Neuropeptide Y: Role in Emotion and Alcohol Dependence

The Role of BDNF and NPY Levels, Effects of Behavioral Systems and Emotion Regulation on Internet Addiction in Adolescents

Internet addiction (IA), one of the behavioral addictions, is also related to impulsivity. Although studies on its etiology and risks continue, the number of studies is limited. In this study, we aimed to assess the roles of behavioral systems, emotional regulation (ER), and impulsivity in the development of IA in adolescents and also to assess the relationship between all these clinical parameters and brain-derived neurotrophic factor (BDNF) and neuropeptide Y (NPY). Forty-two adolescents with IA and 30 healthy controls (ages 12 -17) were included in the study. Self-reported measures included the Internet Addiction Scale. (IAS), Behavioral Activation and Behavioral Inhibition Scale (BAS/BIS), Barratt. Impulsiveness Scale-11 (BIS-11), and Difficulties in Emotion Regulation Scale-16 (DERS-16) were used for the assessment of the participants. The levels of plasma brain BDNF and NPY were evaluated with the ELISA method. BAS/BIS subscale scores, BIS-11, and DERS-16 scale total scores were found to be statistically significantly higher, while BDNF and NPY levels were found to be lower in adolescents with IA compared to the healthy controls. IA severity was not found to correlate with both BDNF and NPY. IA was found to be more related to BIS than to BAS. There is a need for further studies evaluating developmental features and possible diagnostic biomarkers that may be associated with IA in adolescents.

Epigenetics of Autism Spectrum Disorders: A Multi-level Analysis Combining Epi-signature, Age Acceleration, Epigenetic Drift and Rare Epivariations Using Public Datasets

BACKGROUND

Epigenetics of Autism Spectrum Disorders (ASD) is still an understudied field. The majority of the studies on the topic used an approach based on mere classification of cases and controls.

OBJECTIVE

The present study aimed at providing a multi-level approach in which different types of epigenetic analysis (epigenetic drift, age acceleration) are combined.

METHODS

We used publicly available datasets from blood (n = 3) and brain tissues (n = 3), separately. Firstly, we evaluated for each dataset and meta-analyzed the differential methylation profile between cases and controls. Secondly, we analyzed age acceleration, epigenetic drift and rare epigenetic variations.

RESULTS

We observed a significant epi-signature of ASD in blood but not in brain specimens. We did not observe significant age acceleration in ASD, while epigenetic drift was significantly higher compared to controls. We reported the presence of significant rare epigenetic variations in 41 genes, 35 of which were never associated with ASD. Almost all genes were involved in pathways linked to ASD etiopathogenesis (i.e., neuronal development, mitochondrial metabolism, lipid biosynthesis and antigen presentation).

CONCLUSION

Our data support the hypothesis of the use of blood epi-signature as a potential tool for diagnosis and prognosis of ASD. The presence of an enhanced epigenetic drift, especially in brain, which is linked to cellular replication, may suggest that alteration in epigenetics may occur at a very early developmental stage (i.e., fetal) when neuronal replication is still high.

Off-label and investigational drugs in the treatment of alcohol use disorder: A critical review

Compounds known to be successful in the treatment of alcohol use disorder include the aversive agent, Disulfiram, the glutamatergic NMDA receptor antagonist, Acamprosate, and the opioid receptor antagonists, Naltrexone and Nalmefene. Although all four are effective in maintaining abstinence or reduction of alcohol consumption, only a small percentage of patients receive pharmacological treatment. In addition, many other medications have been investigated for their therapeutic potential in the treatment of alcohol use disorder. In this review we summarize and compare Baclofen, Gabapentin, Topiramate, Ondansetron, Varenicline, Aripiprazole, Quetiapine, Clozapine, Antidepressants, Lithium, Neuropeptide Y, Neuropeptide S, Corticotropin-releasing factor antagonists, Oxytocin, PF-05190457, Memantine, Ifenprodil, Samidorphan, Ondelopran, ABT-436, SSR149415, Mifepristone, Ibudilast, Citicoline, Rimonabant, Surinabant, AM4113 and Gamma-hydroxybutyrate While some have shown promising results in the treatment of alcohol use disorder, others have disappointed and should be excluded from further investigation. Here we discuss the most promising results and highlight medications that deserve further preclinical or clinical study. Effective, patient-tailored treatment will require greater understanding provided by many more preclinical and clinical studies.

Structural Perspective on Ancient Neuropeptide Y-like System reveals Hallmark Features for Peptide Recognition and Receptor Activation

The neuropeptide Y (NPY) family is a peptide-activated G protein-coupled receptor system conserved across all bilaterians, and is involved in food intake, learning, and behavior. We hypothesized that comparing the NPY system in evolutionarily ancient organisms can reveal structural determinants of peptide recognition and receptor activation conserved in evolution. To test this hypothesis, we investigated the homologous FLP/NPR system of the protostome C.elegans. For three prototypic peptide-receptor complexes representing different ligand types, we integrate extensive functional data into structural models of the receptors. Common features include acidic patches in the extracellular loops (ECLs) of the receptors that cooperatively 'draw' the peptide into the binding pocket, which was functionally validated in vivo. A structurally conserved glutamate in the ECL2 anchors the peptides by a conserved salt bridge to the arginine of the RFamide motif. Beyond this conserved interaction, peptide binding show variability enabled by receptor-specific interactions. The family-conserved residue Q^3.32 is a key player for peptide binding and receptor activation. Altered interaction patterns at Q^3.32 may drastically increase the efficacy to activate the receptor.

Pharmacological and functional similarities of the human neuropeptide Y system in C. elegans challenges phylogenetic views on the FLP/NPR system

BACKGROUND

The neuropeptide Y system affects various processes, among others food intake, and is frequently discussed in the context of targeting obesity. Studies in model organisms are indispensable to enable molecular studies in a physiological context. Although the NPY system is evolutionarily conserved in all bilaterians, in the widely used model Caenorhabditis elegans there is controversy on the existence of NPY orthologous molecules. While the FMRFamide-like peptide (FLP)/Neuropeptide receptor-Resemblance (NPR) system in the nematode was initially suggested to be orthologous to the mammalian NPY system, later global phylogenetic studies indicate that FLP/NPR is protostome-specific.

METHODS

We performed a comprehensive pharmacological study of the FLP/NPR system in transfected cells in vitro, and tested for functional substitution in C. elegans knockout strains. Further, we phenotypically compared different flp loss-of-function strains. Differences between groups were compared by ANOVA and post-hoc testing (Dunnett, Bonferroni).

RESULTS

Our pharmacological analysis of the FLP/NPR system including formerly functionally uncharacterized NPY-like peptides from C. elegans demonstrates that G protein-coupling and ligand requirements for receptor activation are similar to the human NPY system. In vitro and in vivo analyses show cross-reactivity of NPY with the FLP/NPR system manifesting in the ability of the human GPCRs to functionally substitute FLP/NPR signaling in vivo. The high pharmacological/functional similarities enabled us to identify C. elegans FLP-14 as a key molecule in avoidance behavior.

CONCLUSIONS

Our data demonstrate the pharmacological and functional similarities of human NPY and C. elegans NPR systems. This adds a novel perspective to current phylogenetic reconstructions of the neuropeptide Y system. NPY and NPR receptors are pharmacologically so similar that the human receptors can functionally compensate for the C. elegans ones, suggesting orthologous relationships. This is also underlined by the presence of NPY-like peptides and parallels in peptide requirements for receptor activation. Further, the results presented here highlight the potential of this knowledge for physiological as well as molecular studies on neuropeptide GPCRs such as the NPY system in the future.

Physiological and Therapeutic Roles of Neuropeptide Y on Biological Functions

Neuropeptide Y (NPY), an amino acid, used for various physiological processes for management and treatment of various ailments related to central nervous system, cardiovascular system, respiratory system, gastro-intestinal system and endocrinal system. In nasal mucosa, high concentrations of NPY are stored with noradrenaline in sympathetic nerve fibers. NPY Y₁ receptor mediates nitric oxide levels and reduction in blood flow in nasal mucosa of the human. NPY plays a role in dietary consumption via various factors like signaling the CNS for a prerequisite of energy in hypothalamus by mediating appetite and shows orexigenic effect. NPY emerges as a natural ligand of G-protein coupled receptors which activates the Y-receptors (Y₁-Y₆). But applications of NPY are limited due to shows the cost inefficiency and stability issues in the formulation design and development. In this review, authors present the findings on various therapeutic applications of NPY on different organ systems. Moreover, its role in food intake, sexual behavior, blood pressure, etc. by inhibiting calcium and activating potassium channels. The combination therapies of drugs with neuropeptide Y and its receptors will show new targets for treating diseases. Further evaluation and detection of NPY needs to be investigated for animal models of various diseases like retinal degeneration and immune mechanisms.

Putative transmembrane transporter modulates higher-level aggression in Drosophila

By selection of winners of dyadic fights for 35 generations, we have generated a hyperaggressive Bully line of flies that almost always win fights against the parental wild-type Canton-S stock. Maintenance of the Bully phenotype is temperature dependent during development, with the phenotype lost when flies are reared at 19 °C. No similar effect is seen with the parent line. This difference allowed us to carry out RNA-seq experiments and identify a limited number of genes that are differentially expressed by twofold or greater in the Bullies; one of these was a putative transmembrane transporter, CG13646, which showed consistent and reproducible twofold down-regulation in Bullies. We examined the causal effect of this gene on the phenotype with a mutant line for CG13646, and with an RNAi approach. In all cases, reduction in expression of CG13646 by approximately half led to a hyperaggressive phenotype partially resembling that seen in the Bully flies. This gene is a member of a very interesting family of solute carrier proteins (SLCs), some of which have been suggested as being involved in glutamine/glutamate and GABA cycles of metabolism in excitatory and inhibitory nerve terminals in mammalian systems.

Comparative Evaluation of Pain, Stress, Neuropeptide Y, ACTH, and Cortisol Levels Between a Conventional Postoperative Care Protocol and a Fast-Track Recovery Program in Patients Undergoing Major Abdominal Surgery

BACKGROUND

Fast-track (FT) postoperative protocol in oncological patients after major abdominal surgery reduces complications and length of postoperative stay compared to the conventional (CON) protocol. However, stress and pain responses have not been compared between the two protocols.

OBJECTIVES

To compare stress, pain, and related neuropeptidic responses (adrenocorticotropic hormone [ACTH], cortisol, and neuropeptide Y [NPY]) between FT and CON protocols.

METHOD

A clinical trial with repeated measurements was conducted (May 2012 to May 2014) with a sample of 63 hepatectomized or pancreatectomized patients randomized into two groups: FT ( n = 29) or CON ( n = 34). Demographic and clinical data were collected, and pain (Visual Analog Scale [VAS] and Behavioral Pain Scale [BPS]) and stress responses (3 self-report questions) assessed. NPY, ACTH, and cortisol plasma levels were measured at T1 = day of admission, T2 = day of surgery, and T3 = prior to discharge.

RESULTS

ACTH_T1 and ACTH_T2 levels were positively correlated with self-reported stress levels (ρ = .43 and ρ = .45, respectively, p < .05) in the FT group. NPY levels in the FT group were higher than those in the CON group at all time points ( p ≤ .004); this difference remained significant after adjusting for T1 levels through analysis of covariance for age, gender, and body mass index ( F = .003, F = .149, F = .015, respectively, p > .05).

CONCLUSIONS

Neuropeptidic levels were higher in the FT group. Future research should evaluate this association further, as these biomarkers might serve as objective indicators of postoperative pain and stress.

Changes in the female arcuate nucleus morphology and neurochemistry after chronic ethanol consumption and long-term withdrawal

Ethanol is a macronutrient whose intake is a form of ingestive behavior, sharing physiological mechanisms with food intake. Chronic ethanol consumption is detrimental to the brain, inducing gender-dependent neuronal damage. The hypothalamic arcuate nucleus (ARN) is a modulator of food intake that expresses feeding-regulatory neuropeptides, such as alpha melanocyte-stimulating hormone (α-MSH) and neuropeptide Y (NPY). Despite its involvement in pathways associated with eating disorders and ethanol abuse, the impact of ethanol consumption and withdrawal in the ARN structure and neurochemistry in females is unknown. We used female rat models of 20% ethanol consumption for six months and of subsequent ethanol withdrawal for two months. Food intake and body weights were measured. ARN morphology was stereologically analyzed to estimate its volume, total number of neurons and total number of neurons expressing NPY, α-MSH, tyrosine hydroxylase (TH) and estrogen receptor alpha (ERα). Ethanol decreased energy intake and body weights. However, it did not change the ARN morphology or the expression of NPY, α-MSH and TH, while increasing ERα expression. Withdrawal induced a significant volume and neuron loss that was accompanied by an increase in NPY expression without affecting α-MSH and TH expression. These findings indicate that the female ARN is more vulnerable to withdrawal than to excess alcohol. The data also support the hypothesis that the same pathways that regulate the expression of NPY and α-MSH in long-term ethanol intake may regulate food intake. The present model of long-term ethanol intake and withdrawal induces new physiological conditions with adaptive responses.

Differential patterns of expression of neuropeptide Y throughout abstinence in outbred Swiss mice classified as susceptible or resistant to ethanol-induced locomotor sensitization

Several studies have focused on the negative emotional state associated with drug abstinence. The peptide NPY plays an important role given its involvement in drug addiction, anxiety, and mood disorders. Interestingly, it is well established that outbred Swiss mice exhibit a prominent behavioral variability to ethanol-induced locomotor sensitization. Here, we investigated whether mice that were either susceptible or resistant to ethanol sensitization differed in their NPY expression during abstinence. The mice were treated daily with ethanol (2 g/kg, i.p.) or saline for 21 days. According to the locomotor activity after the last injection, the ethanol group was classified as sensitized (EtOH_High) or non-sensitized (EtOH_Low). To evaluate NPY expression, some of the mice were sacrificed at 18 h or 5 days of abstinence, and others were challenged at the 5th day of abstinence with ethanol (1.4 g/kg) and sacrificed after 1.5 h. At 5 days of abstinence, NPY expression increased in the orbital cortex, dorsomedial striatum, and dentate gyrus in the EtOH_High mice. These changes were counteracted by the ethanol challenge. In the EtOH_Low mice, NPY expression increased in the dentate gyrus only after 18 h of abstinence. Lastly, a decreased level of NPY was found in the prelimbic cortex of the EtOH_Low mice at 5 days of abstinence, and this was reversed by ethanol challenge. Therefore, behavioral variability in ethanol sensitization confers differential neurochemical features during the subsequent abstinence, including distinct patterns of NPY expression.

G protein-linked signaling pathways in bipolar and major depressive disorders

The G-protein linked signaling system (GPLS) comprises a large number of G-proteins, G protein-coupled receptors (GPCRs), GPCR ligands, and downstream effector molecules. G-proteins interact with both GPCRs and downstream effectors such as cyclic adenosine monophosphate (cAMP), phosphatidylinositols, and ion channels. The GPLS is implicated in the pathophysiology and pharmacology of both major depressive disorder (MDD) and bipolar disorder (BPD). This study evaluated whether GPLS is altered at the transcript level. The gene expression in the dorsolateral prefrontal (DLPFC) and anterior cingulate (ACC) were compared from MDD, BPD, and control subjects using Affymetrix Gene Chips and real time quantitative PCR. High quality brain tissue was used in the study to control for confounding effects of agonal events, tissue pH, RNA integrity, gender, and age. GPLS signaling transcripts were altered especially in the ACC of BPD and MDD subjects. Transcript levels of molecules which repress cAMP activity were increased in BPD and decreased in MDD. Two orphan GPCRs, GPRC5B and GPR37, showed significantly decreased expression levels in MDD, and significantly increased expression levels in BPD. Our results suggest opposite changes in BPD and MDD in the GPLS, “activated” cAMP signaling activity in BPD and “blunted” cAMP signaling activity in MDD. GPRC5B and GPR37 both appear to have behavioral effects, and are also candidate genes for neurodegenerative disorders. In the context of the opposite changes observed in BPD and MDD, these GPCRs warrant further study of their brain effects.

Neuropeptide Y Y5 receptor antagonism causes faster extinction and attenuates reinstatement in cocaine-induced place preference

Several studies have suggested a role for neuropeptide Y (NPY) in addiction to drugs of abuse, including cocaine. Recently, our group showed a role for the NPY Y5 receptor in the modulation of acute reinforcing effects of cocaine using self-administration and hyperlocomotion paradigms. In the present study, we further explored potential anti-addiction-related effects of Y5 antagonism in another murine model of cocaine addiction-related behavior: conditioned place-preference (CPP). Using this model, it was tested whether blockade or deficiency of the NPY Y5 receptor could influence the induction, extinction or reinstatement of a conditioned cocaine response. We found that the Y5 antagonist L-152,804 causes faster extinction and reduced reinstatement of cocaine-induced CPP but did not reduce the ability of cocaine to induce CPP. Similarly, Y5-KO mice displayed faster extinction, and reinstatement of cocaine-induced CPP was absent. The development of CPP for cocaine was similar between Y5-KO and WT mice. Taken together, the present data show that Y5 antagonism attenuates relapse to cocaine addiction-related behavior. Prevention of relapse is considered to be of pivotal importance for the development of an effective treatment against cocaine addiction and therefore Y5 receptors could be a potential future therapeutic target in cocaine addiction.

Neuropeptide Y Y5 receptor antagonism attenuates cocaine-induced effects in mice

RATIONALE

Several studies suggest a role for neuropeptide Y (NPY) in addiction to drugs of abuse, including cocaine. However, the NPY receptors mediating addiction-related effects remain to be determined.

OBJECTIVES

To explore the potential role of Y5 NPY receptors in cocaine-induced behavioural effects.

METHODS

The Y5 antagonist L-152,804 and Y5-knockout (Y5-KO) mice were tested in two models of cocaine addiction-related behaviour: acute self-administration and cocaine-induced hyperactivity. We also studied effects of Y5 receptor antagonism on cocaine-induced c-fos expression and extracellular dopamine with microdialysis as well as dopamine transporter-mediated uptake of dopamine in vitro. Immunocytochemistry was used to determine whether dopamine neurons express Y5-like immunoreactivity.

RESULTS

In self-administration, L-152,804 prominently decreased nose-poking for the peak dose of cocaine and shifted the dose-response curve for cocaine downward. Y5-KO mice also showed modestly attenuated self-administration. Cocaine-induced hyperactivity was attenuated by L-152,804 and in Y5-KO mice. Cocaine failed to increase c-fos expression in the nucleus accumbens and striatum of L-152,804-treated mice, indicating that the Y5 antagonist could act by influencing neural activity in these regions. Accordingly, the cocaine-induced increase in accumbal extracellular dopamine was attenuated by L-152,804 and in Y5-KO mice, suggesting that Y5 antagonism influences cocaine-induced behaviour by regulating dopamine. Consistent with this concept, dopamine neurons in the ventral tegmental area appeared to contain Y5 receptors. In contrast, neither L-152,804 nor NPY influenced dopamine transporter-mediated dopamine uptake.

CONCLUSIONS

The present data indicate that Y5 antagonism may attenuate cocaine-induced behavioural effects, suggesting that Y5 receptors could be a potential therapeutic target in cocaine addiction.

Mice lacking neuropeptide Y show increased sensitivity to cocaine

There is increasing data implicating neuropeptide Y (NPY) in the neurobiology of addiction. This study explored the possible role of NPY in cocaine-induced behavior using NPY knockout mice. The transgenic mice showed a hypersensitive response to cocaine in three animal models of cocaine addiction. Whether this is due to an observed compensatory increase in striatal dopamine transporter binding or an anxiogenic phenotype of the transgenic mice remains to be determined.

Proinflammatory and "resiliency" proteins in the CSF of patients with major depression

BACKGROUND

A number of studies have shown that elevated levels of inflammatory cytokines may promote depression and suicidal ideation and that neuroprotective peptides may decrease the response to stress and depression. In this study, cerebrospinal fluid (CSF) levels of three inflammatory cytokines (IL-1, IL-6, and tumor necrosis factor α (TNFα)) and two putative "resiliency" neuropeptides (brain-derived neurotrophic factor (BDNF) and neuropeptide Y (NPY)) were compared between patients with depression and healthy controls.

METHODS

Eighteen patients with major depression and 25 healthy controls underwent a lumbar puncture; CSF samples were withdrawn and assayed for IL-1, IL-6, TNFα, BDNF, and NPY levels. Patients with depression were then entered into an 8-week treatment protocol and had repeated lumbar puncture procedures post-treatment.

RESULTS

Contrary to prediction, we found that at baseline depressed patients had higher CSF NPY concentration compared to the normal comparison group. Within the depressed patients, we found several statistically significant correlations between elevated CSF cytokine levels and clinical severity.

CONCLUSION

Despite the small sample size, given the challenges in obtaining CSF from patients with depression these data are of interest in confirming some aspects of the inflammatory hypothesis of depression.

The novel, selective, brain-penetrant neuropeptide Y Y2 receptor antagonist, JNJ-31020028, tested in animal models of alcohol consumption, relapse, and anxiety

Neuropeptide Y (NPY) signaling has been shown to modulate stress responses and to be involved in regulation of alcohol intake and dependence. The present study explores the possibility that blockade of NPY Y2 autoreceptors using a novel, blood-brain barrier penetrant NPY Y2 receptor antagonist, JNJ-31020028 (N-(4-{4-[2-(diethylamino)-2-oxo-1-phenylethyl]piperazin-1-yl}-3-fluorophenyl)-2-pyridin-3-ylbenzamide), may achieve a therapeutically useful activation of the NPY system in alcohol- and anxiety-related behavioral models. We examined JNJ-31020028 in operant alcohol self-administration, stress-induced reinstatement to alcohol seeking, and acute alcohol withdrawal (hangover)-induced anxiety. Furthermore, we tested its effects on voluntary alcohol consumption in a genetic animal model of alcohol preference, the alcohol-preferring (P) rat. Neither systemic (0, 15, 30, and 40 mg/kg, subcutaneously [s.c.]) nor intracerebroventricular (0.0, 0.3, and 1.0 nmol/rat) administration of JNJ-31020028 affected alcohol-reinforced lever pressing or relapse to alcohol seeking behavior following stress exposure. Also, when its effects were tested on unlimited access to alcohol in P rats, preference for alcohol solution was transiently suppressed but without affecting voluntary alcohol intake. JNJ-31020028 (15 mg/kg, s.c.) did reverse the anxiogenic effects of withdrawal from a single bolus dose of alcohol on the elevated plus-maze, confirming the anxiolytic-like properties of NPY Y2 antagonism. Our data do not support Y2 antagonism as a mechanism for reducing alcohol consumption or relapse-like behavior, but the observed effects on withdrawal-induced anxiety suggest that NPY Y2 receptor antagonists may be a putative treatment for the negative affective states following alcohol withdrawal.

Dipeptidyl peptidase IV in the hypothalamus and hippocampus of monosodium glutamate obese and food-deprived rats

Proline-specific dipeptidyl peptidases are emerging as a protease family with important roles in the regulation of signaling by peptide hormones related to energy balance. The treatment of neonatal rats with monosodium glutamate (MSG) is known to produce a selective damage on the arcuate nucleus with development of obesity. This study investigates the relationship among dipeptidyl peptidase IV (DPPIV) hydrolyzing activity, CD26 protein, fasting, and MSG model of obesity in 2 areas of the central nervous system. Dipeptidyl peptidase IV and CD26 were, respectively, evaluated by fluorometry, and enzyme-linked immunosorbent assay and reverse transcriptase polymerase chain reaction in soluble (SF) and membrane-bound (MF) fractions from the hypothalamus and hippocampus of MSG-treated and normal rats, submitted or not to food deprivation (FD). Dipeptidyl peptidase IV in both areas was distinguished kinetically as insensitive (DI) and sensitive (DS) to diprotin A. Compared with the controls, MSG and/or FD decreased the activity of DPPIV-DI in the SF and MF from the hypothalamus, as well as the activity of DPPIV-DS in the SF from the hypothalamus and in the MF from the hippocampus. Monosodium glutamate and/or FD increased the activity of DPPIV-DI in the MF from the hippocampus. The monoclonal protein expression of membrane CD26 by enzyme-linked immunosorbent assay decreased in the hypothalamus and increased in the hippocampus of MSG and/or FD relative to the controls. The existence of DPPIV-like activity with different sensitivities to diprotin A and the identity of insensitive with CD26 were demonstrated for the first time in the central nervous system. Data also demonstrated the involvement of DPPIV-DI/CD26 hydrolyzing activity in the energy balance probably through the regulation of neuropeptide Y and β-endorphin levels in the hypothalamus and hippocampus.

Role of feeding-related pathways in alcohol dependence: A focus on sweet preference, NPY, and ghrelin

Converging research evidence suggests that alcohol and food-seeking behaviors share common neural pathways. There is preclinical and clinical evidence linking the consumption of sweets to alcohol intake in both animals and humans. In addition, a growing body of animal and human literature suggests the involvement of "feeding-related" peptides in alcohol-seeking behavior. In particular, both central and peripheral appetitive peptides have shown a possible role in alcohol dependence. The present mini-review will summarize the literature on the link between sweet preference and alcohol dependence, and on the role of feeding-related peptides in alcohol dependence. Specifically, in an attempt to narrow the field, the present mini-review will focus on 2 specific pathways, the central neuropeptide Y and the peripheral gut peptide ghrelin. Although more research is needed, data available suggest that studying feeding-related pathways in alcohol dependence may have theoretic, biologic, diagnostic, and therapeutic implications.

In vitro and in vivo characterization of JNJ-31020028 (N-(4-{4-[2-(diethylamino)-2-oxo-1-phenylethyl]piperazin-1-yl}-3-fluorophenyl)-2-pyridin-3-ylbenzamide), a selective brain penetrant small molecule antagonist of the neuropeptide Y Y(2) receptor

RATIONALE

The lack of potent, selective, brain penetrant Y(2) receptor antagonists has hampered in vivo functional studies of this receptor.

OBJECTIVE

Here, we report the in vitro and in vivo characterization of JNJ-31020028 (N-(4-{4-[2-(diethylamino)-2-oxo-1-phenylethyl]piperazin-1-yl}-3-fluorophenyl)-2-pyridin-3-ylbenzamide), a novel Y(2) receptor antagonist.

METHODS

The affinity of JNJ-31020028 was determined by inhibition of the PYY binding to human Y(2) receptors in KAN-Ts cells and rat Y(2) receptors in rat hippocampus. The functional activity was determined by inhibition of PYY-stimulated calcium responses in KAN-Ts cells expressing a chimeric G protein Gqi5 and in the rat vas deferens (a prototypical Y(2) bioassay). Ex vivo receptor occupancy was revealed by receptor autoradiography. JNJ-31020028 was tested in vivo with microdialysis, in anxiety models, and on corticosterone release.

RESULTS

JNJ-31020028 bound with high affinity (pIC(50) = 8.07 +/- 0.05, human, and pIC(50) = 8.22 +/- 0.06, rat) and was >100-fold selective versus human Y(1), Y(4), and Y(5) receptors. JNJ-31020028 was demonstrated to be an antagonist (pK(B) = 8.04 +/- 0.13) in functional assays. JNJ-31020028 occupied Y(2) receptor binding sites (approximately 90% at 10 mg/kg) after subcutaneous administration in rats. JNJ-31020028 increased norepinephrine release in the hypothalamus, consistent with the colocalization of norepinephrine and neuropeptide Y. In a variety of anxiety models, JNJ-31020028 was found to be ineffective, although it did block stress-induced elevations in plasma corticosterone, without altering basal levels, and normalized food intake in stressed animals without affecting basal food intake.

CONCLUSION

These results suggest that Y(2) receptors may not be critical for acute behaviors in rodents but may serve modulatory roles that can only be elucidated under specific situational conditions.

Neuropeptide Y (NPY) suppresses yohimbine-induced reinstatement of alcohol seeking

INTRODUCTION

Reinstatement of responding to a previously alcohol-associated lever following extinction is an established model of relapse-like behavior and can be triggered by stress exposure. Here, we examined whether neuropeptide Y (NPY), an endogenous anti-stress mediator, blocks reinstatement of alcohol-seeking induced by the pharmacological stressor yohimbine.

MATERIALS AND METHODS

NPY [5.0 or 10.0 mug/rat, intracerebroventricularly (ICV)] dose-dependently blocked the reinstatement of alcohol seeking induced by yohimbine (1.25 mg/kg, i.p.) but failed to significantly suppress the maintenance of alcohol self-administration. We then used c-fos expression mapping to examine neuronal activation following treatment with yohimbine or NPY alone or yohimbine following NPY pre-treatment.

RESULTS AND DISCUSSION

The analysis was focused on a network of structures previously implicated in yohimbine-induced reinstatement, comprised of central (CeA) and basolateral (BLA) amygdala and the shell of the nucleus accumbens (Nc AccS). Within this network, both yohimbine and NPY potently induced neuronal activation, and their effects were additive, presumably indicating activation of excitatory and inhibitory neuronal populations, respectively.

CONCLUSION

These results suggest that NPY selectively suppresses relapse to alcohol seeking induced by stressful events and support the NPY system as an attractive target for the treatment of alcohol addiction.

From QTL to candidate gene: a genetic approach to alcoholism research

A major focus of research in alcohol-related disorders is to identify the genes and pathways that modulate alcohol-seeking behavior. In light of this, animal models have been established to study various aspects of alcohol dependence. The selectively bred alcohol-preferring (P) and -nonpreferring (NP) lines were developed from Wistar rats to model high and low voluntary alcohol consumption, respectively. Using inbred P and NP strains, a strong QTL (LOD-9.2) for alcohol consumption was identified on rat chromosome 4. To search for candidate genes that underlie this chromosomal region, complementary molecular-based strategies were implemented to identify genetic targets that likely contribute to the linkage signal. In an attempt to validate these genetic targets, corroborative studies have been utilized including pharmacological studies, knock-out/transgenic models as well as human association studies. Thus far, three candidate genes, neuropeptide Y (Npy), alpha-synuclein (Snca), and corticotrophin-releasing factor receptor 2 (Crhr2), have been identified that may account for the linkage signal. With the recent advancements in bioinformatics and molecular biology, QTL analysis combined with molecular-based strategies provides a systematic approach to identify candidate genes that contribute to various aspects of addictive behavior.

Hungry for life: How the arcuate nucleus and neuropeptide Y may play a critical role in mediating the benefits of calorie restriction

Laboratory studies consistently demonstrate extended lifespan in animals on calorie restriction (CR), where total caloric intake is reduced by 10-40% but adequate nutrition is otherwise maintained. CR has been further shown to delay the onset and severity of chronic diseases associated with aging such as cancer, and to extend the functional health span of important faculties like cognition. Less understood are the underlying mechanisms through which CR might act to induce such alterations. One theory postulates that CR's beneficial effects are intimately tied to the neuroendocrine response to low energy availability, of which the arcuate nucleus in the hypothalamus plays a pivotal role. Neuropeptide Y (NPY), a neurotransmitter in the front line of the arcuate response to low energy availability, is the primary hunger signal affected by CR and therefore may be a critical mechanism for lifespan extension.

Remission and resurgence of anxiety-like behavior across protracted withdrawal stages in ethanol-dependent rats

BACKGROUND

Alcohol dependence is a chronic disorder in which withdrawal symptoms often persist after detoxification. The purpose of the present experiment was to characterize susceptibility to stress and anxiogenic stimuli in rats over an extended time period following ethanol withdrawal.

METHODS

Male Wistar rats were made dependent via ethanol vapor exposure. The rats were then tested in the elevated plus-maze during acute ethanol withdrawal (ACW, approximately 8 hour), early "protracted" withdrawal (EPW, 2 weeks), or late "protracted" withdrawal (LPW, 6, 12 weeks) following brief restraint or no stress. Principal components analysis was used to identify constructs underlying plus-maze behavior.

RESULTS

Three factors characterized plus-maze performance: anxiety, locomotor activity, and risk assessment/decision making. Spontaneous anxiety-like behavior was increased during ACW, decreased to levels of ethanol-naïve controls during EPW, but markedly resurged during LPW. Withdrawal did not alter sensitivity to the anxiety-like effects of restraint stress. All ethanol-dependent rats showed locomotor hypoactivity that, in contrast to anxiety, remained stable throughout all withdrawal stages. Neither ethanol withdrawal nor restraint stress altered mean "risk assessment/decision making" scores, though ethanol withdrawal altered the emission of "risk assessment/decision making" behavior in relation to anxiety-like behavior and behavioral activation state.

CONCLUSIONS

The findings illustrate and model the spontaneous, severe, and long-lasting nature of behavioral abnormalities that accompany withdrawal from chronic, intermittent ethanol intoxication. The dynamic remission and resurgence in symptoms of negative affect (i.e., behavioral signs of anxiety) during "protracted" withdrawal may complicate recovery from alcoholism.

Neuropeptide y receptor selective ligands in the treatment of obesity

Obesity is a serious public health problem throughout the world, affecting both developed societies and developing countries. The central nervous system has developed a meticulously interconnected circuitry in order to keep us fed and in an adequate nutritional state. One of these consequences is that an energy-dense environment favors the development of obesity. Neuropeptide Y (NPY) is one of the most abundant and widely distributed peptides in the central nervous system of both rodents and humans and has been implicated in a variety of physiological actions. Within the hypothalamus, NPY plays an essential role in the control of food intake and body weight. Centrally administered NPY causes robust increases in food intake and body weight and, with chronic administration, can eventually produce obesity. NPY activates a population of at least six G protein-coupled Y receptors. NPY analogs exhibit varying degrees of affinity and specificity for these Y receptors. There has been renewed speculation that ligands for Y receptors may be of benefit for the treatment of obesity. This review highlights the therapeutic potential of Y(1), Y(2), Y(4), and Y(5) receptor agonists and antagonists as additional intervention to treat human obesity.

Expression patterns of promoters for NPY Y1 and Y5 receptors in Y5RitTA and Y1RVenus BAC-transgenic mice

In the rat brain, neuropeptide Y (NPY) Y(1) and Y(5) receptors are coexpressed in various forebrain regions where they mediate several NPY-activated functions, including feeding behaviour, anxiety, neuronal excitability and hormone secretion. We studied the distribution pattern and cellular colocalization of the Y(1) and the Y(5) receptor gene expression in the mouse brain by using transgenic mice with genomically integrated BAC clones, where the coding regions of the Y(1) and Y(5) receptor genes were replaced by Venus and the synthetic transcription factor itTA reporter genes, respectively (Tg(Y5RitTA/Y1RVenus) mice). Analysis of Venus fluorescence and itTA-mediated activation of Cre recombinase revealed copy number-dependent expression levels, between the lines, but similar expression patterns. In three transgenic lines the BAC encoded Y(5) receptor promoter induced strong Cre expression in the olfactory system, cerebral cortex, hippocampus and basal ganglia. Weaker expression was found in most of the hypothalamic nuclei of line 25, the highest-expressing transgenic line. Activation of Cre was itTA-dependent and could be regulated by doxycycline. The Y(1) receptor promoter-induced Venus fluorescence was intense, widely present through the brain and colocalized with Cre immunostaining in neurons of distinct brain regions, including the cerebral cortex, basolateral amygdala, dentate gyrus and paraventricular nucleus. These data provide a detailed and comparative mapping of Y(1) and Y(5) receptor promoter activity within cells of the mouse brain. The Tg(Y5RitTA/Y1RVenus)-transgenic mice generated here also represent a genetic tool for conditional mutagenesis via the Cre lox system, particularly of genes involved in feeding behaviour, neuronal excitability and hormone secretion.

Serotonin and neuropeptide F have opposite modulatory effects on fly aggression

Both serotonin (5-HT) and neuropeptide Y have been shown to affect a variety of mammalian behaviors, including aggression. Here we show in Drosophila melanogaster that both 5-HT and neuropeptide F, the invertebrate homolog of neuropeptide Y, modulate aggression. We show that drug-induced increases of 5-HT in the fly brain increase aggression. Elevating 5-HT genetically in the serotonergic circuits recapitulates these pharmacological effects, whereas genetic silencing of these circuits makes the flies behaviorally unresponsive to the drug-induced increase of 5-HT but leaves them capable of aggression. Genetic silencing of the neuropeptide F (npf) circuit also increases fly aggression, demonstrating an opposite modulation to 5-HT. Moreover, this neuropeptide F effect seems to be independent of 5-HT. The implication of these two modulatory systems in fly and mouse aggression suggest a marked degree of conservation and a deep molecular root for this behavior.

G protein-coupled receptors in major psychiatric disorders

Although the molecular mechanisms underlying psychiatric illnesses such as depression, bipolar disorder and schizophrenia remain incompletely understood, there is increasing clinical, pharmacologic, and genetic evidence that G protein-coupled receptors (GPCRs) play critical roles in these disorders and their treatments. This perspectives paper reviews and synthesizes the available data. Dysfunction of multiple neurotransmitter and neuropeptide GPCRs in frontal cortex and limbic-related regions, such as the hippocampus, hypothalamus and brainstem, likely underlies the complex clinical picture that includes cognitive, perceptual, affective and motoric symptoms. The future development of novel agents targeting GPCR signaling cascades remains an exciting prospect for patients refractory to existing therapeutics.

Physiology and gene regulation of the brain NPY Y1 receptor

Neuropeptide Y (NPY) is one of the most prominent and abundant neuropeptides in the mammalian brain where it interacts with a family of G-protein coupled receptors, including the Y(1) receptor subtype (Y(1)R). NPY-Y(1)R signalling plays a prominent role in the regulation of several behavioural and physiological functions including feeding behaviour and energy balance, sexual hormone secretion, stress response, emotional behaviour, neuronal excitability and ethanol drinking. Y(1)R expression is regulated by neuronal activity and peripheral hormones. The Y(1)R gene has been isolated from rodents and humans and it contains multiple regulatory elements that may participate in the regulation of its expression. Y(1)R expression in the hypothalamus is modulated by changes in energetic balance induced by a wide variety of conditions (fasting, pregnancy, hyperglycaemic challenge, hypophagia, diet induced obesity). Estrogens up-regulate responsiveness to NPY to stimulate preovulatory GnRH and gonadotropin surges by increasing Y(1)R gene expression both in the hypothalamus and the pituitary. Y(1)R expression is modulated by different kinds of brain insults, such as stress and seizure activity, and alteration in its expression may contribute to antidepressant action. Chronic modulation of GABA(A) receptor function by benzodiazepines or neuroactive steroids also affects Y(1)R expression in the amygdala, suggesting that a functional interaction between the GABA(A) receptor and Y(1)R mediated signalling may contribute to the regulation of emotional behaviour. In this paper, we review the state of the art concerning Y(1)R function and gene expression, including our personal contribution to many of the subjects mentioned above.