In vitro and in vivo pharmacological characterization of the neuropeptide s receptor antagonist [D-Cys(tBu)5]neuropeptide S

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.

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.

Pharmacology, Physiology and Genetics of the Neuropeptide S System

The Neuropeptide S (NPS) system is a rather ‘young’ transmitter system that was discovered and functionally described less than 20 years ago. This review highlights the progress that has been made in elucidating its pharmacology, anatomical distribution, and functional involvement in a variety of physiological effects, including behavior and immune functions. Early on, genetic variations of the human NPS receptor (NPSR1) have attracted attention and we summarize current hypotheses of genetic linkage with disease and human behaviors. Finally, we review the therapeutic potential of future drugs modulating NPS signaling. This review serves as an introduction to the broad collection of original research papers and reviews from experts in the field that are presented in this Special Issue.

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.

Pharmacological profile of the neuropeptide S receptor: Dynamic mass redistribution studies

Neuropeptide S (NPS) is the endogenous ligand of the neuropeptide S receptor (NPSR). NPS modulates several biological functions including anxiety, wakefulness, pain, and drug abuse. The aim of this study was the investigation of the pharmacological profile of NPSR using the dynamic mass redistribution (DMR) assay. DMR is a label-free assay that offers a holistic view of cellular responses after receptor activation. HEK293 cells stably transfected with the murine NPSR (HEK293mNPSR) have been used. To investigate the nature of the NPS-evoked DMR signaling, FR900359 (Gq inhibitor), pertussis toxin (Gi inhibitor), and rolipram (phosphodiesterase inhibitor) were used. To determine the pharmacology of NPSR, several selective ligands (agonists, partial agonists, antagonists) have been tested. NPS, through selective NPSR activation, evoked a robust DMR signal with potency in the nanomolar range. This signal was predominantly, but not completely, blocked by FR900359, suggesting the involvement of the Gq-dependent signaling cascade. NPSR ligands (agonists and antagonists) displayed potency values in DMR experiments similar, but not identical, to those reported in the literature. Furthermore, partial agonists produced a higher efficacy in DMR than in calcium experiments. DMR can be successfully used to study the pharmacology and signaling properties of novel NPSR ligands. This innovative approach will likely increase the translational value of in vitro pharmacological studies.

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.

Neuropeptide S Induces Acute Anxiolysis by Phospholipase C-Dependent Signaling within the Medial Amygdala

Neuropeptide S (NPS) is an important anxiolytic substance of the brain. However, the signaling pathways downstream of NPS receptor (NPSR) activation, underlying the behavioral effect of NPS, remain largely unknown. Here, we show that bilateral microinfusion of NPS (0.2 nmol/0.5 μl) into the medial amygdala (MeA) of male adult Wistar rats reduced anxiety-related behavior on both the elevated plus-maze and the open field. Moreover, as shown in amygdala tissue micropunches intracerebroventricular infusion of NPS (1 nmol/5 μl) (1) evoked phosphorylation and synthesis of CaMKIIα in relation to reference protein β-tubulin representing Ca²⁺ influx, and (2) induced phosphorylation of mitogen-activated protein kinase ERK1/2. The NPS-induced anxiolysis was prevented by local inhibition of phospholipase C signaling using U73122 (0.5 nmol/0.5 μl) in the MeA, indicating the behavioral relevance of this pathway. Conversely, local pharmacological blockade of adenylyl cyclase signaling using 2',5'-dideoxyadenosine (12.5 nmol/0.5 μl) failed to inhibit the anxiolytic effect of NPS infused into the MeA. Hence, NPS promotes acute anxiolysis within the MeA dependent on NPSR-mediated phospholipase C signaling. Taken together, our study extends the knowledge about the intracellular signaling mechanisms underlying the potent anxiolytic profile of NPS.

Characterization of NGFFYamide Signaling in Starfish Reveals Roles in Regulation of Feeding Behavior and Locomotory Systems

Neuropeptides in deuterostomian invertebrates that have an Asn-Gly motif (NG peptides) have been identified as orthologs of vertebrate neuropeptide-S (NPS)-type peptides and protostomian crustacean cardioactive peptide (CCAP)-type neuropeptides. To obtain new insights into the physiological roles of NG peptides in deuterostomian invertebrates, here we have characterized the NG peptide signaling system in an echinoderm-the starfish Asterias rubens. The neuropeptide NGFFYamide was identified as the ligand for an A. rubens NPS/CCAP-type receptor, providing further confirmation that NG peptides are orthologs of NPS/CCAP-type neuropeptides. Using mRNA in situ hybridization, cells expressing the NGFFYamide precursor transcript were revealed in the radial nerve cords, circumoral nerve ring, coelomic epithelium, apical muscle, body wall, stomach, and tube feet of A. rubens, indicating that NGFFYamide may have a variety of physiological roles in starfish. One of the most remarkable aspects of starfish biology is their feeding behavior, where the stomach is everted out of the mouth over the soft tissue of prey. Previously, we reported that NGFFYamide triggers retraction of the everted stomach in A. rubens and here we show that in vivo injection of NGFFYamide causes a significant delay in the onset of feeding on prey. To investigate roles in regulating other aspects of starfish physiology, we examined the in vitro effects of NGFFYamide and found that it causes relaxation of acetylcholine-contracted apical muscle preparations and induction of tonic and phasic contraction of tube feet. Furthermore, analysis of the effects of in vivo injection of NGFFYamide on starfish locomotor activity revealed that it causes a significant reduction in mean velocity and distance traveled. Interestingly, experimental studies on mammals have revealed that NPS is an anxiolytic that suppresses appetite and induces hyperactivity in mammals. Our characterization of the actions of NGFFYamide in starfish indicates that NPS/NG peptide/CCAP-type signaling is an evolutionarily ancient regulator of feeding and locomotion.

Neuropeptide S overcomes short term memory deficit induced by sleep restriction by increasing prefrontal cortex activity

Sleep restriction (SR) impairs short term memory (STM) that might be related to different processes. Neuropeptide S (NPS), an endogenous neuropeptide that improves short term memory, activates arousal and decreases anxiety is likely to counteract the SR-induced impairment of STM. The objective of the present study was to find common cerebral pathways in sleep restriction and NPS action in order to ultimately antagonize SR effect on memory. The STM was assessed using a spontaneous spatial alternation task in a T-maze. C57-Bl/6J male mice were distributed in 4 groups according to treatment (0.1nmol of NPS or vehicle intracerebroventricular injection) and to 20h-SR. Immediately after behavioural testing, regional c-fos immunohistochemistry was performed and used as a neural activation marker for spatial short term memory (prefrontal cortex, dorsal hippocampus) and emotional reactivity (basolateral amygdala and ventral hippocampus). Anxiety-like behaviour was assessed using elevated-plus maze task. Results showed that SR impaired short term memory performance and decreased neuronal activation in cingular cortex.NPS injection overcame SR-induced STM deficits and increased neuronal activation in infralimbic cortex. SR spared anxiety-like behavior in the elevated-plus maze. Neural activation in basolateral nucleus of amygdala and ventral hippocampus were not changed after SR.In conclusion, the present study shows that NPS overcomes SR-induced STM deficits by increasing prefrontal cortex activation independently of anxiety-like behaviour.

Neuropeptide S reduces propofol- or ketamine-induced slow wave states through activation of cognate receptors in the rat

Intracerebroventricular injection of NPS reduces the duration of the ketamine- or thiopental-induced loss of the righting reflex in rats. But the specific EEG activities are unknown. We therefore sought to examine the effects of the NPS-NPSR system on anesthetic-induced characteristics of EEG power spectra and sleep-wake profiles. NPS alone or together with an NPSR antagonist was injected intracerebroventricularly, whereas the propofol (50mg/kg) or ketamine (100mg/kg) was administrated intraperitoneally. NPS (1 or 2nmol) significantly reduced the amount of propofol-induced EEG delta activity and slow wave states (SWS). NPS (1 or 5nmol) significantly reduced the amount of ketamine-induced SWS and EEG delta activity. Cortical EEG power spectral analysis showed that, in saline-pretreated rats, propofol induced a marked increase in delta (0.5-4Hz) activity, decrease in theta (4.5-8.5Hz) activity, and decrease in high frequency activity (14.5-60Hz), while, in rats pretreated with 1nmol of NPS, the duration of delta activity was reduced, while its spectral pattern was not changed. Whereas injection of ketamine into saline-pretreated rats induced a marked increase in delta (0.5-4Hz) activity, a moderate increase in theta (4.5-8.5Hz) activity, and a marked decrease in high frequency (14.5-60Hz) activity. However, delta activity was reduced while theta activity increased under pretreatment with 1nmol of NPS. The inhibitory effect of NPS on anesthetic-induced SWS was characterized by a reduced SWS episode duration with no significant change in either episode number or latency to SWS. [D-Val⁵]NPS, an NPSR antagonist (20nmol), significantly attenuated the arousal-promoting effect of 1nmol of NPS, but had no effect on SWS when injected alone. We speculate that NPS significantly reduces anesthetic-induced SWS and EEG slow activity by selective activation of the NPSR, which, in turn, would trigger subsequent arousal pathways.

Neuropeptide S Increases locomotion activity through corticotropin-releasing factor receptor 1 in substantia nigra of mice

Neuropeptide S (NPS), the endogenous ligand of NPS receptor (NPSR), was reported to be involved in the regulation of arousal, anxiety, locomotion, learning and memory. The basal ganglia play a crucial role in regulating of locomotion-related behavior. Here, we found that NPSR protein of mouse was distributed in the substantia nigra (SN) and globus pallidus (LGP) by immunohistochemical analysis. However, less is known about the direct locomotion-related effects of NPS in both SN and LGP. Therefore, we investigated the role of NPS in locomotion processes, using the open field test. The results showed that NPS infused into the SN (0.03, 0.1, 1nmol) or LGP (0.01, 0.03, 0.1nmol) dose-dependently increased the locomotor activity in mice. SHA 68 (50mg/kg), an antagonist of NPSR, blocked the locomotor stimulant effect of NPS in both nuleus. Meanwhile, these effects of NPS were also counteracted by the CRF1 receptor antagonist antalarmin (30mg/kg, i.p.). In addition, we found that the expression of c-Fos was significantly increased after NPS was delivered into SN. In conclusion, these results indicate that NPS-NPSR system may regulate locomotion together with the CRF1 system in SN.

In vitro and in vivo pharmacological characterization of a neuropeptide S tetrabranched derivative

The peptide welding technology (PWT) is a novel chemical strategy that allows the synthesis of multibranched peptides with high yield, purity, and reproducibility. With this approach, a tetrabranched derivative of neuropeptide S (NPS) has been synthesized and pharmacologically characterized. The in vitro activity of PWT1-NPS has been studied in a calcium mobilization assay. In vivo, PWT1-NPS has been investigated in the locomotor activity (LA) and recovery of the righting reflex (RR) tests. In calcium mobilization studies, PWT1-NPS behaved as full agonist at the mouse NPS receptor (NPSR) being threefold more potent than NPS. The selective NPSR antagonists [ (t) Bu-D-Gly(5)]NPS and SHA 68 displayed similar potency values against NPS and PWT1-NPS. In vivo, both NPS (1-100 pmol, i.c.v.) and PWT1-NPS (0.1-100 pmol, i.c.v.) stimulated mouse LA, with PWT1-NPS showing higher potency than NPS. In the RR assay, NPS (100 pmol, i.c.v.) was able to reduce the percentage of mice losing the RR after diazepam administration and their sleep time 5 min after the i.c.v. injection, but it was totally inactive 2 h after the injection. On the contrary, PWT1-NPS (30 pmol, i.c.v.), injected 2 h before diazepam, displayed wake-promoting effects. This PWT1-NPS stimulant effect was no longer evident in mice lacking the NPSR receptor. The PWT1 technology can be successfully applied to the NPS sequence. PWT1-NPS displayed in vitro a pharmacological profile similar to NPS. In vivo PWT1-NPS mimicked NPS effects showing higher potency and long-lasting action.

Evolutionary history of the neuropeptide S receptor/neuropeptide S system

The neuropeptide S receptor (NPSR) belongs to the G protein-coupled receptor (GPCR) superfamily and is activated by the neuropeptide S (NPS). Although recently discovered, the vertebrate NPSR-NPS system has been established as an important signaling system in the central nervous system and is involved in physiological processes such as locomotor activity, wakefulness, asthma pathogenesis, anxiety and food intake. The availability of a large number of genome sequences from multiple bilaterian lineages has provided an opportunity to establish the evolutionary history of the system. This review describes the origin and the molecular evolution of the NPSR-NPS system using data derived primarily from comparative genomic analyses. These analyses indicate that the NPSR-NPS system and the vasopressin-like receptor-vasopressin/oxytocin peptide (VPR-VP/OT) system originated from a single system in an ancestral bilaterian. Multiple duplications of this ancestral system gave rise to the bilaterian VPR-VP/OT system and to the protostomian cardioacceleratory peptide receptor-cardioacceleratory peptide (CCAPR-CCAP) system and to the NPSR-NPS system in the deuterostomes. Gene structure features of the receptors were consistent with the orthology annotations derived from phylogenetic analyses. The orthology of the peptide precursors closely paralleled that of the receptors suggesting an ancient coevolution of the receptor-peptide pair. An important challenge for the coevolution hypothesis will be to establish the molecular and structural basis of the divergence between orthologous receptor-ligand pairs in this system.

Paradoxical response to the sedative effects of diazepam and alcohol in C57BL/6J mice lacking the neuropeptide S receptor

The neuropeptide S (NPS) system is characterized by a unique pharmacology because it has anxiolytic-like effects and promotes arousal and wakefulness. To shed light on this peptidergic system, we tested the sedative effect of the central depressants diazepam and ethanol on the loss of righting reflex in mice lacking the neuropeptide S receptor (NPSR), NPSR(-/-). Furthermore, we tested the effect of the intracerebroventricular (ICV) administration of NPS on the sedative effect of diazepam and ethanol in NPSR(-/-) and their wild type counterpart NPSR(+/+). Finally, we evaluated the effect of the pro-arousal neuropeptides CRF and Hcrt-1/Ox-A in NPSR-deficient mice. Contrary to our expectations, the results showed that the NPSR(-/-) were less sensitive to the hypnotic effects of both diazepam and ethanol compared with their wild type littermates. ICV NPS was able to attenuate the sedative effect of both alcohol and diazepam in wild type mice, but not in the NPSR(-/-) line. The administration of CRF and Hcrt-1/Ox-A, two classic pro-arousal peptides, elicited the same effects in both NPSR(-/-) and wild type mice, ruling out the possibility that adaptive mechanisms occurring at the level of these two systems could have occurred during NPSR(-/-) development to compensate for the lack of NPSR receptors. Our findings demonstrated that the deletion of NPSR leads to minor changes in the arousal behavior of mice. Moreover, we demonstrated that the deletion of NPSR did not lead to compensatory changes in the vigilance-promoting effects of the CRF and Hcrt-1/Ox-A systems.

Endogenous neuropeptide S tone influences sleep-wake rhythm in rats

Neuropeptide S (NPS) is an endogenous peptide that exerts wakefulness promoting, analgesic, and anxiolytic effects when administered exogenously. However, it remains to be determined if endogenous NPS tone is involved in the control of the diurnal sleep-wake cycle, or spontanous behavior. In this study, we examined the effects of the NPS receptor antagonist [D-Cys((t)Bu)(5)]NPS (2 and 20 nmol, icv) on physiological sleep and spontaneous locomotor behavior. The higher dose of [D-Cys((t)Bu)(5)]NPS decreased the amount of time spent in wakefulness [control 782.5 ± 25.5 min, treatment 751.7 ± 28.1 min; p<0.05] and increased the time spent in NREMS [control 572.6 ± 17.2 min, treatment 600.2 ± 26.1 min; p<0.05]. There was no statistically significant difference in time spent in REMS. There were no behavioral changes including abnormal gross motor behavior in response to [D-Cys((t)Bu)(5)]NPS administration. Collectively these data suggest an involvement of the endogenous NPS/NPS receptor system in physiological sleep architecture.

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

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

In vitro and in vivo pharmacological characterization of the novel neuropeptide S receptor ligands QA1 and PI1

The pharmacological activity of the novel neuropeptide S (NPS) receptor (NPSR) ligands QA1 and PI1 was investigated. In vitro QA1 and PI1 were tested in calcium mobilization studies performed in HEK293 cells expressing the recombinant mouse (HEK293mNPSR) and human (HEK293hNPSRIle107 and HEK293hNPSRAsn107) NPSR receptors. In vivo the compounds were studied in mouse righting reflex (RR) and locomotor activity (LA) tests. NPS caused a concentration dependent mobilization of intracellular calcium in the three cell lines with high potency (pEC50 8.73-9.14). In inhibition response curve and Schild protocol experiments the effects of NPS were antagonized by QA1 and PI1. QA1 displayed high potency (pKB 9.60-9.82) behaving as a insurmountable antagonist. However in coinjection experiments QA1 produced a rightward swift of the concentration response curve to NPS without modifying its maximal effects; this suggests that QA1 is actually a slow dissociating competitive antagonist. PI1 displayed a competitive type of antagonism and lower values of potencies (pA2 7.74-8.45). In vivo in mice NPS (0.1 nmol, i.c.v.) elicited arousal promoting action in the RR assay and stimulant effects in the LA test. QA1 (30 mgkg(-1)) was able to partially counteract the arousal promoting NPS effects, while PI1 was inactive in the RR test. In the LA test QA1 and PI1 only poorly blocked the NPS stimulant action. The present data demonstrated that QA1 and PI1 act as potent NPSR antagonists in vitro, however their usefulness for in vivo investigations in mice seems limited probably by pharmacokinetic reasons.

Neuropeptide S: a novel regulator of pain-related amygdala plasticity and behaviors

Amygdala plasticity is an important contributor to the emotional-affective dimension of pain. Recently discovered neuropeptide S (NPS) has anxiolytic properties through actions in the amygdala. Behavioral data also suggest antinociceptive effects of centrally acting NPS, but site and mechanism of action remain to be determined. This is the first electrophysiological analysis of pain-related NPS effects in the brain. We combined whole cell patch-clamp recordings in brain slices and behavioral assays to test the hypothesis that NPS activates synaptic inhibition of amygdala output to suppress pain behavior in an arthritis pain model. Recordings of neurons in the laterocapsular division of the central nucleus (CeLC), which serves pain-related amygdala output functions, show that NPS inhibited the enhanced excitatory drive [monosynaptic excitatory postsynaptic currents (EPSCs)] from the basolateral amygdala (BLA) in the pain state. As shown by miniature EPSC analysis, the inhibitory effect of NPS did not involve direct postsynaptic action on CeLC neurons but rather a presynaptic, action potential-dependent network mechanism. Indeed, NPS increased external capsule (EC)-driven synaptic inhibition of CeLC neurons through PKA-dependent facilitatory postsynaptic action on a cluster of inhibitory intercalated (ITC) cells. NPS had no effect on BLA neurons. High-frequency stimulation (HFS) of excitatory EC inputs to ITC cells also inhibited synaptic activation of CeLC neurons, providing further evidence that ITC activation can control amygdala output. The cellular mechanisms by which EC-driven synaptic inhibition controls CeLC output remain to be determined. Administration of NPS into ITC, but not CeLC, also inhibited vocalizations and anxiety-like behavior in arthritic rats. A selective NPS receptor antagonist ([d-Cys(tBu)(5)]NPS) blocked electrophysiological and behavioral effects of NPS. Thus NPS is a novel tool to control amygdala output and pain-related affective behaviors through a direct action on inhibitory ITC cells.

A novel brain penetrant NPS receptor antagonist, NCGC00185684, blocks alcohol-induced ERK-phosphorylation in the central amygdala and decreases operant alcohol self-administration in rats

The Neuropeptide S receptor, a Gs/Gq-coupled GPCR expressed in brain regions involved in mediating drug reward, has recently emerged as a candidate therapeutic target in addictive disorders. Here, we describe the in vitro and in vivo pharmacology of a novel, selective and brain penetrant NPSR antagonist with nanomolar affinity for the NPSR, NCGC00185684. In vitro, NCGC00185684 shows biased antagonist properties, and preferentially blocks ERK-phosphorylation over intracellular cAMP or calcium responses to NPS. In vivo, systemic NCGC00185684 blocks alcohol-induced ERK-phosphorylation in the rat central amygdala, a region involved in regulation of alcohol intake. NCGC00185684 also decreases operant alcohol self-administration, and lowers motivation for alcohol reward as measured using progressive ratio responding. These effects are behaviorally specific, in that they are observed at doses that do not influence locomotor activity or reinstatement responding following extinction. Together, these data provide an initial validation of the NPSR as a therapeutic target in alcoholism.

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.

Anxiolytic- and panicolytic-like effects of Neuropeptide S in the mouse elevated T-maze

Neuropeptide S (NPS) regulates various biological functions by selectively activating the NPS receptor (NPSR). Recently, epidemiological studies revealed an association between NPSR single nucleotide polymorphisms and susceptibility to panic disorders. Here we investigated the effects of NPS in mice subjected to the elevated T maze (ETM), an assay which has been proposed to model anxiety and panic. Diazepam [1 mg/kg, intraperitoneally (i.p.)] elicited clear anxiolytic effects reducing the latency to emerge from the closed to the open (CO) arm without modifying the latencies from the open to the closed (OC) arm. By contrast, chronic fluoxetine (10 mg/kg i.p., once a day for 21 days) selectively increased OC latency, suggesting a panicolytic-like effect. NPS given intracerebroventricularly at 0.001-1 nmol elicited both anxiolytic- and panicolytic-like effects. However, although the NPS anxiolytic dose-response curve displayed the classical sigmoidal shape, the dose-response curve of the putative panicolytic-like effect was bell shaped with peak effect at 0.01 nmol. The behaviour of wild-type [NPSR(+/+)] and receptor knock out [NPSR(-/-)] mice in the ETM task was superimposable. NPS at 0.01 nmol elicited anxiolytic- and panicolytic-like effects in NPSR(+/+) but not in NPSR(-/-) mice. In conclusion, this study demonstrated that NPS, via selective activation of the NPSR, promotes both anxiolytic- and panicolytic-like actions in the mouse ETM.

Intranasally administered neuropeptide S (NPS) exerts anxiolytic effects following internalization into NPS receptor-expressing neurons

Experiments in rodents revealed neuropeptide S (NPS) to constitute a potential novel treatment option for anxiety diseases such as panic and post-traumatic stress disorder. However, both its cerebral target sites and the molecular underpinnings of NPS-mediated effects still remain elusive. By administration of fluorophore-conjugated NPS, we pinpointed NPS target neurons in distinct regions throughout the entire brain. We demonstrated their functional relevance in the hippocampus. In the CA1 region, NPS modulates synaptic transmission and plasticity. NPS is taken up into NPS receptor-expressing neurons by internalization of the receptor-ligand complex as we confirmed by subsequent cell culture studies. Furthermore, we tracked internalization of intranasally applied NPS at the single-neuron level and additionally demonstrate that it is delivered into the mouse brain without losing its anxiolytic properties. Finally, we show that NPS differentially modulates the expression of proteins of the glutamatergic system involved inter alia in synaptic plasticity. These results not only enlighten the path of NPS in the brain, but also establish a non-invasive method for NPS administration in mice, thus strongly encouraging translation into a novel therapeutic approach for pathological anxiety in humans.

[tBu-D-Gly5]NPS, a pure and potent antagonist of the neuropeptide S receptor: in vitro and in vivo studies

Neuropeptide S (NPS) regulates various biological functions by selectively activating the NPS receptor (NPSR). Recently, the NPSR ligand [(t)Bu-D-Gly(5)]NPS was generated and in vitro characterized as a pure antagonist at the mouse NPSR. In the present study the pharmacological profile of [(t)Bu-D-Gly(5)]NPS has been investigated. [(t)Bu-D-Gly(5)]NPS activity was evaluated in vitro in the calcium mobilization assay at the rat NPSR and in vivo in the locomotor activity and righting reflex tests in mice and in the elevated plus maze and defensive burying assays in rats. In vitro, [(t)Bu-D-Gly(5)]NPS was inactive per se while it inhibited the calcium mobilization induced by 30 nM NPS (pK(B) 7.42). In Schild analysis experiments [(t)Bu-D-Gly(5)]NPS (0.1-10 μM) produced a concentration-dependent rightward shift of the concentration-response curve to NPS, showing a pA(2) value of 7.17. In mouse locomotor activity experiments, supraspinal injection of [(t)Bu-D-Gly(5)]NPS (1-10 nmol) dose dependently counteracted NPS (0.1 nmol) stimulant effects. In the mouse righting reflex assay [(t)Bu-D-Gly(5)]NPS (0.1-10 nmol) fully prevented the arousal-promoting action of the natural peptide (0.1 nmol). Finally, [(t)Bu-D-Gly(5)]NPS (3-30 nmol) was able to completely block NPS (1 nmol) anxiolytic-like actions in rat elevated plus maze and defensive burying assays. Collectively, the present results demonstrated that [(t)Bu-D-Gly(5)]NPS behaves both in vitro and in vivo as a pure and potent NPSR antagonist. This compound represents a novel and useful tool for investigating the pharmacology and neurobiology of the NPS/NPSR system.

Molecular evolution of the neuropeptide S receptor

The neuropeptide S receptor (NPSR) is a recently deorphanized member of the G protein-coupled receptor (GPCR) superfamily and is activated by the neuropeptide S (NPS). NPSR and NPS are widely expressed in central nervous system and are known to have crucial roles in asthma pathogenesis, locomotor activity, wakefulness, anxiety and food intake. The NPS-NPSR system was previously thought to have first evolved in the tetrapods. Here we examine the origin and the molecular evolution of the NPSR using in-silico comparative analyses and document the molecular basis of divergence of the NPSR from its closest vertebrate paralogs. In this study, NPSR-like sequences have been identified in a hemichordate and a cephalochordate, suggesting an earlier emergence of a NPSR-like sequence in the metazoan lineage. Phylogenetic analyses revealed that the NPSR is most closely related to the invertebrate cardioacceleratory peptide receptor (CCAPR) and the group of vasopressin-like receptors. Gene structure features were congruent with the phylogenetic clustering and supported the orthology of NPSR to the invertebrate NPSR-like and CCAPR. A site-specific analysis between the vertebrate NPSR and the well studied paralogous vasopressin-like receptor subtypes revealed several putative amino acid sites that may account for the observed functional divergence between them. The data can facilitate experimental studies aiming at deciphering the common features as well as those related to ligand binding and signal transduction processes specific to the NPSR.

Behavioural phenotypic characterization of CD-1 mice lacking the neuropeptide S receptor

Neuropeptide S (NPS) is the endogenous ligand of a previously orphan receptor now named NPSR. In the brain NPS regulates several biological functions including anxiety, arousal, locomotion, food intake, learning and memory, pain and drug abuse. Mice lacking the NPSR gene (NPSR(-/-)) represent an useful tool to investigate the neurobiology of the NPS/NPSR system. NPSR(-/-) mice have been generated in a 129S6/SvEv genetic background. In the present study we generated CD-1 congenic NPSR(+/+) and NPSR(-/-) mice and investigated their phenotype and sensitivity to NPS in various behavioural assays. The phenotype analysis revealed no locomotor differences between NPSR(+/+) and NPSR(-/-) mice. The behaviour of NPSR(+/+) and NPSR(-/-) mice in the righting reflex test was superimposable. No differences were recorded between the two genotypes in the elevated plus maze, open field and stress-induced hyperthermia tests, with the exception of rearing behaviour that was reduced in knockout animals. Moreover the behaviour of NPSR(+/+) and NPSR(-/-) mice in the forced swimming, novel object recognition and formalin assays was similar. The stimulatory effects of NPS in the locomotor activity test and its anxiolytic-like actions in the elevated plus maze and open field assays were evident in NPSR(+/+) but not NPSR(-/-) animals. In conclusion, the present study indicates that the NPS/NPSR system does not tonically control locomotion, sensitivity to diazepam, anxiety, depressive-like behaviours, memory and pain transmission in mice. Furthermore our results clearly show that the product of the NPSR gene represents the mandatory protein for all the NPS biological effects so far described.

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.

Synthesis and separation of the enantiomers of the neuropeptide S receptor antagonist (9R/S)-3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide (SHA 68)

This study reports the synthesis, chromatographic separation, and pharmacological evaluation of the two enantiomers of the neuropeptide S receptor (NPSR) antagonist (9R/S)-3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide (SHA 68). The (9R)-3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide (compound 10) and (9S)-3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide (compound 10a) were synthesized and their purity assessed by chiral chromatography. The absolute configuration of the enantiomer 10 has been assigned from the crystal structure of the corresponding (S)-phenyl ethyl amine derivative 8. Calcium mobilization studies performed on cells expressing the recombinant NPSR demonstrated that compound 10 is the active enantiomer while the contribution of 10a to the NPSR antagonist properties of the racemic mixture is negligible.

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.

Neurobiology, pharmacology, and medicinal chemistry of neuropeptide S and its receptor

Neuropeptide S (NPS) is the last neuropeptide identified via reverse pharmacology techniques. NPS selectively binds and activates a previous orphan GPCR, now named NPSR, producing intracellular calcium mobilization and increases in cAMP levels. Biological functions modulated by the NPS/NPSR system include anxiety, arousal, locomotion, food intake, memory, and drug addiction. The primary sequence of NPS (in humans SFRNGVGTGMKKTSFQRAKS) is highly conserved among vertebrates especially at the N-terminus. Ala- and D-scan studies demonstrated that this part of the molecule is crucial for biological activity. Focused structure-activity studies performed on Phe(2), Arg(3), and Asn(4) confirmed this indication and revealed the chemical requirements of these positions for NPSR binding and activation. The sequence Gly(5)-Val(6)-Gly(7) seems to be important for shaping the bioactive conformation of the peptide. Structure-activity studies on Gly(5) enabled identification of the first generation of peptidergic NPSR pure antagonists including [D-Cys(tBu)(5)]NPS and [D-Val(5)]NPS whose antagonist properties were confirmed in vivo. Finally, the pharmacological features of substituted bicyclic piperazine molecules (e.g. SHA 68 (3-oxo-1,1-diphenyl-tetrahydro-oxazolo[3,4-a]pyrazine-7-carboxylic acid 4-fluoro-benzylamide) were recently published making available the first generation of nonpeptide NPSR antagonists. The use in future studies of NPSR antagonists will be of paramount importance for understanding which biological functions are controlled by the NPS/NPSR system and for defining the therapeutic potential of selective NPSR ligands.

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.

Effects of central neuropeptide S in the mouse formalin test

Neuropeptide S (NPS), a recently discovered bioactive peptide, was reported to regulate arousal, anxiety, locomotion, feeding behaviors, memory, and drug addiction. NPS receptor (NPSR) mRNA was found in several brain regions related to descending control system of pain, including the periaqueductal gray (PAG). Our previous study had shown that NPS could produce antinociception in mice. The present study was designed to evaluate whether NPS may produce antinociceptive effect observed in the mouse formalin test, a model of inflammatory pain. NPS (0.1-100 pmol) administrated intracerebroventricularly (i.c.v.) dose-dependently attenuated both first-phase and second-phase nociceptive behaviors induced by paw formalin injection. NPS (10 pmol, i.c.v.)-elicited antinociceptive effect was counteracted by co-injection with 1000 and 10,000 pmol [D-Val(5)]NPS, which alone induced neither hyperalgesia nor antinociception. The antinociception induced by NPS (10 pmol, i.c.v.) was not affected by naloxone (i.p., 10 mg/kg) and naloxone alone had no effect in the formalin test. In addition, compared to the saline (i.c.v.) treated group, NPS (10 pmol, i.c.v.) treated group increased c-Fos protein expression in nearly all subdivisions of the PAG in the formalin-injected mice. The above results revealed that NPS could produce antinociception in the formalin test through NPSR, which may be involved in the activation of PAG, suggesting that NPS-NPSR system may be a potential target for developing new analgesic drugs.

Abnormal response to stress and impaired NPS-induced hyperlocomotion, anxiolytic effect and corticosterone increase in mice lacking NPSR1

NPSR1 is a G protein coupled receptor expressed in multiple brain regions involved in modulation of stress. Central administration of NPS, the putative endogenous ligand of NPSR1, can induce hyperlocomotion, anxiolytic effects and activation of the HPA axis. The role of NPSR1 in the brain remains unsettled. Here we used NPSR1 gene-targeted mice to define the functional role of NPSR1 under basal conditions on locomotion, anxiety- and/or depression-like behavior, corticosterone levels, acoustic startle with prepulse inhibition, learning and memory, and under NPS-induced locomotor activation, anxiolysis, and corticosterone release. Male, but not female, NPSR1-deficient mice exhibited enhanced depression-like behavior in a forced swim test, reduced acoustic startle response, and minor changes in the Morris water maze. Neither male nor female NPSR1-deficient mice showed alterations of baseline locomotion, anxiety-like behavior, or corticosterone release after exposure to a forced swim test or methamphetamine challenge in an open-field. After intracerebroventricular (ICV) administration of NPS, NPSR1-deficient mice failed to show normal NPS-induced increases in locomotion, anxiolysis, or corticosterone release compared with WT NPS-treated mice. These findings demonstrate that NPSR1 is essential in mediating NPS effects on behavior.

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

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

Molecular modeling studies on the human neuropeptide S receptor and its antagonists

Neuropeptide S (NPS) is a 20-residue peptide of great interest due to its potential involvement in several biological processes such as arousal, anxiety, and food intake. The NPS receptor belongs to the rhodopsin-like G-protein-coupled receptor superfamily, and several polymorphisms and isoforms of this receptor are associated with asthma, allergies, and bronchial hyper-responsiveness, in particular the Asn 107 Ile mutation. Limited structural information is available for this peptide-receptor system, particularly regarding the NPS receptor structure, its nonpeptide ligands, and the molecular aspects of agonist and antagonist binding processes. In this work, rhodopsin-based homology models of the NPS receptor and its Asn 107 Ile variant were built and refined in a membrane bilayer model, and binding modes for nonpeptide antagonists were simulated. This study provides the first structural study of the human NPS receptor, and the results provide a starting point for further characterization of the binding modes of its antagonists, and for the rational design of new NPS receptor ligands.

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.

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

The recently discovered Neuropeptide S (NPS) and its cognate receptor represent a highly interesting system of neuromodulation with unique physiological effects. On one hand, NPS increases wakefulness and arousal. On the other, NPS produces anxiolytic-like effects by acutely reducing fear responses as well as modulating long-term aspects of fear memory, such as attenuation of contextual fear or enhancement of fear extinction. The main sources of NPS in the brain are a few clusters of NPS-producing neurons in the brainstem. NPS binds to a G-protein-coupled receptor that is highly conserved among vertebrates and stimulates mobilization of intracellular Ca(2+) as well as activation of protein kinases. In synaptic circuits within the amygdala, which are important for processing of acute fear as well as formation and expression of fear memories, NPS causes increased release of the excitatory transmitter glutamate, especially in synaptic contacts to a subset of GABAergic interneurons. Polymorphisms in the human NPS receptor gene have been associated with altered sleep behavior and panic disorder. In conclusion, the NPS system displays a unique physiological profile with respect to the specificity and time course of its actions. These functions could provide interesting opportunities for both basic research and clinical applications.

Lithium attenuates behavioral and biochemical effects of neuropeptide S in mice

Neuropeptide S (NPS) and its receptor NPSR comprise a recently deorphaned G-protein-coupled receptor system. There is a body of evidence suggesting the involvement of NPS in wakefulness, anxiety, locomotor activity and oxidative stress damage. Considering that mood stabilizers block the stimulatory effect of psychostimulants in rodents, the present study aimed to investigate the effects of the pretreatment with lithium and valproate on the hyperlocomotion evoked by NPS. Another relevant action induced by lithium and valproate is the neuroprotection against oxidative stress. Thus, aiming to get further information about the mechanisms of action of NPS, herein we evaluated the effects of NPS, lithium and valproate, and the combination of them on oxidative stress damage. Behavioral studies revealed that the pretreatment with lithium (100 mg/kg, i.p.) and valproate (200 mg/kg, i.p.) prevented hyperlocomotion evoked by NPS 0.1 nmol. Importantly, the dose of valproate used in this study reduced mouse locomotion, although it did not reach the statistical significance. Biochemical analyses showed that lithium attenuated thiobarbituric reactive species (TBARS) formation in the striatum, cerebellum and hippocampus. NPS per se reduced TBARS levels only in the hippocampus. Valproate did not significantly affect TBARS levels in the brain. However, the combination of mood stabilizers and NPS blocked, instead of potentiate, the neuroprotective effects of each one. No relevant alterations were observed in carbonylated proteins after all treatments. Altogether, the present findings suggested that mainly the mood stabilizer lithium evoked antagonistic effects on the mediation of hyperlocomotion and protection against lipid peroxidation induced by NPS.

Further studies at neuropeptide s position 5: discovery of novel neuropeptide S receptor antagonists

Neuropeptide S (NPS) regulates various biological functions by activating the NPS receptor (NPSR). Previous studies demonstrated that the substitution of Gly(5) with d-amino acids generates NPSR antagonists. Eleven [d-Xaa(5)]NPS derivatives were synthesized and pharmacologically tested measuring [Ca(2+)](i) in HEK293(mNPSR) cells. The results confirmed that the [d-Xaa(5)] substitution promotes antagonist activity with potency inversely related to the side chain size and allowed identification of the novel potent NPSR peptide antagonist [(t)Bu-d-Gly(5)]NPS.

Behavioral phenotyping of neuropeptide S receptor knockout mice

Central administration of neuropeptide S (NPS) in rodents induces arousal and prolonged wakefulness as well as anxiolytic-like effects. NPS has also been implicated in modulation of cognitive functions and energy homeostasis. Here we present a comprehensive phenotypical analysis of mice carrying a targeted mutation in the NPS receptor (NPSR) gene. NPSR knockout mice were found to exhibit reduced exploratory activity when challenged with a novel environment, which might indicate attenuated arousal. We also observed attenuated late peak wheel running activity in NPSR knockout mice, representing reduced activity during the subjective evening. These mice also displayed increased anxiety-like behaviors when compared to their wildtype littermates, although analysis of anxiety behaviors was limited by genetic background influences. Unexpectedly, NPSR knockout mice showed enhanced motor performance skills. No phenotypical differences were detected in the forced-swim test, startle habituation and pre-pulse inhibition paradigms. Together, these data indicate that the endogenous NPS system might be involved in setting or maintaining behavioral arousal thresholds and that the NPS system might have other yet undiscovered physiological functions.