motor scores (r = -0.431, p = -0.001; r = -0.434, p = -0.001). Stepwise multiple regression analysis showed that the ratio of CSF iNOS-to-MnSOD was the most influential variable on the BIS-11 motor scores(β = -0.434, t = -3.433, 95 %CI(-0.374, -0.098), p = 0.001).

CONCLUSIONS AND RELEVANCE

The imbalance of central oxidation and antioxidation is related to impulsive behavior, which broadens our understanding of the correlation between impulsive behavior and OS.

Social isolation and aggression training lead to escalated aggression and hypothalamus-pituitary-gonad axis hyperfunction in mice

Although the participation of sex hormones and sex hormone-responsive neurons in aggressive behavior has been extensively studied, the role of other systems within the hypothalamus-pituitary-gonadal (HPG) axis remains elusive. Here we assessed how the gonadotropin-releasing hormone (GnRH) and kisspeptin systems are impacted by escalated aggression in male mice. We used a combination of social isolation and aggression training (IST) to exacerbate mice's aggressive behavior. Next, low-aggressive (group-housed, GH) and highly aggressive (IST) mice were compared regarding neuronal activity in the target populations and hormonal levels, using immunohistochemistry and ELISA, respectively. Finally, we used pharmacological and viral approaches to manipulate neuropeptide signaling and expression, subsequently evaluating its effects on behavior. IST mice exhibited enhanced aggressive behavior compared to GH controls, which was accompanied by elevated neuronal activity in GnRH neurons and arcuate nucleus kisspeptin neurons. Remarkably, IST mice presented an increased number of kisspeptin neurons in the anteroventral periventricular nucleus (AVPV). In addition, IST mice exhibited elevated levels of luteinizing hormone (LH) in serum. Accordingly, activation and blockade of GnRH receptors (GnRHR) exacerbated and reduced aggression, respectively. Surprisingly, kisspeptin had intricate effects on aggression, i.e., viral ablation of AVPV-kisspeptin neurons impaired the training-induced rise in aggressive behavior whereas kisspeptin itself strongly reduced aggression in IST mice. Our results indicate that IST enhances aggressive behavior in male mice by exacerbating HPG-axis activity. Particularly, increased GnRH neuron activity and GnRHR signaling were found to underlie aggression whereas the relationship with kisspeptin remains puzzling.

Chemical cognition: chemoconnectomics and convergent evolution of integrative systems in animals

Neurons underpin cognition in animals. However, the roots of animal cognition are elusive from both mechanistic and evolutionary standpoints. Two conceptual frameworks both highlight and promise to address these challenges. First, we discuss evidence that animal neural and other integrative systems evolved more than once (convergent evolution) within basal metazoan lineages, giving us unique experiments by Nature for future studies. The most remarkable examples are neural systems in ctenophores and neuroid-like systems in placozoans and sponges. Second, in addition to classical synaptic wiring, a chemical connectome mediated by hundreds of signal molecules operates in tandem with neurons and is the most information-rich source of emerging properties and adaptability. The major gap-dynamic, multifunctional chemical micro-environments in nervous systems-is not understood well. Thus, novel tools and information are needed to establish mechanistic links between orchestrated, yet cell-specific, volume transmission and behaviors. Uniting what we call chemoconnectomics and analyses of the cellular bases of behavior in basal metazoan lineages arguably would form the foundation for deciphering the origins and early evolution of elementary cognition and intelligence.

Dysfunctional and Dysregulated Nitric Oxide Synthases in Cardiovascular Disease: Mechanisms and Therapeutic Potential

Nitric oxide (NO) plays an important and diverse signalling role in the cardiovascular system, contributing to the regulation of vascular tone, endothelial function, myocardial function, haemostasis, and thrombosis, amongst many other roles. NO is synthesised through the nitric oxide synthase (NOS)-dependent L-arginine-NO pathway, as well as the nitrate-nitrite-NO pathway. The three isoforms of NOS, namely neuronal (NOS1), inducible (NOS2), and endothelial (NOS3), have different localisation and functions in the human body, and are consequently thought to have differing pathophysiological roles. Furthermore, as we continue to develop a deepened understanding of the different roles of NOS isoforms in disease, the possibility of therapeutically modulating NOS activity has emerged. Indeed, impaired (or dysfunctional), as well as overactive (or dysregulated) NOS activity are attractive therapeutic targets in cardiovascular disease. This review aims to describe recent advances in elucidating the physiological role of NOS isoforms within the cardiovascular system, as well as mechanisms of dysfunctional and dysregulated NOS in cardiovascular disease. We then discuss the modulation of NO and NOS activity as a target in the development of novel cardiovascular therapeutics.

Knock-out of the critical nitric oxide synthase regulator DDAH1 in mice impacts amphetamine sensitivity and dopamine metabolism

The enzyme dimethylarginine dimethylaminohydrolase 1 (DDAH1) plays a pivotal role in the regulation of nitric oxide levels by degrading the main endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA). Growing evidence highlight the potential implication of DDAH/ADMA axis in the etiopathogenesis of several neuropsychiatric and neurological disorders, yet the underlying molecular mechanisms remain elusive. In this study, we sought to investigate the role of DDAH1 in behavioral endophenotypes with neuropsychiatric relevance. To achieve this, a global DDAH1 knock-out (DDAH1-ko) mouse strain was employed. Behavioral testing and brain region-specific neurotransmitter profiling have been conducted to assess the effect of both genotype and sex. DDAH1-ko mice exhibited increased exploratory behavior toward novel objects, altered amphetamine response kinetics and decreased dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) level in the piriform cortex and striatum. Females of both genotypes showed the most robust amphetamine response. These results support the potential implication of the DDAH/ADMA pathway in central nervous system processes shaping the behavioral outcome. Yet, further experiments are required to complement the picture and define the specific brain-regions and mechanisms involved.

nNOS and Neurological, Neuropsychiatric Disorders: A 20-Year Story

In the central nervous system, nitric oxide (NO), a free gas with multitudinous bioactivities, is mainly produced from the oxidation of L-arginine by neuronal nitric oxide synthase (nNOS). In the past 20 years, the studies in our group and other laboratories have suggested a significant involvement of nNOS in a variety of neurological and neuropsychiatric disorders. In particular, the interactions between the PDZ domain of nNOS and its adaptor proteins, including post-synaptic density 95, the carboxy-terminal PDZ ligand of nNOS, and the serotonin transporter, significantly influence the subcellular localization and functions of nNOS in the brain. The nNOS-mediated protein-protein interactions provide new attractive targets and guide the discovery of therapeutic drugs for neurological and neuropsychiatric disorders. Here, we summarize the work on the roles of nNOS and its association with multiple adaptor proteins on neurological and neuropsychiatric disorders.

Understanding the Role of Oxidative Stress, Neuroinflammation and Abnormal Myelination in Excessive Aggression Associated with Depression: Recent Input from Mechanistic Studies

Aggression and deficient cognitive control problems are widespread in psychiatric disorders, including major depressive disorder (MDD). These abnormalities are known to contribute significantly to the accompanying functional impairment and the global burden of disease. Progress in the development of targeted treatments of excessive aggression and accompanying symptoms has been limited, and there exists a major unmet need to develop more efficacious treatments for depressed patients. Due to the complex nature and the clinical heterogeneity of MDD and the lack of precise knowledge regarding its pathophysiology, effective management is challenging. Nonetheless, the aetiology and pathophysiology of MDD has been the subject of extensive research and there is a vast body of the latest literature that points to new mechanisms for this disorder. Here, we overview the key mechanisms, which include neuroinflammation, oxidative stress, insulin receptor signalling and abnormal myelination. We discuss the hypotheses that have been proposed to unify these processes, as many of these pathways are integrated for the neurobiology of MDD. We also describe the current translational approaches in modelling depression, including the recent advances in stress models of MDD, and emerging novel therapies, including novel approaches to management of excessive aggression, such as anti-diabetic drugs, antioxidant treatment and herbal compositions.

Dysfunction of AMPA receptor GluA3 is associated with aggressive behavior in human

Inappropriate aggression in humans hurts the society, families and individuals. The genetic basis for aggressive behavior, however, remains largely elusive. In this study, we identified two rare missense variants in X-linked GRIA3 from male patients who showed syndromes featuring aggressive outbursts. Both G630R and E787G mutations in AMPA receptor GluA3 completely lost their ion channel functions. Furthermore, a guanine-repeat single nucleotide polymorphism (SNP, rs3216834) located in the first intron of human GRIA3 gene was found to regulate GluA3 expression with longer guanine repeats (rs3216834-10G/-11G) suppressing transcription compared to the shorter ones (-7G/-8G/-9G). Importantly, the distribution of rs3216834-10G/-11G was elevated in a male violent criminal sample from Chinese Han population. Using GluA3 knockout mice, we showed that the excitatory neurotransmission and neuronal activity in the medial prefrontal cortex (mPFC) was impaired. Expressing GluA3 back into the mPFC alleviated the aggressive behavior of GluA3 knockout mice, suggesting that the defects in mPFC explained, at least partially, the neural mechanisms underlying the aggressive behavior. Therefore, our study provides compelling evidence that dysfunction of AMPA receptor GluA3 promotes aggressive behavior.

Expression and localization of neuronal nitric oxide synthase in the brain and sensory tissues of the African cichlid fish Astatotilapia burtoni

Nitric oxide (NO) produced by the enzyme neuronal nitric oxide synthase serves as an important neurotransmitter in the central nervous system that is involved in reproductive regulation, learning, sensory processing, and other forms of neural plasticity. Here, we map the distribution of nnos-expressing cells in the brain and retina of the cichlid fish Astatotilapia burtoni using in situ hybridization. In the brain, nnos-expressing cells are found from the olfactory bulbs to the hindbrain, including within specific nuclei involved in decision-making, sensory processing, neuroendocrine regulation, and the expression of social behaviors. In the retina, nnos-expressing cells are found in the inner nuclear layer, presumably in amacrine cells. We also used quantitative PCR to test for differences in nnos expression within the eye and olfactory bulbs of males and females of different reproductive states and social statuses. In the eye, males express more nnos than females, and socially dominant males express more nnos than subordinate males, but expression did not differ among female reproductive states. In the olfactory bulbs, dominant males had greater nnos expression than subordinate males. These results suggest a status-specific function for NO signaling in the visual and olfactory systems that may be important for sensory perception related to mating or territorial interactions to maintain the social hierarchy. The widespread distribution of nnos-expressing cells throughout the cichlid brain is similar to that in other teleosts, with some conserved localization patterns across vertebrates, suggesting diverse functions for this important neurotransmitter system.

Time of day as a critical variable in biology

BACKGROUND

Circadian rhythms are important for all aspects of biology; virtually every aspect of biological function varies according to time of day. Although this is well known, variation across the day is also often ignored in the design and reporting of research. For this review, we analyzed the top 50 cited papers across 10 major domains of the biological sciences in the calendar year 2015. We repeated this analysis for the year 2019, hypothesizing that the awarding of a Nobel Prize in 2017 for achievements in the field of circadian biology would highlight the importance of circadian rhythms for scientists across many disciplines, and improve time-of-day reporting.

RESULTS

Our analyses of these 1000 empirical papers, however, revealed that most failed to include sufficient temporal details when describing experimental methods and that few systematic differences in time-of-day reporting existed between 2015 and 2019. Overall, only 6.1% of reports included time-of-day information about experimental measures and manipulations sufficient to permit replication.

CONCLUSIONS

Circadian rhythms are a defining feature of biological systems, and knowing when in the circadian day these systems are evaluated is fundamentally important information. Failing to account for time of day hampers reproducibility across laboratories, complicates interpretation of results, and reduces the value of data based predominantly on nocturnal animals when extrapolating to diurnal humans.

Social status mediated variation in hypothalamic transcriptional profiles of male mice

Animals of different social status exhibit variation in aggression, territorial and reproductive behavior as well as activity patterns, feeding, drinking and status signaling. This behavioral and physiological plasticity is coordinated by underlying changes in brain gene transcription. Using Tag-based RNA sequencing (Tag-seq), we explore RNA transcriptomes from the medial preoptic area (mPOA) and ventral hypothalamus (vHYP) of male mice of different social ranks in a dominance hierarchy and detect candidate genes and cellular pathways that underlie status-related plasticity. Within the mPOA, oxytocin (Oxt) and vasopressin (Avp) are more highly expressed in subdominant mice compared to other ranks, while nitric oxide synthase (Nos1) has lower expression in subdominant mice. Within the vHYP, we find that both orexigenic and anorexigenic genes involved in feeding behavior, including agouti-related peptide (Agrp), neuropeptide-Y (Npy), galanin (Gal), proopiomelanocortin (Pomc), and Cocaine- and Amphetamine-Regulated Transcript Protein prepropeptide (Cartpt), are less expressed in dominant animals compared to more subordinate ranks. We suggest that this may represent a reshaping of feeding circuits in dominant compared to subdominant and subordinate animals. Furthermore, we determine several genes that are positively and negatively associated with the level of despotism (aggression) in dominant males. Ultimately, we identify hypothalamic genes controlling feeding and social behaviors that are differentially transcribed across animals of varying social status. These changes in brain transcriptomics likely support phenotypic variation that enable animals to adapt to their current social status.

Effects of 3, 4-divanillyltetrahydrofuran from Urtica fissa on sexual dysfunction in diabetic mice

ETHNOPHARMACOLOGICAL RELEVANCE

Urtica fissa E. Pritz. are important herbs and have been traditionally used as ethnic medicine to treat rheumatism, inflammation, diabetes, and benign prostatic hyperplasia by the Han, Uighur, and other minorities in China, and also as an aphrodisiac in Uighur medicine.

AIMS OF THE STUDY

To determine the effect and potential mechanism of 3, 4-divanillyltetrahydrofuran (DVTF), one of the main active components isolated from U. fissa on hypogonadism in diabetic mice.

MATERIALS AND METHODS

The active compound DVTF was extracted and separated from the roots of U. fissa and identified using mass spectrometry and nuclear magnetic resonance spectroscopy. A mouse model of diabetes was established using high fat and sugar diet combined with streptozotocin. In the treatment groups, mice were received different doses of DVTF for 4 weeks. Fasting blood glucose levels, physiological and biochemical indices, and the mating behavior of DM mice were analyzed. Changes in testicular morphology were assessed using light microscopy and transmission electron microscopy. The expression of testosterone synthesis-related signaling proteins was detected using western blotting. Molecular docking was used to determine the binding ability of DVTF to Nur77.

RESULTS

In diabetic mice, body weight and fasting blood glucose levels decreased. Mating behavior, including mount latency, mount number, and intromission number, was improved following DVTF treatment. Plasma total testosterone, free testosterone, and insulin resistance were positively associated with the recovery of testicular pathological structures in diabetic mice. DVTF treatment increased the expression of Nur77, StAR, and P450scc in the testes of diabetic mice. DVTF and Nur77 formed chemical bonds at five sites.

CONCLUSION

As one of the main active components of U. fissa, DVTF exert potential therapeutic effects on testicular injury and hypogonadism caused by diabetes through activating the expression of Nur77 and testosterone synthesis related proteins. Our result will provide new insight for the clinical application of Urtica fissa E. Pritz., especially DVTF, as a potential drug candidate in the treatment of hypogonadism in diabetes.

Differential expression of 10 genes in the hypothalamus of two generations of rats selected for a reaction to humans

Individual behavioral differences are due to an interaction of the genotype and the environment. Phenotypic manifestation of aggressive behavior depends on the coordinated expression of gene ensembles. Nonetheless, the identification of these genes and of combinations of their mutual influence on expression remains a difficult task. Using animal models of aggressive behavior (gray rats that were selected for a reaction to humans; tame and aggressive rat strains), we evaluated the expression of 10 genes potentially associated with aggressiveness according to the literature: Cacna1b, Cacna2d3, Drd2, Egr1, Gad2, Gria2, Mapk1, Nos1, Pomc, and Syn1. To identify the genes most important for the manifestation of aggressiveness, we analyzed the expression of these genes in two generations of rats: 88th and 90th. Assessment of gene expression levels was carried out by real-time PCR in the hypothalamus of tame and aggressive rats. This analysis confirmed that 4 out of the 10 genes differ in expression levels between aggressive rats and tame rats in both generations. Specifically, it was shown that the expression of the Cacna1b, Drd2, Egr1, and Gad2 genes does not differ between the two generations (88th vs 90th) within each strain, but significantly differs between the strains: in the tame rats of both generations, the expression levels of these genes are significantly lower as compared to those in the aggressive rats. Therefore, these genes hold promise for further studies on behavioral characteristics. Thus, we confirmed polygenic causes of phenotypic manifestation of aggressive reactions.

The expression and function of glutamate aspartate transporters in Bergmann glia are decreased in neuronal nitric oxide synthase-knockout mice during postnatal development

Bergmann glia (BG) predominantly use glutamate/aspartate transporters (GLAST) for glutamate uptake in the cerebellum. Recently, nitric oxide (NO) treatment has been shown to upregulate GLAST function and increase glutamate uptake in vitro. We previously discovered that neuronal nitric oxide synthase knockout (nNOS^−/−) mice displayed structural and functional neuronal abnormalities in the cerebellum during development, in addition to previously reported motor deficits. Although these developmental deficits have been identified in the nNOS^−/− cerebellum, it is unknown whether BG morphology and GLAST expression are also affected in the absence of nNOS in vivo. This study is the first to characterize BG morphology and GLAST expression during development in nNOS^−/− mice using immunohistochemistry and western blotting across postnatal development. Results showed that BG in nNOS^−/− mice exhibited abnormal morphology and decreased GLAST expression compared with wildtype (WT) mice across postnatal development. Treating ex vivo WT cerebellar slices with the NOS inhibitor L‐NAME decreased GLAST expression while treating nNOS^−/− slices with the slow‐release NO‐donor NOC‐18 increased GLAST expression when compared with their respective controls. In addition, treating primary BG isolated from WT mice with the selective nNOS inhibitor 7N decreased the membrane expression of GLAST and influx of Ca²⁺/Na⁺, while treating nNOS^−/− BG with SNAP increased the membrane expression of GLAST and Ca²⁺/Na⁺ influx. Moreover, the effects of SNAP on GLAST expression and Ca²⁺/Na⁺ influx in nNOS^−/− BG were significantly reduced by a PKG inhibitor. Together, these results reveal a novel role for nNOS/NO signaling in BG development, regulated by a PKG‐mediated mechanism.

Targeting PSD95/nNOS by ZL006 alleviates social isolation-induced heightened attack behavior in mice

RATIONALE

Deregulated attack behaviors have devastating social consequences; however, satisfactory clinical management for the behavior is still an unmet need so far. Social isolation (SI) has been common during the COVID-19 pandemic and may have detrimental effects on mental health, including eliciting heightened attack behavior.

OBJECTIVES

This study aims to explore whether injection of ZL006 can alleviate SI-induced escalation of attack behavior in mice.

METHODS

Pharmacological tools, biochemical methods, and behavioral tests were used to explore the potential therapeutic effects of ZL006 targeting postsynaptic density 95 (PSD95)/neuronal nitric oxide synthase (nNOS) pathway on escalation of attack behavior induced by SI in mice.

RESULTS

ZL006 mitigated SI-induced escalated attack behaviors and elevated nitric oxide (NO) level in the cortex of the SI mice. The beneficial effects of ZL006 lasted for at least 72 h after a single injection of ZL006. Potentiation of NO levels by L-arginine blocked the effects of ZL006. Moreover, a sub-effective dose of 7-NI in combination with a sub-effective dose of ZL006 decreased both SI-induced escalated attack behaviors and NO levels in mice subjected to SI.

CONCLUSIONS

Our study highlights the importance of the PSD95/nNOS pathway in mediating SI-induced escalation of attack behavior. ZL006 may be a promising therapeutic strategy for treating aggressive behaviors.

Erectile Function and Sexual Behavior: A Review of the Role of Nitric Oxide in the Central Nervous System

Nitric oxide (NO), the neuromodulator/neurotransmitter formed from l-arginine by neuronal, endothelial and inducible NO synthases, is involved in numerous functions across the body, from the control of arterial blood pressure to penile erection, and at central level from energy homeostasis regulation to memory, learning and sexual behavior. The aim of this work is to review earlier studies showing that NO plays a role in erectile function and sexual behavior in the hypothalamus and its paraventricular nucleus and the medial preoptic area, and integrate these findings with those of recent studies on this matter. This revisitation shows that NO influences erectile function and sexual behavior in males and females by acting not only in the paraventricular nucleus and medial preoptic area but also in extrahypothalamic brain areas, often with different mechanisms. Most importantly, since these areas are strictly interconnected with the paraventricular nucleus and medial preoptic area, send to and receive neural projections from the spinal cord, in which sexual communication between brain and genital apparatus takes place, this review reveals that central NO participates in concert with neurotransmitters/neuropeptides to a neural circuit controlling both the consummatory (penile erection, copulation, lordosis) and appetitive components (sexual motivation, arousal, reward) of sexual behavior.

Kr-h1 maintains distinct caste-specific neurotranscriptomes in response to socially regulated hormones

Behavioral plasticity is key to animal survival. Harpegnathos saltator ants can switch between worker and queen-like status (gamergate) depending on the outcome of social conflicts, providing an opportunity to study how distinct behavioral states are achieved in adult brains. Using social and molecular manipulations in live ants and ant neuronal cultures, we show that ecdysone and juvenile hormone drive molecular and functional differences in the brains of workers and gamergates and direct the transcriptional repressor Kr-h1 to different target genes. Depletion of Kr-h1 in the brain caused de-repression of "socially inappropriate" genes: gamergate genes were upregulated in workers, whereas worker genes were upregulated in gamergates. At the phenotypic level, loss of Kr-h1 resulted in the emergence of worker-specific behaviors in gamergates and gamergate-specific traits in workers. We conclude that Kr-h1 is a transcription factor that maintains distinct brain states established in response to socially regulated hormones.

Time-of-day as a critical biological variable

Time-of-day is a crucial, yet often overlooked, biological variable in biomedical research. We examined the top 25 most cited papers in several domains of behavioral neuroscience to determine whether time-of-day information was reported. The majority of studies report behavioral testing conducted during the day, which does not coincide with the optimal time to perform the testing from an functional perspective of the animals being tested. The majority of animal models used in biomedical research are nocturnal rodents; thus, testing during the light phase (i.e. animals' rest period) may alter the results and introduce variability across studies. Time-of-day is rarely considered in analyses or reported in publications; the majority of publications fail to include temporal details when describing their experimental methods, and those few that report testing during the dark rarely report whether measures are in place to protect from exposure to extraneous light. We propose that failing to account for time-of-day may compromise replication of findings across behavioral studies and reduce their value when extrapolating results to diurnal humans.

Targeting GluN2B/NO Pathway Ameliorates Social Isolation-Induced Exacerbated Attack Behavior in Mice

Exacerbated attack behavior has a profound socioeconomic impact and devastating social consequences; however, there is no satisfactory clinical management available for an escalated attack behavior. Social isolation (SI) is widespread during this pandemic and may exert detrimental effects on mental health, such as causing heightened attack behavior. To explore the therapeutic approaches that alleviate the SI-induced heightened attack behavior, we utilized pharmacological methods targeting the GluN2B/NO signaling pathway during the attack behavior. Ifenprodil and TAT-9C peptide targeting GluN2B showed that the inhibition of GluN2B mitigated the SI-induced escalated attack behavior and the SI-induced aberrant nitric oxide (NO) level in the brain. Additionally, the potentiation of the NO level by L-arginine reversed the effects of the inhibition of GluN2B. Moreover, we showed that high doses of L-NAME and 7-NI and subeffective doses of L-NAME in combination with ifenprodil or TAT-9C or subeffective doses of 7-NI plus ifenprodil or TAT-9C all decreased the SI-induced escalated attack behavior and reduced the NO level, further supporting the idea that GluN2B/NO signaling is a crucial modulator of the escalated attack behavior.

Transcriptome Analyses Provide Insights into the Aggressive Behavior toward Conspecific and Heterospecific in Thitarodes xiaojinensis (Lepidoptera: Hepialidae)

Simple Summary

Aggression is an evolutionarily conserved, complex behavior, essential for survival, reproduction, and the organization of social hierarchies. It is well studied in adult insects, such as flies, ants, honey bees, and crickets. However, the study of aggressive behavior in the larval stage is still lacking. T. xiaojinensis is a common species found in mountainous regions of the Tibetan Plateau, the larvae of which are highly aggressive toward conspecifics. High-throughput RNA-seq with a reference genome provides opportunities for in-depth analysis when T. xiaojinensis is aggressive toward conspecifics and heterospecifics. This study provided a set of important pathways and DEGs associated with aggressive behavior. We also constructed the weighted gene co-expression network for traits, and the central and hub genes involved in aggressive behavior were obtained. The results revealed the molecular responses when T. xiaojinensis showed aggressiveness toward conspecifics and heterospecifics. These data are important for better understanding the aggressive behavior of Lepidopteran larvae at the transcriptional level and provide a theoretical basis for the further analysis of the genetic mechanism of the insect’s aggression.

Abstract

Aggressive behavior in animals is important for survival and reproduction. It is well studied in adult insects, such as flies, ants, honey bees, and crickets. However, the larvae of Lepidopteran insects are also aggressive, studies of which are still lacking. Here, RNA-seq was used to generate a high-quality database for the aggressive behavior of Thitarodes xiaojinensis toward conspecifics and heterospecifics. Although there was similar aggressive behavior between the conspecific group and heterospecific group, significant differences were identified at the transcriptional level. When there was aggressive behavior toward conspecifics, T. xiaojinensis trended toward higher expression at the respiratory chain, while cuticle development and metabolism may have interfered. On the other hand, when there was aggressive behavior toward H. armigera, genes related to neuron and cuticle development, cellular processes, and its regulated signaling pathways were significantly upregulated, while the genes associated with oxidation-reduction and metabolism were downregulated. Weighted gene co-expression networks analysis (WGCNA) was performed, and two modules with properties correlating to the aggressive behavior of T. xiaojinensis were identified. Several hub genes were predicted and confirmed by qRT-PCR, such as CLTC, MYH, IGF2BP1, and EMC. This study provides a global view and potential key genes for the aggressive behavior of T. xiaojinensis toward conspecifics and heterospecifics. Further investigation of the hub genes would help us to better understand the aggressive behavior of insects.

SNP rs10420324 in the AMPA receptor auxiliary subunit TARP γ-8 regulates the susceptibility to antisocial personality disorder

In the brain, AMPA receptors mediate fast excitatory neurotransmission, the dysfunction of which leads to neuropsychiatric disorders. Synaptic function of AMPA receptors is tightly controlled by a protein group called transmembrane AMPAR regulatory proteins (TARPs). TARP γ-8 (also known as CACNG8) preferentially expresses in the hippocampus, cortex and subcortical regions that are critical for emotion generation indicating its association with psychiatric disorders. Here, we identified rs10420324 (T/G), a SNP located in the human CACNG8 gene, regulated reporter gene expression in vitro and TARP γ-8 expression in the human brain. A guanine at the locus (rs10420324G) suppressed transcription likely through modulation of a local G-quadruplex DNA structure. Consistent with these observations, the frequency of rs10420324G was higher in patients with anti-social personality disorder (ASPD) than in controls, indicating that rs10420324G in CACNG8 is more voluntary for ASPD. We then characterized the behavior of TARP γ-8 knockout and heterozygous mice and found that consistent with ASPD patients who often exhibit impulsivity, aggression, risk taking, irresponsibility and callousness, a decreased γ-8 expression in mice displayed similar behaviors. Furthermore, we found that a decrease in TARP γ-8 expression impaired synaptic AMPAR functions in layer 2-3 pyramidal neurons of the prefrontal cortex, a brain region that inhibition leads to aggression, thus explaining, at least partially, the neuronal basis for the behavioral abnormality. Taken together, our study indicates that TARP γ-8 expression level is associated with ASPD, and that the TARP γ-8 knockout mouse is a valuable animal model for studying this psychiatric disease.

Nitric Oxide Critically Regulates Purkinje Neuron Dendritic Development Through a Metabotropic Glutamate Receptor Type 1-Mediated Mechanism

Nitric oxide (NO), specifically derived from neuronal nitric oxide synthase (nNOS), is a well-established regulator of synaptic transmission in Purkinje neurons (PNs), governing fundamental processes such as motor learning and coordination. Previous phenotypic analyses showed similar cerebellar structures between neuronal nitric oxide null (nNOS^-/-) and wild-type (WT) adult male mice, despite prominent ataxic behavior within nNOS^-/- mice. However, a study has yet to characterize PN molecular structure and their excitatory inputs during development in nNOS^-/- mice. This study is the first to explore morphological abnormalities within the cerebellum of nNOS^-/- mice, using immunohistochemistry and immunoblotting. This study sought to examine PN dendritic morphology and the expression of metabotropic glutamate receptor type 1 (mGluR1), vesicular glutamate transporter type 1 and 2 (vGluT1 and vGluT2), stromal interaction molecule 1 (STIM1), and calpain-1 within PNs of WT and nNOS^-/- mice at postnatal day 7 (PD7), 2 weeks (2W), and 7 weeks (7W) of age. Results showed a decrease in PN dendritic branching at PD7 in nNOS^-/- cerebella, while aberrant dendritic spine formation was noted in adult ages. Total protein expression of mGluR1 was decreased in nNOS^-/- cerebella across development, while vGluT2, STIM1, and calpain-1 were significantly increased. Ex vivo treatment of WT slices with NOS inhibitor L-NAME increased calpain-1 expression, whereas treating nNOS^-/- cerebellar slices with NO donor NOC-18 decreased calpain-1. Moreover, mGluR1 agonist DHPG increased calpain-1 in WT, but not in nNOS^-/- slices. Together, these results indicate a novel role for nNOS/NO signaling in PN development, particularly by regulating an mGluR1-initiated calcium signaling mechanism.

Neuronal nitric oxide synthase regulates regional brain perfusion in healthy humans

Aims

Neuronal nitric oxide synthase (nNOS) is highly expressed within the cardiovascular and nervous systems. Studies in genetically modified mice suggest roles in brain blood flow regulation while dysfunctional nNOS signalling is implicated in cerebrovascular ischaemia and migraine. Previous human studies have investigated the effects of non-selective NOS inhibition but there has been no direct investigation of the role of nNOS in human cerebrovascular regulation. We hypothesized that inhibition of the tonic effects of nNOS would result in global or localized changes in cerebral blood flow (CBF), as well as changes in functional brain connectivity.

Methods and results

We investigated the acute effects of a selective nNOS inhibitor, S-methyl-L-thiocitrulline (SMTC), on CBF and brain functional connectivity in healthy human volunteers (n = 19). We performed a randomized, placebo-controlled, crossover study with either intravenous SMTC or placebo, using magnetic resonance imaging protocols with arterial spin labelling and functional resting state neuroimaging. SMTC infusion induced an ∼4% decrease in resting global CBF [−2.3 (−0.3, −4.2) mL/100g/min, mean (95% confidence interval, CI), P = 0.02]. In a whole-brain voxel-wise factorial-design comparison of CBF maps, we identified a localized decrease in regional blood flow in the right hippocampus and parahippocampal gyrus following SMTC vs. placebo (2921 voxels; T = 7.0; x = 36; y = −32; z = −12; P < 0.001). This was accompanied by a decrease in functional connectivity to the left superior parietal lobule vs. placebo (484 voxels; T = 5.02; x = −14; y = −56; z = 74; P = 0.009). These analyses adjusted for the modest changes in mean arterial blood pressure induced by SMTC as compared to placebo [+8.7 mmHg (+1.8, +15.6), mean (95% CI), P = 0.009].

Conclusions

These data suggest a fundamental physiological role of nNOS in regulating regional CBF and functional connectivity in the human hippocampus. Our findings have relevance to the role of nNOS in the regulation of cerebral perfusion in health and disease.

Non-neuronal cardiac acetylcholine system playing indispensable roles in cardiac homeostasis confers resiliency to the heart

BACKGROUND

We previously established that the non-neuronal cardiac cholinergic system (NNCCS) is equipped with cardiomyocytes synthesizes acetylcholine (ACh), which is an indispensable endogenous system, sustaining cardiac homeostasis and regulating an inflammatory status, by transgenic mice overexpressing choline acetyltransferase (ChAT) gene in the heart. However, whole body biological significances of NNCCS remain to be fully elucidated.

METHODS AND RESULTS

To consolidate the features, we developed heart-specific ChAT knockdown (ChATKD) mice using 3 ChAT-specific siRNAs. The mice developed cardiac dysfunction. Factors causing it included the downregulation of cardiac glucose metabolism along with decreased signal transduction of Akt/HIF-1alpha/GLUT4, leading to poor glucose utilization, impairment of glycolytic metabolites entering the tricarboxylic (TCA) cycle, the upregulation of reactive oxygen species (ROS) production with an attenuated scavenging potency, and the downregulated nitric oxide (NO) production via NOS1. ChATKD mice revealed a decreased vagus nerve activity, accelerated aggression, more accentuated blood basal corticosterone levels with depression-like phenotypes, several features of which were accompanied by cardiac dysfunction.

CONCLUSION

The NNCCS plays a crucial role in cardiac homeostasis by regulating the glucose metabolism, ROS synthesis, NO levels, and the cardiac vagus nerve activity. Thus, the NNCCS is suggested a fundamentally crucial system of the heart.

Essential role for neuronal nitric oxide synthase in acute ethanol-induced motor impairment

The cerebellum is widely known as a motor structure because it regulates and controls motor learning, coordination, and balance. However, it is also critical for non-motor functions such as cognitive processing, sensory discrimination, addictive behaviors and mental disorders. The cerebellum has the highest relative abundance of neuronal nitric oxide synthase (nNos) and is sensitive to ethanol. Although it has been demonstrated that the interaction of γ-aminobutyric acid (GABA) and nitric oxide (NO) might play an important role in the regulation of ethanol-induced cerebellar ataxia, the molecular mechanisms through which ethanol regulates nNos function to elicit this behavioral effect have not been studied extensively. Here, we investigated the dose-dependent effects of acute ethanol treatment on motor impairment using the rotarod behavioral paradigm and the alterations of nNos mRNA expression in cerebellum, frontal cortex (FC), hippocampus and striatum. We also examined the link between acute ethanol-induced motor impairment and nNos by pharmacological manipulation of nNos function. We found that acute ethanol induced a dose-dependent elevation of ethanol blood levels which was associated with the impairment of motor coordination performance and decreased expression of cerebellar nNos. In contrast, acute ethanol increased nNos expression in FC but did not to change the expression for this enzyme in striatum and hippocampus. The effects of acute ethanol were attenuated by l-arginine, a precursor for NO and potentiated by 7-nitroindazole (7-NI), a selective inhibitor of nNos. Our data suggests that differential regulation of nNos mRNA expression in cerebellum and frontal cortex might be involved in acute ethanol-induced motor impairment.

Non-pharmacological factors that determine drug use and addiction

Based on their pharmacological properties, psychoactive drugs are supposed to take control of the natural reward system to finally drive compulsory drug seeking and consumption. However, psychoactive drugs are not used in an arbitrary way as pure pharmacological reinforcement would suggest, but rather in a highly specific manner depending on non-pharmacological factors. While pharmacological effects of psychoactive drugs are well studied, neurobiological mechanisms of non-pharmacological factors are less well understood. Here we review the emerging neurobiological mechanisms beyond pharmacological reinforcement which determine drug effects and use frequency. Important progress was made on the understanding of how the character of an environment and social stress determine drug self-administration. This is expanded by new evidence on how behavioral alternatives and opportunities for drug instrumentalization generate different patterns of drug choice. Emerging evidence suggests that the neurobiology of non-pharmacological factors strongly determines pharmacological and behavioral drug action and may, thus, give rise for an expanded system's approach of psychoactive drug use and addiction.

Nitric oxide interacts with monoamine oxidase to modulate aggression and anxiety-like behaviour

Nitric oxide (NO) is a gaseous neurotransmitter that has important behavioural functions in the vertebrate brain. In this study we compare the impact of decreased nitric NO signalling upon behaviour and neurobiology using both zebrafish and mouse. nitric oxide synthase mutant (nos1^-/-) zebrafish show significantly reduced aggression and an increase in anxiety-like behaviour without altered production of the stress hormone cortisol. Nos1^-/- mice also exhibit decreased aggression and are hyperactive in an open field test. Upon reduction of NO signalling, monoamine neurotransmitter metabolism is reduced as a consequence of decreased Monoamine oxidase activity. Treatment of nos1^-/- zebrafish with the 5-HT receptor 1A agonist 8-OH-DPAT rescues aggression and some aspects of anxiety-like behaviour. Taken together, the interplay between NO and 5-HT appears to be critical to control behaviour. Our cross-species approach challenges the previous notion that reduced neuronal NOS leads to increased aggression. Rather, Nos1 knock-out can also lead to decreased aggression in some situations, a finding that may have implications for future translational research.

Nitric oxide synthase genotype interacts with stressful life events to increase aggression in male subjects in a population-representative sample

Nitric oxide signalling has been implicated in impulsive and aggressive traits and behaviours in both animals and humans. In the present study, we investigated the effects of a functional variable number of tandem repeats (VNTR) polymorphism in exon 1f (ex1f) of the nitric oxide synthase 1 (NOS1) gene (NOS1 ex1f-VNTR) and stressful life events on aggressive behaviour in population representative sample of adolescents followed up from third grade to 25 years of age. We studied the younger cohort of the longitudinal Estonian Children Personality, Behaviour and Health Study (subjects in the last study wave n = 437, males n = 193; mean age 24.8 ± 0.5 years). Aggressive behaviour was rated at age 25 with the Illinois Bully Scale and Buss-Perry Aggression Questionnaire. Life history of aggression was evaluated in a structured interview. Stressful life events and family relationships were self-reported at age 15. The hypothesized risk genotype (homozygosity for the short allele) was associated with higher levels of aggression in males (statistical significance withstanding the multiple correction procedure). Exposure to stressful life events or adverse family relationships was associated with increased aggressive behaviour in subjects homozygous for either of the alleles, and these associations were mostly observed in males. However, these associations in these stratified analyses did not survive correction for multiple testing. Aggressiveness was relatively unaffected by the NOS1 ex1f-VNTR genotype in the female subjects even when taking exposure to childhood adversity into account. Our findings support the hypothesized involvement of a functional NOS1 polymorphism on aggression in a population representative sample of young adults.

Limited effects of early life manipulations on sex-specific gene expression and behavior in adulthood

Exposure to childhood adversity is associated with increased vulnerability to stress-related disorders in adulthood which has been replicated in rodent stress models, whereas environmental enrichment has been suggested to have beneficial effects. However, the exact neurobiological mechanisms underlying these environment influences on adult brain and behavior are not well understood. Therefore, we investigated the long-term effects of maternal separation (MS) or environmental enrichment (EE) in male and female CD1 mice. We found clear sex-specific effects, but limited influence of environmental manipulations, on adult behavior, fecal corticosterone metabolite (FCM) levels and stress- and plasticity related gene expression in discrete brain regions. In detail, adult females displayed higher locomotor activity and FCM levels compared to males and EE resulted in attenuation in both measures, but only in females. There were no sex- or postnatal manipulation-dependent differences in anxiety-related behaviors in either sex. Gene expression analyses revealed that adult males showed higher Fkbp5 mRNA levels in hippocampus, hypothalamus and raphe nuclei, and higher hippocampal Nos1 levels. Interestingly, MS elevated Nos1 levels in hippocampus but reduced Fkbp5 expression in hypothalamus of males. Finally, we also found higher Maoa expression in the hypothalamus of adult females, however no differences were observed in the expression levels of Bdnf, Crhr1, Nr3c1 and Htr1a. Our findings further contribute to sex-dependent differences in behavior, corticosterone and gene expression and reveal that the effects of postnatal manipulations on these parameters in outbred CD1 mice are limited.

Intervention mechanism of repeated oral GABA administration on anxiety-like behaviors induced by emotional stress in rats

The purpose of this study was to investigate the effects and mechanism of repeated oral administration of gamma-aminobutyric acid (GABA) on anxiety-like behaviors induced by emotional stress. Male Sprague-Dawley rats were randomly divided into five groups (8 rats each): control, emotional stress model, three emotional stress + GABA-treated groups (0.5, 1, 2 mg/kg). The rats were given empty water bottles after the training of drinking water to induce emotional stress. Each group was treated with saline or different doses of GABA respectively for 21 consecutive days. Then open field and elevated plus maze were used to assess anxiety-like behaviors. Both frontal cortex and plasma NO metabolites nitrate and nitrite (NO_x) levels were determined spectrophotometrically. Results showed that oral administration of GABA significantly reversed the stress-induced anxiety-like negative responses dose-dependently. The frontal cortex NO_x levels were lower in stressed rats than in control group (P < 0.05), but higher in 2 mg/kg GABA-treated group than stress model group (P < 0.05). On the other hand, NOx levels in plasma showed a gradual decline trend. Collectively, these results suggest that short repeated oral administration of GABA has an anxiolytic-like effect possibly via preventing NO reduction caused by stress and improving availability of NO in the frontal cortex.

Tat-HA-NR2B9c attenuate oxaliplatin-induced neuropathic pain

Oxaliplatin is a commonly used chemotherapy drug, which can produce acute and chronic peripheral neurotoxicity. Currently, there is no good therapeutic drug in clinic. Excessive stimulation of N-methyl-d-aspartate receptors (NMDARs) is crucial for the transmission of pain signals. However, directly inhibiting NMDARs can cause severe side effects because they have key physiological functions in the Central nervous system (CNS). Several years ago, we prepared a polypeptide Tat-HA-NR2B9c which can disturb NMDARs-postsynaptic density protein-95 (PSD-95) interaction. In this study, we studied whether Tat-HA-NR2B9c could be an effective treatment for oxaliplatin-induced neuropathic pain. To conform it, a rat model of oxaliplatin-induced neuropathic was established, and analgesic effect of Tat-HA-NR2B9c was studied. Here, we show that oxaliplatin induces the interaction of NMDARs with PSD-95. Uncoupling the complex by Tat-HA-NR2B9c has potent analgesic effect in oxaliplatin-induced cold hyperalgesia and mechanical allodynia without suppressing general behavioral. Tat-HA-NR2B9c neither inhibits NMDARs function nor impacts antitumor activity of oxaliplatin. Thus, this new drug may serve as a treatment for oxaliplatin-induced neuropathic pain, perhaps without major side effects.

Hippocampal nuclear factor kappa B accounts for stress-induced anxiety behaviors via enhancing neuronal nitric oxide synthase (nNOS)-carboxy-terminal PDZ ligand of nNOS-Dexras1 coupling

Anxiety disorders are associated with a high social burden worldwide. Recently, increasing evidence suggests that nuclear factor kappa B (NF-κB) has significant implications for psychiatric diseases, including anxiety and depressive disorders. However, the molecular mechanisms underlying the role of NF-κB in stress-induced anxiety behaviors are poorly understood. In this study, we show that chronic mild stress (CMS) and glucocorticoids dramatically increased the expression of NF-κB subunits p50 and p65, phosphorylation and acetylation of p65, and the level of nuclear p65 in vivo and in vitro, implicating activation of NF-κB signaling in chronic stress-induced pathological processes. Using the novelty-suppressed feeding (NSF) and elevated-plus maze (EPM) tests, we found that treatment with pyrrolidine dithiocarbamate (PDTC; intra-hippocampal infusion), an inhibitor of NF-κB, rescued the CMS- or glucocorticoid-induced anxiogenic behaviors in mice. Microinjection of PDTC into the hippocampus reversed CMS-induced up-regulation of neuronal nitric oxide synthase (nNOS), carboxy-terminal PDZ ligand of nNOS (CAPON), and dexamethasone-induced ras protein 1 (Dexras1) and dendritic spine loss of dentate gyrus (DG) granule cells. Moreover, over-expression of CAPON by infusing LV-CAPON-L-GFP into the hippocampus induced nNOS-Dexras1 interaction and anxiety-like behaviors, and inhibition of NF-κB by PDTC reduced the LV-CAPON-L-GFP-induced increases in nNOS-Dexras1 complex and anxiogenic-like effects in mice. These findings indicate that hippocampal NF-κB mediates anxiogenic behaviors, probably via regulating the association of nNOS-CAPON-Dexras1, and uncover a novel approach to the treatment of anxiety disorders.

7-nitroindazol-loaded nanoemulsions: Preparation, characterization and its improved inhibitory effect on nitric oxide synthase-1

Nitric oxide (NO) participates in several physiological processes such as maintenance of blood pressure, host defense, neurotransmission, inhibition of platelet aggregation and learning and memory. NO is also involved in several diseases or dysfunctions in the cardiovascular, central nervous and musculoskeletal systems. NO also has been shown to be a major player in sepsis. NOS-1-derived NO has been shown to be a relevant species in physiology but also is an important element in pathology. There exist some NOS-1 inhibitors and among of them, 7-nitroindazole has been used for its in vivo selectivity. However, 7-NI has a very short half-life (∼2 h) and a poor water solubility. In this study, we describe the preparation and characterization of 7-NI-loaded nanoemulsions (NE_7-NI). The chemical stability of 7-NI was greatly increased and the drug release rate could be controlled after nanoemulsification. NE_7-NI reduced NO production in a long-lasting manner in vascular smooth muscle cells and skeletal muscle, without cytotoxicity. Our results evidenced that nanoemulsification approach increases the effective action time of 7-NI, rendering a suitable dosage form, which may be an interesting tool to study the role of NOS-1 in physiology and disease.

Developmental Alcohol Exposure Impairs Activity-Dependent S-Nitrosylation of NDEL1 for Neuronal Maturation

Neuronal nitric oxide synthase is involved in diverse signaling cascades that regulate neuronal development and functions via S-Nitrosylation-mediated mechanism or the soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway activated by nitric oxide. Although it has been studied extensively in vitro and in invertebrate animals, effects on mammalian brain development and underlying mechanisms remain poorly understood. Here we report that genetic deletion of "Nos1" disrupts dendritic development, whereas pharmacological inhibition of the sGC/cGMP pathway does not alter dendritic growth during cerebral cortex development. Instead, nuclear distribution element-like (NDEL1), a protein that regulates dendritic development, is specifically S-nitrosylated at cysteine 203, thereby accelerating dendritic arborization. This post-translational modification is enhanced by N-methyl-D-aspartate receptor-mediated neuronal activity, the main regulator of dendritic formation. Notably, we found that disruption of S-Nitrosylation of NDEL1 mediates impaired dendritic maturation caused by developmental alcohol exposure, a model of developmental brain abnormalities resulting from maternal alcohol use. These results highlight S-Nitrosylation as a key activity-dependent mechanism underlying neonatal brain maturation and suggest that reduction of S-Nitrosylation of NDEL1 acts as a pathological factor mediating neurodevelopmental abnormalities caused by maternal alcohol exposure.

Mice lacking interleukin-18 gene display behavioral changes in animal models of psychiatric disorders: Possible involvement of immunological mechanisms

Preclinical and clinical evidence suggests pro-inflammatory cytokines might play an important role in the neurobiology of schizophrenia and stress-related psychiatric disorders. Interleukin-18 (IL-18) is a member of the IL-1 family of cytokines and it is widely expressed in brain regions involved in emotional regulation. Since IL-18 involvement in the neurobiology of mental illnesses, including schizophrenia, remains unknown, this work aimed at investigating the behavior of IL-18 null mice (KO) in different preclinical models: 1. the prepulse inhibition test (PPI), which provides an operational measure of sensorimotor gating and schizophrenic-like phenotypes; 2. amphetamine-induced hyperlocomotion, a model predictive of antipsychotic activity; 3. resident-intruder test, a model predictive of aggressive behavior. Furthermore, the animals were submitted to models used to assess depressive- and anxiety-like behavior. IL-18KO mice showed impaired baseline PPI response, which was attenuated by d-amphetamine at a dose that did not modify PPI response in wild-type (WT) mice, suggesting a hypodopaminergic prefrontal cortex function in those mice. d-Amphetamine, however, induced hyperlocomotion in IL-18KO mice compared to their WT counterparts, suggesting hyperdopaminergic activity in the midbrain. Moreover, IL-18KO mice presented increased basal levels of IL-1β levels in the hippocampus and TNF-α in the prefrontal cortex, suggesting an overcompensation of IL-18 absence by increased levels of other proinflammatory cytokines. Although no alteration was observed in the forced swimming or in the elevated plus maze tests in naïve IL-18KO mice, these mice presented anxiogenic-like behavior after exposure to repeated forced swimming stress. In conclusion, deletion of the IL-18 gene resembled features similar to symptoms observed in schizophrenia (positive and cognitive symptoms, aggressive behavior), in addition to increased susceptibility to stress. The IL-18KO model, therefore, could provide new insights into how changes in brain immunological homeostasis induce behavioral changes related to psychiatric disorders, such as schizophrenia.

Synaptic Transmission Optimization Predicts Expression Loci of Long-Term Plasticity

Long-term modifications of neuronal connections are critical for reliable memory storage in the brain. However, their locus of expression-pre- or postsynaptic-is highly variable. Here we introduce a theoretical framework in which long-term plasticity performs an optimization of the postsynaptic response statistics toward a given mean with minimal variance. Consequently, the state of the synapse at the time of plasticity induction determines the ratio of pre- and postsynaptic modifications. Our theory explains the experimentally observed expression loci of the hippocampal and neocortical synaptic potentiation studies we examined. Moreover, the theory predicts presynaptic expression of long-term depression, consistent with experimental observations. At inhibitory synapses, the theory suggests a statistically efficient excitatory-inhibitory balance in which changes in inhibitory postsynaptic response statistics specifically target the mean excitation. Our results provide a unifying theory for understanding the expression mechanisms and functions of long-term synaptic transmission plasticity.

DA Negatively Regulates IGF-I Actions Implicated in Cognitive Function via Interaction of PSD95 and nNOS in Minimal Hepatic Encephalopathy

Insulin-like growth factor I (IGF-I) has been positively correlated with cognitive ability. Cognitive decline in minimal hepatic encephalopathy (MHE) was shown to be induced by elevated intracranial dopamine (DA). The beneficial effect of IGF-I signaling in MHE remains unknown. In this study, we found that IGF-I content was reduced in MHE rats and that IGF-I administration mitigated cognitive decline of MHE rats. A protective effect of IGF-I on the DA-induced interaction between postsynaptic density protein 95 (PSD95) and neuronal nitric oxide synthase (nNOS) was found in neurons. Ribosomal S6 protein kinase (RSK) phosphorylated nNOS in response to IGF-I by recruiting extracellular signal-regulated kinase (ERK1/2). In turn, DA inactivated the ERK1/2/RSK pathway and stimulated the PSD95–nNOS interaction by downregulating IGF-I. Inhibition of the interaction between PSD95 and nNOS ameliorated DA-induced memory impairment. As DA induced deficits in the ERK1/2/RSK pathway and the interaction between PSD95 and nNOS in MHE brains, IGF-I administration exerted a protective effect via interruption of the interaction between PSD95 and nNOS. These results suggest that IGF-I antagonizes DA-induced cognitive loss by disrupting PSD95–nNOS interactions in MHE.

Differential DNA methylation at birth associated with mental disorder in individuals with 22q11.2 deletion syndrome

Individuals with 22q11.2 deletion syndrome (DS) have an increased risk of comorbid mental disorders including schizophrenia, attention deficit hyperactivity disorder, depression, as well as intellectual disability. Although most 22q11.2 deletion carriers have the long 3-Mb form of the hemizygous deletion, there remains a large variation in the development and progression of psychiatric disorders, which suggests that alternative factors contribute to the pathogenesis. In this study we investigated whether neonatal DNA methylation signatures in individuals with the 22q11.2 deletion associate with mental disorder later in life. DNA methylation was measured genome-wide from neonatal dried blood spots in a cohort of 164 individuals with 22q11.2DS, including 48 individuals diagnosed with a psychiatric disorder. Among several CpG sites with P-value<10-6, we identified cg23546855 (P-value=2.15 × 10-7) mapping to STK32C to be associated with a later psychiatric diagnosis. Pathway analysis of the top findings resulted in the identification of several Gene Ontology pathways to be significantly enriched (P-value<0.05 after Benjamini-Hochberg correction); among them are the following: neurogenesis, neuron development, neuron projection development, astrocyte development, axonogenesis and axon guidance. In addition, we identified differentially methylated CpG sites in LRP2BP (P-value=5.37 × 10-8) to be associated with intellectual disability (F70-79), in TOP1 (P-value=1.86 × 10-7) with behavioral disorders (F90-98), in NOSIP (P-value=5.12 × 10-8) with disorders of psychological development (F80-89) and in SEMA4B (P-value=4.02 × 10-7) with schizophrenia spectrum disorders (F20-29). In conclusion, our study suggests an association of DNA methylation differences at birth with development of mental disorder later in life in 22q11.2DS individuals.

Considerations on nonclinical approaches to modeling risk factors of suicidal ideation and behavior

Given the serious nature of suicidal ideation and behavior (SIB) and the possibility of treatment-emergent SIB, pharmaceutical companies are now applying more proactive approaches in clinical trials and are considering the value of nonclinical models to predict SIB. The current review summarizes nonclinical approaches to modeling three common risk factors associated with SIB: aggression, impulsivity, and anhedonia. For each risk factor, a general description, advantages and disadvantages, species considerations, nonclinical to clinical translation, and pharmacological validation with respect to treatments associated with SIB are summarized. From this review, several gaps were identified that need to be addressed before use of these nonclinical models can be considered a viable option to predict the relative risk for SIB. Other future directions that may compliment these nonclinical approaches, including the use of selectively-bred or genetically-modified rodent models, transgenic models, gene expression profiling, and biomarker analysis, are discussed. This article was developed with the support of the DruSafe Leadership Group of the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ, www.iqconsortium.org).

Bi-stability in type 2 diabetes mellitus multi-organ signalling network

Type 2 diabetes mellitus (T2DM) is believed to be irreversible although no component of the pathophysiology is irreversible. We show here with a network model that the apparent irreversibility is contributed by the structure of the network of inter-organ signalling. A network model comprising all known inter-organ signals in T2DM showed bi-stability with one insulin sensitive and one insulin resistant attractor. The bi-stability was made robust by multiple positive feedback loops suggesting an evolved allostatic system rather than a homeostatic system. In the absence of the complete network, impaired insulin signalling alone failed to give a stable insulin resistant or hyperglycemic state. The model made a number of correlational predictions many of which were validated by empirical data. The current treatment practice targeting obesity, insulin resistance, beta cell function and normalization of plasma glucose failed to reverse T2DM in the model. However certain behavioural and neuro-endocrine interventions ensured a reversal. These results suggest novel prevention and treatment approaches which need to be tested empirically.

Peripheral NMDA Receptor/NO System Blockage Inhibits Itch Responses Induced by Chloroquine in Mice

Intradermal administration of chloroquine (CQ) provokes scratching behavior in mice. Chloroquine-induced itch is histamine-independent and we have reported that the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway is involved in CQ-induced scratching behavior in mice. Previous studies have demonstrated that activation of N-methyl-d-aspartate receptors (NMDARs) induces NO production. Here we show that NMDAR antagonists significantly decrease CQ-induced scratching in mice while a non-effective dose of an NMDAR agonist potentiates the scratching behavior provoked by sub-effective doses of CQ. In contrast, combined pre-treatment with sub-effective doses of an NMDAR antagonist, MK-801, and the NO synthase inhibitor, L-N-nitro arginine methyl ester (L-NAME), decreases CQ-induced scrat-ching behavior. While intradermal administration of CQ significantly increases the concentration of intradermal nitrite, the end product of NO metabolism, effective doses of intraperitoneal and intradermal MK-801 significantly decrease intradermal nitrite levels. Likewise, administration of an effective dose of L-NAME significantly decreases CQ-induced nitrite production. We conclude that the NMDA/NO pathway in the skin modulates CQ-induced scratching behavior.