Discovery of a novel series of orally active nociceptin/orphanin FQ (NOP) receptor antagonists based on a dihydrospiro(piperidine-4,7'-thieno[2,3-c]pyran) scaffold

LY2940094, an NOPR antagonist, promotes oligodendrocyte generation and myelin recovery in an NOPR independent manner

The myelin sheath plays crucial roles in brain development and neuronal functions. In the central nervous system, myelin is generated by oligodendrocytes, that differentiate from oligodendrocyte progenitor cells (OPC). In demyelinating diseases, the differentiation capacity of OPC is impaired and remyelination is dampened. Boosting remyelination by promoting OPC differentiation is a novel strategy for the treatment of demyelinating diseases. The opioid system, which consists of four receptors and their ligands, has been implicated in OPC differentiation and myelin formation. However, the exact roles of each opioid receptor and the relevant pharmacological molecules in OPC differentiation and myelin formation remain elusive. In the present study, specific agonists and antagonists of each opioid receptor were used to explore the function of opioid receptors in OPC differentiation. Nociceptin/orphanin FQ receptor (NOPR) specific antagonist LY2940094 was found to stimulate OPC differentiation and myelination in both in vitro and in vivo models. Unexpectedly, other NOPR ligands did not affect OPC differentiation, and NOPR knockdown did not mimic or impede the effect of LY2940094. LY2940094 was found to modulate the expression of the oligodendrocytes differentiation-associated transcription factors ID4 and Myrf, although the exact mechanism remains unclear. Since LY2940094 has been tested clinically to treat depression and alcohol dependency and has displayed an acceptable safety profile, it may provide an alternative approach to treat demyelinating diseases.

Pharmacological blockage of NOP receptors decreases ventral tegmental area dopamine neuronal activity through GABAB receptor-mediated mechanism

The Nociceptin/Orphanin FQ (N/OFQ) peptide and its receptor NOP are highly expressed within several regions of the mesolimbic system, including the ventral tegmental area (VTA). Evidence indicates that the N/OFQ-NOP receptor system is involved in reward processing and historically it has been proposed that activation of NOP receptors attenuates the motivation for substances of abuse. However, recent findings demonstrated that drug self-administration and relapse to drug-seeking are also attenuated after administration of NOP receptor antagonists. Here, to shed light on the mechanisms through which NOP receptor blockers modulate these processes, we utilized ex vivo patch-clamp recordings to investigate the effect of the selective NOP receptor antagonist LY2817412 on VTA dopaminergic (DA) function in male rats. Results showed that, similar to the endogenous NOP receptor agonist N/OFQ, LY2817412 reduced the spontaneous basal firing discharge of VTA DA neurons. Consistently, we found that NOP receptors are expressed both in VTA DA and GABA cells and that LY2817412 slice perfusion increased GABA release onto VTA DA cells. Finally, in the attempt to dissect the role of postsynaptic and presynaptic NOP receptors, we tested the effect of N/OFQ and LY2817412 in the presence of GABA receptors blockers. Results showed that the effect of LY2817412 was abolished following pretreatment with GABABR, but not GABAAR, blockers. Conversely, inhibition of DA neuronal activity by N/OFQ was unaffected by blockade of GABA receptors. Altogether, these results suggest that both NOP receptor agonists and antagonists can decrease VTA DA neuronal activity, but through distinct mechanisms of action. The effect of NOP receptor antagonists occurs through a GABABR-mediated mechanism while NOP receptor agonists seem to act via a direct effect on VTA DA neurons.

Activation of NOP receptor increases vulnerability to stress: role of glucocorticoids and CRF signaling

RATIONALE

Recently, we demonstrated that the activation of the nociceptin/orphanin FQ (N/OFQ) receptor (NOP) signaling facilitates depressive-like behaviors. Additionally, literature findings support the ability of the N/OFQ-NOP system to modulate the hypothalamic-pituitary-adrenal (HPA) axis.

OBJECTIVES

Considering that dysfunctional HPA axis is strictly related to stress-induced psychopathologies, we aimed to study the role of the HPA axis in the pro-depressant effects of NOP agonists.

METHODS

Mice were treated prior to stress with the NOP agonist Ro 65-6570, and immobility time in the forced swimming task and corticosterone levels were measured. Additionally, the role of endogenous glucocorticoids and CRF was investigated using the glucocorticoid receptor antagonist mifepristone and the CRF1 antagonist antalarmin in the mediation of the effects of Ro 65-6570.

RESULTS

The NOP agonist in a dose-dependent manner further increased the immobility of mice in the second swimming session compared to vehicle. By contrast, under the same conditions, the administration of the NOP antagonist SB-612111 before stress reduced immobility, while the antidepressant nortriptyline was inactive. Concerning in-serum corticosterone in mice treated with vehicle, nortriptyline, or SB-612111, a significant decrease was observed after re-exposition to stress, but no differences were detected in Ro 65-6570-treated mice. Administration of mifepristone or antalarmin blocked the Ro 65-6570-induced increase in the immobility time in the second swimming session.

CONCLUSIONS

Present findings suggest that NOP agonists increase vulnerability to depression by hyperactivating the HPA axis and then increasing stress circulating hormones and CRF1 receptor signaling.

Synthesis and characterization of Co-MOF@Ag2O nanocomposite and its application as a nano-organic catalyst for one-pot synthesis of pyrazolopyranopyrimidines

In this study, a Co-MOF was synthesized via a co-precipitation procedure and then used as support for stabilizing Ag ions and producing Co-MOF@Ag2O nanocomposite by microwave irradiation. The characterization of synthesized Co-MOF@Ag2O nanocomposite was performed by using different techniques such as field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analyses, X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) and Fourier-transform infrared (FT-IR). The prepared Co-MOF@Ag2O nanocomposite was applied as a heterogeneous nano-catalyst in the synthesis of pyrazolopyranopyrimidines in water at 50 °C via the one-pot multicomponent reaction of ethyl acetoacetate, hydrazine hydrate, aromatic aldehydes and barbituric acid derivatives. Through this straightforward and effective protocol, different tricyclic fused pyrazolopyranopyrimidines were synthesized at high yields, and short reaction times, through an uncomplicated work-up process with no by-product. The Co-MOF@Ag2O nanocomposite has been effectively recycled for four consecutive cycles without appreciable loss in its activity. Cost-effectiveness, no need for column chromatography, mild conditions, catalyst recyclability, and eco-friendly nature make it a promising candidate compared to other methods.

Imaging Nociceptin Opioid Peptide Receptors in Alcohol Use Disorder With [11C]NOP-1A and Positron Emission Tomography: Findings From a Second Cohort

BACKGROUND

Nociceptin, which binds to the nociceptin opioid peptide receptor (NOP), regulates stress and reward in addiction. In a previous [11C]NOP-1A positron emission tomography (PET) study, we found no differences in NOP in non-treatment-seeking individuals with alcohol use disorder (AUD) relative to healthy control subjects Here, we evaluated NOP in treatment-seeking individuals with AUD to document its relationship with relapse to alcohol.

METHODS

[11C]NOP-1A distribution volume (VT) was measured in recently abstinent individuals with AUD and healthy control subjects (n = 27/group) using an arterial input function-based kinetic analysis in brain regions that regulate reward and stress behaviors. Recent heavy drinking before PET was quantified using hair ethyl glucuronide (≥30 pg/mg was defined as heavy drinking). To document relapse, 22 subjects with AUD were followed with urine ethyl glucoronide tests (3/week) for 12 weeks after PET, where they were incentivized with money to abstain.

RESULTS

There were no differences in [11C]NOP-1A VT between individuals with AUD and healthy control subjects. Individuals with AUD who drank heavily before the study had significantly lower VT than those with no recent heavy drinking history. Significant negative correlations between VT and the number of drinking days and the number of drinks consumed per drinking day in the 30 days before enrollment were also present. Individuals with AUD who relapsed (and dropped out) had significantly lower VT than those who abstained for 12 weeks.

CONCLUSIONS

Lower NOP VT in heavy drinking AUD predicted relapse to alcohol during a 12-week follow-up period. The results of this PET study support the need to investigate medications that act at NOP to prevent relapse in individuals with AUD.

Contribution of the opioid system to depression and to the therapeutic effects of classical antidepressants and ketamine

Major depressive disorder (MDD) afflicts approximately 5 % of the world population, and about 30-50 % of patients who receive classical antidepressant medications do not achieve complete remission (treatment resistant depressive patients). Emerging evidence suggests that targeting opioid receptors mu (MOP), kappa (KOP), delta (DOP), and the nociceptin/orphanin FQ receptor (NOP) may yield effective therapeutics for stress-related psychiatric disorders. As depression and pain exhibit significant overlap in their clinical manifestations and molecular mechanisms involved, it is not a surprise that opioids, historically used to alleviate pain, emerged as promising and effective therapeutic options in the treatment of depression. The opioid signaling is dysregulated in depression and numerous preclinical studies and clinical trials strongly suggest that opioid modulation can serve as either an adjuvant or even an alternative to classical monoaminergic antidepressants. Importantly, some classical antidepressants require the opioid receptor modulation to exert their antidepressant effects. Finally, ketamine, a well-known anesthetic whose extremely efficient antidepressant effects were recently discovered, was shown to mediate its antidepressant effects via the endogenous opioid system. Thus, although opioid system modulation is a promising therapeutical venue in the treatment of depression further research is warranted to fully understand the benefits and weaknesses of such approach.

NiFe2O4@B,N,F-tridoped CeO2 (NFTDNC): a mesoporous nanocatalyst in the synthesis of pyrazolopyranopyrimidine and 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives and as an adsorbent

Mesoporous materials, due to their unique textural and structural features and successful applications in different scientific areas, engrossed our curiosity to form a mesoporous nanostructure. A facile method for the formation of nickel ferrite immobilized over B,N,F tridoped mesoporous cerium oxide (CeO₂) nanostructures (NFTDNC) was designed and communicated in this report. It was characterized by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction study (PXRD), scanning transmission electron microscopy (STEM), high-resolution transmission electron microscopy (HR-TEM), field emission gun-scanning electron microscopy (FE-SEM), vibrating sample magnetometry (VSM), photoluminescence (PL), Brunauer-Emmett-Teller (BET), energy dispersive X-ray analysis (EDX) and elemental mapping, UV-visible spectroscopy (UV-VIS) and Fourier transform infrared spectroscopy (FT-IR). The applications of the mesoporous nanomaterial (NFTDNC) as an adaptable heterogeneous nanocatalyst and as a phenomenal adsorbent for methyl orange (MO) dye were established. It catalyzed the formation of pyrazolopyranopyrimidine and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones derivatives for the five runs. The recycled catalyst exhibited agglomeration in structural features confirmed by PXRD and HR-TEM studies. NFTDNC as an adsorbent fitted the Freundlich isotherm for the adsorption of MO dye. Moreover, it followed the linear pseudo-second-order kinetics rate equation (R² ≥ 0.98914). MO was adsorbed completely in 60 min with the NFTDNC mesoporous nanostructure.

Role of Nociceptin/Orphanin FQ-NOP Receptor System in the Regulation of Stress-Related Disorders

Nociceptin/orphanin FQ (N/OFQ) is a 17-residue neuropeptide that binds the nociceptin opioid-like receptor (NOP). N/OFQ exhibits nucleotidic and aminoacidics sequence homology with the precursors of other opioid neuropeptides but it does not activate either MOP, KOP or DOP receptors. Furthermore, opioid neuropeptides do not activate the NOP receptor. Generally, activation of N/OFQ system exerts anti-opioids effects, for instance toward opioid-induced reward and analgesia. The NOP receptor is widely expressed throughout the brain, whereas N/OFQ localization is confined to brain nuclei that are involved in stress response such as amygdala, BNST and hypothalamus. Decades of studies have delineated the biological role of this system demonstrating its involvement in significant physiological processes such as pain, learning and memory, anxiety, depression, feeding, drug and alcohol dependence. This review discusses the role of this peptidergic system in the modulation of stress and stress-associated psychiatric disorders in particular drug addiction, mood, anxiety and food-related associated-disorders. Emerging preclinical evidence suggests that both NOP agonists and antagonists may represent a effective therapeutic approaches for substances use disorder. Moreover, the current literature suggests that NOP antagonists can be useful to treat depression and feeding-related diseases, such as obesity and binge eating behavior, whereas the activation of NOP receptor by agonists could be a promising tool for anxiety.

NOP receptor antagonism attenuates reinstatement of alcohol-seeking through modulation of the mesolimbic circuitry in male and female alcohol-preferring rats

In patients suffering from alcohol use disorder (AUD), stress and environmental stimuli associated with alcohol availability are important triggers of relapse. Activation of the nociceptin opioid peptide (NOP) receptor by its endogenous ligand Nociceptin/Orphanin FQ (N/OFQ) attenuates alcohol drinking and relapse in rodents, suggesting that NOP agonists may be efficacious in treating AUD. Intriguingly, recent data demonstrated that also blockade of NOP receptor reduced alcohol drinking in rodents. To explore further the potential of NOP antagonism, we investigated its effects on the reinstatement of alcohol-seeking elicited by administration of the α2 antagonist yohimbine (1.25 mg/kg, i.p.) or by environmental conditioning factors in male and female genetically selected alcohol-preferring Marchigian Sardinian (msP) rats. The selective NOP receptor antagonist LY2817412 (0.0, 3.0, 10.0, and 30.0 mg/kg) was first tested following oral (p.o.) administration. We then investigated the effects of LY2817412 (1.0, 3.0, 6.0 μg/μl/rat) microinjected into three candidate mesolimbic brain regions: the ventral tegmental area (VTA), the central nucleus of the amygdala (CeA), and the nucleus accumbens (NAc). We found that relapse to alcohol seeking was generally stronger in female than in male rats and oral administration of LY2817412 reduced yohimbine- and cue-induced reinstatement in both sexes. Following site-specific microinjections, LY2817412 reduced yohimbine-induced reinstatement of alcohol-seeking when administered into the VTA and the CeA, but not in the NAc. Cue-induced reinstatement was suppressed only when LY2817412 was microinjected into the VTA. Infusions of LY2817412 into the VTA and the CeA did not alter saccharin self-administration. These results demonstrate that NOP receptor blockade prevents the reinstatement of alcohol-seeking through modulation of mesolimbic system circuitry, providing further evidence of the therapeutic potential of NOP receptor antagonism in AUD.

Nociceptin/orphanin FQ receptor system blockade as an innovative strategy for increasing resilience to stress

The ability to successfully cope with stress is known as 'resilience', and resilient individuals are less prone to develop psychopathologies. Understanding the neurobiological mechanisms of resilience may be instrumental to improve current therapies and benefit high-risk subjects. This review summarizes the complex interplay that exists between physiological and pathological responses to stressful events and the nociceptin/orphanin FQ (N/OFQ) - N/OFQ receptor (NOP) system, including: the effects of stress in regulating N/OFQ release and NOP expression; the ability of the N/OFQ-NOP system to modulate the hypothalamic-pituitary-adrenal axis; behavioral studies; and evidence in humans correlating this peptidergic system with psychopathologies. Available findings support the view that N/OFQ signaling stimulates the hypothalamic-pituitary-adrenal axis, thus increasing stress circulating hormones and corticotropin-releasing factor signaling. Additionally, activation of the NOP receptor inhibits monoamine transmission, including 5-HT, and this may contribute to maladaptive outcomes of stress. Ultimately, the N/OFQ system seems to have an important role in stress vulnerability, and blockade of NOP signaling may provide an innovative strategy for the treatment of stress related psychopathologies.

Adaptive Changes in the Central Control of Energy Homeostasis Occur in Response to Variations in Energy Status

Energy homeostasis is regulated in coordinate fashion by the brain-gut axis, the homeostatic energy balance circuitry in the hypothalamus and the hedonic energy balance circuitry comprising the mesolimbcortical A10 dopamine pathway. Collectively, these systems convey and integrate information regarding nutrient status and the rewarding properties of ingested food, and formulate it into a behavioral response that attempts to balance fluctuations in consumption and food-seeking behavior. In this review we start with a functional overview of the homeostatic and hedonic energy balance circuitries; identifying the salient neural, hormonal and humoral components involved. We then delve into how the function of these circuits differs in males and females. Finally, we turn our attention to the ever-emerging roles of nociceptin/orphanin FQ (N/OFQ) and pituitary adenylate cyclase-activating polypeptide (PACAP)-two neuropeptides that have garnered increased recognition for their regulatory impact in energy homeostasis-to further probe how the imposed regulation of energy balance circuitry by these peptides is affected by sex and altered under positive (e.g., obesity) and negative (e.g., fasting) energy balance states. It is hoped that this work will impart a newfound appreciation for the intricate regulatory processes that govern energy homeostasis, as well as how recent insights into the N/OFQ and PACAP systems can be leveraged in the treatment of conditions ranging from obesity to anorexia.

Differential Modulation of Ventral Tegmental Area Circuits by the Nociceptin/Orphanin FQ System

The neuropeptide nociceptin/orphanin FQ (N/OFQ) can be released by stressors and is associated with disorders of emotion regulation and reward processing. N/OFQ and its receptor, NOP, are enriched in dopaminergic pathways, and intra-ventricular agonist delivery decreases dopamine levels in the dorsal striatum, nucleus accumbens (NAc), and ventral tegmental area (VTA). We used whole-cell electrophysiology in acute rat midbrain slices to investigate synaptic actions of N/OFQ. N/OFQ was primarily inhibitory, causing outward currents in both immunocytochemically identified dopaminergic (tyrosine hydroxylase positive (TH(+))) and non-dopaminergic (TH(-)) VTA neurons; effect at 1 μm: 20 ± 4 pA. Surprisingly, this effect was mediated by augmentation of postsynaptic GABAAR currents, unlike the substantia nigra pars compacta (SNc), where the N/OFQ-induced outward currents were K+ channel dependent. A smaller population, 17% of all VTA neurons, responded to low concentrations of N/OFQ with inward currents (10 nm: -11 ± 2 pA). Following 100 nm N/OFQ, the response to a second N/OFQ application was markedly diminished in VTA neurons (14 ± 10% of first response) but not in SNc neurons (90 ± 20% of first response). N/OFQ generated outward currents in medial prefrontal cortex (mPFC)-projecting VTA neurons, but inward currents in a subset of posterior anterior cingulate cortex (pACC)-projecting VTA neurons. While N/OFQ inhibited NAc-projecting VTA cell bodies, it had little effect on electrically or optogenetically evoked terminal dopamine release in the NAc measured ex vivo with fast scan cyclic voltammetry (FSCV). These results extend our understanding of the N/OFQ system in brainstem circuits implicated in many neurobehavioral disorders.

Crosstalk between Opioid and Anti-Opioid Systems: An Overview and Its Possible Therapeutic Significance

Opioid peptides and receptors are broadly expressed throughout peripheral and central nervous systems and have been the subject of intense long-term investigations. Such studies indicate that some endogenous neuropeptides, called anti-opioids, participate in a homeostatic system that tends to reduce the effects of endogenous and exogenous opioids. Anti-opioid properties have been attributed to various peptides, including melanocyte inhibiting factor (MIF)-related peptides, cholecystokinin (CCK), nociceptin/orphanin FQ (N/OFQ), and neuropeptide FF (NPFF). These peptides counteract some of the acute effects of opioids, and therefore, they are involved in the development of opioid tolerance and addiction. In this work, the anti-opioid profile of endogenous peptides was described, mainly taking into account their inhibitory influence on opioid-induced effects. However, the anti-opioid peptides demonstrated complex properties and could show opioid-like as well as anti-opioid effects. The aim of this review is to detail the phenomenon of crosstalk taking place between opioid and anti-opioid systems at the in vivo pharmacological level and to propose a cellular and molecular basis for these interactions. A better knowledge of these mechanisms has potential therapeutic interest for the control of opioid functions, notably for alleviating pain and/or for the treatment of opioid abuse.

Pain, Motivation, Migraine, and the Microbiome: New Frontiers for Opioid Systems and Disease

For decades the broad role of opioids in addiction, neuropsychiatric disorders, and pain states has been somewhat well established. However, in recent years, with the rise of technological advances, not only is the existing dogma being challenged, but we are identifying new disease areas in which opioids play a critical role. This review highlights four new areas of exploration in the opioid field. The most recent addition to the opioid family, the nociceptin receptor system, shows promise as the missing link in understanding the neurocircuitry of motivation. It is well known that activation of the kappa opioid receptor system modulates negative affect and dysphoria, but recent studies now implicate the kappa opioid system in the modulation of negative affect associated with pain. Opioids are critical in pain management; however, the often-forgotten delta opioid receptor system has been identified as a novel therapeutic target for headache disorders and migraine. Lastly, changes to the gut microbiome have been shown to directly contribute to many of the symptoms of chronic opioid use and opioid related behaviors. This review summarizes the findings from each of these areas with an emphasis on identifying new therapeutic targets. SIGNIFICANCE STATEMENT: The focus of this minireview is to highlight new disease areas or new aspects of disease in which opioids have been implicated; this includes pain, motivation, migraine, and the microbiome. In some cases, this has resulted in the pursuit of a novel therapeutic target and resultant clinical trial. We believe this is very timely and will be a refreshing take on reading about opioids and disease.

Blockade of NOP receptor modulates anxiety-related behaviors in mice exposed to inescapable stress

RATIONALE

Depression and anxiety frequently co-occur, and this has important clinical implications. Previous studies showed that activation of the nociceptin/orphanin FQ receptor (NOP) elicits anxiolytic effects, while its blockade promotes consistent antidepressant actions. NOP antagonists are effective in reversing footshock-induced depressive-like behaviors, but their effects on stress-induced anxiety are still unclear.

OBJECTIVE

This study aimed to investigate the effects of the NOP antagonist SB-612111 on footshock stress-induced anxiety behaviors.

METHODS

Male Swiss mice were exposed to inescapable electric footshock stress, and behavioral phenotype was screened based on the ability to escape from footshock (i.e., helpless or non-helpless). Animals were then treated with diazepam (1 mg/kg) and SB-612111 (0.1-10 mg/kg), and their behavior was assessed in the elevated plus-maze (EPM) and open field test.

RESULTS

When compared with non-stressed mice, helpless, but not non-helpless, animals displayed significant reductions in the time spent in and entries into open arms in the EPM. Diazepam significantly increased open arms exploration in helpless, non-helpless, and non-stressed mice. However, treatment with the NOP antagonist SB-612111 was inactive in naive mice, while it reversed anxiogenic-related behaviors in helpless mice and increased anxiety states in non-helpless mice. No effects on locomotion were observed.

CONCLUSION

Helpless mice displayed increased anxiety compared to non-stressed and non-helpless animals, thus supporting use of this approach as an animal model to investigate anxiety/depression comorbidity. Additionally, SB-612111 modulated anxiety-like behaviors in male mice depending on individual stress susceptibility. Ultimately, NOP antagonists could be useful for treating anxiety in depressed patients.

NOP receptor antagonism reduces alcohol drinking in male and female rats through mechanisms involving the central amygdala and ventral tegmental area

BACKGROUND AND PURPOSE

Nociceptin/orphanin FQ (N/OFQ) peptide and its cognate receptor (NOP) are widely expressed in mesolimbic brain regions where they play an important role in modulating reward and motivation. Early evidence suggested that NOP receptor activation attenuates the rewarding effects of drugs of abuse, including alcohol. However, emerging data indicate that NOP receptor blockade also effectively attenuates alcohol drinking and relapse. To advance our understanding of the role of the N/OFQ-NOP receptor system in alcohol abuse, we examined the effect of NOP receptor blockade on voluntary alcohol drinking at the neurocircuitry level.

EXPERIMENTAL APPROACH

Using male and female genetically selected alcohol-preferring Marchigian Sardinian (msP) rats, we initially evaluated the effects of the selective NOP receptor antagonist LY2817412 (3, 10, and 30 mg·kg^-1 , p.o.) on alcohol consumption in a two-bottle free-choice paradigm. We then microinjected LY2817412 (3 and 6 μg·μl^-1 per rat) in the central nucleus of the amygdala (CeA), ventral tegmental area (VTA), and nucleus accumbens (NAc).

KEY RESULTS

Peripheral LY2817412 administration dose-dependently and selectively reduced voluntary alcohol intake in male and female msP rats. Central injections of LY2817412 markedly attenuated voluntary alcohol intake in both sexes following administration in the CeA and VTA but not in the NAc.

CONCLUSION AND IMPLICATIONS

The present results revealed that the CeA and VTA are neuroanatomical substrates that mediate the effects of NOP receptor antagonism on alcohol consumption. Overall, our findings support the potential of NOP receptor antagonism as a treatment strategy to attenuate alcohol use and addiction.

Detailed In Vitro Pharmacological Characterization of the Clinically Viable Nociceptin/Orphanin FQ Peptide Receptor Antagonist BTRX-246040

The peptide nociceptin/orphanin FQ (N/OFQ) is the natural ligand of the N/OFQ receptor (NOP), which is widely expressed in the central and peripheral nervous system. Selective NOP antagonists are worthy of testing as innovative drugs to treat depression, Parkinson disease, and drug abuse. The aim of this study was to perform a detailed in vitro characterization of BTRX-246040 (also known as LY2940094, [2-[4-[(2-chloro-4,4-difluoro-spiro[5H-thieno[2,3-c]pyran-7,4'-piperidine]-1'-yl)methyl]-3-methyl-pyrazol-1-yl]-3-pyridyl]methanol), a novel NOP antagonist that has been already studied in humans. BTRX-246040 has been tested in vitro in the following assays: calcium mobilization in cells expressing NOP and classic opioid receptors and chimeric G proteins, bioluminescence resonance energy transfer assay measuring NOP interaction with G proteins and β-arrestins, the label-free dynamic mass redistribution assay, and the electrically stimulated mouse vas deferens. BTRX-246040 was systematically compared with the standard NOP antagonist SB-612111. In all assays, BTRX-246040 behaves as a pure and selective antagonist at human recombinant and murine native NOP receptors displaying 3-10-fold higher potency than the standard antagonist SB-612111. BTRX-246040 is an essential pharmacological tool to further investigate the therapeutic potential of NOP antagonists in preclinical and clinical studies. SIGNIFICANCE STATEMENT: NOP antagonists may be innovative antidepressant drugs. In this research, the novel clinically viable NOP antagonist BTRX-246040 has been deeply characterized in vitro in a panel of assays. BTRX-246040 resulted a pure, potent, and selective NOP antagonist.

Managing Parkinson's disease: moving ON with NOP

The opioid-like neuropeptide nociceptin/orphanin FQ (N/OFQ) and its receptor (NOP receptor) contribute to Parkinson's disease (PD) and motor complications associated with levodopa therapy. The N/OFQ-NOP receptor system is expressed in cortical and subcortical motor areas and, notably, in dopaminergic neurons of the substantia nigra compacta. Dopamine depletion, as in rodent models of PD results in up-regulation of N/OFQ transmission in the substantia nigra and down-regulation of N/OFQ transmission in the striatum. Consistent with this, NOP receptor antagonists relieve motor deficits in PD models by reinstating the physiological balance between excitatory and inhibitory inputs impinging on nigro-thalamic GABAergic neurons. NOP receptor antagonists also counteract the degeneration of nigrostriatal dopaminergic neurons, possibly by attenuating the excitotoxicity or modulating the immune response. Conversely, NOP receptor agonists attenuate levodopa-induced dyskinesia by attenuating the hyperactivation of striatal D1 receptor signalling in neurons of the direct striatonigral pathway. The N/OFQ-NOP receptor system might represent a novel target in the therapy of PD.

Modulation of the NOP receptor signaling affects resilience to acute stress

BACKGROUND

The peptide nociceptin/orphanin FQ (N/OFQ) and its receptor (NOP) are implicated in the modulation of emotional states. Previous human and rodent findings support NOP antagonists as antidepressants. However, the role played by the N/OFQ-NOP receptor system in resilience to stress is unclear.

AIMS

The present study investigated the effects of activation or blockade of NOP receptor signaling before exposure to acute stress.

METHODS

The behavioral effects of the administration before stress of the NOP agonists Ro 65-6570 (0.01-1 mg/kg) and MCOPPB (0.1-10 mg/kg), and the NOP antagonist SB-612111 (1-10 mg/kg) were assessed in mice exposed to inescapable electric footshock and forced swim as stressors. The behavioral phenotype of mice lacking the NOP receptor (NOP(-/-)) exposed to inescapable electric footshock was also investigated.

RESULTS

The activation of NOP receptor signaling with the agonists increased the percentage of mice developing helpless behavior and facilitated immobile posture. In contrast, the blockade of NOP receptor reduced the acquisition of depressive-like phenotypes, and similar resistance to develop helpless behaviors was observed in NOP(-/-) mice. Under the same stressful conditions, the antidepressant nortriptyline (20 mg/kg) did not change the acquisition of helpless behavior and immobile posture.

CONCLUSIONS

These findings support the view that NOP activation during acute stress facilitates the development of depressive-related behaviors, whereas NOP blockade has a protective outcome. This study showed for first time that NOP antagonists are worthy of investigation as preemptive treatments in patients with severe risk factors for depression.

NOP-Targeted Nonpeptide Ligands

The development of nonpeptide systemically active small-molecule NOP-targeted ligands has contributed tremendously to validating the NOP receptor as a promising target for therapeutics. Although a NOP-targeted compound is not yet approved for clinical use, a few NOP ligands are in clinical trials for various indications. Both successful and failed human clinical trials with NOP ligands provide opportunities for rational development of new and improved NOP-targeted compounds. A few years after the discovery of the NOP receptor in 1994, and its de-orphanization upon discovery of the endogenous peptide nociceptin/orphanin FQ (N/OFQ) in 1995, there was a significant effort in the pharmaceutical industry to discover nonpeptide NOP ligands from hits obtained from high-throughput screening campaigns of compound libraries. Depending on the therapeutic indication to be pursued, NOP agonists and antagonists were discovered, and some were optimized as clinical candidates. Advances such as G protein-coupled receptor (GPCR) structure elucidation, functional selectivity in ligand-driven GPCR activation, and multi-targeted ligands provide new scope for the rational design of novel NOP ligands fine-tuned for successful clinical translation. This article reviews the field of nonpeptide NOP ligand drug design in the context of these exciting developments and highlights new optimized nonpeptide NOP ligands possessing interesting functional profiles, which are particularly attractive for several unmet clinical applications involving NOP receptor pharmacomodulation.

NOP-Related Mechanisms in Substance Use Disorders

Nociceptin/orphanin FQ (N/OFQ) is a 17 amino acid peptide that was deorphanized in 1995 and has been widely studied since. The role of the N/OFQ system in drug abuse has attracted researchers' attention since its initial discovery. The first two scientific papers describing the effect of intracranial injection of N/OFQ appeared 20 years ago and reported efficacy of the peptide in attenuating alcohol intake, whereas heroin self-administration was insensitive. Since then more than 100 scientific articles investigating the role of the N/OFQ and N/OFQ receptor (NOP) system in drug abuse have been published. The present article provides an historical overview of the advances in the field with focus on three major elements. First, the most robust data supportive of the efficacy of NOP agonists in treating drug abuse come from studies in the field of alcohol research, followed by psychostimulant and opioid research. In contrast, activation of NOP appears to facilitate nicotine consumption. Second, emerging data challenge the assumption that activation of NOP is the most appropriate strategy to attenuate consumption of substances of abuse. This assumption is based first on the observation that animals carrying an overexpression of NOP system components are more prone to consume substances of abuse, whereas NOP knockout rats are less motivated to self-administer heroin, alcohol, and cocaine. Third, administration of NOP antagonists also reduces alcohol consumption. In addition, NOP blockade reduces nicotine self-administration. Hypothetical mechanisms explaining this apparent paradox are discussed. Finally, we focus on the possibility that co-activation of NOP and mu opioid (MOP) receptors is an alternative strategy, readily testable in the clinic, to reduce the consumption of psychostimulants, opiates, and, possibly, alcohol.

NOP Receptor Ligands and Parkinson's Disease

Nociceptin/Orphanin FQ (N/OFQ) and its NOP receptor are highly expressed in motor areas of the rodent, nonhuman, and human primate brain, such as primary motor cortex, thalamus, globus pallidus, striatum, and substantia nigra. Endogenous N/OFQ negatively regulates motor behavior and dopamine transmission through NOP receptors expressed by dopaminergic neurons of the substantia nigra compacta. Consistent with the existence of an N/OFQ tone over dopaminergic transmission, blockade of NOP receptor antagonists increases striatal dopamine release. In this chapter, we will review the evidence linking the N/OFQ-NOP receptor system to Parkinson's disease (PD). We will first discuss data showing that the central N/OFQ-NOP receptor system undergoes plastic changes in different basal ganglia nuclei following dopamine depletion. Then we will show that NOP receptor antagonists relieve motor deficits in different rodent and nonhuman primate models of PD. Mechanistically, NOP receptor blockade in substantia nigra reticulata results in rebalancing of the inhibitory GABAergic and excitatory glutamatergic inputs impinging on nigro-thalamic GABAergic neurons, leading to thalamic disinhibition. We will also present data showing that, in addition to motor symptoms, N/OFQ also plays a role in the parkinsonian neurodegeneration. In fact, NOP receptor antagonists possess neuroprotective/neurorescue properties in in vitro and in vivo models of PD.

Therapeutic Approaches for NOP Receptor Antagonists in Neurobehavioral Disorders: Clinical Studies in Major Depressive Disorder and Alcohol Use Disorder with BTRX-246040 (LY2940094)

Conventional antidepressants increase the efflux of biogenic amine neurotransmitters (the monoamine hypothesis of depression) in the central nervous system (CNS) and are the principle drugs used to treat major depressive disorder (MDD). However, the lack of efficacy in some patients, the slow onset of action, and the side effect profiles of existing antidepressants necessitate the exploration of additional treatment options. The discovery of the nociceptin/orphanin FQ peptide NOP receptor (N/OFQ-NOP receptor) system and its characterization in preclinical biological and pharmacological stress-related conditions supports the potential antidepressant and anti-stress properties of a NOP receptor antagonist for the treatment of neurobehavioral disorders. BTRX-246040 (formerly LY2940094) was designed to test this hypothesis in the clinic. A small clinical proof of concept study demonstrated efficacy of BTRX-246040 in MDD patients. In this study, BTRX-246040 (40 mg, p.o.) significantly reduced negative bias as assessed by the facial recognition test within 1 week of treatment and decreased depression symptoms after 8 weeks. BTRX-246040 also reduced depression symptoms in a second trial with heavy alcohol drinkers. Given the comorbidity of MDD and alcohol use disorder, a compound with such effects in patients could be a valuable addition to the medications available. A proof of concept study showed efficacy of BTRX-246040 in reducing heavy drinking and increasing the probability of abstinence in individuals diagnosed with alcohol dependence. In addition, plasma levels of gamma-glutamyl transferase were decreased by BTRX-246040 compared to placebo control implying improvement in liver function. Collectively, the clinical data reviewed within this chapter suggest that BTRX-264040 functions to normalize dysfunction in reward circuits. The overall efficacy and safety of this compound with a novel mechanism of action are encouraging of further clinical development. BTRX-246040 is currently under development for MDD by BlackThorn Therapeutics.

NOP agonists prevent the antidepressant-like effects of nortriptyline and fluoxetine but not R-ketamine

RATIONALE

Nociceptin/orphanin FQ (N/OFQ) is the endogenous ligand of a Gi protein-coupled receptor named NOP. Both N/OFQ and NOP receptor are widely expressed in brain areas involved in the control of emotional processes. Clinical and preclinical studies support antidepressant effects due to the blockade of NOP receptor signaling. By contrast, NOP receptor activation did not evoke any change in behavioral despair tests.

OBJECTIVES

The present study aimed to investigate the effects of the co-administration of NOP agonists and classic antidepressant drugs in the forced swimming test (FST) and learned helplessness model (LH) in mice.

METHODS

Male Swiss mice were co-administered with NOP agonists (N/OFQ and Ro 65-6570) and antidepressants (nortriptyline, fluoxetine, and R-ketamine) or SB-612111 (NOP antagonist) and the behavioral effects were assessed in the FST and LH tests.

RESULTS

Fluoxetine, nortriptyline, R-ketamine and the NOP antagonist SB-612111 displayed antidepressant-like effects in the FST. The administration of the NOP agonists N/OFQ and Ro 65-6570 did not induce any behavioral change. However, co-administration of NOP agonists blocked the antidepressant effects of SB-612111, fluoxetine, and nortriptyline, but not R-ketamine in the FST. Similarly, in the LH, the systemic injection of SB-612111, nortriptyline, and R-ketamine reversed helplessness. The co-administration of Ro 65-6570 blocked the antidepressant-like effects of SB-612111 and nortriptyline, but not R-ketamine.

CONCLUSIONS

NOP receptor activation inhibits the acute antidepressant effects of nortriptyline and fluoxetine, but not R-ketamine. The present findings contribute to further understand the role played by the N/OFQ-NOP receptor system in regulating mood states.

Nociceptin/orphanin FQ receptor ligands and translational challenges: focus on cebranopadol as an innovative analgesic

Opioids are characterised as classical (mu, delta, and kappa) along with the non-classical nociceptin/orphanin FQ (N/OFQ) receptor or NOP. Targeting NOP has therapeutic indications in control of the cardiovascular and respiratory systems and micturition, and a profile as an antidepressant. For all of these indications, there are translational human data. Opioids such as morphine and fentanyl (activating the mu receptor) are the mainstay of pain treatment in the perioperative period, despite a challenging side-effect profile. Opioids in general have poor efficacy in neuropathic pain. Moreover, longer term use is associated with tolerance. There is good evidence interactions between opioid receptors, and receptor co-activation can reduce side-effects without compromising analgesia; this is particularly true for mu and NOP co-activation. Recent pharmaceutical development has produced a mixed opioid/NOP agonist, cebranopadol. This new chemical entity is effective in animal models of nociceptive and neuropathic pain with greater efficacy in the latter. In animal models, there is little evidence for respiratory depression, and tolerance (compared with morphine) only develops after long treatment periods. There is now early phase clinical development in diabetic neuropathy, cancer pain, and low back pain where cebranopadol displays significant efficacy. In 1996, N/OFQ was formally identified with an innovative analgesic profile. Approximately 20 yr later, cebranopadol as a clinical ligand is advancing through the human trials process.

NOP Ligands for the Treatment of Anxiety and Mood Disorders

Many studies point toward the nociceptin/orphanin FQ (N/OFQ) and the N/OFQ peptide receptor (NOP) as targets for the development of innovative drugs for treating anxiety- and mood-related disorders. Evidence supports the view that the activation of NOP receptors with agonists elicits anxiolytic-like effects, while its blockade with NOP antagonists promotes antidepressant-like actions in rodents. Genetic studies showed that NOP receptor knockout mice display an antidepressant-like phenotype, and NOP antagonists are inactive in these animals. In contrast, the genetic blockade of NOP receptor signaling generally displays an increase of anxiety states in the elevated plus-maze test. In this chapter we summarized the most relevant findings of NOP receptor ligands in the modulation of anxiety and mood disorders, and the putative mechanisms of action are discussed.

Modified synthesis of NOP receptor antagonist SB612111

SB612111 ((5S,7S)-7-{[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl}-1-methyl-6,7,8,9-tetrahydro-5H-benzo[7]annulen-5-ol) is a potent and selective antagonist of the nociception/orphanin FQ peptide (NOP) receptor. In the process of synthesizing cis-SB612111 to support ongoing animal studies, several key steps of the published syntheses in the patent literature proceeded in low yields in our hands, particularly with the route to the key intermediate piperidine 3, the reduction of amide 14, lactone 17 formation and the final reductive amination between 18 and 3 in the diastereoselective synthesis. We have thus explored various reaction conditions and successfully improved the yields for the necessary synthetic steps. We herein report our modified synthesis of SB612111 as the cis-diastereomers.

Genetic Deletion of the Nociceptin/Orphanin FQ Receptor in the Rat Confers Resilience to the Development of Drug Addiction

The nociceptin (NOP) receptor is a G-protein-coupled receptor whose natural ligand is the NOP/orphanin FQ (N/OFQ) peptide. Evidence from pharmacological studies suggests that the N/OFQ system is implicated in the regulation of several addiction-related phenomena, such as drug intake, withdrawal, and relapse. Here, to further explore the role of NOP system in addiction, we used NOP (-/-) rats to study the motivation for cocaine, heroin, and alcohol self-administration in the absence of N/OFQ function. Conditioned place preference (CPP) and saccharin (0.2% w/v) self-administration were also investigated. Results showed that NOP (-/-) rats self-administer less cocaine (0.25, 0.125, or 0.5 mg/infusion) both under a fixed ratio 1 and a progressive ratio schedule of reinforcement compared with wild-type (Wt) controls. Consistently, cocaine (10 mg/kg, i.p.) was able to induce CPP in Wt but not in NOP (-/-). When NOP (-/-) rats were tested for heroin (20 μg/infusion) and ethanol (10% v/v) self-administration, they showed significantly lower drug intake compared with Wt. Conversely, saccharin self-administration was not affected by NOP deletion, excluding the possibility of nonspecific learning deficits or generalized disruption of reward mechanisms in NOP (-/-) rats. These findings were confirmed with pharmacological experiments using two selective NOP antagonists, SB-612111 and LY2817412. Both drugs attenuated alcohol self-administration in Wt rats but not in NOP (-/-) rats. In conclusion, our results demonstrate that genetic deletion of NOP receptors confers resilience to drug abuse and support a role for NOP receptor antagonism as a potential treatment option for drug addiction.

Preclinical findings predicting efficacy and side-effect profile of LY2940094, an antagonist of nociceptin receptors

Nociceptin/Orphanin FQ (N/OFQ) is a 17 amino acid peptide whose receptor is designated ORL1 or nociceptin receptor (NOP). We utilized a potent, selective, and orally bioavailable antagonist with documented engagement with NOP receptors in vivo to assess antidepressant‐ and anxiolytic‐related pharmacological effects of NOP receptor blockade along with measures of cognitive and motor impingement. LY2940094 ([2‐[4‐[(2‐chloro‐4,4‐difluoro‐spiro[5H‐thieno[2,3‐c]pyran‐7,4′‐piperidine]‐1′‐yl)methyl]‐3‐methyl‐pyrazol‐1‐yl]‐3‐pyridyl]methanol) displayed antidepressant‐like behavioral effects in the forced‐swim test in mice, an effect absent in NOP^−/− mice. LY2940094 also augmented the behavioral effect of fluoxetine without changing target occupancies (NOP and serotonin reuptake transporter [SERT]). LY2940094 did not have effects under a differential‐reinforcement of low rate schedule. Although anxiolytic‐like effects were not observed in some animal models (conditioned suppression, 4‐plate test, novelty‐suppressed feeding), LY2940094 had effects like that of anxiolytic drugs in three assays: fear‐conditioned freezing in mice, stress‐induced increases in cerebellar cGMP in mice, and stress‐induced hyperthermia in rats. These are the first reports of anxiolytic‐like activity with a systemically viable NOP receptor antagonist. LY2940094 did not disrupt performance in either a 5‐choice serial reaction time or delayed matching‐to‐position assay. LY2940094 was also not an activator or suppressor of locomotion in rodents nor did it induce failures of rotarod performance. These data suggest that LY2940094 has unique antidepressant‐ and anxiolytic‐related pharmacological effects in rodents. Clinical proof of concept data on this molecule in depressed patients have been reported elsewhere.

Nociceptin receptor antagonist SB 612111 decreases high fat diet binge eating

Binge eating is a dysregulated form of feeding behavior that occurs in multiple eating disorders including binge-eating disorder, the most common eating disorder. Feeding is a complex behavioral program supported through the function of multiple brain regions and influenced by a diverse array of receptor signaling pathways. Previous studies have shown the overexpression of the opioid neuropeptide nociceptin (orphanin FQ, N/OFQ) can induce hyperphagia, but the role of endogenous nociceptin receptor (NOP) in naturally occurring palatability-induced hyperphagia is unknown. In this study we adapted a simple, replicable form of binge eating of high fat food (HFD). We found that male and female C57BL/6J mice provided with daily one-hour access sessions to HFD eat significantly more during this period than those provided with continuous 24h access. This form of feeding is rapid and entrained. Chronic intermittent HFD binge eating produced hyperactivity and increased light zone exploration in the open field and light-dark assays respectively. Treatment with the potent and selective NOP antagonist SB 612111 resulted in a significant dose-dependent reduction in binge intake in both male and female mice, and, unlike treatment with the serotonin selective reuptake inhibitor fluoxetine, produced no change in total 24-h food intake. SB 612111 treatment also significantly decreased non-binge-like acute HFD consumption in male mice. These data are consistent with the hypothesis that high fat binge eating is modulated by NOP signaling and that the NOP system may represent a promising novel receptor to explore for the treatment of binge eating.

Antidepressant activity of nociceptin/orphanin FQ receptor antagonists in the mouse learned helplessness

RATIONALE

Pharmacological and genetic evidence support antidepressant-like effects elicited by the blockade of the NOP receptor. The learned helplessness (LH) model employs uncontrollable and unpredictable electric footshocks as a stressor stimulus to induce a depressive-like phenotype that can be reversed by classical antidepressants.

OBJECTIVES

The present study aimed to evaluate the action of NOP receptor antagonists in helpless mice.

METHODS

Male Swiss mice were subjected to the three steps of the LH paradigm (i.e., (1) induction, (2) screening, and (3) test). Only helpless animals were subjected to the test session. During the test session, animals were placed in the electrified chamber and the latency to escape after the footshock and the frequency of escape failures were recorded. The effect of the following treatments administered before the test session were evaluated: nortriptyline (30 mg/kg, ip, 60 min), fluoxetine (30 mg/kg, ip, four consecutive days of treatment), and NOP antagonists SB-612111 (1-10 mg/kg, ip, 30 min) and UFP-101 (1-10 nmol, icv, 5 min). To rule out possible biases, the effects of treatments on controllable stressful and non stressful situations were assessed.

RESULTS

In helpless mice, nortriptyline, fluoxetine, UFP-101 (3-10 nmol), and SB-612111 (3-10 mg/kg) significantly reduced escape latencies and escape failures. No effects of drug treatments were observed in mice subjected to the controllable electric footshocks and non stressful situations.

CONCLUSIONS

Acute treatment with NOP antagonists reversed helplessness similarly to the classical antidepressants. These findings support the proposal that NOP receptor antagonists are worthy of development as innovative antidepressant drugs.

A Selective Nociceptin Receptor Antagonist to Treat Depression: Evidence from Preclinical and Clinical Studies

Nociceptin/Orphanin FQ (N/OFQ) is an endogenous ligand of the N/OFQ peptide (NOP) receptor, which is a G protein-coupled receptor in brain regions associated with mood disorders. We used a novel, potent, and selective orally bioavailable antagonist, LY2940094, to test the hypothesis that blockade of NOP receptors would induce antidepressant effects. In this study we demonstrate that targeting NOP receptors with LY2940094 translates to antidepressant-like effects in rodent models and, importantly, to antidepressant efficacy in patients with major depressive disorder (MDD). The proof-of-concept study (POC) was an 8-week, double-blind, placebo-controlled trial that evaluated LY2940094 as a novel oral medication for the treatment of patients with MDD. Once daily oral dosing of LY2940094 at 40 mg for 8 weeks vs placebo provided some evidence for an antidepressant effect based on the change from baseline to week 8 in the GRID-Hamilton Depression Rating Scale-17 item total score, although the predefined POC efficacy criterion (probability of LY2940094 being better than placebo⩾88%) was not met (82.9%). LY2940094 also had an early effect on the processing of emotional stimuli at Week 1 as shown by an increased recognition of positive relative to negative facial expressions in an emotional test battery. LY2940094 was safe and well tolerated. Overall, these are the first human data providing evidence that the blockade of NOP receptor signaling represents a promising strategy for the treatment of MDD.

A Novel, Orally Bioavailable Nociceptin Receptor Antagonist, LY2940094, Reduces Ethanol Self-Administration and Ethanol Seeking in Animal Models

BACKGROUND

The nociceptin/orphanin-FQ (or opioid receptor-like [ORL1]) receptor (NOP) is localized in the mesolimbic reward pathway and has been suggested to play a role in feeding, mood, stress, and addiction. Since its deorphanization in 1995, there has been a clear dichotomy in the literature regarding whether an agonist or antagonist would provide therapeutic benefit. Specifically, the literature reports indicate that NOP receptor antagonists produce efficacy in animal models of hyperphagia and antidepressant-like activity, whereas NOP agonists produce anxiolytic-like effects and dampen reward/addiction behaviors including ethanol consumption.

METHODS

We characterize here the potent, orally bioavailable NOP antagonist, LY2940094, in rodent models of ethanol consumption, including ethanol self-administration, progressive ratio operant self-administration, stress-induced reinstatement of ethanol seeking, and in vivo microdialysis in the nucleus accumbens.

RESULTS

LY2940094 dose dependently reduced homecage ethanol self-administration in Indiana alcohol-preferring (P) and Marchigian Sardinian alcohol-preferring (msP) rats, without affecting food/water intake or locomotor activity. Reduced ethanol intake in P rats did not show significant tolerance over 4 days of subchronic dosing. LY2940094 attenuated progressive ratio operant responding and break points for ethanol in P rats. Moreover, stress-induced reinstatement of ethanol seeking in msP rats was completely blocked by LY2940094. Furthermore, LY2940094 blocked ethanol-stimulated dopamine release in response to ethanol challenge (1.1 g/kg, intraperitoneally).

CONCLUSIONS

Our findings demonstrate for the first time that blockade of NOP receptors attenuates ethanol self-administration and ethanol-motivated behaviors, stress-induced ethanol seeking, and ethanol-induced stimulation of brain reward pathways in lines of rats that exhibit excessive ethanol consumption. Results suggest that LY2940094 may have potential therapeutic utility in treating alcohol addiction.

Endogenous opiates and behavior: 2014

This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants). This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants).

A Novel Nociceptin Receptor Antagonist LY2940094 Inhibits Excessive Feeding Behavior in Rodents: A Possible Mechanism for the Treatment of Binge Eating Disorder

Nociceptin/orphanin FQ (N/OFQ), a 17 amino acid peptide, is the endogenous ligand of the ORL1/nociceptin-opioid-peptide (NOP) receptor. N/OFQ appears to regulate a variety of physiologic functions including stimulating feeding behavior. Recently, a new class of thienospiro-piperidine-based NOP antagonists was described. One of these molecules, LY2940094 has been identified as a potent and selective NOP antagonist that exhibited activity in the central nervous system. Herein, we examined the effects of LY2940094 on feeding in a variety of behavioral models. Fasting-induced feeding was inhibited by LY2940094 in mice, an effect that was absent in NOP receptor knockout mice. Moreover, NOP receptor knockout mice exhibited a baseline phenotype of reduced fasting-induced feeding, relative to wild-type littermate controls. In lean rats, LY2940094 inhibited the overconsumption of a palatable high-energy diet, reducing caloric intake to control chow levels. In dietary-induced obese rats, LY2940094 inhibited feeding and body weight regain induced by a 30% daily caloric restriction. Last, in dietary-induced obese mice, LY2940094 decreased 24-hour intake of a high-energy diet made freely available. These are the first data demonstrating that a systemically administered NOP receptor antagonist can reduce feeding behavior and body weight in rodents. Moreover, the hypophagic effect of LY2940094 is NOP receptor dependent and not due to off-target or aversive effects. Thus, LY2940094 may be useful in treating disorders of appetitive behavior such as binge eating disorder, food choice, and overeating, which lead to obesity and its associated medical complications and morbidity.

Meglumine catalyzed expeditious four-component domino protocol for synthesis of pyrazolopyranopyrimidines in aqueous medium

Meglumine has been found to be an efficient catalyst for the synthesis of structurally diverse tricyclic fused pyrazolopyranopyrimidines by one-pot, four-component reaction of ethyl acetoacetate, hydrazine hydrate, aromatic aldehydes and barbituric acid in water.

1,1′-Sulfinyldipyridinium bis (hydrogen sulfate) ionic liquid: synthesis and application in the temperature-influenced synthesis of novel pyranopyrimidinediones and pyranopyrimidinetriones

A novel and robust dication Brønsted acidic ionic liquid as a catalyst for the temperature influenced synthesis of novel pyranopyrimidinediones and pyranopyrimidinetriones.