Neuropeptide S: a novel modulator of stress and arousal

Pituitary adenylyl cyclase-activating polypeptide modulates the stress response: the involvement of different brain areas and microglia

Stress is necessary for survival. However, chronic unnecessary stress exposure leads to cardiovascular, gastrointestinal and neuropsychiatric disorders. Thus, understanding the mechanisms involved in the initiation and maintenance of the stress response is essential since it may reveal the underpinning pathophysiology of these disorders and may aid in the development of medication to treat stress-mediated diseases. Pituitary adenylyl cyclase activating polypeptide (PACAP) and its receptors (PAC1, VPAC1 and VPAC2) are expressed in the hypothalamus and other brain areas as well as in the adrenal gland. Previous research has shown that this peptide/receptor system serves as a modulator of the stress response. In addition to modulating the stress response, this system may also be connected to its emerging role as neuroprotective against hypoxia, ischemia, and neurodegeneration. This article aims to review the literature regarding the role of PACAP and its receptors in the stress response, the involvement of different brain regions and microglia in PACAP-mediated modulation of the stress response, and the long-term adaptation to stress recognizable clinically as survival with resilience while manifested in anxiety, depression and other neurobehavioral disorders.

Chronic treatment with escitalopram and venlafaxine affects the neuropeptide S pathway differently in adult Wistar rats exposed to maternal separation

Neuropeptide S (NPS), which is a peptide that is involved in the regulation of the stress response, seems to be relevant to the mechanism of action of antidepressants that have anxiolytic properties. However, to date, there have been no reports regarding the effect of long-term treatment with escitalopram or venlafaxine on the NPS system under stress conditions. This study aimed to investigate the effects of the above-mentioned antidepressants on the NPS system in adult male Wistar rats that were exposed to neonatal maternal separation (MS). Animals were exposed to MS for 360 min. on postnatal days (PNDs) 2-15. MS causes long-lasting behavioral, endocrine and neurochemical consequences that mimic anxiety- and depression-related features. MS and non-stressed rats were given escitalopram or venlafaxine (10mg/kg) IP from PND 69 to 89. The NPS system was analyzed in the brainstem, hypothalamus, amygdala and anterior olfactory nucleus using quantitative RT-PCR and immunohistochemical methods. The NPS system was vulnerable to MS in the brainstem and amygdala. In the brainstem, escitalopram down-regulated NPS and NPS mRNA in the MS rats and induced a tendency to reduce the number of NPS-positive cells in the peri-locus coeruleus. In the MS rats, venlafaxine insignificantly decreased the NPSR mRNA levels in the amygdala and a number of NPSR cells in the basolateral amygdala, and increased the NPS mRNA levels in the hypothalamus. Our data show that the studied antidepressants affect the NPS system differently and preliminarily suggest that the NPS system might partially mediate the pharmacological effects that are induced by these drugs.

Roles of Neuropeptides in Sleep-Wake Regulation

Sleep and wakefulness are basic behavioral states that require coordination between several brain regions, and they involve multiple neurochemical systems, including neuropeptides. Neuropeptides are a group of peptides produced by neurons and neuroendocrine cells of the central nervous system. Like traditional neurotransmitters, neuropeptides can bind to specific surface receptors and subsequently regulate neuronal activities. For example, orexin is a crucial component for the maintenance of wakefulness and the suppression of rapid eye movement (REM) sleep. In addition to orexin, melanin-concentrating hormone, and galanin may promote REM sleep. These results suggest that neuropeptides play an important role in sleep–wake regulation. These neuropeptides can be divided into three categories according to their effects on sleep–wake behaviors in rodents and humans. (i) Galanin, melanin-concentrating hormone, and vasoactive intestinal polypeptide are sleep-promoting peptides. It is also noticeable that vasoactive intestinal polypeptide particularly increases REM sleep. (ii) Orexin and neuropeptide S have been shown to induce wakefulness. (iii) Neuropeptide Y and substance P may have a bidirectional function as they can produce both arousal and sleep-inducing effects. This review will introduce the distribution of various neuropeptides in the brain and summarize the roles of different neuropeptides in sleep–wake regulation. We aim to lay the foundation for future studies to uncover the mechanisms that underlie the initiation, maintenance, and end of sleep–wake states.

The influence of early-life and adulthood stressors on brain neuropeptide-S system

Central administered neuropeptide-S (NPS) was shown to reduce stress response in rodents. This study aimed to investigate the alterations in NPS system upon chronic exposure to early-life and adulthood stressors. Newborn pups underwent maternal separation (MS) from postnatal day 1 to 14 comprised of daily 3-h separations. In the adulthood, 90-min of restraint stress was loaded to males as an acute stress (AS) model. For chronic homotypic stress (CHS), same stressor was applied for 5 consecutive days. The changes in the expression and the release of NPS were monitored by immunohistochemistry and microdialysis, respectively. Throughout the CHS, heart rate variability (HRV) was analyzed on a daily basis. The immunoreactivity for NPS receptor (NPSR) was detected in basolateral amygdala (BLA) and hypothalamic paraventricular nucleus (PVN) by immunofluorescence staining. The NPS expression in the brainstem was increased upon AS which was more prominent following CHS, whereas these responses were found to be blunted in MS counterparts. Similar to histological data, the stress-induced release of NPS in BLA was attenuated in MS rats. CHS-induced elevations in sympatho-vagal balance were alleviated in control rats; which was not observed in MS rats. The expression of NPSR in BLA and PVN was down-regulated in MS rats. The brain NPS/NPSR system appears to be susceptible to the early-life stressors and the subsequent chronic stress exposure in adulthood which results in altered autonomic outflow.

Centrally Administered Neuropeptide-S Alleviates Gastrointestinal Dysmotility Induced by Neonatal Maternal Separation

BACKGROUND

Neuropeptide-S (NPS) regulates autonomic outflow, stress response, and gastrointestinal (GI) motor functions. This study aimed to investigate the effects of NPS on GI dysmotility induced by neonatal maternal separation (MS).

METHODS

MS was conducted by isolating newborn pups from dams from postnatal day 1 to day 14. In adulthood, rats were also exposed to chronic homotypic stress (CHS). Visceral sensitivity was assessed by colorectal distension-induced abdominal contractions. Gastric emptying (GE) was measured following CHS, whereas fecal output was monitored daily. NPS or NPS receptor (NPSR) antagonist was centrally applied simultaneously with electrocardiography and gastric motility recording. Immunoreactivities for NPS, NPSR, corticotropin-releasing factor (CRF), choline acetyltransferase (ChAT), tyrosine hydroxylase (TH), and c-Fos were assessed by immunohistochemistry.

KEY RESULTS

NPS alleviated the MS-induced visceral hypersensitivity. Under basal conditions, central exogenous or endogenous NPS had no effect on GE and gastric motility. NPS restored CHS-induced gastric and colonic dysmotility in MS rats while increasing sympatho-vagal balance without affecting vagal outflow. NPSR expression was detected in CRF-producing cells of hypothalamic paraventricular nucleus, and central amygdala, but not in Barrington's nucleus. Moreover, NPSR was present in ChAT-expressing neurons in dorsal motor nucleus of the vagus (DMV), and nucleus ambiguus (NAmb) in addition to the TH-positive neurons in C1/A1, and locus coeruleus (LC). Neurons adjacent to the adrenergic cells in LC were found to produce NPS. NPS administration caused c-Fos expression in C1/A1 cells, while no immunoreactivity was detected in DMV or NAmb.

CONCLUSIONS

NPS/NPSR system might be a novel target for the treatment of stress-related GI dysmotility.

Role of the Neuropeptide S System in Emotionality, Stress Responsiveness and Addiction-Like Behaviours in Rodents: Relevance to Stress-Related Disorders

The neuropeptide S (NPS) and its receptor (NPSR1) have been extensively studied over the last two decades for their roles in locomotion, arousal/wakefulness and anxiety-related and fear-related behaviours in rodents. However, the possible implications of the NPS/NPSR1 system, especially those of the single nucleotide polymorphism (SNP) rs324981, in stress-related disorders and substance abuse in humans remain unclear. This is possibly due to the fact that preclinical and clinical research studies have remained separated, and a comprehensive description of the role of the NPS/NPSR1 system in stress-relevant and reward-relevant endpoints in humans and rodents is lacking. In this review, we describe the role of the NPS/NPSR1 system in emotionality, stress responsiveness and addiction-like behaviour in rodents. We also summarize the alterations in the NPS/NPSR1 system in individuals with stress-related disorders, as well as the impact of the SNP rs324981 on emotion, stress responses and neural activation in healthy individuals. Moreover, we discuss the therapeutic potential and possible caveats of targeting the NPS/NPSR1 system for the treatment of stress-related disorders. The primary goal of this review is to highlight the importance of studying some rodent behavioural readouts modulated by the NPS/NPSR1 system and relevant to stress-related disorders.

Human-Specific Neuropeptide S Receptor Variants Regulate Fear Extinction in the Basal Amygdala of Male and Female Mice Depending on Threat Salience

BACKGROUND

A nonsynonymous single nucleotide polymorphism in the neuropeptide S receptor 1 (NPSR1) gene (rs324981) results in isoleucine-to-asparagine substitution at amino acid 107. In humans, the ancestral variant (NPSR1 I107) is associated with increased anxiety sensitivity and risk of panic disorder, while the human-specific variant (NPSR1 N107) is considered protective against excessive anxiety. In rodents, neurobiological constituents of the NPS system have been analyzed in detail and their anxiolytic-like effects have been endorsed. However, their implication for anxiety and related disorders in humans remains unclear, as rodents carry only the ancestral NPSR1 I107 variant.

METHODS

We hypothesized that phenotypic correlates of NPSR1 variants manifest in fear-related circuits in the amygdala. We used CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/Cas9)-mediated gene editing to generate a "humanized" mouse strain, in which individuals express either NPSR1 I107 or NPSR1 N107.

RESULTS

Stimulation of NPSR1 evoked excitatory responses in principal neurons of the anterior basal amygdala with significant differences in magnitude between genotypes, resulting in synaptic disinhibition of putative extinction neurons in the posterior basal amygdala in mice expressing the human-specific hypofunctional N107 but not the ancestral I107 variant. N107 mice displayed improved extinction of conditioned fear, which was phenocopied after pharmacological antagonism of NPSR1 in the anterior basal amygdala of I107 mice. Differences in fear extinction between male and female mice were related to an interaction of Npsr1 genotype and salience of fear training.

CONCLUSIONS

The NPS system regulates extinction circuits in the amygdala depending on the Npsr1 genotype, contributing to sex-specific differences in fear extinction and high anxiety sensitivity of individuals bearing the ancestral NPSR1 I107 variant.

Stress induces reinstatement of extinguished cocaine conditioned place preference by a sequential signaling via neuropeptide S, orexin, and endocannabinoid

Neurons containing neuropeptide S (NPS) and orexins are activated during stress. Previously, we reported that orexins released during stress, via orexin OX₁ receptors (OX₁ Rs), contribute to the reinstatement of cocaine seeking through endocannabinoid/CB₁ receptor (CB₁ R)-mediated dopaminergic disinhibition in the ventral tegmental area (VTA). Here, we further demonstrated that NPS released during stress is an up-stream activator of this orexin-endocannabinoid cascade in the VTA, leading to the reinstatement of cocaine seeking. Mice were trained to acquire cocaine conditioned place preference (CPP) by context-pairing cocaine injections followed by the extinction training with context-pairing saline injections. Interestingly, the extinguished cocaine CPP in mice was significantly reinstated by intracerebroventricular injection (i.c.v.) of NPS (1 nmol) in a manner prevented by intraperitoneal injection (i.p.) of SHA68 (50 mg/kg), an NPS receptor antagonist. This NPS-induced cocaine reinstatement was prevented by either i.p. or intra-VTA microinjection (i.vta.) of SB-334867 (15 mg/kg, i.p. or 15 nmol, i.vta.) and AM 251 (1.1 mg/kg, i.p. or 30 nmol, i.vta.), antagonists of OX₁ Rs and CB₁ Rs, respectively. Besides, NPS (1 nmol, i.c.v.) increased the number of c-Fos-containing orexin neurons in the lateral hypothalamus (LH) and increased orexin-A level in the VTA. The latter effect was blocked by SHA68. Furthermore, a 30-min restraint stress in mice reinstated extinguished cocaine CPP and was prevented by SHA68. These results suggest that NPS is released upon stress and subsequently activates LH orexin neurons to release orexins in the VTA. The released orexins then reinstate extinguished cocaine CPP via an OX₁ R- and endocannabinoid-CB₁ R-mediated signaling in the VTA.

The Neural Network of Neuropeptide S (NPS): Implications in Food Intake and Gastrointestinal Functions

The Neuropeptide S (NPS), a 20 amino acids peptide, is recognized as the endogenous ligand of a previously orphan G protein-coupled receptor, now termed NPS receptor (NPSR). The limited distribution of the NPS-expressing neurons in few regions of the brainstem is in contrast with the extensive expression of NPSR in the rodent central nervous system, suggesting the involvement of this receptor in several brain functions. In particular, NPS promotes locomotor activity, behavioral arousal, wakefulness, and unexpectedly, at the same time, it exerts anxiolytic-like properties. Intriguingly, the NPS system is implicated in the rewarding properties of drugs of abuse and in the regulation of food intake. Here, we focus on the anorexigenic effect of NPS, centrally injected in different brain areas, in both sated and fasted animals, fed with standard or palatable food, and, in addition, on its influence in the gastrointestinal tract. Further investigations, regarding the role of the NPS/NPSR system and its potential interaction with other neurotransmitters could be useful to understand the mechanisms underlying its action and to develop novel pharmacological tools for the treatment of aberrant feeding patterns and obesity.

New quinolone derivatives as neuropeptide S receptor antagonists: Design, synthesis, homology modeling, dynamic simulations and modulation of Gq/Gs signaling pathways

In a search for new neuropeptide S receptor antagonists, we have described a new series of quinolone-pyranopyrimidine hybrid derivatives aiming to modify the inhibitory characters towards NPSR to develop new therapeutic strategies against anxiety, addiction and food disorders. We identified six potent antagonists 3, 4b, 6, 8, 9 and 10 which counteracted the stimulatory effect of NPS at both Gq and Gs pathways, at low micromolar concentrations, through modulation of Ca²⁺ and cAMP signaling, respectively. Molecular docking predicted the orientation mode of the top active compounds; 10 and 4b with ΔG value of -23.94 and -23.87 kcal/mol, respectively that is considered good when compared to that of the reference compound ML154 (ΔG = -25.75 kcal/mol) . Molecular dynamic simulations confirmed the stability of binding of compound 10 to the homology model of NPSR as it reached the equilibrium after 4 ns at RMSD of 1.00 Å while ML154 was faster to achieve the equilibrium after 2 ns at RMSD of 1.00 Å.

BNST and amygdala activation to threat: Effects of temporal predictability and threat mode

Recent animal and human studies highlight the uncertainty about the onset of an aversive event as a crucial factor for the involvement of the centromedial amygdala (CM) and bed nucleus of the stria terminalis (BNST) activity. However, studies investigating temporally predictable or unpredictable threat anticipation and confrontation processes are rare. Furthermore, the few existing fMRI studies analyzing temporally predictable and unpredictable threat processes used small sample sizes or limited fMRI paradigms. Therefore, we measured functional brain activity in 109 predominantly female healthy participants during a temporally predictable-unpredictable threat paradigm, which aimed to solve limited aspects of recent studies. Results showed higher BNST activity compared to the CM during the cue indicating that the upcoming confrontation is aversive relative to the cue indicating an upcoming neutral confrontation. Both the CM and BNST showed higher activity during the confrontation with unpredictable and aversive stimuli, but the reaction to aversive confrontation relative to neutral confrontation was stronger in the CM compared to the BNST. Additional modulation analyses by NPSR1 rs324981 genotype revealed higher BNST activity relative to the CM in unpredictable anticipation relative to predictable anticipation in T-carriers compared to AA carriers. Our results indicate that during the confrontation with aversive or neutral stimuli, temporal unpredictability modulates CM and BNST activity. Further, there is a differential activity concerning threat processing, as BNST is more involved when focussing on fear-related anticipation processes and CM is more involved when focussing on threat confrontation.

Corticosterone Treatment and Incubation Time After Contextual Fear Conditioning Synergistically Induce Fear Memory Generalization in Neuropeptide S Receptor-Deficient Mice

Fear memory generalization is a learning mechanism that promotes flexible fear responses to novel situations. While fear generalization has adaptive value, overgeneralization of fear memory is a characteristic feature of the pathology of anxiety disorders. The neuropeptide S (NPS) receptor (NPSR) has been shown to be associated with anxiety disorders and has recently been identified as a promising target for treating anxiety disorders. Moreover, stress hormones play a role in regulating both physiological and pathological fear memories and might therefore also be involved in anxiety disorders. However, little is known about the interplay between stress hormone and the NPS system in the development of overgeneralized fear. Here, we hypothesize that NPSR-deficient mice with high corticosterone (CORT) levels during the fear memories consolidation are more prone to develop generalized fear. To address this hypothesis, NPSR-deficient mice were submitted to a contextual fear conditioning procedure. Immediately after conditioning, mice received CORT injections (2.5 or 5 mg/kg). One day and 1 month later, the mice were tested for the specificity and strength of their fear memory, their anxiety level, and their startle response. Moreover, CORT blood levels were monitored throughout the experiment. Using this protocol, a specific contextual fear memory was observed in all experimental groups, despite the 5-mg/kg CORT-treated NPSR-deficient mice. This group of mice showed a generalization of contextual fear memory and a decreased startle response, and the females of this group had significantly less body weight gain. These findings indicate that interplay between CORT and the NPS system during the consolidation of fear memories is critical for the generalization of contextual fear.

Neuropeptide S-initiated sequential cascade mediated by OX1, NK1, mGlu5 and CB1 receptors: a pivotal role in stress-induced analgesia

Background

Stress-induced analgesia (SIA) is an evolutionarily conserved phenomenon during stress. Neuropeptide S (NPS), orexins, substance P, glutamate and endocannabinoids are known to be involved in stress and/or SIA, however their causal links remain unclear. Here, we reveal an unprecedented sequential cascade involving these mediators in the lateral hypothalamus (LH) and ventrolateral periaqueductal gray (vlPAG) using a restraint stress-induced SIA model.

Methods

Male C57BL/6 mice of 8–12 week-old were subjected to intra-cerebroventricular (i.c.v.) and/or intra-vlPAG (i.pag.) microinjection of NPS, orexin-A or substance P alone or in combination with selective antagonists of NPS receptors (NPSRs), OX₁ receptors (OX₁Rs), NK₁ receptors (NK₁Rs), mGlu₅ receptors (mGlu₅Rs) and CB₁ receptors (CB₁Rs), respectively. Antinociceptive effects of these mediators were evaluated via the hot-plate test. SIA in mice was induced by a 30-min restraint stress. NPS levels in the LH and substance P levels in vlPAG homogenates were compared in restrained and unrestrained mice.

Results

NPS (i.c.v., but not i.pag.) induced antinociception. This effect was prevented by i.c.v. blockade of NPSRs. Substance P (i.pag.) and orexin-A (i.pag.) also induced antinociception. Substance P (i.pag.)-induced antinociception was prevented by i.pag. Blockade of NK₁Rs, mGlu₅Rs or CB₁Rs. Orexin-A (i.pag.)-induced antinociception has been shown previously to be prevented by i.pag. blockade of OX₁Rs or CB₁Rs, and here was prevented by NK₁R or mGlu₅R antagonist (i.pag.). NPS (i.c.v.)-induced antinociception was prevented by i.pag. blockade of OX₁Rs, NK₁Rs, mGlu₅Rs or CB₁Rs. SIA has been previously shown to be prevented by i.pag. blockade of OX₁Rs or CB₁Rs. Here, we found that SIA was also prevented by i.c.v. blockade of NPSRs or i.pag. blockade of NK₁Rs or mGlu₅Rs. Restrained mice had higher levels of NPS in the LH and substance P in the vlPAG than unrestrained mice.

Conclusions

These results suggest that, during stress, NPS is released and activates LH orexin neurons via NPSRs, releasing orexins in the vlPAG. Orexins then activate OX₁Rs on substance P-containing neurons in the vlPAG to release substance P that subsequently. Activates NK₁Rs on glutamatergic neurons to release glutamate. Glutamate then activates perisynaptic mGlu₅Rs to initiate the endocannabinoid retrograde inhibition of GABAergic transmission in the vlPAG, leading to analgesia.

Mechanisms Responsible for Genetic Hypertension in Schlager BPH/2 Mice

It has been 45 years since Gunther Schlager used a cross breeding program in mice to develop inbred strains with high, normal, and low blood pressure (BPH/2, BPN/3, and BPL/1 respectively). Thus, it is timely to gather together the studies that have characterized and explored the mechanisms associated with the hypertension to take stock of exactly what is known and what remains to be determined. Growing evidence supports the notion that the mechanism of hypertension in BPH/2 mice is predominantly neurogenic with some of the early studies showing aberrant brain noradrenaline levels in BPH/2 compared with BPN/3. Analysis of the adrenal gland using microarray suggested an association with the activity of the sympathetic nervous system. Indeed, in support of this, there is a larger depressor response to ganglion blockade, which reduced blood pressure in BPH/2 mice to the same level as BPN/3 mice. Greater renal tyrosine hydroxylase staining and greater renal noradrenaline levels in BPH/2 mice suggest sympathetic hyperinnervation of the kidney. Renal denervation markedly reduced the blood pressure in BPH/2 but not BPN/3 mice, confirming the importance of renal sympathetic nervous activity contributing to the hypertension. Further, there is an important contribution to the hypertension from miR-181a and renal renin in this strain. BPH/2 mice also display greater neuronal activity of amygdalo-hypothalamic cardiovascular regulatory regions. Lesions of the medial nucleus of the amygdala reduced the hypertension in BPH/2 mice and abolished the strain difference in the effect of ganglion blockade, suggesting a sympathetic mechanism. Further studies suggest that aberrant GABAergic inhibition may play a role since BPH/2 mice have low GABA_A receptor δ, α4 and β2 subunit mRNA expression in the hypothalamus, which are predominantly involved in promoting tonic neuronal inhibition. Allopregnanolone, an allosteric modulator of GABA_A receptors, which increase the expression of these subunits in the amygdala and hypothalamus, is shown to reduce the hypertension and sympathetic nervous system contribution in BPH/2 mice. Thus far, evidence suggests that BPH/2 mice have aberrant GABAergic inhibition, which drives neuronal overactivity within amygdalo-hypothalamic brain regions. This overactivity is responsible for the greater sympathetic contribution to the hypertension in BPH/2 mice, thus making this an ideal model of neurogenic hypertension.

Central neuropeptide-S treatment improves neurofunctions of 6-OHDA-induced Parkinsonian rats

Parkinson's disease (PD) is characterized by degeneration of the dopaminergic neurons in substantia nigra (SN). The motor symptoms of PD include tremor, rigidity, bradykinesia and postural impairment. In rodents, central administration of neuropeptide-S (NPS) has been shown to induce locomotor activity, dopamine release and neuronal survival by decreasing lipid peroxidation, additionally, the NPS receptor (NPSR) was detected in SN. Accumulating findings suggest that central NPS may ameliorate the parkinsonian symptoms, however, this has been explored incompletely due to the scarcity of experimental studies. Therefore, the present study was designed to test whether central NPS treatment exerts protective and/or alleviative effects on 6-OHDA-induced rat experimental PD model. Adult male Wistar rats received acute (alleviate; 10 nmol, icv) or chronic (protective; 1 nmol, icv for 7 days) NPS treatment following the central injection of 6-OHDA in medial forebrain bundle. Motor performance tests and in vivo nigral microdialysis were performed before and 7 days after the central 6-OHDA injection. The immunoreactivities for tyrosine hydroxylase (TH), NPSR, 4-hydroxynonenal (4-HNE) and c-Fos were detected by immunohistochemistry in frozen SN sections. Our double immunofluorescence labeling studies demonstrated that NPSR is present in the nigral TH-positive neurons. Central NPS injection caused a remarkable c-Fos expression in SN; whereas, no change was observed following vehicle injection. In both chronic and acute treatment groups, the 6-OHDA-induced motor dysfunction and impaired nigral dopamine release were improved significantly. However, only chronic, but not acute treatment restored the loss of nigral TH-positive cells, while decreasing the 4-HNE immunoreactivity in SN. Our findings demonstrate that central NPS treatment not only exerts a neuroprotective action on nigral dopaminergic neurons, it also improves the striatal dopaminergic signaling. Therefore, the present study candidates the NPSR agonism as a novel therapeutic approach for PD treatment.

Altered Gene Expression in Prefrontal Cortex of a Fabry Disease Mouse Model

Fabry disease is an X-chromosome linked hereditary disease that is caused by loss of function mutations in the α-galactosidase A (α-Gal A) gene, resulting in defective glycolipid degradation and subsequent accumulation of globotriaosylceramide (Gb3) in different tissues, including vascular endothelial cells and neurons in the peripheral and central nervous system. We recently reported a differential gene expression profile of α-Gal A^(−/0) mouse dorsal root ganglia, an established animal model of Fabry disease, thereby providing new gene targets that might underlie the neuropathic pain related symptoms. To investigate the cognitive symptoms experienced by Fabry patients, we performed one-color based hybridization microarray expression profiling of prefrontal cortex samples from adult α-Gal A^(−/0) mice and age-matched wildtype controls, followed by protein-protein interaction and pathway analyses for the differentially regulated mRNAs. We found that from a total of 381 differentially expressed genes, 135 genes were significantly upregulated, whereas 246 genes were significantly downregulated between α-Gal A^(−/0) mice and wildtype controls. Enrichment analysis for downregulated genes revealed mainly immune related pathways, including immune/defense responses, regulation of cytokine production, as well as signaling and transport regulation pathways. Further analysis of the regulated genes revealed a large number of genes involved in neurodegeneration. The current analysis for the first time presents a differential gene expression profile of central nervous system tissue from α-Gal A^(−/0) mice, thereby providing novel knowledge on the deregulation and a possible contribution of gene expression to Fabry disease related brain pathologies.

Neuropeptide S Receptor Gene Variation Differentially Modulates Fronto-Limbic Effective Connectivity in Childhood and Adolescence

The neuropeptide S (NPS) system contributes to the pathogenesis of anxiety. The more active T allele of the functional rs324981 variant in the neuropeptide S receptor gene (NPSR1) is associated with panic disorder (PD) and distorted cortico-limbic activity during emotion processing in healthy adults and PD patients. This study investigated the influence of NPSR1 genotype on fronto-limbic effective connectivity within the developing brain. Sixty healthy subjects (8-21 years) were examined using an emotional go-nogo task and fMRI. Fronto-limbic connectivity was determined using Dynamic Causal Modeling. In A allele carriers, connectivity between the right middle frontal gyrus (MFG) and the right amygdala was higher in older (≥14 years) than that in younger (<14 years) probands, whereas TT homozygotes ≥14 years showed a reduction of fronto-limbic connectivity between the MFG and both the amygdala and the insula. Fronto-limbic connectivity varied between NPSR1 genotypes in the developing brain suggesting a risk-increasing effect of the NPSR1T allele for anxiety-related traits via impaired top-down control of limbic structures emerging during adolescence. Provided robust replication in longitudinal studies, these findings may constitute valuable biomarkers for early targeted prevention of anxiety disorders.

Neuropeptide S precursor knockout mice display memory and arousal deficits

Activation of neuropeptide S (NPS) signaling has been found to produce arousal, wakefulness, anxiolytic-like behaviors, and enhanced memory formation. In order to further study physiological functions of the NPS system, we generated NPS precursor knockout mice by homologous recombination in embryonic stem cells. NPS^-/- mice were viable, fertile, and anatomically normal, when compared to their wild-type and heterozygous littermates. The total number of NPS neurons-although no longer synthesizing the peptide - was not affected by the knockout, as analyzed in NPS^-/- /NPS^EGFP double transgenic mice. Analysis of behavioral phenotypes revealed significant deficits in exploratory activity in NPS^-/- mice. NPS precursor knockout mice displayed attenuated arousal in the hole board test, visible as reduced total nose pokes and number of holes inspected, that was not confounded by increased repetitive or stereotypic behavior. Importantly, long-term memory was significantly impaired in NPS^-/- mice in the inhibitory avoidance paradigm. NPS precursor knockout mice displayed mildly increased anxiety-like behaviors in three different tests measuring responses to stress and novelty. Interestingly, heterozygous littermates often presented behavioral deficits similar to NPS^-/- mice or displayed intermediate phenotype. These observations may suggest limited ligand availability in critical neural circuits. Overall, phenotypical changes in NPS^-/- mice are similar to those observed in NPS receptor knockout mice and support earlier findings that suggest major functions of the NPS system in arousal, regulation of anxiety and stress, and memory formation.

Neuropeptide S (NPS) variants modify the signaling and risk effects of NPS Receptor 1 (NPSR1) variants in asthma

Single nucleotide polymorphisms (SNPs) close to the gain-of-function substitution, Asn(107)Ile (rs324981, A>T), in Neuropeptide S Receptor 1 (NPSR1) have been associated with asthma. Furthermore, a functional SNP (rs4751440, G>C) in Neuropeptide S (NPS) encodes a Val(6)Leu substitution on the mature peptide that results in reduced bioactivity. We sought to examine the effects of different combinations of these NPS and NPSR1 variants on downstream signaling and genetic risk of asthma. In transfected cells, the magnitude of NPSR1-induced activation of cAMP/PKA signal transduction pathways and downstream gene expression was dependent on the combination of the NPS and NPSR1 variants with NPS-Val(6)/NPSR1-Ile(107) resulting in strongest and NPS-Leu(6)/NPSR1-Asn(107) in weakest effects, respectively. One or two copies of the NPS-Leu(6) (rs4751440) were associated with physician-diagnosed childhood asthma (OR: 0.67, 95%CI 0.49–0.92, p = 0.01) and together with two other linked NPS variants (rs1931704 and rs10830123) formed a protective haplotype (p = 0.008) in the Swedish birth cohort BAMSE (2033 children). NPS rs10830123 showed epistasis with NPSR1 rs324981 encoding Asn(107)Ile (p = 0.009) in BAMSE and with the linked NPSR1 rs17199659 (p = 0.005) in the German MAGIC/ISAAC II cohort (1454 children). In conclusion, NPS variants modify asthma risk and should be considered in genetic association studies of NPSR1 with asthma and other complex diseases.

Neuropeptide S differently modulates alcohol-related behaviors in alcohol-preferring and non-preferring rats

RATIONALE

Neuropeptide S (NPS) displays unique pharmacological properties and induces both anxiolytic and pro-stress/arousal activities. Previous studies performed using Wistar rats demonstrated that NPS facilitated alcohol and cocaine seeking but did not affect alcohol or cocaine consumption.

OBJECTIVES

Here, we investigated the effects of NPS in Marchigian Sardinian alcohol-preferring (msP) rats, a rat strain characterized by excessive alcohol consumption comorbid with heightened anxiety and depressive-like phenotypes. Specifically, we evaluated the effect of NPS on operant alcohol self-administration by msP rats compared to Wistar rats. The effect of NPS on cue-induced reinstatement of alcohol seeking in msP rats was also evaluated. Finally, using the open field test (OFT) and the elevated plus maze (EPM), we evaluated the effects of NPS on locomotor activity and anxiety.

RESULTS

NPS reduced alcohol self-administration but did not affect cue-induced reinstatement in the msP rat. In addition, NPS induced reinstatement of extinguished alcohol seeking in Wistar rats without affecting alcohol intake. In the EPM task, NPS, in accordance with its anxiolytic activity, increased the time spent in the open arm of the arena by msP rats, although this effect was not observed in Wistar rats.

CONCLUSIONS

These data suggest that the effect of NPS is strongly influenced by the genetic background of the animal. In Wistar rats, NPS acts as a pro-arousal agent to promote the reinstatement of alcohol seeking. However, when alcohol drinking is motivated by or associated with a state of pathological anxiety, NPS attenuates alcohol consumption and seeking due to its anxiolytic activity.

Dynorphin-Dependent Reduction of Excitability and Attenuation of Inhibitory Afferents of NPS Neurons in the Pericoerulear Region of Mice

The Neuropeptide S system, consisting of the 20-amino acid peptide neuropeptide S (NPS) and its G-protein coupled receptor (NPSR), modulates arousal, wakefulness, anxiety, and fear-extinction in mice. In addition, recent evidence indicates that the NPS system attenuates stress-dependent impairment of fear extinction, and that NPS-expressing neurons in close proximity to the locus coeruleus region (LC; pericoerulear, periLC) are activated by stress. Furthermore, periLC NPS neurons receive afferents from neurons of the centrolateral nucleus of the amygdala (CeL), of which a substantial population expresses the kappa opioid receptor (KOR) ligand precursor prodynorphin. This study aims to identify the effect of the dynorphinergic system on NPS neurons in the periLC via pre- and postsynaptic mechanisms. Using electrophysiological recordings in mouse brain slices, we provide evidence that NPS neurons in the periLC region are directly inhibited by dynorphin A (DynA) via activation of κ-opioid receptor 1 (KOR1) and a subsequent increase of potassium conductances. Thus, the dynorphinergic system is suited to inactivate NPS neurons in the periLC. In addition to this direct, somatic effect, DynA reduces the efficacy of GABAergic synapses on NPS neurons via KOR1 and KOR2. In conclusion, the present study provides evidence for the interaction of the NPS and the kappa opioid system in the periLC. Therefore, the endogenous opioid dynorphin is suited to inhibit NPS neurons with a subsequent decrease in NPS release in putative target regions leading to a variety of physiological consequences such as increased anxiety or vulnerability to stress exposure.

Neuropeptide S inhibits gastrointestinal motility and increases mucosal permeability through nitric oxide

Neuropeptide S (NPS) receptor (NPSR1) polymorphisms are associated with enteral dysmotility and inflammatory bowel disease (IBD). This study investigated the role of NPS in conjunction with nitrergic mechanisms in the regulation of intestinal motility and mucosal permeability. In rats, small intestinal myoelectric activity and luminal pressure changes in small intestine and colon, along with duodenal permeability, were studied. In human intestine, NPS and NPSR1 were localized by immunostaining. Pre- and postprandial plasma NPS was measured by ELISA in healthy and active IBD humans. Effects and mechanisms of NPS were studied in human intestinal muscle strips. In rats, NPS 100-4,000 pmol·kg(-1)·min(-1) had effects on the small intestine and colon. Low doses of NPS increased myoelectric spiking (P < 0.05). Higher doses reduced spiking and prolonged the cycle length of the migrating myoelectric complex, reduced intraluminal pressures (P < 0.05-0.01), and increased permeability (P < 0.01) through NO-dependent mechanisms. In human intestine, NPS localized at myenteric nerve cell bodies and fibers. NPSR1 was confined to nerve cell bodies. Circulating NPS in humans was tenfold below the ∼0.3 nmol/l dissociation constant (Kd) of NPSR1, with no difference between healthy and IBD subjects. In human intestinal muscle strips precontracted by bethanechol, NPS 1-1,000 nmol/l induced NO-dependent muscle relaxation (P < 0.05) that was sensitive also to tetrodotoxin (P < 0.01). In conclusion, NPS inhibits motility and increases permeability in neurocrine fashion acting through NO in the myenteric plexus in rats and humans. Aberrant signaling and upregulation of NPSR1 could potentially exacerbate dysmotility and hyperpermeability by local mechanisms in gastrointestinal functional and inflammatory reactions.

Opposite roles for neuropeptide S in the nucleus accumbens and bed nucleus of the stria terminalis in learned helplessness rats

The role of neuropeptide S (NPS) in depression remains unclear. We examined the antidepressant-like effects of NPS infusions into the shell or core regions of the nucleus accumbens (NAc) and into the bed nucleus of the stria terminalis (BNST) of learned helplessness (LH) rats (an animal model of depression). Infusions of NPS (10 pmol/side) into the NAc shell, but not the NAc core and BNST, exerted antidepressant-like effects in the LH paradigm. Implying that behavioral deficits could be improved in the conditioned avoidance test. Coinfusion of SHA68 (an NPS receptor antagonist, 100 pmol/side) with NPS into the NAc shell blocked these effects. In contrast, NPS receptor antagonism by SHA68 in the BNST induced antidepressant-like effects. Infusions of NPS into the NAc shell or SHA68 into the BNST did not produce memory deficits or locomotor activation in the passive avoidance and open field tests. These results suggest that excitatory and inhibitory actions by the NPS system are integral to the depression in LH animals.

Modulation of prefrontal functioning in attention systems by NPSR1 gene variation

Evidence has accumulated for a dysfunction of arousal and executive attention in anxiety. The neuropeptide S (NPS) system has been shown to play a pivotal role in the mediation of arousal and to be associated with anxiety/panic disorder. The present study aims at investigating the impact of functional neuropeptide S receptor (NPSR1) gene variation on neural attention patterns applying an imaging genetics approach. In an event-related functional magnetic resonance imaging (fMRI) setting, 47 healthy subjects (f=23) evenly pre-stratified for NPSR1 rs324981 A/T genotype were investigated for brain activation patterns while performing the Attention Network Task (ANT), simultaneously probing alerting and executive control functions. Anxiety sensitivity was ascertained by the Anxiety Sensitivity Index (ASI). In the alerting condition, NPSR1 TT homozygotes showed higher activations in the right prefrontal cortex and the locus coeruleus region as compared to A allele carriers. In the executive control condition, TT homozygotes displayed increased activations in fronto-parietal regions. Genotype-driven activation differences in the prefrontal cortex correlated with anxiety sensitivity, in both the alerting and the executive control system. The present results for the first time suggest NPSR1 gene variation to be associated with alterations of prefrontal functioning in the attentional functions alerting and executive control partly modulated by anxiety sensitivity. These findings may aid in unraveling the neurobiological underpinnings of distorted arousal and attention in anxiety and thereby possibly in the biomarker-guided development of preventive/therapeutic strategies targeting attention processes in anxiety disorders.

NPSR1 polymorphisms influence recurrent abdominal pain in children: a population-based study

BACKGROUND

Recurrent abdominal pain (RAP) occurs frequently among children and is one of the cardinal symptoms of functional gastrointestinal disorders (FGID). The mechanisms of visceral pain and RAP are not fully understood. A heritable component has been demonstrated and a few candidate genes proposed. NPSR1 encodes the receptor for neuropeptide S (NPS) and NPS-NPSR1 signaling is involved in anxiety, inflammation, and nociception. NPSR1 polymorphisms are associated with asthma and chronic inflammatory diseases, but also with IBS-related intermediate phenotypes such as colonic transit time and rectal sensory ratings. Here, we sought to determine whether genetic variability in the NPSR1 gene influences the presence of RAP in children.

METHODS

Twenty-eight single-nucleotide polymorphisms (SNPs) in the NPSR1 gene region were successfully genotyped in 1744 children from the Swedish birth cohort BAMSE. Questionnaire information was used to define RAP as episodes of abdominal pain occurring at least once a month in 12-year-olds.

KEY RESULTS

The prevalence of RAP was 9% in BAMSE. Association with RAP was observed for seven NPSR1 SNPs, five of which withstood false discovery rate (FDR) correction for multiple testing (best p = 0.00054, OR: 1.55 for SNP rs2530566). The associated SNPs all map in a putative regulatory region upstream NPSR1, where they may exert their genetic effects through the modulation of gene expression.

CONCLUSIONS & INFERENCES

Genetic variation at the NPSR1 locus impacts children's predisposition to RAP episodes in a Swedish population.

Neuropeptide S receptor 1 (NPSR1) activates cancer-related pathways and is widely expressed in neuroendocrine tumors

Neuroendocrine tumors (NETs) arise from disseminated neuroendocrine cells and express general and specific neuroendocrine markers. Neuropeptide S receptor 1 (NPSR1) is expressed in neuroendocrine cells and its ligand neuropeptide S (NPS) affects cell proliferation. Our aim was to study whether NPS/NPSR1 could be used as a biomarker for neuroendocrine neoplasms and to identify the gene pathways affected by NPS/NPSR1. We collected a cohort of NETs comprised of 91 samples from endocrine glands, digestive tract, skin, and lung. Tumor type was validated by immunostaining of chromogranin-A and synaptophysin expression and tumor grade was analyzed by Ki-67 proliferation index. NPS and NPSR1 expression was quantified by immunohistochemistry using polyclonal antibodies against NPS and monoclonal antibodies against the amino-terminus and carboxy-terminus of NPSR1 isoform A (NPSR1-A). The effects of NPS on downstream signaling were studied in a human SH-SY5Y neuroblastoma cell line which overexpresses NPSR1-A and is of neuroendocrine origin. NPSR1 and NPS were expressed in most NET tissues, with the exception of adrenal pheochromocytomas in which NPS/NPSR1 immunoreactivity was very low. Transcriptome analysis of NPSR1-A overexpressing cells revealed that mitogen-activated protein kinase (MAPK) pathways, circadian activity, focal adhesion, transforming growth factor beta, and cytokine-cytokine interactions were the most altered gene pathways after NPS stimulation. Our results show that NETs are a source of NPS and NPSR1, and that NPS affects cancer-related pathways.

Neuropeptide S receptor gene (NPSR) and life events: G × E effects on anxiety sensitivity and its subdimensions

OBJECTIVES

The pathogenesis of anxiety is assumed to be interactively influenced by genetic and environmental factors. Thus, a gene-environment interaction (G × E) study of the neuropeptide S receptor gene (NPSR) A/T polymorphism (rs324981) and life events was conducted with respect to anxiety sensitivity (AS) as an intermediate phenotype of anxiety disorders.

METHODS

A sample of 475 healthy German subjects was genotyped for NPSR and assessed for AS, childhood maltreatment (CTQ) and recent life events (LTE). Influences on AS and its subdimensions were determined by a step-wise hierarchical regression and a multiple indicator multiple cause (MIMIC) model.

RESULTS

Significant main effects of NPSR and CTQ as well as significant G × E were observed, with T/T homozygosity and a high CTQ score resulting in increased anxiety sensitivity. MIMIC modelling yielded association of AS subfactor "concern about mental/cognitive incapacitation" and the basal somatic subdimension "concern about physical sensations" to be associated with CTQ and its interaction with NPSR, while the acute somatic subfactor "concern about heart/lung failure" was associated with NPSR and its interaction with LTE.

CONCLUSIONS

Results indicate G × E effects of the more active NPSR rs324981 T allele and life events on AS with differential effects of temporally proximal and distal factors on specific AS subdimensions.

The integrative role of the sigh in psychology, physiology, pathology, and neurobiology

"Sighs, tears, grief, distress" expresses Johann Sebastian Bach in a musical example for the relationship between sighs and deep emotions. This review explores the neurobiological basis of the sigh and its relationship with psychology, physiology, and pathology. Sighs monitor changes in brain states, induce arousal, and reset breathing variability. These behavioral roles homeostatically regulate breathing stability under physiological and pathological conditions. Sighs evoked in hypoxia evoke arousal and thereby become critical for survival. Hypoarousal and failure to sigh have been associated with sudden infant death syndrome. Increased breathing irregularity may provoke excessive sighing and hyperarousal, a behavioral sequence that may play a role in panic disorders. Essential for generating sighs and breathing is the pre-Bötzinger complex. Modulatory and synaptic interactions within this local network and between networks located in the brainstem, cerebellum, cortex, hypothalamus, amygdala, and the periaqueductal gray may govern the relationships between physiology, psychology, and pathology. Unraveling these circuits will lead to a better understanding of how we balance emotions and how emotions become pathological.

A single-nucleotide polymorphism of human neuropeptide s gene originated from Europe shows decreased bioactivity

Using accumulating SNP (Single-Nucleotide Polymorphism) data, we performed a genome-wide search for polypeptide hormone ligands showing changes in the mature regions to elucidate genotype/phenotype diversity among various human populations. Neuropeptide S (NPS), a brain peptide hormone highly conserved in vertebrates, has diverse physiological effects on anxiety, fear, hyperactivity, food intake, and sleeping time through its cognate receptor-NPSR. Here, we report a SNP rs4751440 (L⁶-NPS) causing non-synonymous substitution on the 6^th position (V to L) of the NPS mature peptide region. L⁶-NPS has a higher allele frequency in Europeans than other populations and probably originated from European ancestors ∼25,000 yrs ago based on haplotype analysis and Approximate Bayesian Computation. Functional analyses indicate that L⁶-NPS exhibits a significant lower bioactivity than the wild type NPS, with ∼20-fold higher EC₅₀ values in the stimulation of NPSR. Additional evolutionary and mutagenesis studies further demonstrate the importance of the valine residue in the 6^th position for NPS functions. Given the known physiological roles of NPS receptor in inflammatory bowel diseases, asthma pathogenesis, macrophage immune responses, and brain functions, our study provides the basis to elucidate NPS evolution and signaling diversity among human populations.

Structure-activity relationship of imidazopyridinium analogues as antagonists of neuropeptide s receptor

The discovery and characterization of a novel chemical series of phosphorothioyl-containing imidazopyridines as potent neuropeptide S receptor antagonists is presented. The synthesis of analogues and their structure-activity relationship with respect to the Gq, Gs, and ERK pathways is detailed. The pharmacokinetics and in vivo efficacy of a potent analogue in a food intake rodent model are also included, underscoring its potential therapeutic value for the treatment of sleep, anxiety, and addiction disorders.

Neural markers of errors as endophenotypes in neuropsychiatric disorders

Learning from errors is fundamental to adaptive human behavior. It requires detecting errors, evaluating what went wrong, and adjusting behavior accordingly. These dynamic adjustments are at the heart of behavioral flexibility and accumulating evidence suggests that deficient error processing contributes to maladaptively rigid and repetitive behavior in a range of neuropsychiatric disorders. Neuroimaging and electrophysiological studies reveal highly reliable neural markers of error processing. In this review, we evaluate the evidence that abnormalities in these neural markers can serve as sensitive endophenotypes of neuropsychiatric disorders. We describe the behavioral and neural hallmarks of error processing, their mediation by common genetic polymorphisms, and impairments in schizophrenia, obsessive-compulsive disorder, and autism spectrum disorders. We conclude that neural markers of errors meet several important criteria as endophenotypes including heritability, established neuroanatomical and neurochemical substrates, association with neuropsychiatric disorders, presence in syndromally-unaffected family members, and evidence of genetic mediation. Understanding the mechanisms of error processing deficits in neuropsychiatric disorders may provide novel neural and behavioral targets for treatment and sensitive surrogate markers of treatment response. Treating error processing deficits may improve functional outcome since error signals provide crucial information for flexible adaptation to changing environments. Given the dearth of effective interventions for cognitive deficits in neuropsychiatric disorders, this represents a potentially promising approach.

Central relaxin-3 receptor (RXFP3) activation decreases anxiety- and depressive-like behaviours in the rat

Relaxin-3 is a recently discovered neuropeptide and the results of earlier anatomical and pharmacological studies suggest it plays a physiological role in modulating functions such as arousal, learning and memory, food intake and neuroendocrine homeostasis. Relaxin-3 is also postulated to modulate affective behaviour, based on high densities of the relaxin-3 G-protein coupled receptor (RXFP3) in brain areas involved in stress and mood/anxiety, including the central amygdala, bed nucleus of the stria terminalis and hypothalamic paraventricular nucleus (PVN); and strong activation of relaxin-3 neurons by stressors, via activation of corticotropin-releasing factor receptor-1 (CRF1). This study assessed the effect of central administration of a newly developed RXFP3-selective agonist, on anxiety- and depressive-like behaviour in rats. Adult, male Sprague-Dawley rats administered 5 μg [R3A(11-24,C15→A)B] (referred to as RXFP3-A2), intracerebroventricularly, demonstrated decreased anxiety-like behaviour in the light-dark box and elevated plus maze, but not in the open field. Notably, in the repeat forced swim test, central RXFP3-A2 administration decreased immobility in rats that had been subjected to the 'stress' of former exposure to the anxiety tests, but not in experimentally naïve rats. These data implicate relaxin-3/RXFP3 signalling in the modulation of effects of acute (anxiety) and cumulative (depression) neurogenic stressors on behaviour; and suggest a potential for RXFP3 agonists as anxiolytic and anti-depressant agents. In addition, our results demonstrate that exposure of adult Sprague-Dawley rats to tests of anxiety-like behaviour (∼10-14 days prior) can significantly increase immobility time in the repeat forced swim test.

Antagonism of the neuropeptide S receptor with RTI-118 decreases cocaine self-administration and cocaine-seeking behavior in rats

Neuropeptide S (NPS) is a neuromodulatory peptide, acting via a G-protein-coupled receptor to regulate sleep, anxiety and behavioral arousal. Recent research has found that intracerebroventricular NPS can increase cocaine and alcohol self-administration in rodents, suggesting a key role in reward-related neurocircuitry. It is hypothesized that antagonism of the NPS system might represent a novel strategy for the pharmacological treatment of cocaine abuse. To this end, a small-molecule NPSR antagonist (RTI-118) was developed and tested in animal models of cocaine seeking and cocaine taking. Male Wistar rats (n=54) trained to self-administer cocaine and food under a concurrent alternating FR4 schedule exhibited specific dose-dependent decreases in cocaine intake when administered RTI-118. RTI-118 also decreased the reinstatement of extinguished cocaine-seeking behavior induced by conditioned cues, yohimbine and a priming dose of cocaine. These data support the hypothesis that antagonism of the neuropeptide S receptor may ultimately show efficacy in reducing cocaine use and relapse.

Increased in vivo release of neuropeptide S in the amygdala of freely moving rats after local depolarisation and emotional stress

Intracerebral microdialysis in conjunction with a highly sensitive radioimmunoassay was used to study the in vivo release of neuropeptide S (NPS) within the amygdala of freely moving rats. NPS was consistently detected in basolateral amygdala dialysates and the release considerably enhanced in response to local depolarisation as well as exposure to forced swim stress. Thus, our data demonstrate for the first time emotional stress-induced release of NPS in the amygdala supporting a functional role of endogenous NPS in stress/anxiety-related phenomena.

Neuropeptide S receptor gene -- converging evidence for a role in panic disorder

Animal studies have suggested neuropeptide S (NPS) and its receptor (NPSR) to be involved in the pathogenesis of anxiety-related behavior. In this study, a multilevel approach was applied to further elucidate the role of NPS in the etiology of human anxiety. The functional NPSR A/T (Asn¹⁰⁷Ile) variant (rs324981) was investigated for association with (1) panic disorder with and without agoraphobia in two large, independent case-control studies, (2) dimensional anxiety traits, (3) autonomic arousal level during a behavioral avoidance test and (4) brain activation correlates of anxiety-related emotional processing in panic disorder. The more active NPSR rs324981 T allele was found to be associated with panic disorder in the female subgroup of patients in both samples as well as in a meta-analytic approach. The T risk allele was further related to elevated anxiety sensitivity, increased heart rate and higher symptom reports during a behavioral avoidance test as well as decreased activity in the dorsolateral prefrontal, lateral orbitofrontal and anterior cingulate cortex during processing of fearful faces in patients with panic disorder. The present results provide converging evidence for a female-dominant role of NPSR gene variation in panic disorder potentially through heightened autonomic arousal and distorted processing of anxiety-relevant emotional stimuli.

Neuropeptide-S (NPS) receptor genotype modulates basolateral amygdala responsiveness to aversive stimuli

Recent studies point to a role of neuropeptide-S (NPS) in the etiology of anxiety disorders. In animal models, NPS and its receptor (NPSR) were shown to be highly expressed in the amygdala, a central structure in the fear circuit, also known to be hyper-responsive in anxiety disorders. Recently, a functional polymorphism in the NPSR gene (rs324981 A/T) has been associated with panic disorder and anxiety sensitivity. However, the role of NPSR gene variation in the modulation of fear-related amygdala responsiveness remains to be clarified. In 79 healthy subjects genotyped for NPSR rs324981, amygdala responses were assessed by means of fMRI. The participants were presented with fear-relevant faces in a robust emotion-processing paradigm frequently used to study amygdala responsiveness. We observed a strong association of NPSR T-alleles with right amygdala responsiveness to fear-relevant faces. The association peak was located in the BLA. Furthermore, responsiveness to aversive stimuli within this BLA cluster predicted a participant's self-reported harm avoidance but not depression level. We conclude that NPSR genotype is associated with increased amygdala responsiveness to fear-relevant stimuli. Thereby, NPSR rs324981 apparently causes an indirect effect on anxiety-related traits and potentially contributes to the pathogenesis of anxiety disorders by shaping fear-related limbic activity.

Global identification of the genes and pathways differentially expressed in hypothalamus in early and established neurogenic hypertension

The hypothalamus has an important etiological role in the onset and maintenance of hypertension and stress responses in the Schlager high blood pressure (BP) (BPH/2J) mouse, a genetic model of neurogenic hypertension. Using Affymetrix GeneChip Mouse Gene 1.0 ST Arrays we identified 1,019 hypothalamic genes whose expression differed between 6 wk old BPH/2J and normal BP (BPN/3J) strains, and 466 for 26 wk old mice. Of these, 459 were in 21 mouse BP quantitative trait loci. We validated 46 genes by qPCR. Gene changes that would increase sympathetic outflow at both ages were: Dynll1 encoding dynein light chain LC8-type 1, which physically destabilizes neuronal nitric oxide synthase, decreasing neuronal nitric oxide, and Hcrt encoding hypocretin and Npsr1 encoding neuropeptide S receptor 1, each involved in sympathetic response to stress. At both ages we identified genes for inflammation, such as CC-chemokine ligand 19 ( Ccl19), and oxidative stress. Via reactive oxygen species generation, these could contribute to oxidative damage. Other genes identified could be responding to such perturbations. Atp2b1, the major gene from genome-wide association studies of BP variation, was underexpressed in the early phase. Comparison of profiles of young and adult BPH/2J mice, after adjusting for maturation genes, pointed to the proopiomelanocortin-α gene ( Pomc) and neuropeptide Y gene ( Npy), among others, as potentially causative. The present study has identified a diversity of genes and possible mechanisms involved in hypertension etiology and maintenance in the hypothalamus of BPH/2J mice, highlighting both common and divergent processes in each phase of the condition.

Neuropeptide S receptor: recent updates on nonpeptide antagonist discovery

Neuropeptide S (NPS) is a 20-amino acid peptide of great interest due to its possible involvement in several biological processes, including food intake, locomotion, wakefulness, arousal, and anxiety. Structure-activity relationship studies of NPS have identified key points for structural modifications with the goal of modulating NPS receptor (NPSR) agonist activity or achieving antagonism at the same receptor. Only limited information is available for nonpeptide NPSR antagonists. In the last year, several studies have been reported in literature which present various series of small molecules as antagonists of this receptor. The results allow a comparison of the structures and activities of these molecules, leading to the design of new ligands with increased potency and improved pharmacological and pharmacokinetic profiles. This work presents a brief overview of the available information regarding structural features and pharmacological characterization of published nonpeptide NPSR antagonists.

Neuropeptide S enhances memory during the consolidation phase and interacts with noradrenergic systems in the brain

Neuropeptide S (NPS) has been shown to promote arousal and anxiolytic-like effects, as well as facilitation of fear extinction. In rodents, NPS receptors (NPSR) are prominently expressed in brain structures involved in learning and memory. Here, we investigate whether exogenous or endogenous NPS signaling can modulate acquisition, consolidation, or recall of emotional, spatial, and contextual memory traces, using two common behavioral paradigms, inhibitory avoidance (IA) and novel object recognition. In the IA paradigm, immediate and delayed post-training central NPS administration dose dependently enhanced memory retention in mice, indicating that NPS may act during the consolidation phase to enhance long-term memory. In contrast, pre-training or pre-test NPS injections were ineffective, suggesting that NPS had no effect on IA memory acquisition or recall. Peripheral administration of a synthetic NPSR antagonist attenuated NPS-induced IA memory enhancement, showing pharmacological specificity. NPS also enhanced hippocampal-dependent non-aversive memory in the novel object recognition task. In contrast, NPSR knockout mice displayed deficits in IA memory, novel object recognition, and novel place or context recognition, suggesting that activity of the endogenous NPS system is required for memory formation. Blockade of adrenergic signaling by propranolol attenuated NPS-induced memory enhancement in the IA task, indicating involvement of central noradrenergic systems. These results provide evidence for a facilitatory role of NPS in long-term memory, independent of memory content, possibly by acting as a salience signal or as an arousal-promoting factor.

Novel neuropeptides as ligands of orphan G protein-coupled receptors

Neuropeptides control a wide spectrum of physiological functions. They are central to our understanding of brain functions. They exert their actions by interacting with specific G protein-coupled receptors. We however have not found all the neuropeptides that exist in organisms. The search for novel neuropeptides is thus of great interest as it will lead to a better understanding of brain function and disorders. In this review, we will discuss the historical as well as the current approaches to neuropeptide discovery, with a particular emphasis on the orphan GPCR-based strategies. We will also discuss two novel peptides, neuropeptide S and neuromedin S, as examples of the impact of neuropeptide discovery on our understanding of brain functions. Finally, the challenges facing neuropeptide discovery will be discussed.

A multiplex calcium assay for identification of GPCR agonists and antagonists

Activation of G(q) protein-coupled receptors can be monitored by measuring the increase in intracellular calcium with fluorescent dyes. Recent advances in fluorescent kinetic plate readers and liquid-handling technology have made it possible to follow these transient changes in intracellular calcium in a 1,536-well plate format for high-throughput screening (HTS). Here, we have applied the latest generation of fluorescence kinetic plate readers to multiplex the agonist and antagonist screens of a G protein-coupled receptor (GPCR). This multiplexed assay format provides an efficient and cost-effective method for HTS of G(q)-coupled GPCR targets.

Early life environment, neurodevelopment and the interrelation with atopy

Both neurological and immunological systems are vulnerable to early life exposures. Neurological disorders and atopy have been related in animals and humans. Our main objective was to assess whether multiple exposures to early life determinants remain associated with neurodevelopment after considering the potential intermediate role of atopy. A second objective was to assess whether genes associated with atopy may inform about the potential neurotoxical mechanisms. Children were members of the AMICS birth cohort in Menorca (n=418, 87% of the recruited). General cognition was measured with the McCarthy Scales at age 4 and atopy through specific IgE at age 4 and prick test at age 6; 85 single nucleotide polymorphisms (SNPs) in 16 atopy and detoxification genes were genotyped. Among the 27 risk factors assessed, lower maternal social class, maternal smoking during pregnancy, being first born, shorter breastfeeding, higher DDT levels in cord blood, and higher indoor levels of NO2 (among the non-detoxifiers by GSTP1 polymorphism) were independently associated with poorer cognition. These associations were apparently not mediated by the relation between atopy and general cognition. Among the candidate atopic genes, variants in NQ01 (a detoxification gene) and NPRS1 (related with affective disorders like anxiety and stress management) had a significant association with general cognition (p-value<0.001). However, adjustment for the corresponding SNPs did not change the association between the early life determinants and general cognition. Multiple environmental pre-natal exposures were associated with neurodevelopment independently of their role in the immunological system. Atopic genes related to neurodevelopment suggest some potential mechanisms.

Neuropeptide S receptor deficiency modulates spontaneous locomotor activity and the acoustic startle response

The present study investigated the phenotype of heterozygous and homozygous neuropeptide S receptor (Npsr) deficient C57BL/6 mice in NPS- and cocaine induced hyperactivity, spontaneous and reactive locomotor activity, elevated plus maze, conditioned fear, and prepulse inhibition of the acoustic startle response. In Npsr-deficient mice, a strong reduction of spontaneous locomotor activity and of the startle magnitude was observed; heterozygous mice had an intermediate phenotype. In the other experiments, Npsr deficiency leads to no or only a very modest phenotype. These results support an important role of neuropeptide S in regulating locomotor activity.

Neuropeptide S stimulates dopaminergic neurotransmission in the medial prefrontal cortex

Neuropeptide S (NPS) is known to produce anxiolytic-like effects and facilitate extinction of conditioned fear. Catecholaminergic neurotransmission in the medial prefrontal cortex (mPFC) has been suggested to be crucially involved in these brain functions. In the current study, we investigated the effect of NPS on the release of dopamine and serotonin in the mPFC by in vivo microdialysis in rats. Central administration of NPS dose-dependently enhanced extracellular levels of dopamine and its major metabolite 3,4-dihydroxyphenylacetic acid, with maximal effects lasting up to 120 min. In contrast, no effect on serotonergic neurotransmission was detected. Dopamine release in the mPFC has been previously linked to modulation of anxiety states and fear extinction. The present results may thus provide a physiological and anatomical basis for the reported effects of NPS on these behaviors.

Selective Modulation of Gq/Gs pathways by Naphtho Pyrano Pyrimidines as antagonists of the Neuropeptide S Receptor

Antagonists of the Neuropeptide S Receptor have been postulated as promising therapeutics in the treatment of respiratory, sleep, anxiety, and addictive disorders. Here we present the SAR of a new series of orthosteric antagonists. Neuropeptide S Receptor signaling is coupled to both Gq and Gs proteins, and we observe that different analogues in this structural series can selectively antagonize these two pathways. Many G-protein coupled receptors transduce signals through multiple pathways. Selective antagonism of these pathways may lead the way to the development of more targeted pharmacological profiles and therapies.