The paraventricular nucleus of the hypothalamus is a neuroanatomical substrate for the inhibition of palatable food intake by neuropeptide S

Pathophysiological and therapeutic implications of neuropeptide S system in neurological disorders

Neuropeptide S (NPS) is a 20 amino acids-containing neuroactive molecule discovered by the reverse pharmacology method. NPS is detected in specific brain regions like the brainstem, amygdala, and hypothalamus, while its receptor (NPSR) is ubiquitously expressed in the central nervous system (CNS). Besides CNS, NPS and NPSR are also expressed in the peripheral nervous system. NPSR is a G-protein coupled receptor that primarily uses Gq and Gs signaling pathways to mediate the actions of NPS. In animal models of Parkinsonism and Alzheimer's disease, NPS exerts neuroprotective effects. NPS suppresses oxidative stress, anxiety, food intake, and pain, and promotes arousal. NPSR facilitates reward, reinforcement, and addiction-related behaviors. Genetic variation and single nucleotide polymorphism in NPSR are associated with depression, schizophrenia, rheumatoid arthritis, and asthma. NPS interacts with several neurotransmitters including glutamate, noradrenaline, serotonin, corticotropin-releasing factor, and gamma-aminobutyric acid. It also modulates the immune system via augmenting pro-inflammatory cytokines and plays an important role in the pathogenesis of rheumatoid arthritis and asthma. In the present review, we discussed the distribution profile of NPS and NPSR, signaling pathways, and their importance in the pathophysiology of various neurological disorders. We have also proposed the areas where further investigations on the NPS system are warranted.

Neuropeptide S promotes maintenance of newly formed dendritic spines and performance improvement after motor learning in mice

Neuropeptide S (NPS), an endogenous neuropeptide consisting of 20 amino acids, selectively binds and activates G protein-coupled receptor named neuropeptide S receptor (NPSR) to regulate a variety of physiological functions. NPS/NPSR system has been shown to play a pivotal role in regulating learning and memory in rodents. However, it remains unclear that how NPS/NPSR system affects neuronal functions and synaptic plasticity after learning. We found that intracerebroventricular (i.c.v.) injection of NPS promoted performance improvement and reduced sleep duration after motor learning, which could be blocked by pre-treatment with intraperitoneal (i.p.) injection of NPSR antagonist SHA 68. Using intravital two-photon imaging, we examined the effect of NPS on the postsynaptic dendritic spines of layer V pyramidal neurons in the mouse primary motor cortex after motor learning. We found that i.c.v. injection of NPS strengthened learning-induce new spines and facilitated their survival over time. Furthermore, i.c.v. injection of NPS increased calcium activity of apical dendrites and dendritic spines of layer V pyramidal neurons in the mouse primary motor cortex during the running period. These findings suggest that activation of NPSR by NPS increases synaptic calcium activity and learning-related synapse maintenance, thereby contributing to performance improvement after motor learning.

A Role for Neuropeptide S in Alcohol and Cocaine Seeking

The neuropeptide S (NPS) is the endogenous ligand of the NPS receptor (NPSR). The NPSR is widely expressed in brain regions that process emotional and affective behavior. NPS possesses a unique physio-pharmacological profile, being anxiolytic and promoting arousal at the same time. Intracerebroventricular NPS decreased alcohol consumption in alcohol-preferring rats with no effect in non-preferring control animals. This outcome is most probably linked to the anxiolytic properties of NPS, since alcohol preference is often associated with high levels of basal anxiety and intense stress-reactivity. In addition, NPSR mRNA was overexpressed during ethanol withdrawal and the anxiolytic-like effects of NPS were increased in rodents with a history of alcohol dependence. In line with these preclinical findings, a polymorphism of the NPSR gene was associated with anxiety traits contributing to alcohol use disorders in humans. NPS also potentiated the reinstatement of cocaine and ethanol seeking induced by drug-paired environmental stimuli and the blockade of NPSR reduced reinstatement of cocaine-seeking. Altogether, the work conducted so far indicates the NPS/NPSR system as a potential target to develop new treatments for alcohol and cocaine abuse. An NPSR agonist would be indicated to help individuals to quit alcohol consumption and to alleviate withdrawal syndrome, while NPSR antagonists would be indicated to prevent relapse to alcohol- and cocaine-seeking behavior.

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.

Identification of a Novel Neuropeptide S Receptor Antagonist Scaffold Based on the SHA-68 Core

Activation of the neuropeptide S receptor (NPSR) system has been shown to produce anxiolytic-like actions, arousal, and enhance memory consolidation, whereas blockade of the NPSR has been shown to reduce relapse to substances of abuse and duration of anesthetics. We report here the discovery of a novel core scaffold (+) N-benzyl-3-(2-methylpropyl)-1-oxo-3-phenyl-1H,3H,4H,5H,6H,7H-furo[3,4-c]pyridine-5-carboxamide with potent NPSR antagonist activity in vitro. Pharmacokinetic parameters demonstrate that 14b reaches pharmacologically relevant levels in plasma and the brain following intraperitoneal (i.p.) administration, but is cleared rapidly from plasma. Compound 14b was able to block NPS (0.3 nmol)-stimulated locomotor activity in C57/Bl6 mice at 3 mg/kg (i.p.), indicating potent in vivo activity for the structural class. This suggests that 14b can serve as a useful tool for continued mapping of the pharmacological functions of the NPS receptor system.

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.

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.

The hypothalamic mechanism of neuropeptide S-induced satiety in Japanese quail (Coturnix japonica) involves the paraventricular nucleus and corticotropin-releasing factor

Neuropeptide S (NPS), a 20-amino acid neuropeptide, is produced in the brain and is associated with appetite suppression.Our group was the first to report this anorexigenic effect in birds using chicken as a model, although a hypothalamic molecular mechanism remains to be elucidated. Thus, we designed the present study using Japanese quail(Coturnix japonica).In Experiment 1, quail intracerebroventricularly injected with NPS reduced both food and water intake. In Experiment 2, food-restricted quail injected with NPS displayed a reduction in water intake.In Experiment 3, NPS-injected quail reduced their feeding and exploratory pecks.In Experiment 4, we quantified the number of cells expressing the early intermediate gene product c-Fos (as a marker of neuronal activation) in appetite associated hypothalamic nuclei and found that immunoreactivity was increased in the paraventricular nucleus (PVN). In Experiment 5, we utilized real-time PCR to screen for neuropeptide changes within the PVN of NPS-injected quail. Mesotocin and corticotropin-releasing factor (CRF) mRNAs increased in response to NPS injection. In Experiment 6, co-injection of astressin, a CRF receptor antagonist, was sufficient to block the food intake-suppressive effects of NPS, but in Experiment 7, co-injection of an oxytocin receptor antagonist was not sufficient to block the food intake-suppressive effects of NPS. Collectively, results support that NPS induces an anorexigenic response in Japanese quail that is mediated within the PVN and is associated with CRF.

Physiology, pharmacology, and pathophysiology of neuropeptide S receptor

Neuropeptide S receptor 1 (NPSR1), originally named G protein-coupled receptor 154 (GPR154), was deorphanized in 2002 with neuropeptide S identified as the endogenous ligand. NPSR1 is primarily expressed in bronchus, brain as well as immune cells. It regulates multiple physiological processes, including immunoregulation, locomotor activity, anxiety, arousal, learning and memory, and food intake and energy balance. SNPs of NPSR1 are significantly associated with several diseases, including asthma, anxiolytic and arousal disorders, and rheumatoid arthritis. This chapter will summarize studies on NPSR1, including its molecular structure, tissue distribution, physiology, pharmacology, and pathophysiology.

Hypothalamic CRF1 receptor mechanisms are not sufficient to account for binge-like palatable food consumption in female rats

OBJECTIVE

The present study evaluated the effect of systemic injection of the CRF1 receptor antagonist R121919, the corticosterone synthesis inhibitor metyrapone and central amygdala (CeA) injections of the nonselective CRF antagonist D-Phe-CRF_(12-41) in rats in which binge eating was evoked by stress and cycles of food restriction.

METHOD

Female rats were subjected or not to repeated cycles of regular chow food restriction/ad libitum feeding during which they were also given limited access (2 h) to palatable food. On the test day, rats were either exposed or not to the sight of the palatable food for 15 min without allowing access, before assessing food consumption.

RESULTS

Systemic injections of R121919, but not of the metyrapone, blocked binge-like eating behavior. Restricted and stressed rats showed up-regulation of crh1 receptor mRNA signal in the bed nucleus of the stria terminalis and CeA but not in basolateral amygdala (BLA) or in the paraventricular nucleus. Injection D-Phe-CRF_(12-41) in CeA but not in the BLA-blocked binge-like eating behavior.

DISCUSSION

These findings demonstrate that extra-hypothalamic CRF1 receptors, rather than those involved in endocrine functions, are involved in binge eating and the crucial role of CRF receptors in CeA. CRF1 receptor antagonism may represent a novel pharmacological treatment for binge-related eating disorders.

Neuropeptide S increases motor activity and thermogenesis in the rat through sympathetic activation

The central role of neuropeptide S (NPS), identified as the endogenous ligand for GPR154, now named neuropeptide S receptor (NPSR), has not yet been fully clarified. We examined the central role of NPS for body temperature, energy expenditure, locomotor activity and adrenal hormone secretion in rats. Intracerebroventricular (icv) injection of NPS increased body temperature in a dose-dependent manner. Energy consumption and locomotor activity were also significantly increased by icv injection of NPS. In addition, icv injection of NPS increased the peripheral blood concentration of adrenalin and corticosterone. Pretreatment with the β1- and β2-adrenergic receptor blocker timolol inhibited the NPS-induced increase of body temperature. The expression of both NPS mRNA in the brainstem and NPSR mRNA in the hypothalamus showed a nocturnal rhythm with a peak occurring during the first half of the dark period. To examine whether the endogenous NPS is involved in regulation of body temperature, NPSR antagonist SHA68 was administered one hour after darkness. SHA68 attenuated the nocturnal rise of body temperature. These results suggest that NPS contributes to the regulation of the sympathetic nervous system.

Suckling induced activation pattern in the brain of rat pups

OBJECTIVES

The aim of the study was to understand the effects of suckling on the brain of the pups by mapping their brain activation pattern in response to suckling.

METHODS

The c-fos method was applied to identify activated neurons. Fasted rat pups were returned to their mothers for suckling and sacrificed 2 hours later for Fos immunohistochemistry. Double labeling was also performed to characterize some of the activated neurons. For comparison, another group of fasted pups were given dry food before Fos mapping.

RESULTS

After suckling, we found an increase in the number of Fos-immunoreactive neurons in the insular and somatosensory cortices, central amygdaloid nucleus (CAm), paraventricular (PVN) and supraoptic hypothalamic nuclei, lateral parabrachial nucleus (LPB), nucleus of the solitary tract (NTS), and the area postrema. Double labeling experiments demonstrated the activation of calcitonin gene-related peptide-ir (CGRP-ir) neurons in the LPB, corticotropin-releasing hormone-ir (CRH-ir) but not oxytocin-ir neurons in the PVN, and noradrenergic neurons in the NTS. In the CAm, Fos-ir neurons did not contain CRH but were apposed to CGRP-ir fiber terminals. Refeeding with dry food-induced Fos activation in all brain areas activated by suckling. The degree of activation was higher following dry food consumption than suckling in the insular cortex, and lower in the supraoptic nucleus and the NTS. Furthermore, the accumbens, arcuate, and dorsomedial hypothalamic nuclei, and the lateral hypothalamic area, which were not activated by suckling, showed activation by dry food.

DISCUSSION

Neurons in a number of brain areas are activated during suckling, and may participate in the signaling of satiety, taste perception, reward, food, and salt balance regulation.

Epigenetic-Imprinting Changes Caused by Neonatal Fasting Stress Protect From Future Fasting Stress

Unfavourable nutritional conditions during the neonatal critical period can cause both acute metabolic disorders and severe metabolic syndromes in later life. These phenomena have been tightly related to the epigenetic modification controlling the balance between satiety and hunger in the hypothalamus. In the present study, we investigated epigenetic modification associated with both the fasting stress effects and the short-term resilience to fasting stress in the hypothalamic paraventricular nucleus (PVN) of chicks. Fasting for 24 h at 3 days of age (D) (i.e. D3) significantly increased global methylation at lysine 27 of histone 3 (H3K27) and its specific histone methyltransferase (HMT) expression level in the PVN. Because global methylation could not fully reveal the changes at specific genes, the regulation of the gene for brain-derived neurotrophic factor (Bdnf), which was recently also found to have an anorexigenic effect, was evaluated as a potential target. Chromatin immunoprecipitation assay analysis revealed that tri- (me3) and di-methylated (me2) H3K27 exhibited an instant (on D4 only) and latent increase (on both D11 and D41), respectively, at the putative promoter of Bdnf after 24 h of fasting on D3. This indicated that fasting could regulate energy-expenditure-related genes via modifying methylation at H3K27, which we suspected might be a protective mechanism for keeping the inner environment homeostatic. To test this hypothesis, a short-term repetitive fasting stress was applied to chickens, which were fasted for 24 h either on D10 only or on both D3 and D10. It was found that pre-existing fasting on D3 could induce a short-term fasting resilience, which rescued the reduction of Bdnf expression from future fasting on D10. We call this phenomenon the ‘molecular memory’, which was mainly conducted by HMTs and H3K27me2/me3 in the PVN. In conclusion, chicks respond to fasting with dynamic methylation at H3K27 in the PVN during the neonatal critical period. This allows the PVN to form a ‘molecular memory’, which keeps the individual inner environment homeostatic and resilient to future fasting over the short term.

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.

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.

Morphine dependence is associated with changes in neuropeptide S receptor expression and function in rat brain

Neuropeptide S (NPS) is a newly identified ligand for the previously discovered G-protein coupled receptor 154 now named NPSR. Recently, it has been found that NPSR gene expression is altered during ethanol withdrawal. In this study we tried to elucidate if NPSR gene expression is modified in response to morphine withdrawal and its protracted abstinence. To induce opioid dependence Wistar rats were treated for 7 days with morphine. Twelve hours and 7 days after the last morphine administration brains were removed and the expression of NPSR mRNA was analyzed by in situ hybridization (ISH). Successful induction of opioid dependence was confirmed by the naloxone-precipitated withdrawal test 2 h after the last morphine administration. Moreover, 7 days after the last morphine dose animals were checked for signs of anxiety and for intracerebroventricular (ICV) NPS (0.3 and 1.0 nmol) induced anxiolytic effects by elevated plus maze (EPM). Results showed that in morphine treated rats strong somatic signs of naloxone-precipitated withdrawal occurred. ISH data revealed changes in NPSR gene expression in the ventral tegmental area as well as in the basolateral amygdaloid and bed nucleus of stria terminalis at 12 h and 7 days into abstinence, respectively. At 7 days into abstinence post dependent animals showed higher levels of anxiety than controls which were significantly attenuated by NPS. These results demonstrated that morphine dependence induction led to (i) changes in NPSR mRNA expression; (ii) increased anxiety; and (iii) more potent anxiolytic-like effect of NPS.

Neuropeptide S facilitates mice olfactory function through activation of cognate receptor-expressing neurons in the olfactory cortex

Neuropeptide S (NPS) is a newly identified neuromodulator located in the brainstem and regulates various biological functions by selectively activating the NPS receptors (NPSR). High level expression of NPSR mRNA in the olfactory cortex suggests that NPS-NPSR system might be involved in the regulation of olfactory function. The present study was undertaken to investigate the effects of intracerebroventricular (i.c.v.) injection of NPS or co-injection of NPSR antagonist on the olfactory behaviors, food intake, and c-Fos expression in olfactory cortex in mice. In addition, dual-immunofluorescence was employed to identify NPS-induced Fos immunereactive (-ir) neurons that also bear NPSR. NPS (0.1–1 nmol) i.c.v. injection significantly reduced the latency to find the buried food, and increased olfactory differentiation of different odors and the total sniffing time spent in olfactory habituation/dishabituation tasks. NPS facilitated olfactory ability most at the dose of 0.5 nmol, which could be blocked by co-injection of 40 nmol NPSR antagonist [D-Val⁵]NPS. NPS administration dose-dependently inhibited food intake in fasted mice. Ex-vivo c-Fos and NPSR immunohistochemistry in the olfactory cortex revealed that, as compared with vehicle-treated mice, NPS markedly enhanced c-Fos expression in the anterior olfactory nucleus (AON), piriform cortex (Pir), ventral tenia tecta (VTT), the anterior cortical amygdaloid nucleus (ACo) and lateral entorhinal cortex (LEnt). The percentage of Fos-ir neurons that also express NPSR were 88.5% and 98.1% in the AON and Pir, respectively. The present findings demonstrated that NPS, via selective activation of the neurons bearing NPSR in the olfactory cortex, facilitates olfactory function in mice.

Hypothalamic neuropeptide S receptor blockade decreases discriminative cue-induced reinstatement of cocaine seeking in the rat

RATIONALE

Previous studies have shown that activation of brain neuropeptide S receptor (NPSR) facilitates reinstatement of cocaine seeking elicited by environmental cues predictive of drug availability. This finding suggests the possibility that blockade of NPSR receptors may be of therapeutic benefit in cocaine addiction. To evaluate this hypothesis, we investigated the effect of two newly synthetized NPSR antagonists, namely the quinolinone-amide derivative NPSR-QA1 and the NPS peptidic analogue [D-Cys(tBu)⁵]NPS on cocaine self-administration and on discriminative cue-induced relapse to cocaine seeking in the rat.

METHODS

Separate groups of rats self-administered food and cocaine 0.25 mg/kg/inf in FR1 and FR5 (fixed ratio reinforcement schedules) for 30-min and 2-h sessions per day. After food and cocaine intake reached baseline levels, the effect of NPSR-QA1 was tested on cocaine and food self-administration. The NPSR-QA1 was injected intraperitoneally and its effect on discriminative cue-induced reinstatement was evaluated, while [D-Cys(tBut)⁵]NPS was injected intracranially, intra-lateral hypothalamus, intra-perifornical area of the hypothalamus, and intra-central amygdala. The effect of the NPSR-QA1 on extinction of cocaine seeking was also assessed.

RESULTS

Intraperitoneal administration of NPSR-QA1 (15-30 mg/kg) did not affect cocaine self-administration. Conversely, NPSR-QA1 (15-30 mg/kg) decreased discriminative cue-induced cocaine relapse. At the lowest dose, this effect was specific, while at the highest dose, NPSR-QA1 also reduced food self-administration. The efficacy of NPSR antagonism on cocaine seeking was confirmed with [D-Cys(tBu)⁵]NPS (10-30 nmol/rat) as it markedly inhibited relapse behavior following site-specific injection into the lateral hypothalamus and the perifornical area of the hypothalamus but not into the central amygdala.

CONCLUSIONS

The identification of the NPS/NPSR system as an important new element involved in the physiopathology of cocaine addiction and the discovery of the anti-addictive properties of NPSR antagonists opens the possibility of exploring a new mechanism for cocaine addiction treatment.

Neuropeptide S stimulates human monocyte chemotaxis via NPS receptor activation

Neuropeptide S (NPS) produces several biological actions by activating a formerly orphan GPCR, now named NPS receptor (NPSR). It has been previously demonstrated that NPS stimulates murine leukocyte chemotaxis in vitro. In the present study we investigated the ability of NPS, in comparison with the proinflammatory peptide formyl-Met-Leu-Phe (fMLP), to stimulate human monocyte chemotaxis. At a concentration of 10(-8)M fMLP significantly stimulated chemotaxis. NPS produced a concentration dependent chemotactic action over the concentration range 10(-12) to 10(-5)M. The NPSR antagonists [D-Cys((t)Bu)(5)]NPS, [(t)Bu-D-Gly(5)]NPS and SHA 68 were used to pharmacologically characterize NPS action. Monocyte chemoattractant effect of NPS, but not fMLP, was completely blocked by either peptide antagonists or SHA with the nonpeptide molecule being more potent. None of the NPSR antagonists modified per se random cell migration. Thus, the present study demonstrated that NPS is able to stimulate human monocyte chemotaxis and that this effect is entirely due to selective NPSR activation.

The role of the neuropeptide S system in addiction: focus on its interaction with the CRF and hypocretin/orexin neurotransmission

Recent behavioral, pharmacological and molecular findings have linked the NPS system to drug dependence. Most of the evidence supports the possibility that increased NPS activity may contribute to shaping vulnerability to addiction, especially relapse. However, data suggesting that the anxiolytic-like properties of NPS may have protective effects on addiction have been also published. In addition, evidence from conditioned place preference experiments, though not unequivocal, suggests that NPS per se is devoid of motivational properties. Intriguingly, several effects of NPS on drugs of abuse appear to be mediated by downstream activation of brain corticotrophin releasing factor (CRF) and hypocretin-1/orexin-A (Hcrt-1/Ox-A) systems. The major objective of the present article is to review the existing work on NPS and addiction. Particular attention is devoted to the interpretation of findings revealing complex neuroanatomical and functional interactions between NPS, CRF, and the Hcrt-1/Ox-A systems. Original data aimed at shedding light on the role of NPS in reward processing are also shown. Finally, existing findings are discussed within the framework of addiction theories, and the potential of the NPS system as a treatment target for addiction is analyzed.

Effects of neuropeptide S on seizures and oxidative damage induced by pentylenetetrazole in mice

Neuropeptide S (NPS) and its receptor were recently discovered in the central nervous system. In rodents, NPS promotes hyperlocomotion, wakefulness, anxiolysis, anorexia, and analgesia and enhances memory when injected intracerebroventricularly (i.c.v.). Herein, NPS at different doses (0.01, 0.1 and 1nmol) was i.c.v. administered in mice challenged with pentylenetetrazole (PTZ; 60mg/kg) repeatedly injected. Aiming to assess behavioral alterations and oxidative damage to macromolecules in the brain, NPS was injected 5min prior to the last dose of PTZ. The administration of NPS only at 1nmol increased the duration of seizures evoked by PTZ, without modifying frequency and latency of seizures. Biochemical analysis revealed that NPS attenuated PTZ-induced oxidative damage to proteins and lipids in the hippocampus and cerebral cortex. In contrast, the administration of NPS to PTZ-treated mice increased DNA damage in the hippocampus, but not cerebral cortex. In conclusion, this is the first evidence of the potential proconvulsive effects of NPS in mice. The protective effects of NPS against lipid and protein oxidative damage in the mouse hippocampus and cerebral cortex evoked by PTZ-induced seizures are quite unexpected. The present findings were discussed analyzing the paradoxical effects of NPS: facilitation of convulsive behavior and protection against oxidative damage to lipids and proteins.

Hyperthyroidism differentially regulates neuropeptide S system in the rat brain

Thyroid hormones play an important role in the regulation of energy balance, sleep and emotional behaviors. Neuropeptide S (NPS) is a recently discovered neuropeptide, regulating feeding, sleep and anxiety. Here, we examined the effect of hyperthyroidism on the gene and protein expression of neuropeptide S and its receptor (NPS-R) in the hypothalamus, brainstem and amygdala of rats. Our results showed that the expression of NPS and NPS-R was differentially modulated by hyperthyroidism in the rat brain. NPS and NPS-R mRNA and protein levels were decreased in the hypothalamus of hyperthyroid rats. Conversely NPS-R expression was highly increased in the brainstem and NPS and NPS-R expression were unchanged in the amygdala of these rats. These data suggest that changes in anxiety and food intake patterns observed in hyperthyroidism could be associated with changes in the expression of NPS and NPS-R. Thus, the NPS/NPS-R system may be involved in several hyperthyroidism-associated comorbidities.

Corticotropin-releasing factor in the nucleus accumbens shell induces swim depression, anxiety, and anhedonia along with changes in local dopamine/acetylcholine balance

The nucleus accumbens shell (NAcS) has been implicated in controlling stress responses through corticotropin-releasing factor (CRF). In addition to studies indicating that CRF in the NAcS increases appetitive motivation, there is indirect evidence suggesting that NAcS CRF may also cause aversive responses and that these behaviors may be mediated through local dopamine (DA) and acetylcholine (ACh) systems. To provide a direct test of this hypothesis, we used male Sprague-Dawley rats with implanted cannulas aimed at the NAcS. Experiment 1 showed local CRF injection (10 or 50 ng/side) to increase immobility in the forced swim test and a CRF antagonist D-Phe-CRF ((12-41)) to attenuate this depressive-like behavior. In Experiment 2, injection of CRF (250 ng/side) also decreased the rats' preference for sucrose, while in Experiment 3, CRF (50 or 250 ng/side) induced anxiety-like behaviors in an elevated plus maze and open field. These same doses of CRF in Experiment 4 failed to alter the rats' locomotor activity, indicating that these behavioral changes were not caused by deficits in activity. In Experiment 5, results from in vivo microdialysis revealed that CRF in the NAcS markedly increased local extracellular ACh, while also producing a small increase in DA. These results show that NAcS CRF can generate a variety of aversive behaviors, including swim depression, anhedonia, and anxiety, in addition to approach behavior. They suggest that these behaviors may occur, in part, through enhanced activation of ACh and DA in the NAcS, respectively, supporting a role for this brain area in mediating the dual effects of stress.

G protein-coupled receptors in the hypothalamic paraventricular and supraoptic nuclei--serpentine gateways to neuroendocrine homeostasis

G protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors in the mammalian genome. They are activated by a multitude of different ligands that elicit rapid intracellular responses to regulate cell function. Unsurprisingly, a large proportion of therapeutic agents target these receptors. The paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus are important mediators in homeostatic control. Many modulators of PVN/SON activity, including neurotransmitters and hormones act via GPCRs--in fact over 100 non-chemosensory GPCRs have been detected in either the PVN or SON. This review provides a comprehensive summary of the expression of GPCRs within the PVN/SON, including data from recent transcriptomic studies that potentially expand the repertoire of GPCRs that may have functional roles in these hypothalamic nuclei. We also present some aspects of the regulation and known roles of GPCRs in PVN/SON, which are likely complemented by the activity of 'orphan' GPCRs.

Molecular fingerprint of neuropeptide S-producing neurons in the mouse brain

Neuropeptide S (NPS) has been associated with a number of complex brain functions, including anxiety-like behaviors, arousal, sleep-wakefulness regulation, drug-seeking behaviors, and learning and memory. In order to better understand how NPS influences these functions in a neuronal network context, it is critical to identify transmitter systems that control NPS release and transmitters that are co-released with NPS. For this purpose, we generated several lines of transgenic mice that express enhanced green-fluorescent protein (EGFP) under control of the endogenous NPS precursor promoter. NPS/EGFP-transgenic mice show anatomically correct and overlapping expression of both NPS and EGFP. A total number of ∼500 NPS/EGFP-positive neurons are present in the mouse brain, located in the pericoerulear region and the Kölliker-Fuse nucleus. NPS and transgene expression is first detectable around E14, indicating a potential role for NPS in brain development. EGFP-positive cells were harvested by laser-capture microdissection, and mRNA was extracted for expression profiling by using microarray analysis. NPS was found co-localized with galanin in the Kölliker-Fuse nucleus of the lateral parabrachial area. A dense network of orexin/hypocretin neuronal projections contacting pericoerulear NPS-producing neurons was observed by immunostaining. Expression of a distinct repertoire of metabotropic and ionotropic receptor genes was identified in both NPS neuronal clusters that will allow for detailed investigations of incoming neurotransmission, controlling neuronal activity of NPS-producing neurons. Stress-induced functional activation of NPS-producing neurons was detected by staining for the immediate-early gene c-fos, thus supporting earlier findings that NPS might be part of the brain stress response network.

Anatomical characterization of the neuropeptide S system in the mouse brain by in situ hybridization and immunohistochemistry

Neuropeptide S (NPS) is the endogenous ligand for GPR154, now referred to as neuropeptide S receptor (NPSR). Physiologically, NPS has been characterized as a modulator of arousal and has been shown to produce anxiolytic-like effects in rodents. Neuroanatomical analysis in the rat revealed that the NPS precursor mRNA is strongly expressed in the brainstem in only three distinct regions: the locus coeruleus area, the principal sensory trigeminal nucleus, and the lateral parabrachial nucleus. NPSR mRNA expression in the rat is widely distributed, with the strongest expression in the olfactory nuclei, amygdala, subiculum, and some cortical structures, as well as various thalamic and hypothalamic regions. Here we report a comprehensive map of NPS precursor and receptor mRNA expression in the mouse brain. NPS precursor mRNA is only expressed in two regions in the mouse brainstem: the Kölliker-Fuse nucleus and the pericoerulear area. Strong NPSR mRNA expression was found in the dorsal endopiriform nucleus, the intra-midline thalamic and hypothalamic regions, the basolateral amgydala, the subiculum, and various cortical regions. In order to elucidate projections from NPS-producing nuclei in the brainstem to NPSR-expressing structures throughout the brain, we performed immunohistochemical analysis in the mouse brain by using two polyclonal anti-NPS antisera. The distribution of NPS-immunopositive fibers overlaps well with NPSR mRNA expression in thalamic and hypothalamic regions. Mismatches between NPSR expression and NPS-immunoreactive fiber staining were observed in hippocampal, olfactory, and cortical regions. These data demonstrate that the distribution pattern of the central NPS system is only partially conserved between mice and rats.

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.

The effects of neuropeptide S on general anesthesia in rats

BACKGROUND

Neuropeptide S (NPS) and its receptor (NPSR) is a novel neuropeptide system that regulates arousal and anxiety. A link between natural sleep and general anesthesia has been suggested. Therefore, we hypothesized that the NPS neuronal system may also modulate general anesthesia.

METHODS

The effects of intracerebroventricular NPS and [D-Cys(tBu)(5)]NPS, a peptide NPSR antagonist, on ketamine and thiopental anesthesia time were measured in rats. Anesthesia time was defined as the interval between the loss of righting reflex and its recovery.

RESULTS

Intracerebroventricular NPS 1 to 30 nmol significantly reduced ketamine anesthesia time, showing a bell-shaped dose-response curve. [D-Cys(tBu)(5)]NPS 20 nmol antagonized NPS 1 nmol effects and was per se able to increase ketamine anesthesia time. Similar results were obtained investigating thiopental anesthesia time that was significantly reduced by NPS and prolonged by [D-Cys(tBu)(5)]NPS.

CONCLUSION

NPS via selective NPSR activation stimulates the wakefulness-promoting pathway, thus reducing anesthesia duration. The endogenous NPS/NPSR system seems to tonically control these pathways.

Effect of neuropeptide S receptor antagonists and partial agonists on palatable food consumption in the rat

Neuropeptide S (NPS) is the endogenous ligand for the previously orphan G-protein-coupled-receptor, now termed NPS receptor (NPSR). NPS has both anxiolytic and pro-arousal properties and decreases food intake. In this work we use a rat model of palatable food intake to test in vivo different analogs of human NPS developed in our laboratories and characterized in previous in vitro experiments as partial agonists ([Ala(3)]NPS and [Aib(5)]NPS), or antagonists ([D-Cys((t)Bu)(5)]NPS and [(t)Bu-D-Gly(5)]NPS). Our results confirmed that intracerebroventricular (ICV) injection of NPS (1 nmol) decreases standard chow intake in food restricted rats as well as in freely feeding animals fed with standard or palatable food diets. [Aib(5)]NPS (30 and 60 nmol), like NPS, reduced palatable food intake, thus confirming in vivo its ability to activate NPSR. [Ala(3)]NPS (60 nmol) did not affect palatable food intake per se but blocked the anorectic effect of NPS, thus suggesting its ability to function as an antagonist in this model. Finally, [D-Cys((t)Bu)(5)]NPS (20-60 nmol) and [(t)Bu-D-Gly(5)]NPS (10-30 nmol), described in previous in vitro studies as pure NPSR antagonists, did not affect palatable food intake when given alone, but fully blocked the anorectic effect of NPS. These results provide an important characterization of the pharmacological properties of these NPS analogs in vivo. Of particular relevance are the data showing that [D-Cys((t)Bu)(5)]NPS and [(t)Bu-D-Gly(5)]NPS behave as pure antagonists at NPSR regulating food intake, indicating that these molecules are suitable tools for further investigation of the physiopharmacology of the NPS/NPSR system.

Central Neuropeptide S inhibits food intake in mice through activation of Neuropeptide S receptor

Neuropeptide S (NPS), the endogenous ligand of NPS receptor (NPSR), can regulate a variety of biological functions, including arousal, anxiety, locomotion, memory and drug abuse. Previous studies have shown that central NPS inhibited food intake in rats and chicks. In the present study, we investigated the role of central NPS on food intake in fasted mice, and detected the underlying mechanism(s) by using NPSR antagonist [D-Val(5)]NPS and Corticotropin-Releasing Factor 1 (CRF₁) Receptor antagonist NBI-27914. The present results indicated that intracerebroventricular injection of NPS (0.001-0.1 nmol) dose-dependently inhibited food intake in fasted mice. The anorectic effect of NPS reached the maximum at the dose of 0.1 nmol, which could be antagonized by co-injection of 10 nmol NPSR antagonist [D-Val(5)]NPS. Furthermore, CRF₁ receptor antagonist NBI-27914 at the dose of 2 μg antagonized the hyperlocomotor action of NPS, but did not affect the role of NPS on food intake. In conclusion, our results demonstrated central NPS inhibited food intake in fasted mice, mediated by its cognate NPSR, but not by CRF₁ receptor.

Neuropeptide S facilitates cue-induced relapse to cocaine seeking through activation of the hypothalamic hypocretin system

Drug addiction is a chronic relapsing disorder characterized by compulsive drug seeking and use. Environmental conditioning factors are among the major determinants of relapse in abstinent cocaine users. Here we describe a role of the neuropeptide S (NPS) system in regulating relapse. In rats with a history of cocaine self-administration, presentation of stimuli predictive of drug availability reinstates drug seeking, triggering relapse. Intracerebroventricular (ICV) injection of NPS increased conditioned reinstatement of cocaine seeking, whereas peripheral administration of the NPS receptor antagonist SHA 68 reduced it. Manipulation of the NPS receptor system did not modify cocaine self-administration. We also found that ICV NPS administration activates c-Fos expression in hypocretin-1/orexin-A (Hcrt-1/Ox-A) immunoreactive neurons in the lateral hypothalamus (LH) and in the perifornical area (PeF). Of note, intra-LH and intra-PeF administration of NPS increased conditioned reinstatement of cocaine responding, an effect that was selectively blocked with the Hcrt-1/Ox-A receptor selective antagonist SB334867. Finally, results showed that intra-LH injection of the NPS antagonist [D-Cys(tBu) (5)]NPS blocked cue-induced cocaine seeking, indicating a role for this system in the pathophysiology of drug relapse.

Immunohistochemical localization of the neuropeptide S receptor in the rat central nervous system

The neuropeptide S receptor (NPSR) is a G-protein coupled receptor that is potently activated by the linear 20 amino acid peptide, neuropeptide S (NPS). Central administration of NPS promotes arousal and anxiolytic-like effects in rodents, and fails to promote such effects in NPSR knockout animals or in the presence of NPSR-selective antagonists. In situ hybridization (ISH) studies in rat brain have revealed that the mRNAs encoding the NPS precursor and the NPS receptor are expressed at high levels in discrete regions of the rat CNS. The distribution of the NPSR protein in brain has not been reported due to a lack of available antibodies. We have generated and validated a NPSR-specific antibody and used it to determine the distribution of the NPSR in male Sprague-Dawley (SD) rat brain. The anti-NPSR antibody identified a single protein by Western blot with an estimated molecular weight of 65 kD, which was prevented by pre-incubation of the antibody with the immunizing peptide. The protein distribution identified with this antibody in rat brain was consistent both with the mRNA distribution identified by in situ hybridization, and to the localization pattern identified by a second NPSR-specific antibody against a distinct NPSR epitope. NPSR protein was identified in the medial amygdala (MeA), substantia nigra pars compacta, subiculum, dorsal raphe, and several hypothalamic and thalamic regions. Additionally, NPSR protein was localized in the pyramidal cell layer of the ventral hippocampus, the medial habenula (MHb), and was widely distributed in the cortex. The distribution of NPSR protein provides further insight into the organization of the NPS system and may guide future studies on the role of the NPSR in brain.

Microinjection of neuropeptide S into the rat ventral tegmental area induces hyperactivity and increases extracellular levels of dopamine metabolites in the nucleus accumbens shell

The newly identified neuropeptide S (NPS) is mainly expressed in a group of neurons located between the locus coeruleus and Barrington's nucleus in the brainstem. Central administration of NPS increases motor activity and wakefulness, and it decreases anxiety-like behavior and feeding. The NPS receptor (NPSR) is widely distributed in various brain regions including the ventral tegmental area (VTA). The mesolimbic dopaminergic system originates in the VTA, and activation of the system produces hypermotor activity. Therefore, we hypothesized that NPS-induced hypermotor activity might be mediated by activation of the mesolimbic dopaminergic pathway via the NPSR expressed in the VTA. Intra-VTA injection of NPS significantly and dose-dependently increased horizontal and vertical motor activity in rats, and the hyperactivity was significantly and dose-dependently inhibited by pre-administration of sulpiride, a DA D(2)-like receptor antagonist, into the shell of the nucleus accumbens (NAcSh). Intra-VTA injection of NPS also significantly increased extracellular 3,4-dihydroxy-phenyl acetic acid and homovanillic acid levels in the NAcSh of freely moving rats. These results support the idea that NPS activates the mesolimbic dopaminergic system presumably via the NPSR located in the VTA, thereby stimulating motor activity.

Further studies on the pharmacological profile of the neuropeptide S receptor antagonist SHA 68

Neuropeptide S (NPS) regulates various biological functions by selectively activating the NPS receptor (NPSR). Previous studies demonstrated that the non-peptide molecule SHA 68 acts as a selective NPSR antagonist. In the present study the pharmacological profile of SHA 68 has been further investigated in vitro and in vivo. In cells expressing the mouse NPSR SHA 68 was inactive per se up to 10microM while it antagonized NPS-stimulated calcium mobilization in a competitive manner showing a pA(2) value of 8.06. In the 10-50mg/kg range of doses, SHA 68 counteracted the stimulant effects elicited by NPS, but not those of caffeine, in mouse locomotor activity experiments. In the mouse righting reflex assay SHA 68 fully prevented the arousal-promoting action of the peptide. The anxiolytic-like effects of NPS were slightly reduced by SHA 68 in the mouse open field, fully prevented in the rat elevated plus maze and partially antagonized in the rat defensive burying paradigm. Finally, SHA 68 was found poorly active in antagonizing the NPS inhibitory effect on palatable food intake in rats. In all assays SHA 68 did not produce any effect per se. In conclusion, the present study demonstrated that SHA 68 behaves as a selective NPSR antagonist that can be used to characterize the in vivo actions of NPS. However the usefulness of this research tool is limited by its poor pharmacokinetic properties.