Blunted stress responses in delayed type hypersensitivity in mice lacking the neuronal isoform of nitric oxide synthase

Disrupting the nNOS/NOS1AP interaction in the medial prefrontal cortex impairs social recognition and spatial working memory in mice

The neuronal isoform of nitric oxide synthase (nNOS) and its interacting protein NOS1AP have been linked to several mental disorders including schizophrenia and depression. An increase in the interaction between nNOS and NOS1AP in the frontal cortex has been suggested to contribute to the emergence of these disorders. Here we aimed to uncover whether disruption of their interactions in the frontal cortex leads to mental disorder endophenotypes. Targeting the medial prefrontal cortex (mPFC), we stereotaxically injected wild-type C57BL/6J mice with recombinant adeno-associated virus (rAAV) expressing either full-length NOS1AP, the nNOS binding region of NOS1AP (i.e. NOS1AP_396-503), or the nNOS amino-terminus (i.e. nNOS_1-133), which was shown to disrupt the interaction of endogenous nNOS with PSD-95. We tested these mice in a comprehensive behavioural battery, assessing different endophenotypes related to mental disorders. We found no differences in anxiety-related and exploratory behaviours. Likewise, social interaction was comparable in all groups. However, social recognition was impaired in NOS1AP and NOS1AP_396-503 mice. These mice, as well as mice overexpressing nNOS_1-133 also displayed impaired spatial working memory (SWM) capacity, while spatial reference memory (SRM) remained intact. Finally, mice overexpressing NOS1AP and nNOS_1-133, but not NOS1AP_396-503, failed to habituate to the startling pulses in an acoustic startle response (ASR) paradigm, though we found no difference in overall startle intensity or prepulse inhibition (PPI) of the ASR. Our findings indicate a distinct role of NOS1AP/nNOS/PSD-95 interactions in the mPFC to contribute to specific endophenotypic changes observed in different mental disorders.

Oxidative Stress and Male Infertility: Evidence From a Research Perspective

Male fertility potential can be influenced by a variety of conditions that frequently coincide. Spermatozoa are particularly susceptible to oxidative damage due to their limited antioxidant capacity and cell membrane rich in polyunsaturated fatty acids (PUFAs). The role of oxidative stress (OS) in the etiology of male infertility has been the primary focus of our Stellenbosch University Reproductive Research Group (SURRG) over the last 10 years. This review aims to provide a novel insight into the impact of OS on spermatozoa and male reproductive function by reviewing the OS-related findings from a wide variety of studies conducted in our laboratory, along with those emerging from other investigators. We will provide a concise overview of the production of reactive oxygen species (ROS) and the development of OS in the male reproductive tract along with the physiological and pathological effects thereof on male reproductive functions. Recent advances in methods and techniques used for the assessment of OS will also be highlighted. We will furthermore consider the current evidence regarding the association between OS and ejaculatory abstinence period, as well as the potential mechanisms involved in the pathophysiology of various systemic diseases such as obesity, insulin resistance, hypertension, and certain mental health disorders which have been shown to cause OS induced male infertility. Finally, special emphasis will be placed on the potential for transferring and incorporating research findings emanating from different experimental studies into clinical practice.

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.

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.

Influence of two functional polymorphisms in NOS1 on baseline cortisol and working memory in healthy subjects

INTRODUCTION

The neuronal isoform of the nitric oxide synthase (NOS-I) encoded by NOS1 is the main source of nitric oxide (NO) in the brain. Reduced NO signaling in the prefrontal cortex has been linked to schizophrenia and cognitive processes while reduced striatal NOS1 expression has been associated with impulsive behavior.

METHODS

To evaluate the effect of two functional polymorphisms in alternative first exons of NOS1, ex1f-VNTR and ex1c-SNP rs41279104, on the HPA stress axis and neurocognitive abilities, 280 healthy subjects were genotyped, had their salivary cortisol levels measured and were assessed in verbal memory, verbal fluency, working memory and verbal IQ by using the California Verbal Learning Test (CVLT), the Regensburger test of verbal fluency (RWT), a n-back task and subscales of the Wechsler Adult Intelligence Scale III (WAIS-III).

RESULTS

Schizophrenia risk (A)-allele carriers of NOS1 ex1c-SNP rs41279104 displayed significantly lower baseline cortisol levels (p = 0.004). NOS1 ex1f-VNTR genotype carriers showed differences in working memory performance (p = 0.05) in a gene-dose effect manner, with homozygous carriers of the short impulsivity-risk allele committing most commission errors. Finally, A-allele carriers of the NOS1 ex1c-SNP rs41279104 tended to react faster during the working memory task (p = 0.065).

CONCLUSION

For the first time, we demonstrated an influence of the NOS1 ex1c-SNP rs41279104 on salivary cortisol levels and additionally implicate the A-allele in an enhanced reaction time during a working memory task. Regarding the NOS1 ex1f-VNTR our study supports the previously reported influence on impulsivity, lending further support to the hypothesis that this genetic variant underlies impulsive behavior.

Neuronal nitric oxide synthase and affective disorders

Affective disorders including major depressive disorder (MDD), bipolar disorder (BPD), and general anxiety affect more than 10% of population in the world. Notably, neuronal nitric oxide synthase (nNOS), a downstream signal molecule of N-methyl-D-aspartate receptors (NMDARs) activation, is abundant in many regions of the brain such as the prefrontal cortex (PFC), hippocampus, amygdala, dorsal raphe nucleus (DRN), locus coeruleus (LC), and hypothalamus, which are closely associated with the pathophysiology of affective disorders. Decreased levels of the neurotransmitters including 5-hydroxytryptamine or serotonin (5-HT), noradrenalin (NA), and dopamine (DA) as well as hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis are common pathological changes of MDD, BPD, and anxiety. Increasing data suggests that nNOS in the hippocampus play a crucial role in the etiology of MDD whereas nNOS-related dysregulation of the nitrergic system in the LC is closely associated with the pathogenesis of BPD. Moreover, hippocampal nNOS is implicated in the role of serotonin receptor 1 A (5-HTR1 A) in modulating anxiety behaviors. Augment of nNOS and its carboxy-terminal PDZ ligand (CAPON) complex mediate stress-induced anxiety and disrupting the nNOS-CAPON interaction by small molecular drug generates anxiolytic effect. To date, however, the function of nNOS in affective disorders is not well reviewed. Here, we summarize works about nNOS and its signal mechanisms implicated in the pathophysiology of affective disorders. On the basis of this review, it is suggested that future research should more fully focus on the role of nNOS in the pathomechanism and treatment of affective disorders.

The short-term stress response - Mother nature's mechanism for enhancing protection and performance under conditions of threat, challenge, and opportunity

Our group has proposed that in contrast to chronic stress that can have harmful effects, the short-term (fight-or-flight) stress response (lasting for minutes to hours) is nature's fundamental survival mechanism that enhances protection and performance under conditions involving threat/challenge/opportunity. Short-term stress enhances innate/primary, adaptive/secondary, vaccine-induced, and anti-tumor immune responses, and post-surgical recovery. Mechanisms and mediators include stress hormones, dendritic cell, neutrophil, macrophage, and lymphocyte trafficking/function and local/systemic chemokine and cytokine production. Short-term stress may also enhance mental/cognitive and physical performance through effects on brain, musculo-skeletal, and cardiovascular function, reappraisal of threat/anxiety, and training-induced stress-optimization. Therefore, short-term stress psychology/physiology could be harnessed to enhance immuno-protection, as well as mental and physical performance. This review aims to provide a conceptual framework and targets for further investigation of mechanisms and conditions under which the protective/adaptive aspects of short-term stress/exercise can be optimized/harnessed, and for developing pharmacological/biobehavioral interventions to enhance health/healing, and mental/cognitive/physical performance.

Photoperiodic time measurement and seasonal immunological plasticity

Seasonal variations in immunity are common in nature, and changes in day length are sufficient to trigger enhancement and suppression of immune function in many vertebrates. Drawing primarily on data from Siberian hamsters, this review describes formal and physiological aspects of the neuroendocrine regulation of seasonal changes in mammalian immunity. Photoperiod regulates immunity in a trait-specific manner, and seasonal changes in gonadal hormone secretion and thyroid hormone signaling all participate in seasonal immunomodulation. Photoperiod-driven changes in the hamster reproductive and immune systems are associated with changes in iodothyronine deiodinase-mediated thyroid hormone signaling, but photoperiod exerts opposite effects on select aspects of the epigenetic regulation of reproductive neuroendocrine and lymphoid tissues. Photoperiodic changes in immunocompetence may explain a proportion of the annual variance in disease incidence and severity in nature, and provide a useful framework to help understand brain-immune interactions.

Neuronal nitric oxide synthase and NADPH oxidase interact to affect cognitive, affective, and social behaviors in mice

Both nitric oxide (NO) and reactive oxygen species (ROS) generated by nNOS and NADPH oxidase (NOX), respectively, in the brain have been implicated in an array of behaviors ranging from learning and memory to social interactions. Although recent work has elucidated how these separate redox pathways regulate neural function and behavior, the interaction of these two pathways in the regulation of neural function and behavior remains unspecified. Toward this end, the p47phox subunit of NOX, and nNOS were deleted to generate double knockout mice that were used to characterize the behavioral outcomes of concurrent impairment of the NO and ROS pathways in the brain. Mice were tested in a battery of behavioral tasks to evaluate learning and memory, as well as social, affective, and cognitive behaviors. p47phox deletion did not affect depressive-like behavior, whereas nNOS deletion abolished it. Both p47phox and nNOS deletion singly reduced anxiety-like behavior, increased general locomotor activity, impaired spatial learning and memory, and impaired preference for social novelty. Deletion of both genes concurrently had synergistic effects to elevate locomotor activity, impair spatial learning and memory, and disrupt prepulse inhibition of acoustic startle. Although preference for social novelty was impaired in single knockouts, double knockout mice displayed elevated levels of preference for social novelty above that of wild type littermates. These data demonstrate that, depending upon modality, deletion of p47phox and nNOS genes have dissimilar, similar, or additive effects. The current findings provide evidence that the NOX and nNOS redox signaling cascades interact in the brain to affect both cognitive function and social behavior.

Psychological stress and immunoprotection versus immunopathology in the skin

Stress is thought to suppress immune function and increase susceptibility to infections and cancer. Paradoxically, stress is also known to exacerbate autoimmune/proinflammatory disorders (eg, psoriasis, atopic dermatitis) that should be ameliorated by immunosuppression. Here we review studies showing that although chronic stress (lasting for weeks/months/years) can suppress/dysregulate immune function, acute stress (lasting for minutes to hours) can have immunoenhancing effects. Short-term stress experienced at the time of immune activation enhances dendritic cell, neutrophil, macrophage, and lymphocyte trafficking, maturation, and function, and has been shown to augment innate and adaptive immunity; therefore, depending on the conditions of immune activation, and the nature of the activating antigen, short-term stress can enhance the acquisition and expression of immunoprotection or immunopathology. In contrast, chronic stress suppresses or dysregulates innate and adaptive immune responses by altering the Type 1-Type 2 cytokine balance, inducing low-grade chronic increases in proinflammatory factors, and suppressing numbers, trafficking, and function of immunoprotective cells. Chronic stress also increases susceptibility to skin cancer by suppressing Type 1 cytokines and protective T cells while increasing regulatory/suppressor T cell number/function. It is important to recognize that the adaptive function of a physiological stress response is to promote survival. Stress-related neurotransmitters, hormones, and factors act as biological alarm signals that prepare the immune and other physiological systems for potential challenges (eg, wounding or infection) perceived by the brain (eg, detection of an attacker); however, this may exacerbate immunopathology (eg, psoriasis, atopic dermatitis) if the enhanced immune response is directed against innocuous or self-antigens, or if the system is chronically activated as seen during long-term stress. In view of the ubiquitous nature of stress and its significant effects on immunoprotection and immunopathology, it is important to further elucidate the mechanisms mediating both the salubrious and the harmful effects of stress, and to meaningfully translate findings from bench to bedside.

Functional organization of the dorsal raphe efferent system with special consideration of nitrergic cell groups

The serotonin (5HT) system of the brain is involved in many CNS functions including sensory perception, stress responses and psychological disorders such as anxiety and depression. Of the nine 5HT nuclei located in the mammalian brain, the dorsal raphe nucleus (DRN) has the most extensive forebrain connectivity and is implicated in the manifestation of stress-related psychological disturbances. Initial investigations of DRN efferent connections failed to acknowledge the rostrocaudal and mediolateral organization of the nucleus or its neurochemical heterogeneity. More recent studies have focused on the non-5HT contingent of DRN cells and have revealed an intrinsic intranuclear organization of the DRN which has specific implications for sensory signal processing and stress responses. Of particular interest are spatially segregated subsets of nitric oxide producing neurons that are activated by stressors and that have unique efferent projection fields. In this regard, both the midline and lateral wing subregions of the DRN have emerged as prominent loci for future investigation of nitric oxide function and modulation of sensory- and stressor-related signals in the DRN and coinciding terminal fields.

Pharmacological modulators of nitric oxide signaling and contextual fear conditioning in mice

RATIONALE

Nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) is a retrograde neuronal messenger that participates in synaptic plasticity, including late-phase long-term potentiation (LTP) and long-term memory (LTM) formation. Our recent studies have shown that nNOS knockout (KO) mice have a severe deficit in contextual fear conditioning compared to wild type (WT) counterparts (Kelley et al. 2009).

OBJECTIVES

Given the role of the nNOS gene in fear conditioning, we investigated whether systemic administration of modulators of NO signaling affect the formation of contextual and cued fear memories and the effects of these modulators on cyclic 3'5'-guanosine monophosphate (cGMP) levels in the hippocampus and amygdala.

METHODS

The preferential nNOS inhibitor S-methyl-L-thiocitrulline (SMTC; 10-200 mg/kg) was administered (IP) to WT mice, and the NO donor molsidomine (10 mg/kg) was administered (IP) to nNOS KO mice either 30 min pretraining or immediately posttraining.

RESULTS

Pretraining SMTC administration to WT mice impaired both short- and long-term memories of contextual (36% inhibition) but not cued fear conditioning. Pretraining molsidomine administration to nNOS KO mice improved their deficit in short- and long-term memories of contextual fear conditioning (46% increase). Posttraining drug administration had no effect on WT and nNOS KO mice. The systemic administration of SMTC dose-dependently decreased cGMP concentrations down to 25% of control, while molsidomine increased cGMP concentration (three- and five-fold) in amygdala and hippocampus, respectively.

CONCLUSIONS

These findings suggest that neuronal NO and its downstream second messenger cGMP are important for acquisition and subsequent consolidation of LTM of contextual fear conditioning.

Abnormal social behavior, hyperactivity, impaired remote spatial memory, and increased D1-mediated dopaminergic signaling in neuronal nitric oxide synthase knockout mice

Background

Neuronal nitric oxide synthase (nNOS) is involved in the regulation of a diverse population of intracellular messenger systems in the brain. In humans, abnormal NOS/nitric oxide metabolism is suggested to contribute to the pathogenesis and pathophysiology of some neuropsychiatric disorders, such as schizophrenia and bipolar disorder. Mice with targeted disruption of the nNOS gene exhibit abnormal behaviors. Here, we subjected nNOS knockout (KO) mice to a battery of behavioral tests to further investigate the role of nNOS in neuropsychiatric functions. We also examined the role of nNOS in dopamine/DARPP-32 signaling in striatal slices from nNOS KO mice and the effects of the administration of a dopamine D1 receptor agonist on behavior in nNOS KO mice.

Results

nNOS KO mice showed hyperlocomotor activity in a novel environment, increased social interaction in their home cage, decreased depression-related behavior, and impaired spatial memory retention. In striatal slices from nNOS KO mice, the effects of a dopamine D1 receptor agonist, SKF81297, on the phosphorylation of DARPP-32 and AMPA receptor subunit GluR1 at protein kinase A sites were enhanced. Consistent with the biochemical results, intraperitoneal injection of a low dose of SKF81297 significantly decreased prepulse inhibition in nNOS KO mice, but not in wild-type mice.

Conclusion

These findings indicate that nNOS KO upregulates dopamine D1 receptor signaling, and induces abnormal social behavior, hyperactivity and impaired remote spatial memory. nNOS KO mice may serve as a unique animal model of psychiatric disorders.

Impairments in fear conditioning in mice lacking the nNOS gene

The fear conditioning paradigm is used to investigate the roles of various genes, neurotransmitters, and substrates in the formation of fear learning related to contextual and auditory cues. In the brain, nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) functions as a retrograde neuronal messenger that facilitates synaptic plasticity, including the late phase of long-term potentiation (LTP) and formation of long-term memory (LTM). Evidence has implicated NO signaling in synaptic plasticity and LTM formation following fear conditioning, yet little is known about the role of the nNOS gene in fear learning. Using knockout (KO) mice with targeted mutation of the nNOS gene and their wild-type (WT) counterparts, the role of NO signaling in fear conditioning was investigated. Plasma levels of the stress hormone corticosterone were measured to determine the relationship between physiological and behavioral response to fear conditioning. Contextual fear learning was severely impaired in male and female nNOS KO mice compared with WT counterparts; cued fear learning was slightly impaired in nNOS KO mice. Sex-dependent differences in both contextual and cued fear learning were not observed in either genotype. Deficits in contextual fear learning in nNOS KO mice were partially overcome by multiple trainings. A relationship between increase in plasma corticosterone levels following footshock administration and the magnitude of contextual, but not cued freezing was also observed. Results suggest that the nNOS gene contributes more to optimal contextual fear learning than to cued fear learning, and therefore, inhibition of the nNOS enzyme may ameliorate context-dependent fear response.

Behavioural and expressional phenotyping of nitric oxide synthase-I knockdown animals

The gaseous messenger nitric oxide (NO) has been implicated in a wide range of behaviors, including aggression, anxiety, depression, and cognitive functioning. To further elucidate the physiological role of NO and its down-stream mechanisms, we conducted behavioral and expressional phenotyping of mice lacking the neuronal isoform of nitric oxide synthase (NOS-I), the major source of NO in the central nervous system. No differences were observed in activity-related parameters; in contrast to the a priori hypothesis, derived from pharmacological treatments, depression-related tests (Forced Swim Test, Learned Helplessness) also yielded no significantly different results. A subtle anxiolytic phenotype however was present, with knockdown mice displaying a higher open arm time as compared to their respective wildtypes, yet all other investigated anxiety-related parameters were unchanged. The most prominent feature however was gender-independent cognitive impairment in spatial learning and memory, as assessed by the Water Maze test and an automatized holeboard paradigm. No significant dysregulation of monoamine transporters was evidenced by qRT PCR. To further examine the underlying molecular mechanisms, the transcriptome of knockdown animals was thus examined in the hippocampus, striatum and cerebellum by microarray analysis. A set of >120 differentially expressed genes was identified, whereat the hippocampus and the striatum showed similar expressional profiles as compared to the cerebellum in hierarchical clustering. Among the most significantly up-regulated genes were Peroxiredoxon 3, Atonal homologue 1, Kcnj1, Kcnj8, CCAAT/enhancer binding protein (C/EBP), alpha, 3 genes involved in GABA(B) signalling and, intriguingly, the glucocorticoid receptor GR. While GABAergic genes might underlie reduced anxiety, dysregulation of the glucocorticoid receptor can well contribute to a blunted stress response as found in NOS1 knockdown mice. Furthermore, by CREB inhibition, glucocorticoid receptor upregulation could at least partially explain cognitive deficits in these animals. Taken together, NOS1 knockdown mice display a characteristic behavioural profile consisting of reduced anxiety and impaired learning and memory, paralleled by differential expression of the glucocorticoid receptor and GABAergic genes. Further research has to assess the value of these mice as animal models e.g. for Alzheimer's disease or attention deficit disorder, in order to clarify a possible pathophysiological role of NO therein.

Pleiotropic contributions of nitric oxide to aggressive behavior

Male mice with targeted deletion of the genes encoding the neuronal (NOS-1-/- or nNOS-/-) isoform of nitric oxide synthase display altered aggressive behaviors. Male nNOS-1-/- mice are more aggressive than wild-type (WT) mice in all testing paradigms. Testosterone is necessary, but not sufficient, for evoking the persistent aggression, and that serotonin (5-HT) metabolism is altered in male nNOS-1-/- mice. The specific deletion of the nNOS-1 gene not only results in a lack of nNOS-1 protein, but in common with many genes, affects several 'down-stream' processes. In this review, we address whether the elevated aggression in male nNOS-1-/- mice reflects pleiotropic effects of the nNOS-1 gene on pain sensitivity, 'anxiety-like', or 'depressive-like' behaviors. For example, male nNOS-1-/- mice display increased sensitivity to painful stimuli, which may prolong aggressive interactions. Despite elevated corticosterone concentrations, nNOS-1 knockout mice appear to be less 'anxious' or fearful than WT mice. Male nNOS-1-/- mice display longer latencies to right themselves on an inverted platform and spend more time in the center of an open field than WT mice. Because of reduced serotonin turnover, the excessive aggressiveness displayed by nNOS-1-/- mice may be symptomatic of a depressive-like syndrome. However, nNOS-1-/- mice rarely display behavioral 'despair' when assessed with the Porsolt forced swim test; rather, nNOS-1-/- mice show vigorous swimming throughout the assessment suggesting that the aggressive behavior does not represent depressive-like behavior. Importantly, aggressive behavior is not a unitary process, but is the result of complex interactions among several physiological, motivational, and behavioral systems, with contributions from the social as well as the physical environment. Lastly, the multiple, and often unanticipated, effects of targeted gene disruption on aggressive behavior are considered.

Importance of NO/cGMP signalling via cGMP-dependent protein kinase II for controlling emotionality and neurobehavioural effects of alcohol

Cyclic GMP is a second messenger for nitric oxide (NO) that acts as a mediator for many different physiological functions. The cGMP-dependent protein kinases (cGKs) mediate cellular signalling induced by NO and cGMP. Here, we explored the localization of cGMP-dependent protein kinase type II (cGKII) in the mouse brain. In situ hybridization revealed high levels of cGKII mRNA in cerebral cortex, thalamic nuclei, hypothalamic nuclei, and in several basal forebrain regions including medial septum, striatum and amygdala. The close link to NO and the distribution pattern of cGKII suggested that this enzyme might be involved in emotional reactions and responses to drugs of abuse. Therefore, cGKII knockout animals (cGKII-/-) were compared with littermate controls in behavioural tests (i) for emotion-linked and (ii) for acute and chronic ethanol responses. Deletion of cGKII did not influence aggressive behaviour but led to enhanced anxiety-like behaviour. In terms of acute responses to ethanol, cGKII-/- mice were hyposensitive to hypnotic doses of ethanol as measured by the loss of righting reflex, without an alteration in their blood alcohol elimination. In a two-bottle free choice test, cGKII-/- mice showed elevated alcohol consumption. No taste differences to sweet solutions were observed compared to control animals. In summary, our data show that cGKII activity modulates anxiety-like behaviour and neurobehavioural effects of alcohol.

Suppressive effects of milk-derived lactoferrin on psychological stress in adult rats

Lactoferrin (LF) is known as an iron-binding glycoprotein. It has been shown that bovine LF (bLF) is transported into cerebrospinal fluid via blood although its physiological effects in the central nervous system (CNS) are still unclear. In this study, a suppressive effect of bLF on psychological distress was investigated in adult rats. Intraperitoneal injection of bLF (100 mg/kg) reduced stressful behaviors in a conditioned fear-induced freezing test and an elevated plus-maze test. Interestingly, the suppressive effect of bLF was enhanced by pretreatment with electric foot-shock (FS). This suppressive effect of bLF in the elevated plus-maze test was reversed by pretreatment with naloxone, an opioid receptor antagonist, at a dose of 1 mg/kg (ip). N(omega)-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase (NOS) inhibitor, also blocked the suppressive effect of bLF and foot-shock. In addition, combined application of a low dose of bLF (30 mg/kg, ip) and l-arginine (30 and 100 mg/kg, ip) showed significant potentiated effects on psychological stress. These results suggest that bLF has suppressive effects on psychological distress, especially under the condition of moderate stress. Furthermore, it is suggested that bLF possibly activates an endogenous opioidergic system via nitric oxide synthase activation.

Influenza virus-induced sleep responses in mice with targeted disruptions in neuronal or inducible nitric oxide synthases

Influenza viral infection induces increases in non-rapid eye movement sleep and decreases in rapid eye movement sleep in normal mice. An array of cytokines is produced during the infection, and some of them, such as IL-1β and TNF-α, are well-defined somnogenic substances. It is suggested that nitric oxide (NO) may mediate the sleep-promoting effects of these cytokines. In this study, we use mice with targeted disruptions of either the neuronal NO synthase (nNOS) or the inducible NO synthase (iNOS) gene, commonly referred to as nNOS or iNOS knockouts (KOs), to investigate sleep changes after influenza viral challenge. We report that the magnitude of viral-induced non-rapid eye movement sleep responses in both nNOS KOs and iNOS KOs was less than that of their respective controls. In addition, the duration of rapid eye movement sleep in nNOS KO mice did not decrease compared with baseline values. All strains of mice had similar viral titers and cytokine gene expression profiles in the lungs. Virus was not isolated from the brains of any strain. However, gene expression in the brain stem differed between nNOS KOs and their controls: mRNA for the interferon-induced gene 2′,5′-oligoadenylate synthase 1a was elevated in nNOS KOs relative to their controls at 15 h, and IL-1β mRNA was elevated in nNOS KOs relative to their controls at 48 h. Our results suggest that NO synthesized by both nNOS and iNOS plays a role in virus-induced sleep changes and that nNOS may modulate cytokine expression in the brain.