Neuropeptide S: a transmitter system in the brain regulating fear and anxiety

Efferent projections of Nps-expressing neurons in the parabrachial region

In the brain, connectivity determines function. Neurons in the parabrachial nucleus (PB) relay diverse information to widespread brain regions, but the connections and functions of PB neurons that express Nps (neuropeptide S) remain mysterious. Here, we use Cre-dependent anterograde tracing and whole-brain analysis to map their output connections. While many other PB neurons project ascending axons through the central tegmental tract, NPS axons reach the forebrain via distinct periventricular and ventral pathways. Along the periventricular pathway, NPS axons target the tectal longitudinal column and periaqueductal gray then continue rostrally to target the paraventricular nucleus of the thalamus. Along the ventral pathway, NPS axons blanket much of the hypothalamus but avoid the ventromedial and mammillary nuclei. They also project prominently to the ventral bed nucleus of the stria terminalis, A13 cell group, and magnocellular subparafasciular nucleus. In the hindbrain, NPS axons have fewer descending projections, targeting primarily the superior salivatory nucleus, nucleus of the lateral lemniscus, and periolivary region. Combined with what is known about NPS and its receptor, the output pattern of Nps-expressing neurons in the PB region predicts a role in threat response and circadian behavior.

Augmented impulsive behavior in febrile seizure-induced mice

Febrile seizure (FS) is one of the most prevalent etiological events in childhood affecting 2-5% of children from 3 months to 5 years old. Debates on whether neurodevelopmental consequences rise in later life following a febrile seizure or not are still ongoing however there is limited evidence of its effect, especially in a laboratory setting. Moreover, the comparative study using both male and female animal models is sparse. To examine the effect of FS on the behavioral features of mice, both sexes of ICR mice were induced with hyperthermic seizures through exposure to an infrared heat lamp. The mice were divided into two groups, one receiving a single febrile seizure at postnatal day 11 (P11) and one receiving three FS at P11, P13, and P15. Starting at P30 the FS-induced mice were subjected to a series of behavioral tests. Mice with seizures showed no locomotor and motor coordination deficits, repetitive, and depressive-like behavior. However, the FS-induced mice showed impulsive-like behavior in both elevated plus maze and cliff avoidance tests, which is more prominent in male mice. A greater number of mice displayed impaired CAT in both males and females in the three-time FS-induced group compared to the single induction group. These results demonstrate that after induction of FS, male mice have a higher susceptibility to consequences of febrile seizure than female mice and recurrent febrile seizure has a higher chance of subsequent disorders associated with decreased anxiety and increased impulsivity. We confirmed the dysregulated expression of impulsivity-related genes such as 5-HT1A and tryptophan hydroxylase 2 from the prefrontal cortices of FS-induced mice implying that the 5-HT system would be one of the mechanisms underlying the increased impulsivity after FS. Taken together, these findings are useful in unveiling future discoveries about the effect of childhood febrile seizure and the mechanism behind it.

High Dimensional Multiomics Reveals Unique Characteristics of Early Plasma Administration in Polytrauma Patients With TBI

OBJECTIVES

The authors sought to identify causal factors that explain the selective benefit of prehospital administration of thawed plasma (TP) in traumatic brain injury (TBI) patients using mediation analysis of a multiomic database.

BACKGROUND

The Prehospital Air Medical Plasma (PAMPer) Trial showed that patients with TBI and a pronounced systemic response to injury [defined as endotype 2 (E2)], have a survival benefit from prehospital administration of TP. An interrogation of high dimensional proteomics, lipidomics and metabolomics previously demonstrated unique patterns in circulating biomarkers in patients receiving prehospital TP, suggesting that a deeper analysis could reveal causal features specific to TBI patients.

METHODS

A novel proteomic database (SomaLogic Inc., aptamer-based assay, 7K platform) was generated using admission blood samples from a subset of patients (n=149) from the PAMPer Trial. This proteomic dataset was combined with previously reported metabolomic and lipidomic datasets from these same patients. A 2-step analysis was performed to identify factors that promote survival in E2-TBI patients who had received early TP. First, features were selected using both linear and multivariate-latent-factor regression analyses. Then, the selected features were entered into the causal mediation analysis.

RESULTS

Causal mediation analysis of observable features identified 16 proteins and 41 lipids with a high proportion of mediated effect (>50%) to explain the survival benefit of early TP in E2-TBI patients. The multivariate latent-factor regression analyses also uncovered 5 latent clusters of features with a proportion effect >30%, many in common with the observable features. Among the observable and latent features were protease inhibitors known to inhibit activated protein C and block fibrinolysis (SERPINA5 and CPB2), a clotting factor (factor XI), as well as proteins involved in lipid transport and metabolism (APOE3 and sPLA(2)-XIIA).

CONCLUSIONS

These findings suggest that severely injured patients with TBI process exogenous plasma differently than those without TBI. The beneficial effects of early TP in E2-TBI patients may be the result of improved blood clotting and the effect of brain protective factors independent of coagulation.

Neuropeptide S Encodes Stimulus Salience in the Paraventricular Thalamus

Evaluation of stimulus salience is critical for any higher organism, as it allows for prioritizing of vital information, preparation of responses, and formation of valuable memory. The paraventricular nucleus of the thalamus (PVT) has recently been identified as an integrator of stimulus salience but the neurochemical basis and afferent input regarding salience signaling have remained elusive. Here we report that neuropeptide S (NPS) signaling in the PVT is necessary for stimulus salience encoding, including aversive, neutral and reinforcing sensory input. Taking advantage of a striking deficit of both NPS receptor (NPSR1) and NPS precursor knockout mice in fear extinction or novel object memory formation, we demonstrate that intra-PVT injections of NPS can rescue the phenotype in NPS precursor knockout mice by increasing the salience of otherwise low-intensity stimuli, while intra-PVT injections of NPSR1 antagonist in wild type mice partially replicates the knockout phenotype. The PVT appears to provide stimulus salience encoding in a dose- and NPS-dependent manner. PVT NPSR1 neurons recruit the nucleus accumbens shell and structures in the prefrontal cortex and amygdala, which were previously linked to the brain salience network. Overall, these results demonstrate that stimulus salience encoding is critically associated with NPS activity in the PVT.

Modulatory effect of long-term treatment with escitalopram and clonazepam on the expression of anxiety-related neuropeptides: neuromedin U, neuropeptide S and their receptors in the rat brain

BACKGROUND

Newly identified multifunctional peptidergic modulators of stress responses: neuromedin U (NMU) and neuropeptide S (NPS) are involved in the wide spectrum of brain functions. However, there are no reports dealing with potential molecular relationships between the action of diverse anxiolytic or antidepressant drugs and NMU and NPS signaling in the brain. The present work was therefore focused on local expression of the aforementioned stress-related neuropeptides in the rat brain after long-term treatment with escitalopram and clonazepam.

METHODS

Studies were carried out on adult, male Sprague-Dawley rats that were divided into 3 groups: animals injected with saline (control) and experimental individuals treated with escitalopram (at single dose 5 mg/kg daily), and clonazepam (at single dose 0.5 mg/kg). All individuals were sacrificed under anaesthesia and the whole brain excised. Total mRNA was isolated from homogenized samples of amygdala, hippocampus, hypothalamus, thalamus, cerebellum and brainstem. Real time-PCR method was used for estimation of related NPS, NPS receptor (NPSR), NMU, NMU and receptor 2 (NMUR2) mRNA expression. The whole brains were also sliced for general immunohistochemical assessment of the neuropeptides expression.

RESULTS

Chronic administration of clonazepam resulted in an increase of NMU mRNA expression and formation of NMU-expressing fibers in the amygdala, while escitalopram produced a significant decrease in NPSR mRNA level in hypothalamus. Long-term escitalopram administration affects the local expression of examined neuropeptides mRNA in a varied manner depending on the brain structure.

CONCLUSIONS

Pharmacological effects of escitalopram may be connected with local at least partially NPSR-related alterations in the NPS/NMU/NMUR2 gene expression at the level selected rat brain regions. A novel alternative mode of SSRI action can be therefore cautiously proposed.

Escitalopram alters local expression of noncanonical stress-related neuropeptides in the rat brain via NPS receptor signaling

BACKGROUND

Neuropeptide S (NPS) is a multifunctional regulatory factor that exhibits a potent anxiolytic activity in animal models. However, there are no reports dealing with the potential molecular relationships between the anxiolytic activity of selective serotonin reuptake inhibitors (SSRIs) and NPS signaling, especially in the context of novel stress-related neuropeptides action. The present work therefore focused on gene expression of novel stress neuropeptides in the rat brain after acute treatment with escitalopram and in combination with neuropeptide S receptor (NPSR) blockade.

METHODS

Studies were carried out on adult, male Sprague-Dawley rats that were divided into five groups: animals injected with saline (control) and experimental rats treated with escitalopram (at single dose 10 mg/kg daily), escitalopram and SHA-68, a selective NPSR antagonist (at a single dose of 40 mg/kg), SHA-68 alone and corresponding vehicle (solvent SHA-68) control. To measure anxiety-like behavior and locomotor activity the open field test was performed. All individuals were killed under anaesthesia and the whole brain was excised. Total mRNA was isolated from homogenized samples of the amygdala, hippocampus, hypothalamus, thalamus, cerebellum, and brainstem. Real-time PCR was used for estimation of related NPS, NPSR, neuromedin U (NMU), NMU receptor 2 (NMUR2) and nesfatin-1 precursor nucleobindin-2 (NUCB2) gene expression.

RESULTS

Acute escitalopram administration affects the local expression of the examined neuropeptides mRNA in a varied manner depending on brain location. An increase in NPSR and NUCB2 mRNA expression in the hypothalamus and brainstem was abolished by SHA-68 coadministration, while NMU mRNA expression was upregulated after NPSR blockade in the hippocampus and cerebellum.

CONCLUSIONS

The pharmacological effects of escitalopram may be connected with local NPSR-related alterations in NPS/NMU/NMUR2 and nesfatin-1 gene expression at the level of selected rat brain regions. A novel alternative mode of SSRI action can be therefore cautiously proposed.

Effect of Escitalopram on the Number of DCX-Positive Cells and NMUR2 Receptor Expression in the Rat Hippocampus under the Condition of NPSR Receptor Blockade

BACKGROUND

Neuropeptide S (NPS) is a multifunctional regulatory factor that exhibits a potent anxiolytic activity in animal models. However, there are no reports dealing with the potential molecular interactions between the activity of selective serotonin reuptake inhibitors (SSRIs) and NPS signaling, especially in the context of adult neurogenesis and the expression of noncanonical stress-related neuropeptides such as neuromedin U (NMU). The present work therefore focused on immunoexpression of neuromedin U receptor 2 (NMUR2) and doublecortin (DCX) in the rat hippocampus after acute treatment with escitalopram and in combination with selective neuropeptide S receptor (NPSR) blockade.

METHODS

Studies were carried out on adult, male Sprague-Dawley rats that were divided into five groups: animals injected with saline (control) and experimental individuals treated with escitalopram (at single dose 10 mg/kg daily), escitalopram + SHA-68, a selective NPSR antagonist (at single dose 40 mg/kg), SHA-68 alone, and corresponding vehicle control. All animals were sacrificed under halothane anaesthesia. The whole hippocampi were quickly excised, fixed, and finally sliced for general qualitative immunohistochemical assessment of the NPSR and NMUR2 expression. The number of immature neurons was enumerated using immunofluorescent detection of doublecortin (DCX) expression within the subgranular zone (SGZ).

RESULTS

Acute escitalopram administration affects the number of DCX and NMUR2-expressing cells in the adult rat hippocampus. A decreased number of DCX-expressing neuroblasts after treatment with escitalopram was augmented by SHA-68 coadministration.

CONCLUSIONS

Early pharmacological effects of escitalopram may be at least partly connected with local NPSR-related alterations of neuroblast maturation in the rat hippocampus. Escitalopram may affect neuropeptide and DCX-expression starting even from the first dose. Adult neurogenesis may be regulated via paracrine neuropeptide S and NMU-related signaling.

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.

Neural circuits of anxiolytic and antidepressant pherine molecules

In this review, we describe proposed circuits mediating the mechanism of action of pherines, a new class of synthetic neuroactive steroids with demonstrated antianxiety and antidepressant properties, that engage nasal chemosensory receptors. We hypothesize that afferent signals triggered by activation of these peripheral receptors could reach subgroups of olfactory bulb neurons broadcasting information to gamma-aminobutyric acid (GABAergic) and corticotropin-releasing hormone (CRH) neurons in the limbic amygdala. We propose that chemosensory inputs triggered by pherines project to centrolateral (CeL) and centromedial (CeM) amygdala neurons, with downstream effects mediating behavioral actions. Anxiolytic pherines could activate the forward inhibitory GABAergic neurons that facilitate the release of neuropeptide S (NPS) in the locus coeruleus (LC) and GABA in the bed nucleus of the stria terminalis (BNST) and inhibit catecholamine release in the LC and ventral tegmental area (VTA) leading to rapid anxiolytic effect. Alternatively, antidepressant pherines could facilitate the CRH and GABAergic neurons that inhibit the release of NPS from the LC, increase glutamate release from the BNST, and increase norepinephrine (NE), dopamine (DA), and serotonin release from the LC, VTA, and raphe nucleus, respectively. Activation of these neural circuits leads to rapid antidepressant effect. The information provided is consistent with this model, but it should be noted that some steps on these pathways have not been demonstrated conclusively in the human brain.

Neuropeptide S Attenuates the Alarm Pheromone-Evoked Defensive and Risk Assessment Behaviors Through Activation of Cognate Receptor-Expressing Neurons in the Posterior Medial Amygdala

Neuropeptide S (NPS) acts by activating its cognate receptor (NPSR). High level expression of NPSR in the posterior medial amygdala suggests that NPS-NPSR system should be involved in regulation of social behaviors induced by social pheromones. The present study was undertaken to investigate the effects of central administration of NPS or with NPSR antagonist on the alarm pheromone (AP)-evoked defensive and risk assessment behaviors in mice. Furthermore, H129-H8, a novel high-brightness anterograde multiple trans-synaptic virus, c-Fos and NPSR immunostaining were employed to reveal the involved neurocircuits and targets of NPS action. The mice exposed to AP displayed an enhancement in defensive and risk assessment behaviors. NPS (0.1–1 nmol) intracerebroventricular (i.c.v.) injection significantly attenuated the AP-evoked defensive and risk assessment behaviors. NPSR antagonist [D-Val⁵]NPS at the dose of 40 nmol completely blocked the effect of 0.5 nmol of NPS which showed the best effective among dose range. The H129-H8-labeled neurons were observed in the bilateral posterodorsal medial amygdala (MePD) and posteroventral medial amygdala (MePV) 72 h after the virus injection into the unilateral olfactory bulb (OB), suggesting that the MePD and MePV receive olfactory information inputs from the OB. The percentage of H129-H8-labeled neurons that also express NPSR were 90.27 ± 3.56% and 91.67 ± 2.46% in the MePD and MePV, respectively. NPS (0.5 nmol, i.c.v.) remarkably increased the number of Fos immunoreactive (-ir) neurons in the MePD and MePV, and the majority of NPS-induced Fos-ir neurons also expressed NPSR. The behavior characteristic of NPS or with [D-Val⁵]NPS can be better replicated in MePD/MePV local injection within lower dose. The present findings demonstrated that NPS, via selective activation of the neurons bearing NPSR in the posterior medial amygdala, attenuates the AP-evoked defensive and risk assessment behaviors in mice.

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.

DNA Microarray-Based Global Gene Expression Profiling in Human Amniotic Epithelial Cells Predicts the Potential of Microalgae-Derived Squalene for the Nervous System and Metabolic Health

In recent years, perinatal stem cells, such as human amniotic epithelial cells (hAECs), have attracted increasing interest as a novel tool of stem cell-based high-throughput drug screening. In the present study, we investigated the bioactivities of squalene (SQ) derived from ethanol extract (99.5%) of a microalgae Aurantiochytrium Sp. (EEA-SQ) in hAECs using whole-genome DNA microarray analysis. Tissue enrichment analysis showed that the brain was the most significantly enriched tissue by the differentially expressed genes (DEGs) between EEA-SQ-treated and control hAECs. Further gene set enrichment analysis and tissue-specific functional analysis revealed biological functions related to nervous system development, neurogenesis, and neurotransmitter modulation. Several adipose tissue-specific genes and functions were also enriched. Gene-disease association analysis showed nervous system-, metabolic-, and immune-related diseases were enriched. Altogether, our study suggests the potential health benefits of microalgae-derived SQ and we would further encourage investigation in EEA-SQ and its derivatives as potential therapeutics for nervous system- and metabolism-related diseases.

Neuropeptide-S affects cognitive impairment and depression-like behavior on MPTP induced experimental mouse model of Parkinson’s disease

Background/aim

The present study proposes to investigate the effect of neuropeptide–S (NPS) on cognitive functions and depression-like behavior of MPTP-induced experimental model of Parkinson’s disease (PD).

Materials and methods

Three-month-old C57BL/6 mice were randomly divided into three groups as; Control, Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and MPTP + NPS 0.1 nmol (received intraperitoneal injection of MPTP and intracerebroventricular injection of NPS, 0.1 nmol for seven days). The radial arm maze and pole tests were carried out, and the levels of tyrosine hydroxylase (TH) were determined using western blotting. A mass spectrometer was used to measure the levels of dopamine, glutamic acid, and glutamine.

Results

The T-turn and time to descend enhanced in MPTP group, while these parameters were decreased by NPS treatment. In the MPTP group, the number of working memory errors (WME) and reference memory errors (RME) increased, whereas NPS administration decreased both parameters. Sucrose preference decreased in the MPTP group while increasing in the NPS group. MPTP injection significantly reduced dopamine, glutamic acid, and glutamine levels. NPS treatment restored the MPTP-induced reduction in glutamine and glutamic acid levels.

Conclusion

NPS may be involved in the future treatment of cognitive impairments and depression-like behaviors in PD.

A neuropeptide making memories

Neuropeptides are the most diverse class of signaling molecules in the brain. Despite evidence for their involvement in several behavioral functions, the precise circuit elements and neuronal computations they control remain elusive. In this issue, Melzer et al. (2021) reveal how the neuropeptide GRP facilitates memory in the neocortex.

Central neuropeptide-S administration alleviates stress-induced impairment of gastric motor functions through orexin-A

BACKGROUND/AIMS

The novel brain peptide neuropeptide-S (NPS) is produced exclusively by a small group of cells adjacent to the noradrenergic locus coeruleus. The NPSR mRNA has been detected in several brain areas involved in stress response and autonomic outflow, such as amygdala and hypothalamus, suggesting that central NPS may play a regulatory role in stress-induced changes in gastrointestinal (GI) motor functions. In rodents, exogenous central NPS was shown to inhibit stress-stimulated fecal output. Moreover, exogenous NPS was demonstrated to activate hypothalamic neurons that produce orexin-A (OXA), which has been shown to stimulate postprandial gastric motor functions via central vagal pathways. Therefore, we tested whether OXA mediates the NPS-induced alterations in gastric motor functions under stressed conditions.

MATERIALS AND METHODS

We investigated the effect of central exogenous NPS on solid gastric emptying (GE) and gastric postprandial motility in acute restraint stress (ARS)-loaded conscious rats. The OXA receptor antagonist SB-334867 was administered centrally prior to the central NPS injection. The expression of NPSR in the hypothalamus and dorsal vagal complex was analyzed by immunofluorescence.

RESULTS

Central administration of NPS restored the ARS-induced delayed GE and uncoordinated postprandial antro-pyloric contractions. The alleviative effect of NPS on GE was abolished by pretreatment of the OX1R antagonist SB-334867. In addition to hypothalamus, NPSR was detected in the dorsal motor nucleus of vagus, which suggest a direct stimulatory action of exogenous NPS on gastric motility.

CONCLUSION

NPS may be a novel candidate for the treatment of stress-related gastric disorders.

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.

Neuropeptide S Receptor as an Innovative Therapeutic Target for Parkinson Disease

Parkinson disease (PD) is a neurodegenerative disease mainly characterized by the loss of nigral dopaminergic neurons in the substantia nigra pars compacta. Patients suffering from PD develop severe motor dysfunctions and a myriad of non-motor symptoms. The treatment mainly consists of increasing central dopaminergic neurotransmission and alleviating motor symptoms, thus promoting severe side effects without modifying the disease’s progress. A growing body of evidence suggests a close relationship between neuropeptide S (NPS) and its receptor (NPSR) system in PD: (i) double immunofluorescence labeling studies showed that NPSR is expressed in the nigral tyrosine hydroxylase (TH)-positive neurons; (ii) central administration of NPS increases spontaneous locomotion in naïve rodents; (iii) central administration of NPS ameliorates motor and nonmotor dysfunctions in animal models of PD; (iv) microdialysis studies showed that NPS stimulates dopamine release in naïve and parkinsonian rodents; (v) central injection of NPS decreases oxidative damage to proteins and lipids in the rodent brain; and, (vi) 7 days of central administration of NPS protects from the progressive loss of nigral TH-positive cells in parkinsonian rats. Taken together, the NPS/NPSR system seems to be an emerging therapeutic strategy for alleviating motor and non-motor dysfunctions of PD and, possibly, for slowing disease progress.

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.

Neuropeptide S Receptor Stimulation Excites Principal Neurons in Murine Basolateral Amygdala through a Calcium-Dependent Decrease in Membrane Potassium Conductance

Background: The neuropeptide S system, consisting of the 20 amino acid neuropeptide NPS and its G-protein-coupled receptor (GPCR) neuropeptide S receptor 1 (NPSR1), has been studied intensively in rodents. Although there is a lot of data retrieved from behavioral studies using pharmacology or genetic interventions, little is known about intracellular signaling cascades in neurons endogenously expressing the NPSR1. Methods: To elucidate possible G-protein-dependent signaling and effector systems, we performed whole-cell patch-clamp recordings on principal neurons of the anterior basolateral amygdala of mice. We used pharmacological interventions to characterize the NPSR1-mediated current induced by NPS application. Results: Application of NPS reliably evokes inward-directed currents in amygdalar neurons recorded in brain slice preparations of male and female mice. The NPSR1-mediated current had a reversal potential near the potassium reversal potential (E_K) and was accompanied by an increase in membrane input resistance. GDP-β-S and BAPTA, but neither adenylyl cyclase inhibition nor 8-Br-cAMP, abolished the current. Intracellular tetraethylammonium or 4-aminopyridine reduced the NPS-evoked current. Conclusion: NPSR1 activation in amygdalar neurons inhibits voltage-gated potassium (K⁺) channels, most likely members of the delayed rectifier family. Intracellularly, G_αq signaling and calcium ions seem to be mandatory for the observed current and increased neuronal excitability.

Transcriptome Analysis Reveals Differentially Expressed Genes and Long Non-coding RNAs Associated With Fecundity in Sheep Hypothalamus With Different FecB Genotypes

Small-tailed Han sheep, with different FecB genotypes, manifest distinct ovulation rates and fecundities, which are due to differences in reproductive hormones secreted by the hypothalamic-pituitary-ovarian axis. Nevertheless, the function of the hypothalamus against a FecB mutant background on increasing ovulation rate is rarely reported. Therefore, we determined the expression profiles of hypothalamus tissue collected from six wild-type (WW) and six FecB mutant homozygous (BB) ewes at the follicular and luteal phases by whole-transcriptome sequencing. We identified 53 differentially expressed mRNAs (DEGs) and 40 differentially expressed long non-coding RNAs (DELs) between the two estrus states. Functional annotation analysis revealed that one of the DEGs, PRL, was particularly enriched in the hypothalamic function, hormone-related, and reproductive pathways. The lncRNA-target gene interaction networks and KEGG analysis in combination suggest that the lncRNAs LINC-676 and WNT3-AS cis-acting on DRD2 and WNT9B in different phases may induce gonadotropin-releasing hormone (GnRH) secretion. Furthermore, there were differences of regulatory elements and WNT gene family members involved in the follicular-luteal transition in the reproductive process between wild-type (WNT7A) and FecB mutant sheep (WNT9B). We combined the DEG and DEL data sets screened from different estrus states and genotypes. The overlap of these two sets was identified to select the mRNAs and lncRNAs that have major effects on ovulation. Among the overlapping molecules, seven DEGs and four DELs were involved in the follicular-luteal transition regulated by FecB mutation. Functional annotation analysis showed that two DEGs (FKBP5 and KITLG) were enriched in melanogenesis, oxytocin, and GnRH secretion. LINC-219386 and IGF2-AS were highly expressed in the BB ewes compared with WW ewes, modulating their target genes (DMXL2 and IGF2) to produce more GnRH during follicular development, which explains why mutated ewes produced more mature follicles. These results from expression profiling of the hypothalamus with the FecB mutation at different estrus states provide new insights into how the hypothalamus regulates ovulation under the effect of the FecB mutation.

Combination therapy with neuropeptides for the treatment of anxiety disorder

Anxiety is a neurological disorder that is characterized by excessive, persistent, and unreasonable worry about everyday things like family, work, money, and relationships. The current therapy used for the treatment has many disadvantages like higher cost, severe adverse reactions, and has suboptimal efficiency. There is a need to look for more innovative approaches for the treatment of anxiety disorder which overcomes the disadvantages of conventional treatment. Recent findings suggest a strong correlation of glutamate with anxiety. Some promising drugs which have a novel mechanism for anxiolytic action are currently under clinical development for generalized anxiety disorder, social anxiety disorder, panic disorder, obsessive-compulsive disorder, or post-traumatic stress disorder. Similarly, an interrelation of oxytocin with neuropeptide S or glutamate or vasopressin can also be considered for further evaluation for the development of new drugs for anxiety treatment. Anxiolytic drug development is a multi-target approach, with the idea of more efficiently equilibrating perturbed circuits. This review focuses on targeting unconventional targets like the glutamate system, voltage-gated ion channels, and neuropeptides system either alone or in combination for the treatment of anxiety disorder.

Neuropeptide S receptor gene Asn107 polymorphism in obese male individuals in Pakistan

Neuropeptide S (NPS) is a naturally occurring appetite stimulant, associated with anxiety, stress, and excitement regulation. Neuropeptide S serves as a hypothalamic energy regulator that enhances food intake with a reduced level of satiety. NPS activates fat angiogenesis and the proliferation of new adipocytes in obesity. NPS has an established role in energy regulation by many pre-clinical investigations; however we have limited data available to support this notion in humans. We found significant association of Neuropeptide S receptor (NPSR1) Asn107Ile (rs324981, A>T) polymorphism with obese male participants. The current investigation carried out genotype screening of NPSR1 allele to assess the spectrum of the Asn107Ile polymorphism in obese and healthy Pakistani individuals. We revealed a significant (p = 0.04) difference between AA vs TT + AT genotype distribution of NPSR1 (SNP rs324981,) between obese and healthy individuals (p = 0.04). In this genotype analysis of (SNP rs324981) of the NPSR1 gene, T allele was marked as risk allele with higher frequency in the obese (38%) compared to its frequency in the controls (25%). Single Nucleotide Polymorphism (SNP, rs324981) Asn107Ile of NPSR1gene, that switches an amino acid from Asn to Ile, has been found associated with increased susceptibility to obesity in Pakistani individuals. Furthermore, molecular simulation studies predicted a lower binding affinity of NPSR1 Asn107Ile variant to NPS than the wild-type consistent with the genotype studies. These molecular simulation studies predict a possible molecular mechanism of this interaction by defining the key amino acid residues. However, a significantly (p<0.0001) lower concentration of NPS was recorded independent of genotype frequencies in obese subjects compared to healthy controls. We believe that large scale polymorphism data of population for important gene players including NPSR1 will be more useful to understand obesity and its associated risk factors.

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.

Gene polymorphisms (rs324957, rs324981) in NPSR1 are associated with increased risk of primary insomnia: A cross-sectional study

Neuropeptide S and neuropeptide S receptor (NPSR1) are associated with sleep regulation. Herein, the possible contribution of 6 polymorphisms in NPSR1 on the chromosome to primary insomnia (PI) and objective sleep phenotypes was investigated.The study included 157 patients with PI and 133 age- and sex-matched controls. All subjects were investigated by polysomnography for 3 consecutive nights. The genotyping of 6 polymorphisms was carried out by polymerase chain reaction-restriction fragment length polymorphism method.A significant difference was detected for rs324957 and rs324981 between PI and controls. The PI patients had a higher frequency of AA than controls in rs324957 (P = .02) and rs324981 (P = .04). However, for other single nucleotide polymorphisms (rs323922, rs324377, rs324396, and rs324987), no significant differences were observed between PI patients and controls. There were 2 different allelic combinations that were associated with PI susceptibility (CATGTC, GCCAAT) and its risk factor. A significant difference in sleep latency was observed among 3 genotype carriers of NPSR1 gene polymorphism rs324957 in PI group (P = .04), with carriers of the A/A genotype having the longest sleep latency (mean ± SD: 114.80 ± 58.27), followed by the A/G genotype (112.77 ± 46.54) and the G/G genotype (92.12 ± 42.72).This study provided the evidence that the NPSR1 gene polymorphisms (rs324957, rs324981) might be susceptibility loci for PI. Further studies are needed to explore the role of NPSR1 gene polymorphisms in molecular mechanisms of PI in a larger sample size.

The effect of polymorphisms in startle-related genes on anxiety symptom severity

Given the limited effectiveness of treatments for pathological anxiety, there is a pressing need to identify genetic markers that can aid the precise selection of treatments and optimize treatment response. Anxiety and startle response levels demonstrate a direct relationship, and previous literature suggests that exaggerated startle reactivity may serve as an endophenotype of pathological anxiety. In addition, genetic variants related to startle reactivity may play a role in the etiology of pathological anxiety. In the current study, we selected 22 single nucleotide polymorphisms (SNPs) related to startle reactivity in the literature, and examined their association with anxiety symptom severity across psychiatric disorders (n = 508), and in a subset of patients with an anxiety disorder (n = 298). Overall, none of the SNPs pass correction for multiple independent tests. However, across psychiatric patients, rs6323 from the monoamine oxidase A (MAOA) gene and rs324981 from the neuropeptide S receptor 1 (NPSR1) gene were nominally associated with baseline anxiety symptom severity (p = 0.017, 0.023). These preliminary findings provide support for investigating startle-related genetic variants to identify biomarkers of anxiety symptom severity.

Amygdala, neuropeptides, and chronic pain-related affective behaviors

Neuropeptides play important modulatory roles throughout the nervous system, functioning as direct effectors or as interacting partners with other neuropeptide and neurotransmitter systems. Limbic brain areas involved in learning, memory and emotions are particularly rich in neuropeptides. This review will focus on the amygdala, a limbic region that plays a key role in emotional-affective behaviors and pain modulation. The amygdala is comprised of different nuclei; the basolateral (BLA) and central (CeA) nuclei and in between, the intercalated cells (ITC), have been linked to pain-related functions. A wide range of neuropeptides are found in the amygdala, particularly in the CeA, but this review will discuss those neuropeptides that have been explored for their role in pain modulation. Calcitonin gene-related peptide (CGRP) is a key peptide in the afferent nociceptive pathway from the parabrachial area and mediates excitatory drive of CeA neurons. CeA neurons containing corticotropin releasing factor (CRF) and/or somatostatin (SOM) are a source of long-range projections and serve major output functions, but CRF also acts locally to excite neurons in the CeA and BLA. Neuropeptide S (NPS) is associated with inhibitory ITC neurons that gate amygdala output. Oxytocin and vasopressin exert opposite (inhibitory and excitatory, respectively) effects on amygdala output. The opioid system of mu, delta and kappa receptors (MOR, DOR, KOR) and their peptide ligands (β-endorphin, enkephalin, dynorphin) have complex and partially opposing effects on amygdala function. Neuropeptides therefore serve as valuable targets to regulate amygdala function in pain conditions. This article is part of the special issue on Neuropeptides.

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.

The repertoire of family A-peptide GPCRs in archaic hominins

Given the importance of G-protein coupled receptors in the regulation of many physiological functions, deciphering the relationships between genotype and phenotype in past and present hominin GPCRs is of main interest to understand the evolutionary process that contributed to the present-day variability in human traits and health. Here, we carefully examined the publicly available genomic and protein sequence databases of the archaic hominins (Neanderthal and Denisova) to draw up the catalog of coding variations in GPCRs for peptide ligands, in comparison with living humans. We then searched in the literature the functional changes, phenotypes and risk of disease possibly associated with the detected variants. Our survey suggests that Neanderthal and Denisovan hominins were likely prone to lower risk of obesity, to enhanced platelet aggregation in response to thrombin, to better response to infection, to less anxiety and aggressiveness and to favorable sociability. While some archaic variants were likely advantageous in the past, they might be responsible for maladaptive disorders today in the context of modern life and/or specific regional distribution. For example, an archaic haplotype in the neuromedin receptor 2 is susceptible to confer risk of diabetic nephropathy in type 1 diabetes in present-day Europeans. Paying attention to the pharmacological properties of some of the archaic variants described in this study may be helpful to understand the variability of therapeutic efficacy between individuals or ethnic groups.

Association of NPSR1 gene variation and neural activity in patients with panic disorder and agoraphobia and healthy controls

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Higher amygdala activation in T risk allele carriers during the perception of agoraphobia-specific stimuli

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Amygdala activation correlated negatively trendwise with the trait neuroticism in healthy controls carrying A/A genotype

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A diagnosis x genotype interaction as a trend in the inferior orbitofrontal cortex during the perception of agoraphobia-specific stimuli

Introduction

The neurobiological mechanisms behind panic disorder with agoraphobia (PD/AG) are not completely explored. The functional A/T single nucleotide polymorphism (SNP) rs324981 in the neuropeptide S receptor gene (NPSR1) has repeatedly been associated with panic disorder and might partly drive function respectively dysfunction of the neural “fear network”. We aimed to investigate whether the NPSR1 T risk allele was associated with malfunctioning in a fronto-limbic network during the anticipation and perception of agoraphobia-specific stimuli.

Method

121 patients with PD/AG and 77 healthy controls (HC) underwent functional magnetic resonance imaging (fMRI) using the disorder specific “Westphal-Paradigm”. It consists of neutral and agoraphobia-specific pictures, half of the pictures were cued to induce anticipatory anxiety.

Results

Risk allele carriers showed significantly higher amygdala activation during the perception of agoraphobia-specific stimuli than A/A homozygotes. A linear group x genotype interaction during the perception of agoraphobia-specific stimuli showed a strong trend towards significance. Patients with the one or two T alleles displayed the highest and HC with the A/A genotype the lowest activation in the inferior orbitofrontal cortex (iOFC).

Discussion

The study demonstrates an association of the NPSR1rs324981 genotype and the perception of agoraphobia-specific stimuli. These results support the assumption of a fronto-limbic dysfunction as an intermediate phenotype of PD/AG.

Tinbergen's challenge for the neuroscience of behavior

Nobel laureate Nikolaas Tinbergen provided clear criteria for declaring a neuroscience problem solved, criteria which despite the passage of more than 50 years and vastly expanded neuroscience tool kits remain applicable today. Tinbergen said for neuroscientists to claim that a behavior is understood, they must correspondingly understand its (i) development and its (ii) mechanisms and its (iii) function and its (iv) evolution. Now, all four of these domains represent hotbeds of current experimental work, each using arrays of new techniques which overlap only partly. Thus, as new methodologies come online, from single-nerve-cell RNA sequencing, for example, to smart FISH, large-scale calcium imaging from cortex and deep brain structures, computational ethology, and so on, one person, however smart, cannot master everything. Our response to the likely “fracturing” of neuroscience recognizes the value of ever larger consortia. This response suggests new kinds of problems for (i) funding and (ii) the fair distribution of credit, especially for younger scientists.

Memory generalization after one-trial contextual fear conditioning: Effects of sex and neuropeptide S receptor deficiency

One-trial contextual fear conditioning in laboratory mice results in a fear memory which is relatively specific to the original conditioning context shortly after conditioning but becomes more unspecific after an incubation time of one month. This process is called generalization of fear memory and is used to investigate processes which might be involved in the pathogenesis of post-traumatic stress disorder. In the present study, we investigated the effects of sex and neuropeptide S receptor (NPSR) deficiency in one-trial contextual fear conditioning. In addition to contextual fear, we also measured startle reactivity, anxiety and corticosterone plasma levels of the mice. Our data show main effects of sex and NPSR-deficiency on freezing behavior, startle magnitude, and anxiety levels. However, generalization of contextual fear memory after incubation time was not affected by sex. Notably, NPSR-deficient mice had a more specific fear memory shortly after conditioning than their wildtype littermates but after incubation time, all genotypes had a generalized fear memory. The present data further show that plasma corticosterone levels are increased after incubation time. This increase was significantly more pronounced in NPSR-deficient mice. Taken together, our study confirms the suitability of one-trial contextual fear conditioning to study the effects of incubation time on fear memory generalization but also indicates the need for control groups without incubation. We further demonstrate that the increase of plasma corticosterone levels after incubation time is exaggerated in NPSR-deficient mice. The latter finding suggests an important role of the NPS system in the regulation of corticosterone release.

Cortico-limbic pain mechanisms

Pain has a strong emotional component and is defined by its unpleasantness. Chronic pain represents a complex disorder with anxio-depressive symptoms and cognitive deficits. Underlying mechanisms are still not well understood but an important role for interactions between prefrontal cortical areas and subcortical limbic structures has emerged. Evidence from preclinical studies in the rodent brain suggests that neuroplastic changes in prefrontal (anterior cingulate, prelimbic and infralimbic) cortical and subcortical (amygdala and nucleus accumbens) brain areas and their interactions (corticolimbic circuitry) contribute to the complexity and persistence of pain and may be predetermining factors as has been proposed in recent human neuroimaging studies.

Association of NPSR1 rs324981 polymorphism and treatment response to antidepressants in Chinese Han population with generalized anxiety disorder

In previous studies, neuropeptide S (NPS) and its cognate receptor (NPSR) have been involved in the pathogenesis of anxiety disorders in previous studies. Here, we aimed to investigate the association of NPSR1 polymorphism with generalized anxiety disorder (GAD) and its treatment response in Chinese Han population. Three hundred and thirty seven patients and one hundred and seventy seven healthy controls were involved in our study for 8 weeks. Further, Hamilton Anxiety Scale (HAMA) was used to assess anxiety symptom at baseline and the 1st, 2nd, 4th, 8th week. And all participants were genotyped for NPSR1 (rs324981) variants by polymerase chain reaction. Using Repeated-measures analysis, it showed significant reduction on HAMA scores in patients treated with escitalopram (F = 1.03, P = 0.362) and venlafaxine (F = 0.27, P = 0.763) respectively through 8 weeks treatment. Additionally, patients with AA and TT homozygous genotypes treated with venlafaxine XR had a higher reduction of HAMA scores compared to AT heterozygotic carriers (F = 4.18, P = 0.004), while no significant differences were found in patients treated with escitalopram (F = 1.05, P = 0.383). Thus, our study provides preliminary evidence that NPSR1 AA and TT homozygous genotypes have better treatment responses to venlafaxine XR in Chinese GAD patients, but not to escitalopram. Further studies are needed to verify the observation.

Associations Between Gene Polymorphisms and Psychological Stress in the Guangxi Minority Region of China

To investigate whether there is an association between gene polymorphisms, genetic and environmental interactions, and psychological stress reactivity in Chinese subjects living in the Guangxi minority region. This cross-sectional study enrolled subjects older than 18 years, living in Nandan county, Guangxi minority region, China for at least 1 year. All participants were healthy, without any mental diseases, and were able to communicate. Eligible participants were randomly selected. The Life Event Scale Questionnaire, Simplified Coping Style Questionnaire, and Social Support Rating Scale were used to measure the physiological stress, coping style, and social support, respectively, in individuals. A total of 600 participants were recruited. A decreased risk of psychological stress was only found in TT of NPSR1 (rs324981): A allele carriers vs. TT genotype (OR 1.64, 95% CI 1.11, 2.42), and AT genotype vs. TT genotype (OR 1.76, 95% CI 1.17, 2.65). The overall coping style was positively associated with psychological stress, and no significant interactions between genetics and environment were found. We found that the NPSR1 (rs324981) T/T genotype decreased the risk of psychological stress, while the overall coping style was a risk factor for psychological stress. However, there was no interactive effects of genes and environment on psychological stress. Our findings will improve understanding of the biological basis underlying psychological stress if the results can be replicated in further research.

Brain neuropeptide S: via GPCR activation to a powerful neuromodulator of socio-emotional behaviors

Neuropeptide S (NPS) has attracted the attention of the scientific community due to its potent anxiolytic-like and fear-attenuating effects studied in rodents. Therefore, NPS might represent a treatment option for neuropsychiatric disorders, such as anxiety disorders, even more so as single nucleotide polymorphisms in the human NPS receptor gene have been associated with increased anxiety traits that contribute to the pathogenesis of fear- and anxiety-related disorders. However, the signaling mechanisms underlying the behavioral effects of NPS and the interaction with other brain neuropeptides are still rather unknown. To illuminate how NPS modulates the expression of selected emotional and social behaviors, the present review focuses on neuroanatomical and electrophysiological studies, as well as intracellular signaling mechanisms following NPS receptor stimulation in rodents. We will also discuss interactions of the NPS system with two well-described neuropeptides, namely corticotropin-releasing factor and oxytocin, which may contribute to the fear- and anxiety-reducing effects.

Imaging neuropeptide effects on human brain function

The discovery of prosocial effects of oxytocin (OT) opened new directions for studying neuropeptide effects on the human brain. However, despite obvious effects of OT on neural responses as reported in numerous studies, other peptides have received less attention. Therefore, we will only briefly summarize evidence of OT effects on human functional magnetic resonance imaging (fMRI) and primarily focus on OT's sister neuropeptide arginine-vasopressin by presenting our own coordinated-based activation likelihood estimation meta-analysis. In addition, we will recapitulate rather limited data on few other neuropeptides, including pharmacological and genetic fMRI studies. Finally, we will review experiments with external neuropeptide administration to patients afflicted with mental disorders, such as autism or schizophrenia. In conclusion, despite remaining uncertainty regarding the penetrance of exogenous neuropeptides through the blood-brain barrier, it is evident that neuropeptides simultaneously influence the activity of limbic and cortical areas, indicating that these systems have a good potential for therapeutic drug development. Hence, this calls for further systematic studies of a wide spectrum of known and less known neuropeptides to understand their normal function in the brain and, subsequently, to tackle their potential contribution for pathophysiological mechanisms of mental disorders.

Novel transmitters in brain stem vagal neurocircuitry: new players on the pitch

The last few decades have seen a major increase in the number of neurotransmitters and neuropeptides recognized as playing a role in brain stem neurocircuits, including those involved in homeostatic functions such as stress responsiveness, gastrointestinal motility, feeding, and/or arousal/wakefulness. This minireview will focus on the known physiological role of three of these novel neuropeptides, i.e., apelin, nesfatin-1, and neuropeptide-S, with a special emphasis on their hypothetical roles in vagal signaling related to gastrointestinal motor functions.

Neurogenetic Approaches to Stress and Fear in Humans as Pathophysiological Mechanisms for Posttraumatic Stress Disorder

In this review article, genetic variation associated with brain responses related to acute and chronic stress reactivity and fear learning in humans is presented as an important mechanism underlying posttraumatic stress disorder. We report that genes related to the regulation of the hypothalamic-pituitary-adrenal axis, as well as genes that modulate serotonergic, dopaminergic, and neuropeptidergic functions or plasticity, play a role in this context. The strong overlap of the genetic targets involved in stress and fear learning suggests that a dimensional and mechanistic model of the development of posttraumatic stress disorder based on these constructs is promising. Genome-wide genetic analyses on fear and stress mechanisms are scarce. So far, reliable replication is still lacking for most of the molecular genetic findings, and the proportion of explained variance is rather small. Further analysis of neurogenetic stress and fear learning needs to integrate data from animal and human studies.

Investigating the relationship between plasma neuropeptide-S levels and clinical depression

PURPOSE

Neuropeptide-S (NPS) is a novel 20-amino acid peptide, mainly expressed in the central nervous system and endocrine tissues. NPS has been linked to anxiety and fear-related behaviors. The association of NPS with depression in a human population has not been previously examined. The aim of the current study was to explore the potential association of NPS with clinical depression and comorbid anxiety.

MATERIALS AND METHODS

Seventy-nine patients diagnosed with major depressive disorder and seventy-eight controls were included in the study. The Hamilton Depression Scale (HAM-D) and Hamilton Anxiety Scale (HAM-A) were used to measure depression and anxiety levels, respectively. Venous blood samples were obtained to measure plasma NPS levels.

RESULTS

There were no statistically significant differences between the patients and controls in terms of sex, marital status, and smoking status. Plasma NPS levels were also not significantly different between the patients and controls. In patients with major depressive disorder, HAM-A and HAM-D scores were significantly higher than those of controls. No correlation was found between plasma NPS levels and age, body mass index (BMI), median HAM-A scores, and median HAM-D scores.

CONCLUSIONS

Despite a significantly high level of comorbid anxiety among the patient group, we found no relationship between plasma NPS levels and depressive symptomatology.

Plasma Neuropeptide-S Levels in Populations Diagnosed with Generalized Anxiety Disorder: A Controlled Study

Introduction

Neuropeptide S (NPS) is a novel neuropeptide reported to be involved in fear-and stress-related conditions and their corresponding neuroendocrine processes. The aim of this study was to compare the plasma NPS levels in patients suffering from generalized anxiety disorder (GAD) and those of healthy controls.

Methods

A total of 40 subjects diagnosed with GAD and 40 healthy controls were recruited in the study. The Hamilton Anxiety Scale (HAM-A), Generalized Anxiety Disorder-7 (GAD-7), and Hamilton Depression Scale (HAM-D) were administered to all participants to determine the severity of participants' anxiety and concomitant depressive symptoms. The plasma NPS levels were measured from the fasting venous blood samples obtained from each participant.

Results

The median plasma NPS level was found to be significantly higher in the GAD group in comparison to the control group (28.8 pg/mL as against 19.1 pg/mL, p=0.01). A significant positive correlation was observed between the plasma NPS levels and HAM-A scores (rs=0.23, p=0.04) as well as the GAD-7 scores (rs=0.28, p=0.01). The p-value obtained from the correlation analysis between the plasma NPS levels and HAM-D scores was 0.052. A receiver operating characteristic (ROC) analysis revealed that the plasma NPS levels could enable the identification of GAD with 67.5% sensitivity and 62.5% specificity, when the cut-off value was determined as 25.06 pg/mL.

Conclusions

Our results support the view that plasma NPS levels, which has demonstrated anxiolytic effects on the central nervous system, is related to the severity of anxiety in GAD and could be considered as a candidate marker for the identification of GAD.

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 in the basolateral amygdala mediates an adaptive behavioral stress response in a rat model of posttraumatic stress disorder by increasing the expression of BDNF and the neuropeptide YY1 receptor

Neuropeptide S (NPS) is a regulatory peptide that has anxiolytic and arousal-promoting effects in rodents. We used an animal model of posttraumatic stress disorder (PTSD) to assess long-term behavioral effects of a single dose of NPS, microinjected into the basolateral amygdala (BLA) 1h following exposure to predator-scent stress (PSS). To elucidate the molecular mechanism by which NPS attenuates behavioral stress responses, expression levels of neuropeptide Y (NPY), NPY-Y1 receptor (NPY-Y1R), and brain-derived neurotrophic factor (BDNF) were evaluated in the hippocampus. The behavioral and molecular effects of NPS receptor antagonist (NPS-RA), NPY-Y1R antagonist (NPY-Y1RA), or both administered centrally were evaluated in the same manner. Circulating corticosterone levels were measured at different time points following PSS-exposure. Immediate post-exposure treatment with NPS had a marked protective effect; BLA microinfusion of NPS completely abolished the extreme behavioral response to PSS, restored the decreased expression of BDNF and, unexpectedly, PY-Y1R, but didn't affect the decreased expression of NPY. BLA microinfusion of both NPY-Y1RA and NPS-RA together had an additive effect, which completely prevented the anxiolytic effects of NPS in rats exposed to PSS and disrupted the expression of NPY-Y1R in the hippocampus following NPS infusion. It may therefore be hypothesized that NPS acts, directly or indirectly, on both the NPY-Y1R and NPS receptors and that the cross-talk between NPS and NPY-Y1R may be necessary for the anxiolytic effects of NPS post-exposure. The NPS system might thus contribute to a potential endogenous mechanism underlying the shift towards adaptive behavioral response and thereby might be relevant as a pharmacological target for attenuating stress-related sequelae.

Neuropeptide S Activates Paraventricular Oxytocin Neurons to Induce Anxiolysis

Neuropeptides, such as neuropeptide S (NPS) and oxytocin (OXT), represent potential options for the treatment of anxiety disorders due to their potent anxiolytic profile. In this study, we aimed to reveal the mechanisms underlying the behavioral action of NPS, and present a chain of evidence that the effects of NPS within the hypothalamic paraventricular nucleus (PVN) are mediated via actions on local OXT neurons in male Wistar rats. First, retrograde studies identified NPS fibers originating in the brainstem locus coeruleus, and projecting to the PVN. FACS identified prominent NPS receptor expression in PVN-OXT neurons. Using genetically encoded calcium indicators, we further demonstrated that NPS reliably induces a transient increase in intracellular Ca2+ concentration in a subpopulation of OXT neurons, an effect mediated by NPS receptor. In addition, intracerebroventricular (i.c.v.) NPS evoked a significant somatodendritic release of OXT within the PVN as assessed by microdialysis in combination with a highly sensitive radioimmunoassay. Finally, we could show that the anxiolytic effect of NPS seen after i.c.v. or intra-PVN infusion requires responsive OXT neurons of the PVN and locally released OXT. Thus, pharmacological blockade of OXT receptors as well as chemogenetic silencing of OXT neurons within the PVN prevented the effect of synthetic NPS. In conclusion, our results indicate a significant role of the OXT system in mediating the effects of NPS on anxiety, and fill an important gap in our understanding of brain neuropeptide interactions in the context of regulation of emotional behavior within the hypothalamus.SIGNIFICANCE STATEMENT Given the rising scientific interest in neuropeptide research in the context of emotional and stress-related behaviors, our findings demonstrate a novel intrahypothalamic mechanism involving paraventricular oxytocin neurons that express the neuropeptide S receptor. These neurons respond with transient Ca2+ increase and somatodendritic oxytocin release following neuropeptide S stimulation. Thereby, oxytocin neurons seem essential for neuropeptide S-induced anxiolysis, as this effect was blocked by pharmacological and chemogenetic inhibition of the oxytocin system.

Amygdala Plasticity and Pain

The amygdala is a limbic brain region that plays a key role in emotional processing, neuropsychiatric disorders, and the emotional-affective dimension of pain. Preclinical and clinical studies have identified amygdala hyperactivity as well as impairment of cortical control mechanisms in pain states. Hyperactivity of basolateral amygdala (BLA) neurons generates enhanced feedforward inhibition and deactivation of the medial prefrontal cortex (mPFC), resulting in pain-related cognitive deficits. The mPFC sends excitatory projections to GABAergic neurons in the intercalated cell mass (ITC) in the amygdala, which project to the laterocapsular division of the central nucleus of the amygdala (CeLC; output nucleus) and serve gating functions for amygdala output. Impairment of these cortical control mechanisms allows the development of amygdala pain plasticity. Mechanisms of abnormal amygdala activity in pain with particular focus on loss of cortical control mechanisms as well as new strategies to correct pain-related amygdala dysfunction will be discussed in the present review.

High diversity in neuropeptide immunoreactivity patterns among three closely related species of Dinophilidae (Annelida)

Neuropeptides are conserved metazoan signaling molecules, and represent useful markers for comparative investigations on the morphology and function of the nervous system. However, little is known about the variation of neuropeptide expression patterns across closely related species in invertebrate groups other than insects. In this study, we compare the immunoreactivity patterns of 14 neuropeptides in three closely related microscopic dinophilid annelids (Dinophilus gyrociliatus, D. taeniatus and Trilobodrilus axi). The brains of all three species were found to consist of around 700 somata, surrounding a central neuropil with 3-5 ventral and 2-5 dorsal commissures. Neuropeptide immunoreactivity was detected in the brain, the ventral cords, stomatogastric nervous system, and additional nerves. Different neuropeptides are expressed in specific, non-overlapping cells in the brain in all three species. FMRFamide, MLD/pedal peptide, allatotropin, RNamide, excitatory peptide, and FVRIamide showed a broad localization within the brain, while calcitonin, SIFamide, vasotocin, RGWamide, DLamide, FLamide, FVamide, MIP, and serotonin were present in fewer cells in demarcated regions. The different markers did not reveal ganglionic subdivisions or physical compartmentalization in any of these microscopic brains. The non-overlapping expression of different neuropeptides may indicate that the regionalization in these uniform, small brains is realized by individual cells, rather than cell clusters, representing an alternative to the lobular organization observed in several macroscopic annelids. Furthermore, despite the similar gross brain morphology, we found an unexpectedly high variation in the expression patterns of neuropeptides across species. This suggests that neuropeptide expression evolves faster than morphology, representing a possible mechanism for the evolutionary divergence of behaviors.

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 systems and new treatments for nicotine addiction

RATIONALE

The mildly euphoric and cognitive enhancing effects of nicotine play a role in the initiation of smoking, while dysphoria and anxiety associated with smoking cessation contribute to relapse. After the acute withdrawal phase, smoking cues, a few cigarettes (i.e., lapse), and stressors can cause relapse. Human and animal studies have shown that neuropeptides play a critical role in nicotine addiction.

OBJECTIVES

The goal of this paper is to describe the role of neuropeptide systems in the initiation of nicotine intake, nicotine withdrawal, and the reinstatement of extinguished nicotine seeking.

RESULTS

The reviewed studies indicate that several drugs that target neuropeptide systems diminish the rewarding effects of nicotine by preventing the activation of dopaminergic systems. Other peptide-based drugs diminish the hyperactivity of brain stress systems and diminish withdrawal-associated symptom severity. Blockade of hypocretin-1 and nociceptin receptors and stimulation of galanin and neurotensin receptors diminishes the rewarding effects of nicotine. Both corticotropin-releasing factor type 1 and kappa-opioid receptor antagonists diminish dysphoria and anxiety-like behavior associated with nicotine withdrawal and inhibit stress-induced reinstatement of nicotine seeking. Furthermore, blockade of vasopressin 1b receptors diminishes dysphoria during nicotine withdrawal, and melanocortin 4 receptor blockade prevents stress-induced reinstatement of nicotine seeking. The role of neuropeptide systems in nicotine-primed and cue-induced reinstatement is largely unexplored, but there is evidence for a role of hypocretin-1 receptors in cue-induced reinstatement of nicotine seeking.

CONCLUSION

Drugs that target neuropeptide systems might decrease the euphoric effects of smoking and improve relapse rates by diminishing withdrawal symptoms and improving stress resilience.

Neuropeptide S reduces duodenal bicarbonate secretion and ethanol-induced increases in duodenal motility in rats

Alcohol disrupts the intestinal mucosal barrier by inducing metabolic and functional changes in epithelial cells. Recently, we showed that neuropeptide S (NPS) decreases duodenal motility and increases mucosal paracellular permeability, suggesting a role of NPS in the pathogenesis of disorders and dysfunctions in the small intestine. The aim of the present study was to investigate the effects of NPS on ethanol- and HCl-induced changes of duodenal mucosal barrier function and motility. Rats were anaesthetized with thiobarbiturate, and a 30-mm segment of the proximal duodenum with an intact blood supply was perfused in situ. The effects on duodenal bicarbonate secretion, the blood-to-lumen clearance of 51Cr-EDTA, motility and transepithelial net fluid flux were investigated. Intravenous (i.v.) administration of NPS significantly reduced duodenal mucosal bicarbonate secretion and stimulated mucosal transepithelial fluid absorption, mechanisms dependent on nitrergic signaling. NPS dose-dependently reduced ethanol-induced increases in duodenal motility. NPS (83 pmol·kg-1·min-1, i.v.) reduced the bicarbonate and fluid secretory response to luminal ethanol, whereas a 10-fold higher dose stimulated fluid secretion but did not influence bicarbonate secretion. In NPS-treated animals, duodenal perfusion of acid (pH 3) induced greater bicarbonate secretory rates than in controls. Pre-treating animals with Nω-nitro-L-arginine methyl ester (L-NAME) inhibited the effect of NPS on bicarbonate secretion. In response to luminal acid, NPS-treated animals had significantly higher paracellular permeability compared to controls, an effect that was abolished by L-NAME. Our findings demonstrate that NPS reduces basal and ethanol-induced increases in duodenal motility. In addition, NPS increases luminal alkalinization and mucosal permeability in response to luminal acid via mechanisms that are dependent on nitric oxide signaling. The data support a role for NPS in neurohumoral regulation of duodenal mucosal barrier function and motility.