Neuronal nitric oxide synthase knock-out mice show impaired cognitive performance

Genes and gene networks underlying spatial cognition in food-caching chickadees

Substantial progress has been made in understanding the genetic architecture of phenotypes involved in a variety of evolutionary processes. Behavioral genetics remains, however, among the least understood. We explore the genetic architecture of spatial cognitive abilities in a wild passerine bird, the mountain chickadee (Poecile gambeli). Mountain chickadees cache thousands of seeds in the fall and require specialized spatial memory to recover these caches throughout the winter. We previously showed that variation in spatial cognition has a direct effect on fitness and has a genetic basis. It remains unknown which specific genes and developmental pathways are particularly important for shaping spatial cognition. To further dissect the genetic basis of spatial cognitive abilities, we combine experimental quantification of spatial cognition in wild chickadees with whole-genome sequencing of 162 individuals, a new chromosome-scale reference genome, and species-specific gene annotation. We have identified a set of genes and developmental pathways that play a key role in creating variation in spatial cognition and found that the mechanism shaping cognitive variation is consistent with selection against mildly deleterious non-coding mutations. Although some candidate genes were organized into connected gene networks, about half do not have shared regulation, highlighting that multiple independent developmental or physiological mechanisms contribute to variation in spatial cognitive abilities. A large proportion of the candidate genes we found are associated with synaptic plasticity, an intriguing result that leads to the hypothesis that certain genetic variants create antagonism between behavioral plasticity and long-term memory, each providing distinct benefits depending on ecological context.

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.

The eNOS isoform exhibits increased expression and activation in the main olfactory bulb of nNOS knock-out mice

The main olfactory bulb (MOB) is a neural structure that processes olfactory information. Among the neurotransmitters present in the MOB, nitric oxide (NO) is particularly relevant as it performs a wide variety of functions. In this structure, NO is produced mainly by neuronal nitric oxide synthase (nNOS) but also by inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS). The MOB is considered a region with great plasticity and the different NOS also show great plasticity. Therefore, it could be considered that this plasticity could compensate for various dysfunctional and pathological alterations. We examined the possible plasticity of iNOS and eNOS in the MOB in the absence of nNOS. For this, wild-type and nNOS knock-out (nNOS-KO) mice were used. We assessed whether the absence of nNOS expression could affect the olfactory capacity of mice, followed by the analysis of the expression and distribution of the NOS isoforms using qPCR and immunofluorescence. NO production in MOB was examined using both the Griess and histochemical NADPH-diaphorase reactions. The results indicate nNOS-KO mice have reduced olfactory capacity. We observed that in the nNOS-KO animal, there is an increase both in the expression of eNOS and NADPH-diaphorase, but no apparent change in the level of NO generated in the MOB. It can be concluded that the level of eNOS in the MOB of nNOS-KO is related to the maintenance of normal levels of NO. Therefore, our findings suggest that nNOS could be essential for the proper functioning of the olfactory system.

Potential role of dietary nitrate in relation to cardiovascular and cerebrovascular health, cognition, cognitive decline and dementia: a review

There is currently no effective treatment for dementia, of which Alzheimer's disease (AD) is the most common form. It is, therefore, imperative to focus on evidence-based preventive strategies to combat this extremely debilitating chronic disease. Nitric oxide (NO) is a key signalling molecule in the cardiovascular, cerebrovascular, and central nervous systems. Vegetables rich in nitrate, such as spinach and beetroot, are an important source of NO, with beneficial effects on validated markers of cardiovascular health and an association with a lower risk of cardiovascular disease. Given the link between cardiovascular disease risk factors and dementia, together with the important role of NO in vascular health and cognition, it is important to determine whether dietary nitrate could also improve cognitive function, markers of brain health, and lower risk of dementia. This review presents an overview of NO's role in the cardiovascular, cerebrovascular, and central nervous systems; an overview of the available evidence that nitrate, through effects on NO, improves cardiovascular health; and evaluates the current evidence regarding dietary nitrate's potential role in cerebrovascular health, cognitive function, and brain health assessed via biomarkers.

Mechanisms of NO-Mediated Protein S-Nitrosylation in the Lens-Induced Myopia

Background. Myopia is a chronic ocular disease, emerging as the most common type of refractive error. This study intends to preliminarily explore the roles of protein S-nitrosylation of nitric oxide (NO) in the regulation of myopia by detecting the expression of neuronal nitric oxide synthase (nNOS) and downstream S-nitrosylation, using the animal model of lens-induced myopia (LIM) in mice. Methods. The 3-week-old C57BL/6 J mice were divided into three groups: group I, lens-induced 0-week group (take eyeballs at the age of 3 weeks); group II, self-control eyes of experimental group (take eyeballs at the age of 7 weeks); and group III, lens-induced 4-week group (take eyeballs at the age of 7 weeks). The diopter and axial length of each group were measured by streak retinoscopes and optical coherence tomography (OCT) before and after model establishment. The protein expressions and locations of nNOS and S-nitrosylated proteins (PSNOs) were measured by western blot and immunofluorescence staining. Site-specific proteomic for protein S-nitrolysation was used to detect the existence and location of S-nitrosylation proteins in the retina of myopic and nonmyopic mice. The Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and motif enrichment analyses were performed. The differential sites were analyzed by GO, KEGG, and motif. Irreversible biotinylation procedure combined with protein purification and western blot was used to detect the protein expression of α-enolase (ENO1), a key player in the hypoxia-related signal pathway. Results. The expressions of nNOS and PSNOs were significantly lower in the retina of experimental eyes than that in self-control eyes and 3-week-old baseline group. A total of 595 S-nitrosylated proteins, 709 S-nitrosylated peptides, and 708 S-nitrosylated sites were identified by site-specific S-nitrolysation proteomics in the retina of myopic and control eyes. A total of 19 differentiation loci were screened, of which 13 sites were downregulated and 6 sites were upregulated in experimental eyes compared with the self-control group. Specifically, the expression of SNO-ENO1 was significantly lower in the retina of experimental eyes than that in self-control eyes and 3-week-old baseline group. Conclusion. LIM induces the decrease of nNOS and PSNO protein levels in the retina of myopic mice. NO-mediated nonclassical protein S-nitrosylation modification may play an important role in the regulation of lens-induced myopia. ENO1 may be a key factor in the regulation of S-nitrosylation modification of myopia.

The Multiple Faces of Nitric Oxide in Chronic Granulomatous Disease: A Comprehensive Update

Nitric oxide (NO), a signaling molecule, regulates multiple biological functions, including a variety of physiological and pathological processes. In this regard, NO participates in cutaneous inflammations, modulation of mitochondrial functions, vascular diseases, COVID-19, neurologic diseases, and obesity. It also mediates changes in the skeletal muscle function. Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder characterized by the malfunction of phagocytes caused by mutations in some of the genes encoding subunits of the superoxide-generating phagocyte NADPH (NOX). The literature consulted shows that there is a relationship between the production of NO and the NADPH oxidase system, which regulates the persistence of NO in the medium. Nevertheless, the underlying mechanisms of the effects of NO on CGD remain unknown. In this paper, we briefly review the regulatory role of NO in CGD and its potential underlying mechanisms.

NOS1 mutations cause hypogonadotropic hypogonadism with sensory and cognitive deficits that can be reversed in infantile mice

The nitric oxide (NO) signaling pathway in hypothalamic neurons plays a key role in the regulation of the secretion of gonadotropin-releasing hormone (GnRH), which is crucial for reproduction. We hypothesized that a disruption of neuronal NO synthase (NOS1) activity underlies some forms of hypogonadotropic hypogonadism. Whole-exome sequencing was performed on a cohort of 341 probands with congenital hypogonadotropic hypogonadism to identify ultrarare variants in NOS1. The activity of the identified NOS1 mutant proteins was assessed by their ability to promote nitrite and cGMP production in vitro. In addition, physiological and pharmacological characterization was carried out in a Nos1-deficient mouse model. We identified five heterozygous NOS1 loss-of-function mutations in six probands with congenital hypogonadotropic hypogonadism (2%), who displayed additional phenotypes including anosmia, hearing loss, and intellectual disability. NOS1 was found to be transiently expressed by GnRH neurons in the nose of both humans and mice, and Nos1 deficiency in mice resulted in dose-dependent defects in sexual maturation as well as in olfaction, hearing, and cognition. The pharmacological inhibition of NO production in postnatal mice revealed a critical time window during which Nos1 activity shaped minipuberty and sexual maturation. Inhaled NO treatment at minipuberty rescued both reproductive and behavioral phenotypes in Nos1-deficient mice. In summary, lack of NOS1 activity led to GnRH deficiency associated with sensory and intellectual comorbidities in humans and mice. NO treatment during minipuberty reversed deficits in sexual maturation, olfaction, and cognition in Nos1 mutant mice, suggesting a potential therapy for humans with NO deficiency.

Nitric oxide and thyroid carcinoma: A review

Thyroid carcinoma is the most common endocrine cancer in the world, and its incidence has been steadily increasing in recent years. Despite its relatively good prognosis, therapies have not improved greatly in recent years. Therefore, exploring new therapies for thyroid carcinoma represents an unmet need. Nitric oxide (NO) is a short-term endogenous signaling molecule that plays a vital role in various physiological and pathological processes and is synthesized by nitric oxide synthase (NOS). Many studies have been conducted over the past decades to explain its correlation to cancer. NO exerts a wide range of effects on cancer, involving angiogenesis, apoptosis, cell cycle, invasion, and metastasis. It also serves a dual function by promoting and halting tumor development simultaneously. The relationship between NO and thyroid carcinoma has been intensively studied and discussed. This paper reviews the role and molecular mechanism of NO in thyroid carcinoma and discusses potentials of prevention and treatment of thyroid carcinoma.

New insights on nitric oxide: Focus on animal models of schizophrenia

Schizophrenia is a devastating complex disorder characterised by a constellation of behavioral deficits with the underlying mechanisms not fully known. Nitric oxide (NO) has emerged as a key signaling molecule implicated in schizophrenia. Three nitric oxide sinthases (NOS), endothelial, neuronal, and inducible, release NO within the cell. Animal models of schizophrenia are grouped in four groups, neurovedelopmental, glutamatergic, dopaminergic and genetic. In this review, we aim to evaluate changes in NO levels in animal models of schizophrenia and the resulting long-lasting behavioral and neural consequences. In particular, NO levels are substantially modified, region-specific, in various neurodevelopmental models, e.g. bilateral excitotoxic lesion of the ventral hippocampus (nVHL), maternal immune activation and direct NO manipulations early in development, among others. In regards to glutamatergic models of schizophrenia, phencyclidine (PCP) administration increases NO levels in the prefrontal cortex (PFC) and ventral hippocampus. As far as genetic models are concerned, neuronal NOS knock-out mice display schizophrenia-related behaviors. Administration of NO donors can reverse schizophrenia-related behavioral deficits. While most modifications in NO are derived from neuronal NOS, recent evidence indicates that PCP treatment increases NO from the inducible NOS isoform. From a pharmacological perspective, treatment with various antipsychotics including clozapine, haloperidol and risperidone normalize NO levels in the PFC as well as improve behavioral deficits in nVHL rats. NO induced from the neuronal and inducible NOS is relevant to schizophrenia and warrants further research.

Inhibition of PACAP/PAC1/VPAC2 signaling impairs the consolidation of social recognition memory and nitric oxide prevents this deficit

Social recognition memory (SRM) forms the basis of social relationships of animals. It is essential for social interaction and adaptive behavior, reproduction and species survival. Evidence demonstrates that social deficits of psychiatric disorders such as autism and schizophrenia are caused by alterations in SRM processing by the hippocampus and amygdala. Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and its receptors PAC1, VPAC1 and VPAC2 are highly expressed in these regions. PACAP is a pleiotropic neuropeptide that modulates synaptic function and plasticity and is thought to be involved in social behavior. PACAP signaling also stimulates the nitric oxide (NO) production and targets outcomes to synapses. In the present work, we investigate the effect of the infusion of PACAP-38 (endogenous neuropeptide and potent stimulator of adenylyl cyclase), PACAP 6-38 (PAC1/VPAC2 receptors antagonist) and S-Nitroso-N-acetyl-DL-penicillamine (SNAP, NO donor) in the CA1 region of the hippocampus and in the basolateral amygdala (BLA) on the consolidation of SRM. For this, male Wistar rats with cannulae implanted in CA1 or in BLA were subjected to a social discrimination paradigm, which is based on the natural ability of rodents to investigate unfamiliar conspecifics more than familiar one. In the sample phase (acquisition), animals were exposed to a juvenile conspecific for 1 h. Immediately, 60 or 150 min after, animals received one of different pharmacological treatments. Twenty-four hours later, they were submitted to a 5 min retention test in the presence of the previously presented juvenile (familiar) and a novel juvenile. Animals that received infusions of PACAP 6-38 (40 pg/side) into CA1 immediately after the sample phase or into BLA immediately or 60 min after the sample phase were unable to recognize the familiar juvenile during the retention test. This impairment was abolished by the coinfusion of PACAP 6-38 plus SNAP (5 μg/side). These results show that the blockade of PACAP/PAC1/VPAC2 signaling in the CA1 and BLA during a restricted post-acquisition time window impairs the consolidation of SRM and that the SNAP is able to abolish this deficit. Findings like this could potentially be used in the future to influence studies of psychiatric disorders involving social behavior.

Nitric Oxide in Hematological Cancers: Partner or Rival?

Significance: Hematological malignancies represent the fourth most diagnosed cancer. Relapse and acquired resistance to anticancer therapy constitute two actual issues that need to be overcome. Nitric oxide (NO) plays a pivotal role in regulating cancer progression. At present, many studies are attempting to uncover the potentials of modulating NO levels to improve the efficacy of currently available treatments against lymphoma, leukemia, and myeloma. Recent Advances: It is becoming progressively clear that NO modulation may help hematological cancer management, either by targeting directly tumor cells or by driving the immune system to eliminate cancer cells. Critical Issues: NO is a dual molecule that can have a tumor-protecting or stimulating effect, depending on its local concentration. Moreover, NO is able to target a wide range of molecules involved in both cancer genesis and evolution. In this review, an overview of the recent findings regarding the pivotal role played by NO and nitric oxide synthase in cancer progression and anticancer therapy is presented, with particular focus on hematological malignancies. Future Directions: It is critical to establish the cancer-specific function of NO and critically drive its modulation to improve cancer management toward a personalized approach. This has a special importance in hematological tumors, where the urgency of finding eradicative therapies is constant. Antioxid. Redox Signal. 34, 383-401.

Nitric oxide signalling in the brain and its control of bodily functions

Nitric oxide (NO) is a versatile molecule that plays key roles in the development and survival of mammalian species by endowing brain neuronal networks with the ability to make continual adjustments to function in response to moment-to-moment changes in physiological input. Here, we summarize the progress in the field and argue that NO-synthetizing neurons and NO signalling in the brain provide a core hub for integrating sensory- and homeostatic-related cues, control key bodily functions, and provide a potential target for new therapeutic opportunities against several neuroendocrine and behavioural abnormalities.

Mitochondrial NAD(P)+ Transhydrogenase is Unevenly Distributed in Different Brain Regions, and its Loss Causes Depressive-like Behavior and Motor Dysfunction in Mice

NAD(P)⁺ transhydrogenase (NNT) links redox states of the mitochondrial NAD(H) and NADP(H) via a reaction coupled to proton-motive force across the inner mitochondrial membrane. NNT is believed to be ubiquitously present in mammalian cells, but its expression may vary substantially in different tissues. The present study investigated the tissue distribution and possible roles of NNT in the mouse brain. The pons exhibited high NNT expression/activity, and immunohistochemistry revealed intense NNT labeling in neurons from brainstem nuclei. In some of these regions, neuronal NNT labeling was strongly colocalized with enzymes involved in the biosynthesis of 5-hydroxytryptamine (5-HT) and nitric oxide (NO), which directly or indirectly require NADPH. Behavioral tests were performed in mice lacking NNT activity (Nnt^-/-, mice carrying the mutated Nnt^C57BL/6J allele from the C57BL/6J strain) and the Nnt^+/+ controls. Our data demonstrated that aged Nnt^-/- mice (18-20 months old), but not adult mice (3-4 months old), showed an increased immobility time in the tail suspension test that was reversed by fluoxetine treatment, providing evidence of depressive-like behavior in these mice. Aged Nnt^-/- mice also exhibited behavioral changes and impaired locomotor activity in the open field and rotarod tests. Despite the colocalization between NNT and NO synthase, the S-nitrosation and cGMP levels were independent of the Nnt genotype. Taken together, our results indicated that NNT is unevenly distributed throughout the brain and associated with 5-THergic and NOergic neurons. The lack of NNT led to alterations in brain functions related to mood and motor behavior/performance in aged mice.

Age-Associated DNA Methylation Patterns Are Shared Between the Hippocampus and Peripheral Blood Cells

As the population ages, interest in identifying biomarkers of healthy aging and developing antiaging interventions has increased. DNA methylation has emerged as a potentially powerful molecular marker of aging. Methylation changes at specific sites in the human genome that have been identified in peripheral blood have been used as robust estimators of chronological age. Similar age-related DNA methylation signatures are also seen in various tissue types in rodents. However, whether these peripheral alterations in methylation status reflect changes that also occur in the central nervous system remains unknown. This study begins to address this issue by identifying age-related methylation patterns in the hippocampus and blood of young and old mice. Reduced-representation bisulfite sequencing (RBSS) was used to identify differentially methylated regions (DMRs) in the blood and hippocampus of 2- and 20-month-old C57/Bl6 mice. Of the thousands of DMRs identified genome-wide only five were both found in gene promoters and significantly changed in the same direction with age in both tissues. We analyzed the hippocampal expression of these five hypermethylated genes and found that three were expressed at significantly lower levels in aged mice [suppressor of fused homolog (Sufu), nitric oxide synthase 1 (Nos1) and tripartite motif containing 2 (Trim2)]. We also identified several transcription factor binding motifs common to both hippocampus and blood that were enriched in the DMRs. Overall, our findings suggest that some age-related methylation changes that occur in the brain are also evident in the blood and could have significant translational relevance.

Nitric oxide signalling and antidepressant action revisited

Studies about the pathogenesis of mood disorders have consistently shown that multiple factors, including genetic and environmental, play a crucial role on their development and neurobiology. Multiple pathological theories have been proposed, of which several ultimately affects or is a consequence of dysfunction in brain neuroplasticity and homeostatic mechanisms. However, current clinical available pharmacological intervention, which is predominantly monoamine-based, suffers from a partial and lacking response even after weeks of continuous treatment. These issues raise the need for better understanding of aetiologies and brain abnormalities in depression, as well as developing novel treatment strategies. Nitric oxide (NO) is a gaseous unconventional neurotransmitter, which regulates and governs several important physiological functions in the central nervous system, including processes, which can be associated with the development of mood disorders. This review will present general aspects of the NO system in depression, highlighting potential targets that may be utilized and further explored as novel therapeutic targets in the future pharmacotherapy of depression. In particular, the review will link the importance of neuroplasticity mechanisms governed by NO to a possible molecular basis for the antidepressant effects.

Impaired neural stem cell expansion and hypersensitivity to epileptic seizures in mice lacking the EGFR in the brain

Mice lacking the epidermal growth factor receptor (EGFR) develop an early postnatal degeneration of the frontal cortex and olfactory bulbs and show increased cortical astrocyte apoptosis. The poor health and early lethality of EGFR^−/− mice prevented the analysis of mechanisms responsible for the neurodegeneration and function of the EGFR in the adult brain. Here, we show that postnatal EGFR‐deficient neural stem cells are impaired in their self‐renewal potential and lack clonal expansion capacity in vitro. Mice lacking the EGFR in the brain (EGFR^Δbrain) show low penetrance of cortical degeneration compared to EGFR^−/− mice despite genetic recombination of the conditional allele. Adult EGFR^Δ mice establish a proper blood–brain barrier and perform reactive astrogliosis in response to mechanical and infectious brain injury, but are more sensitive to Kainic acid‐induced epileptic seizures. EGFR‐deficient cortical astrocytes, but not midbrain astrocytes, have reduced expression of glutamate transporters Glt1 and Glast, and show reduced glutamate uptake in vitro, illustrating an excitotoxic mechanism to explain the hypersensitivity to Kainic acid and region‐specific neurodegeneration observed in EGFR‐deficient brains.

A meta-analytic approach to genes that are associated with impaired and elevated spatial memory performance

Spatial memory deficits are a common hallmark of psychiatric conditions, possibly due to a genetic predisposition. Thus, unravelling the relationship between genes and memory might suggest novel therapeutic targets and pathogenetic pathways. Genetic deletions are known to lead to memory deficits (post-deletion "forgetfulness" genes, PDF), or, in few instances to improve spatial memory (post-deletion "hypermnesic" genes, PDH). To assess this topic, we performed a meta-analytic approach on memory behavior in knock-out mice. We screened 300 studies from PubMed and retrieved 87 genes tested for possible effects on spatial memory. This database was crossed with the Allen Brain Atlas (brain distribution) and the Enrichr (gene function) databases. The results show that PDF genes have higher expression level in several ventral brain structures, particularly the encephalic trunk and in the hypothalamus. Moreover, part of these genes are implicated in synaptic functions. Conversely, the PDH genes are associated to G-protein coupled receptors downstream signalling. Some candidate drugs were also found to interfere with some of the PDH genes, further suggesting that this approach might help in identifying drugs to improve memory performance in psychiatric conditions.

A daily single dose of a novel modafinil analogue CE-123 improves memory acquisition and memory retrieval

Dopamine reuptake inhibitors have been shown to improve cognitive parameters in various tasks and animal models. We recently reported a series of modafinil analogues, of which the most promising, 5-((benzhydrylsulfinyl)methyl) thiazole (CE-123), was selected for further development. The present study aims to characterize pharmacological properties of CE-123 and to investigate the potential to enhance memory performance in a rat model. In vitro transporter assays were performed in cells expressing human transporters. CE-123 blocked uptake of [3H] dopamine (IC50 = 4.606 μM) while effects on serotonin (SERT) and the norepinephrine transporter (NET) were negligible. Blood-brain barrier and pharmacokinetic studies showed that the compound reached the brain and lower elimination than R-modafinil. The Pro-cognitive effect was evaluated in a spatial hole-board task in male Sprague-Dawley rats and CE-123 enhances memory acquisition and memory retrieval, represented by significantly increased reference memory indices and shortened latency. Since DAT blockers can be considered as indirect dopamine receptor agonists, western blotting was used to quantify protein levels of dopamine receptors D1R, D2R and D5R and DAT in the synaptosomal fraction of hippocampal subregions CA1, CA3 and dentate gyrus (DG). CE-123 administration in rats increased total DAT levels and D1R protein levels were significantly increased in CA1 and CA3 in treated/trained groups. The increase of D5R was observed in DG only. Dopamine receptors, particularly D1R, seem to play a role in mediating CE-123-induced memory enhancement. Dopamine reuptake inhibition by CE-123 may represent a novel and improved stimulant therapeutic for impairments of cognitive functions.

Heterocyclic Analogues of Modafinil as Novel, Atypical Dopamine Transporter Inhibitors

Modafinil is a wake promoting compound with high potential for cognitive enhancement. It is targeting the dopamine transporter (DAT) with moderate selectivity, thereby leading to reuptake inhibition and increased dopamine levels in the synaptic cleft. A series of modafinil analogues have been reported so far, but more target-specific analogues remain to be discovered. It was the aim of this study to synthesize and characterize such analogues and, indeed, a series of compounds were showing higher activities on the DAT and a higher selectivity toward DAT versus serotonin and norepinephrine transporters than modafinil. This was achieved by substituting the amide moiety by five- and six-membered aromatic heterocycles. In vitro studies indicated binding to the cocaine pocket on DAT, although molecular dynamics revealed binding different from that of cocaine. Moreover, no release of dopamine was observed, ruling out amphetamine-like effects. The absence of neurotoxicity of a representative analogue may encourage further preclinical studies of the above-mentioned compounds.

Roles of Nitric Oxide Synthase Isoforms in Neurogenesis

Nitric oxide (NO), a free radical gas, acts as a neurotransmitter or neuromodulator in the central nervous system (CNS). It has been widely explored as a mediator of neuroinflammation, neuronal damages, and neurodegeneration at its pathological levels. Recently, increasing evidence suggests that NO plays key roles in mediating adult neurogenesis, the process of neural stem cells (NSCs) to generate newborn neurons for replacing damaged neurons or maintaining the function of the brain. NO synthase (NOS) is a major enzyme catalyzing the generation of NO in the brain. Recent studies indicate that three homologous NOS isoforms are involved in the proliferation of NSCs and neurogenesis. Therefore, the impact of NOS isoforms on NSC functions needs to be elucidated. Here, we summarize the studies on the role of NO and NOS with different isoforms in NSC proliferation and neurogenesis with the focus on introducing action mechanisms involved in the regulation of NSC function. This growing research area provides the new insight into controlling NSC function via regulating NO microenvironment in the brain. It also provides the evidence on targeting NOS for the treatment of brain diseases.

Small molecule inhibitors of PSD95-nNOS protein-protein interactions suppress formalin-evoked Fos protein expression and nociceptive behavior in rats

Excessive activation of NMDA receptor (NMDAR) signaling within the spinal dorsal horn contributes to central sensitization and the induction and maintenance of pathological pain states. However, direct antagonism of NMDARs produces undesirable side effects which limit their clinical use. NMDAR activation produces central sensitization, in part, by initiating a signaling cascade that activates the enzyme neuronal nitric oxide synthase (nNOS) and generates the signaling molecule nitric oxide. NMDAR-mediated activation of nNOS requires a scaffolding protein, postsynaptic density protein 95kDa (PSD95), which tethers nNOS to NMDARs. Thus, disrupting the protein-protein interaction between PSD95 and nNOS may inhibit pro-nociceptive signaling mechanisms downstream of NMDARs and suppress central sensitization while sparing unwanted side effects associated with NMDAR antagonists. We examined the impact of small molecule PSD95-nNOS protein-protein interaction inhibitors (ZL006, IC87201) on both nociceptive behavior and formalin-evoked Fos protein expression within the lumbar spinal cord of rats. Comparisons were made with ZL007, an inactive analog of ZL006, and the NMDAR antagonist MK-801. IC87201 and ZL006, but not ZL007, suppressed phase 2 of formalin-evoked pain behavior and decreased the number of formalin-induced Fos-like immunoreactive cells in spinal dorsal horn regions associated with nociceptive processing. MK-801 suppressed Fos protein expression in both dorsal and ventral horns. MK-801 produced motor ataxia in the rotarod test whereas IC87201 and ZL006 failed to do so. ZL006 but not ZL007 suppressed paclitaxel-induced mechanical and cold allodynia in a model of chemotherapy-induced neuropathic pain. Co-immunoprecipitation experiments revealed the presence of the PSD95-nNOS complex in lumbar spinal cord of paclitaxel-treated rats, although ZL006 did not reliably disrupt the complex in all subjects. The present findings validate use of putative small molecule PSD95-nNOS protein-protein interaction inhibitors as novel analgesics and demonstrate, for the first time, that these inhibitors suppress inflammation-evoked neuronal activation at the level of the spinal dorsal horn.

HIV-1 Tat causes cognitive deficits and selective loss of parvalbumin, somatostatin, and neuronal nitric oxide synthase expressing hippocampal CA1 interneuron subpopulations

Memory deficits are characteristic of HIV-associated neurocognitive disorders (HAND) and co-occur with hippocampal pathology. The HIV-1 transactivator of transcription (Tat), a regulatory protein, plays a significant role in these events, but the cellular mechanisms involved are poorly understood. Within the hippocampus, diverse populations of interneurons form complex networks; even subtle disruptions can drastically alter synaptic output, resulting in behavioral dysfunction. We hypothesized that HIV-1 Tat would impair cognitive behavior and injure specific hippocampal interneuron subtypes. Male transgenic mice that inducibly expressed HIV-1 Tat (or non-expressing controls) were assessed for cognitive behavior or had hippocampal CA1 subregions evaluated via interneuron subpopulation markers. Tat exposure decreased spatial memory in a Barnes maze and mnemonic performance in a novel object recognition test. Tat reduced the percentage of neurons expressing neuronal nitric oxide synthase (nNOS) without neuropeptide Y immunoreactivity in the stratum pyramidale and the stratum radiatum, parvalbumin in the stratum pyramidale, and somatostatin in the stratum oriens, which are consistent with reductions in interneuron-specific interneuron type 3 (IS3), bistratified, and oriens-lacunosum-moleculare interneurons, respectively. The findings reveal that an interconnected ensemble of CA1 nNOS-expressing interneurons, the IS3 cells, as well as subpopulations of parvalbumin- and somatostatin-expressing interneurons are preferentially vulnerable to HIV-1 Tat. Importantly, the susceptible interneurons form a microcircuit thought to be involved in feedback inhibition of CA1 pyramidal cells and gating of CA1 pyramidal cell inputs. The identification of vulnerable CA1 hippocampal interneurons may provide novel insight into the basic mechanisms underlying key functional and neurobehavioral deficits associated with HAND.

Nitric Oxide Is Required for L-Type Ca(2+) Channel-Dependent Long-Term Potentiation in the Hippocampus

Nitric oxide (NO) has long been implicated in the generation of long-term potentiation (LTP) and other types of synaptic plasticity, a role for which the intimate coupling between NMDA receptors (NMDARs) and the neuronal isoform of NO synthase (nNOS) is likely to be instrumental in many instances. While several types of synaptic plasticity depend on NMDARs, others do not, an example of which is LTP triggered by opening of L-type voltage-gated Ca²⁺ channels (L-VGCCs) in postsynaptic neurons. In CA3-CA1 synapses in the hippocampus, NMDAR-dependent LTP (LTP_NMDAR) appears to be primarily expressed postsynaptically whereas L-VGCC-dependent LTP (LTP_L−VGCC), which often coexists with LTP_NMDAR, appears mainly to reflect enhanced presynaptic transmitter release. Since NO is an excellent candidate as a retrograde messenger mediating post-to-presynaptic signaling, we sought to determine if NO functions in LTP_L−VGCC in mouse CA3-CA1 synapses. When elicited by a burst type of stimulation with NMDARs and the associated NO release blocked, LTP_L−VGCC was curtailed by inhibition of NO synthase or of the NO-receptor guanylyl cyclase to the same extent as occurred with inhibition of L-VGCCs. Unlike LTP_NMDAR at these synapses, LTP_L−VGCC was unaffected in mice lacking endothelial NO synthase, implying that the major source of the NO is neuronal. Transient delivery of exogenous NO paired with tetanic synaptic stimulation under conditions of NMDAR blockade resulted in a long-lasting potentiation that was sensitive to inhibition of NO-receptor guanylyl cyclase but was unaffected by inhibition of L-VGCCs. The results indicate that NO, acting through its second messenger cGMP, plays an unexpectedly important role in L-VGCC-dependent, NMDAR-independent LTP, possibly as a retrograde messenger generated in response to opening of postsynaptic L-VGCCs and/or as a signal acting postsynaptically, perhaps to facilitate changes in gene expression.

Decreased hippocampal homoarginine and increased nitric oxide and nitric oxide synthase levels in rats parallel training in a radial arm maze

L-homoarginine (hArg) is derived from enzymatic guanidination of lysine. It was demonstrated that hArg is a substrate for nitric oxide (NO) synthesis, blocks lysine transport and inhibits the uptake of arginine into synaptosomes and modulates GABA responses ex vivo. As there is limited information on its physiological roles in the brain, the aim of the study was to show whether hippocampal or frontal lobe (FL) hArg is paralleling training in the radial arm maze (RAM) or NO formation. Hippocampi and FL of male Sprague-Dawley rats were taken from trained or yoked in a RAM. Then hArg and metabolites, NO and NO synthase (NOS) were determined by standard methods. The animals learned the task in the RAM showing significant reduction of working memory errors. hArg showed decreased levels in both brain regions of trained animals as compared to yoked animals. Nitrate plus nitrite (NOx) concentrations and NOS activity were significantly increased in hippocampi, F(1,36) = 170.5; P ≤ 0.0001 and FL, F(1,36) = 74.67; P ≤ 0.0001 of trained animals as compared to yoked animals. Levels of hArg were negatively correlated with NOx in hippocampus (r = -0.6355; P = 0.0483) but not in FL and with lysine in the FL (r = -0.6650; P = 0.0358). NOx levels were positively correlated with NOS in both the hippocampus (r = 0.7474; P = 0.0129) and FL (r = 0.9563; P ≤  0.0001). These novel findings indicate that hArg is linked to NO formation in hippocampus but not in FL and is paralleling spatial memory in the RAM.

Reactive Oxygen-Related Diseases: Therapeutic Targets and Emerging Clinical Indications

SIGNIFICANCE

Enhanced levels of reactive oxygen species (ROS) have been associated with different disease states. Most attempts to validate and exploit these associations by chronic antioxidant therapies have provided disappointing results. Hence, the clinical relevance of ROS is still largely unclear.

RECENT ADVANCES

We are now beginning to understand the reasons for these failures, which reside in the many important physiological roles of ROS in cell signaling. To exploit ROS therapeutically, it would be essential to define and treat the disease-relevant ROS at the right moment and leave physiological ROS formation intact. This breakthrough seems now within reach.

CRITICAL ISSUES

Rather than antioxidants, a new generation of protein targets for classical pharmacological agents includes ROS-forming or toxifying enzymes or proteins that are oxidatively damaged and can be functionally repaired.

FUTURE DIRECTIONS

Linking these target proteins in future to specific disease states and providing in each case proof of principle will be essential for translating the oxidative stress concept into the clinic.

Lack of neuronal nitric oxide synthase results in attention deficit hyperactivity disorder-like behaviors in mice

Nitric oxide (NO) is an important molecule for the proper development and function of the central nervous system. In this study, we investigated the behavioral alterations in the neuronal NO synthase knockout mice (NOS1 KO) with a deficient NO production mechanism in the brain, characterizing it as a potential rodent model for attention deficit hyperactivity disorder (ADHD). NOS1 KO exhibited higher locomotor activity than their wildtype counterparts in a novel environment, as measured by open field (OF) test. In a 2-way active avoidance paradigm (TWAA), we found sex-dependent effects, where male KO displayed deficits in avoidance and escape behavior, sustained higher incidences of shuttle crossings, and higher incidences of intertrial interval crossings, suggesting learning, and/or performance impairments. On the other hand, female KO demonstrated few deficits in TWAA. Molsidomine (MSD), a NO donor, rescued TWAA deficits in male KO when acutely administered before training. In a passive avoidance paradigm, KO of both sexes displayed significantly shorter step-through latencies after training. Further, abnormal spontaneous motor activity rhythms were found in the KO during the dark phase of the day, indicating dysregulation of rhythmic activities. These data indicate that NOS1 KO mimics certain ADHD-like behaviors and could potentially serve as a novel rodent model for ADHD.

Hypomorphic variants of cationic amino acid transporter 3 in males with autism spectrum disorders

Cationic amino acid transporters (CATs) mediate the entry of L-type cationic amino acids (arginine, ornithine and lysine) into the cells including neurons. CAT-3, encoded by the SLC7A3 gene on chromosome X, is one of the three CATs present in the human genome, with selective expression in brain. SLC7A3 is highly intolerant to variation in humans, as attested by the low frequency of deleterious variants in available databases, but the impact on variants in this gene in humans remains undefined. In this study, we identified a missense variant in SLC7A3, encoding the CAT-3 cationic amino acid transporter, on chromosome X by exome sequencing in two brothers with autism spectrum disorder (ASD). We then sequenced the SLC7A3 coding sequence in 148 male patients with ASD and identified three additional rare missense variants in unrelated patients. Functional analyses of the mutant transporters showed that two of the four identified variants cause severe or moderate loss of CAT-3 function due to altered protein stability or abnormal trafficking to the plasma membrane. The patient with the most deleterious SLC7A3 variant had high-functioning autism and epilepsy, and also carries a de novo 16p11.2 duplication possibly contributing to his phenotype. This study shows that rare hypomorphic variants of SLC7A3 exist in male individuals and suggest that SLC7A3 variants possibly contribute to the etiology of ASD in male subjects in association with other genetic factors.

A Diffusive Homeostatic Signal Maintains Neural Heterogeneity and Responsiveness in Cortical Networks

Gaseous neurotransmitters such as nitric oxide (NO) provide a unique and often overlooked mechanism for neurons to communicate through diffusion within a network, independent of synaptic connectivity. NO provides homeostatic control of intrinsic excitability. Here we conduct a theoretical investigation of the distinguishing roles of NO-mediated diffusive homeostasis in comparison with canonical non-diffusive homeostasis in cortical networks. We find that both forms of homeostasis provide a robust mechanism for maintaining stable activity following perturbations. However, the resulting networks differ, with diffusive homeostasis maintaining substantial heterogeneity in activity levels of individual neurons, a feature disrupted in networks with non-diffusive homeostasis. This results in networks capable of representing input heterogeneity, and linearly responding over a broader range of inputs than those undergoing non-diffusive homeostasis. We further show that these properties are preserved when homeostatic and Hebbian plasticity are combined. These results suggest a mechanism for dynamically maintaining neural heterogeneity, and expose computational advantages of non-local homeostatic processes.

Regulation of brain glutamate metabolism by nitric oxide and S-nitrosylation

Nitric oxide (NO) is a signaling intermediate during glutamatergic neurotransmission in the central nervous system (CNS). NO signaling is in part accomplished through cysteine S-nitrosylation, a posttranslational modification by which NO regulates protein function and signaling. In our investigation of the protein targets and functional impact of S-nitrosylation in the CNS under physiological conditions, we identified 269 S-nitrosocysteine residues in 136 proteins in the wild-type mouse brain. The number of sites was significantly reduced in the brains of mice lacking endothelial nitric oxide synthase (eNOS(-/-)) or neuronal nitric oxide synthase (nNOS(-/-)). In particular, nNOS(-/-) animals showed decreased S-nitrosylation of proteins that participate in the glutamate/glutamine cycle, a metabolic process by which synaptic glutamate is recycled or oxidized to provide energy. (15)N-glutamine-based metabolomic profiling and enzymatic activity assays indicated that brain extracts from nNOS(-/-) mice converted less glutamate to glutamine and oxidized more glutamate than those from mice of the other genotypes. GLT1 [also known as EAAT2 (excitatory amino acid transporter 2)], a glutamate transporter in astrocytes, was S-nitrosylated at Cys(373) and Cys(561) in wild-type and eNOS(-/-) mice, but not in nNOS(-/-) mice. A form of rat GLT1 that could not be S-nitrosylated at the equivalent sites had increased glutamate uptake compared to wild-type GLT1 in cells exposed to an S-nitrosylating agent. Thus, NO modulates glutamatergic neurotransmission through the selective, nNOS-dependent S-nitrosylation of proteins that govern glutamate transport and metabolism.

Genetic Modulation of Neurocognitive Function in Glioma Patients

PURPOSE

Accumulating evidence supports the contention that genetic variation is associated with neurocognitive function in healthy individuals and increased risk for neurocognitive decline in a variety of patient populations, including cancer patients. However, this has rarely been studied in glioma patients.

EXPERIMENTAL DESIGN

To identify the effect of genetic variants on neurocognitive function, we examined the relationship between the genotype frequencies of 10,967 single-nucleotide polymorphisms in 580 genes related to five pathways (inflammation, DNA repair, metabolism, cognitive, and telomerase) and neurocognitive function in 233 newly diagnosed glioma patients before surgical resection. Four neuropsychologic tests that measured memory (Hopkins Verbal Learning Test-Revised), processing speed (Trail Making Test A), and executive function (Trail Making Test B, Controlled Oral Word Association) were examined.

RESULTS

Eighteen polymorphisms were associated with processing speed and 12 polymorphisms with executive function. For processing speed, the strongest signals were in IRS1 rs6725330 in the inflammation pathway (P = 2.5 × 10(-10)), ERCC4 rs1573638 in the DNA repair pathway (P = 3.4 × 10(-7)), and ABCC1 rs8187858 in metabolism pathway (P = 6.6 × 10(-7)). For executive function, the strongest associations were in NOS1 rs11611788 (P = 1.8 × 10(-8)) and IL16 rs1912124 (P = 6.0 × 10(-7)) in the inflammation pathway, and POLE rs5744761 (P = 6.0 × 10(-7)) in the DNA repair pathway. Joint effect analysis found significant gene polymorphism-dosage effects for processing speed (Ptrend = 9.4 × 10(-16)) and executive function (Ptrend = 6.6 × 10(-15)).

CONCLUSIONS

Polymorphisms in inflammation, DNA repair, and metabolism pathways are associated with neurocognitive function in glioma patients and may affect clinical outcomes.

Effects of nitric oxide-related compounds in the acute ketamine animal model of schizophrenia

Background

Better treatments for schizophrenia are urgently needed. The therapeutic use of the nitric oxide (NO)-donor sodium nitroprusside (SNP) in patients with schizophrenia has shown promising results. The role of NO in schizophrenia is still unclear, and NO modulation is unexplored in ketamine (KET) animal models to date. In the present study, we compared the behavioral effects of pre- and post-treatment with SNP, glyceryl trinitrate (GTN), and methylene blue (MB) in the acute KET animal model of schizophrenia.

The present study was designed to test whether acute SNP, GTN, and MB treatment taken after (therapeutic effect) or before (preventive effect) a single KET injection would influence the behavior of rats in the sucrose preference test, object recognition task and open field.

Results

The results showed that KET induced cognitive deficits and hyperlocomotion. Long- term memory improvement was seen with the therapeutic GTN and SNP treatment, but not with the preventive one. MB pretreatment resulted in long-term memory recovery. GTN pre-, but not post-treatment, tended to increase vertical and horizontal activity in the KET model. Therapeutic and preventive SNP treatment consistently decreased KET-induced hyperlocomotion.

Conclusion

NO donors – especially SNP – are promising new pharmacological candidates in the treatment of schizophrenia. In addition, we showed that the potential impact of NO-related compounds on KET-induced behavioral changes may depend on the temporal window of drug administration.

Increased Contextual Fear Conditioning in iNOS Knockout Mice: Additional Evidence for the Involvement of Nitric Oxide in Stress-Related Disorders and Contribution of the Endocannabinoid System

BACKGROUND

Inducible or neuronal nitric oxide synthase gene deletion increases or decreases anxiety-like behavior in mice, respectively. Since nitric oxide and endocannabinoids interact to modulate defensive behavior, the former effect could involve a compensatory increase in basal brain nitric oxide synthase activity and/or changes in the endocannabinoid system. Thus, we investigated the expression and extinction of contextual fear conditioning of inducible nitric oxide knockout mice and possible involvement of endocannabinoids in these responses.

METHODS

We evaluated the effects of a preferential neuronal nitric oxide synthase inhibitor, 7-nitroindazol, nitric oxide synthase activity, and mRNA changes of nitrergic and endocannabinoid systems components in the medial prefrontal cortex and hippocampus of wild-type and knockout mice. The effects of URB597, an inhibitor of the fatty acid amide hydrolase enzyme, which metabolizes the endocannabinoid anandamide, WIN55,212-2, a nonselective cannabinoid agonist, and AM281, a selective CB1 antagonist, on contextual fear conditioning were also evaluated.

RESULTS

Contextual fear conditioning expression was similar in wild-type and knockout mice, but the latter presented extinction deficits and increased basal nitric oxide synthase activity in the medial prefrontal cortex. 7-Nitroindazol decreased fear expression and facilitated extinction in wild-type and knockout mice. URB597 decreased fear expression in wild-type and facilitated extinction in knockout mice, whereas WIN55,212-2 and AM281 increased it in wild-type mice. Nonconditioned knockout mice showed changes in the mRNA expression of nitrergic and endocannabinoid system components in the medial prefrontal cortex and hippocampus that were modified by fear conditioning.

CONCLUSION

These data reinforce the involvement of the nitric oxide and endocannabinoids (anandamide) in stress-related disorders and point to a deregulation of the endocannabinoid system in situations where nitric oxide signaling is increased.

The effect of a selective neuronal nitric oxide synthase inhibitor 3-bromo 7-nitroindazole on spatial learning and memory in rats

Since the discovery of nitric oxide (NO) as a neuronal messenger, its way to modulate learning and memory functions is subject of intense research. NO is an intercellular messenger in the central nervous system and is formed on demand through the conversion of L-arginine to L-citrulline via the enzyme nitric oxide synthase (NOS). Neuronal form of nitric oxide synthase may play an important role in a wide range of physiological and pathological conditions. Therefore the aim of this study was to investigate the effects of chronic 3-bromo 7-nitroindazole (3-Br 7-NI), specific neuronal nitric oxide synthase (nNOS) inhibitor, administration on spatial learning and memory performance in rats using the Morris water maze (MWM) paradigm. Male rats received either 3-Br 7-NI (20mg/kg/day) or saline via intraperitoneal injection for 5days. Daily administration of the specific neuronal nitric oxide synthase (nNOS) inhibitor, 3-Br 7-NI impaired the acquisition of the MWM task. 3-Br 7-NI also impaired the probe trial. The MWM training was associated with a significant increase in the brain-derived neurotrophic factor (BDNF) mRNA expression in the hippocampus. BDNF mRNA expression in the hippocampus did not change after 3-Br 7-NI treatment. L-arginine significantly reversed behavioural parameters, and the effect of 3-Br 7-NI was found to be NO-dependent. There were no differences in locomotor activity and blood pressure in 3-Br 7-NI treated rats. Our results may suggest that nNOS plays a key role in spatial memory formation in rats.

Importance of genetics in fetal alcohol effects: null mutation of the nNOS gene worsens alcohol-induced cerebellar neuronal losses and behavioral deficits

The cerebellum is a major target of alcohol-induced damage in the developing brain. However, the cerebella of some children are much more seriously affected than others by prenatal alcohol exposure. As a consequence of in utero alcohol exposure, some children have substantial reductions in cerebellar volume and corresponding neurodevelopmental problems, including microencephaly, ataxia, and balance deficits, while other children who were exposed to similar alcohol quantities are spared. One factor that likely plays a key role in determining the impact of alcohol on the fetal cerebellum is genetics. However, no specific gene variant has yet been identified that worsens cerebellar function as a consequence of developmental alcohol exposure. Previous studies have revealed that mice carrying a homozygous mutation of the gene for neuronal nitric oxide synthase (nNOS-/- mice) have more severe acute alcohol-induced neuronal losses from the cerebellum than wild type mice. Therefore, the goals of this study were to determine whether alcohol induces more severe cerebellum-based behavioral deficits in nNOS-/- mice than in wild type mice and to determine whether these worsened behavior deficits are associated with worsened cerebellar neuronal losses. nNOS-/- mice and their wild type controls received alcohol (0.0, 2.2, or 4.4mg/g) daily over postnatal days 4-9. In adulthood, the mice underwent behavioral testing, followed by neuronal quantification. Alcohol caused dose-related deficits in rotarod and balance beam performance in both nNOS-/- and wild type mice. However, the alcohol-induced behavioral deficits were substantially worse in the nNOS-/- mice than in wild type. Likewise, alcohol exposure led to losses of Purkinje cells and cerebellar granule cells in mice of both genotypes, but the cell losses were more severe in the nNOS-/- mice than in wild type. Behavioral performances were correlated with neuronal number in the nNOS-/- mice, but not in wild type. Thus, homozygous mutation of the nNOS gene increases vulnerability to alcohol-induced cerebellar dysfunction and neuronal loss. nNOS is the first gene identified whose mutation worsens alcohol-induced cerebellar behavioral deficits.

Long term creatine monohydrate supplementation, following neonatal hypoxic ischemic insult, improves neuromuscular coordination and spatial learning in male albino mouse

Creatine is known to rescue animals following brain damage. Present study was designed to demonstrate the effect of long term (15 week) supplementation of 2% creatine monohydrate (Cr), following neonatal hypoxic ischemic insult, on learning and memory formation in male albino mouse. Albino mice pups were subjected to right common carotid artery ligation followed by 8% hypoxia for 25 minutes. Following weaning, animals were separated and grouped on the basis of dietry supplementation for 15 weeks followed by a battery of neurological tests including Morris water maze, open field and rota rod. It was observed that HI mice fed on 2% Cr for 15 weeks performed better than their littermates mice on normal rodent diet during water maze (learning and memory) and rotating rod (neuro-muscular coordination and balance) test while the results of open field test remained unaffected. It was also observed that Cr treated animals had a reduced brain infarct volume than untreated but this difference did not reached statistical significance. We have also observed an overall increase in body weight in Cr treated mice during the study. Over all our results are indicating that long term Cr supplementation is beneficial for male albino following hypoxic ischemic insult.

Effect of 7-Nitroindazole, a Neuronal Nitric Oxide Synthase Inhibitor, on Behavioral and Physiological Parameters

The role of brain derived nitric oxide in the physiology and behavior remains disputable. One of the reasons of the controversies might be systemic side effects of nitric oxide synthase inhibitors. Therefore, under nNOS inhibition by 7-nitroindazole (7-NI) we carried out recordings of blood gasses, blood pressure and spontaneous EEG in conscious adult rats. Locomotion and spontaneous behavior were assessed in an open field. In addition skilled walking and limb coordination were evaluated using a ladder rung walking test. The blood gas analysis revealed a significant increase in pCO2 180 min and 240 min after the application of 7-NI. The power and entropy decreased simultaneously with a shift of the mean frequency of the spontaneous EEG toward slow oscillations after 7-NI treatment. The thresholds of evoked potentials underwent a significant drop and a trend towards a slight increase in the I-O curve slope was observed. 7-NI significantly suppressed open field behavior expressed as distance moved, exploratory rearing and grooming. As for the ladder rung walking test the 7-NI treated animals had more errors in foot placement indicating impairment in limb coordination. Therefore our findings suggest that 7-NI increased cortical excitability and altered some physiological and behavioral parameters.

Anxiety- and depression-like phenotype of hph-1 mice deficient in tetrahydrobiopterin

Decreased tetrahydrobiopterin (BH4) biosynthesis has been implicated in the pathophysiology of anxiety and depression. The aim of this study was therefore to characterise the phenotype of homozygous hph-1 (hph) mice, a model of BH4 deficiency, in behavioural tests of anxiety and depression as well as determine hippocampal monoamine and plasma nitric oxide levels. In the elevated zero maze test, hph mice displayed increased anxiety-like responses compared to wild-type mice, while the marble burying test revealed decreased anxiety-like behaviour. This was particularly observed in male mice. In the tail suspension test, hph mice of both sexes displayed increased depression-like behaviours compared to wild-type counterparts, whereas the forced swim test showed a trend towards increased depression-like behaviours in male hph mice, but significant decrease in depression-like behaviours in female mice. This study provides the first evidence that congenital BH4 deficiency regulates anxiety- and depression-like behaviours. The altered responses observed possibly reflect decreased hippocampal serotonin and dopamine found in hph mice compared to wild-type mice, but also reduced nitric oxide formation. We propose that the hph-1 mouse may be a novel tool to investigate the role of BH4 deficiency in anxiety and depression.

Redox signal regulation via nNOS phosphorylation at Ser847 in PC12 cells and rat cerebellar granule neurons

Phosphorylation is considered a main mechanism modulating nNOS (neuronal nitric oxide synthase) function to reduce NO production. In the present study, the effects of nNOS phosphorylation on redox signalling, including that of NO, ROS (reactive oxygen species), and 8-nitro-cGMP (8-nitroguanosine 3',5'-cyclic monophosphate), a downstream messenger of redox signalling, were investigated. In vitro experiments revealed that a phosphorylation-mimic mutant of nNOS (Ser847 replaced with aspartic acid, 847D) increased uncoupling to produce a superoxide. In addition, nicotine, which triggers an influx of Ca2+, induced more ROS and 8-nitro-cGMP production in 847D-expressing PC12 cells than WT (wild-type)-expressing cells. Additionally, nicotine-induced phosphorylation of nNOS at Ser847 and increased ROS and 8-nitro-cGMP production in rat CGNs (cerebellar granule neurons). In CGNs, the NOS (nitric oxide synthase) inhibitor L-NAME (NG-nitro-L-arginine methyl ester) and superoxide dismutase completely inhibited ROS and 8-nitro-cGMP production, whereas the CaMK (Ca2+/calmodulin-dependent protein kinase) inhibitor KN93 mildly reduced this effect. Nicotine induced HO-1 (haem oxygenase 1) expression in CGNs and showed cytoprotective effects against apoptosis. Moreover, 8-nitro-cGMP treatment showed identical effects that were attenuated by KN93 pre-treatment. The present paper provides the first substantial corroboration for the biological effects of nNOS phosphorylation at Ser847 on redox signalling, including ROS and intracellular 8-nitro-cGMP generation in neurons, which possibly play roles in neuroprotection.

CGP 35348, GABA B receptor antagonist, has a potential to improve neuromuscular coordination and spatial learning in albino mouse following neonatal brain damage

To study the effect of CGP 35348 on learning and memory in albino mice following hypoxia ischemia insult, 10 days old albino mice were subjected to right common carotid artery ligation followed by 8% hypoxia for 25 minutes. Following brain damage, mice were fed on normal rodent diet till they were 13 week old. At this time point, mice were divided into two groups. Group 1 received saline and group 2 intrapertoneally CGP 35348 (1 mg/mL solvent/Kg body weight) for 12 days. A battery of tests used to assess long term neurofunction (Morris water maze, Rota rod and open field) along with brain infarct measurement. Overall CGP 35348 has improved the motor function in male and female albino mice but effects were more pronounced in female albino mice. In open field, CGP 35348 treated female albino mice had demonstrated poor exploratory behavior. During Morris water maze test, gender specific effects were observed as CGP 35348 had improved spatial learning and memory and swimming speed in male albino mice but had no effect in female albino mice following hypoxia ischemia encephalopathy (HIE). We concluded that GABAB receptor antagonists CGP 35348 can be used to improve gender based spatial memory.

Oxidative imbalance and anxiety disorders

The oxidative imbalance appears to have an important role in anxiety development. Studies in both humans and animals have shown a strong correlation between anxiety and oxidative stress. In humans, for example, the increased malondialdehyde levels and discrepancies in antioxidant enzymes in erythrocytes have been observed. In animals, several studies also show that anxiety-like behavior is related to the oxidative imbalance. Moreover, anxiety-like behavior can be caused by pharmacological-induced oxidative stress. Studies using knockout or overexpression of antioxidant enzymes have shown a relationship between anxiety-like behavior and oxidative stress. Related factors of oxidative stress that could influence anxious behavior are revised, including impaired function of different mitochondrial proteins, inflammatory cytokines, and neurotrophic factors. It has been suggested that a therapy specifically focus in reducing reactive species production may have a beneficial effect in reducing anxiety. However, the neurobiological pathways underlying the effect of oxidative stress on anxiety symptoms are not fully comprehended. The challenge now is to identify the oxidative stress mechanisms likely to be involved in the induction of anxiety symptoms. Understanding these pathways could help to clarify the neurobiology of the anxiety disorder and provide tools for new discovery in therapies and preventive strategies.

Sex-influence of nicotine and nitric oxide on motor coordination and anxiety-related neurophysiological responses

RATIONALE

Nitric oxide (NO) is a messenger synthesized in both the neuronal and glial populations by nitric oxide synthase type 1 (NOS1). Nicotine regulates NO production in a sex-dependent manner, both molecules being involved in motor function.

OBJECTIVE

The present study evaluates sex differences in motor coordination, general movement, and anxiety-related responses resulting from both constant and continuous nicotine treatment and the genetic depletion of NOS1 activity.

METHODS

Male and female mice were analyzed with the open-field and the rotarod tests. To understand the role of NO, knockout mice for NOS1 (NOS1-/-) were analyzed. Nicotine was administered continuously at a dose of 24 mg/kg/day via osmotic mini-pumps over 14 days because the behavioral effects elicited are similar to those observed with discontinuous administration.

RESULTS

Data analyses revealed noteworthy sex differences derived from NOS1 depletion. Control NOS1-/- males exhibited an exacerbated anxiety-related response in relation to control NOS1-/- females and control wild-type (WT) males; these differences disappeared in the nicotine-administered NOS1-/- males. Additionally, nicotine administration differentially affected the horizontal movements of NOS1-/- females with respect to WT animals. NO depletion affected male but not female motor coordination improvement along the test days. However, the drug affected female motor coordination only at the end of the administration period.

CONCLUSIONS

We show for the first time that NO affects motor and anxiety behaviors in a sex-dependent manner. Moreover, the behavioral effects of constant nicotine administration are dimorphic and dependent on NO production.

Effect of GABAB receptor antagonist (CGP35348) on learning and memory in albino mice

The present study was designed to demonstrate the potential effect of CGP 35348 (GABA_B receptor antagonist) on the learning, memory formation, and neuromuscular coordination in albino mouse. Mice were intrapertoneally injected with 1 mg CGP 35348/mL of distilled water/Kg body weight, while the control animals were injected with equal volume of saline solution. A battery of neurological tests was applied following the intrapertoneal injections. Results of rota rod indicated that CGP 35348 had no effect on neuromuscular coordination in both male (P = 0.528) and female (P = 0.125) albino mice. CGP 35348 treated females demonstrated poor exploratory behavior during open filed for several parameters (time mobile (P = 0.04), time immobile (P = 0.04), rotations (P = 0.04), and anticlockwise rotations (P = 0.038)). The results for Morris water maze (MWM) retention phase indicated that CGP 35348 treated male mice took shorter latency to reach the hidden platform (P = 0.04) than control indicating improved memory. This observation was complemented by the swim strategies used by mice during training days in MWM as CGP 35348 treated males used more direct and focal approach to reach the platform as the training proceeded.

Effects of polyprenols from pine needles of Pinus massoniana on ameliorating cognitive impairment in a D-galactose-induced mouse model

Cognitive deficiency and oxidative stress have been well documented in aging and in neurodegenerative disorders such as Alzheimer's disease. In this study, we assessed the therapeutic effect of polyprenols on D-galactose-induced cognitive impairment in mice by testing on of behavioral and cognitive performance. In order to explore the possible role of polyprenols against D-galactose-induced oxidative damages, we assessed various biochemical indicators. Chronic administration of D-galactose (150 mg/kg·d, s.c.) for 7 weeks significantly impaired cognitive performance (both in step-through passive and active avoidance tests) and locomotor activity (in open-field test) and the ability of spatial learning and memory (in Morris water maze test) compared with the control group. The results revealed that polyprenols treatment for 2 weeks significantly ameliorated model mice's cognitive performance and oxidative defense. All groups of polyprenols enhanced the learning and memory ability in step-through passive and active avoidance tests, locomotor activity in open-field test, and the ability of spatial learning and memory in Morris water maze test. Furthermore, high and middle level of polyprenols significantly increased total antioxidative capacity (T-AOC), glutathione peroxidase (GSH-Px), super oxide dismutase (SOD) activity, neprilysin (NEP), and β-site AβPP cleaving enzyme 1 (BACE1) expression, while nitric oxide (NO), nitric oxide synthase (NOS) activity, malondialdehyde (MDA) concentration, and the level of Aβ1-42 and presenilin 1 (PS1) were decreased. Polyprenols have a significant relieving effect on learning, memory, and spontaneous activities in a D-galactose-induced mouse model and ameliorates cognitive impairment and biochemical dysfunction in mice. In summary, we have demonstrated that polyprenols may ameliorate memory and cognitive impairment via enhancing oxidative defense and affecting generation and dissimilation of Aβ-related enzymes, suggesting that polyprenols represent a novel drug for treating Alzheimer's disease.