Diverse functions of neuropeptide Y revealed using genetically modified animals

Development of a Neuropeptide Y-Sensitive Implantable Microelectrode for Continuous Measurements

In this work, we present the development of the first implantable aptamer-based platinum microelectrode for continuous measurement of a nonelectroactive molecule, neuropeptide Y (NPY). The aptamer immobilization was performed via conjugation chemistry and characterized using cyclic voltammetry before and after the surface modification. The redox label, methylene blue (MB), was attached at the end of the aptamer sequence and characterized using square wave voltammetry (SWV). NPY standard solutions in a three-electrode cell were used to test three aptamers in steady-state measurement using SWV for optimization. The aptamer with the best performance in the steady-state measurements was chosen, and continuous measurements were performed in a flow cell system using intermittent pulse amperometry. Dynamic measurements were compared against confounding and similar peptides such as pancreatic polypeptide and peptide YY, as well as somatostatin to determine the selectivity in the same modified microelectrode. Our Pt-microelectrode aptamer-based NPY biosensor provides signals 10 times higher for NPY compared to the confounding molecules. This proof-of-concept shows the first potential implantable microelectrode that is selectively sensitive to NPY concentration changes.

Seasonal Differences in Expression of Neuropeptide Y (NPY) in Visual Centers of Spotted Munia (Lonchura punctulata)

The visual perception of birds is an incredibly exciting subject of research. Birds have significantly higher visual acuity than most other animals, which helps them stay safe in flight and detect their prey. Understanding how the eyes send information to the brain for additional processing is crucial. The brain has sections (nuclei) that accept input from the retina. The key areas where information is processed are the hyperpallium apicale (HA), hippocampus (HP), optic tectum (TeO), nucleus rotundus (RoT), and the geniculatus lateralis ventralis (Glv); among these, the RoT is one of the most investigated nuclei for vision. This study looked at how the visual centers of non-photoperiodic songbirds (Spotted Munia) adapt in different life history stages by looking at NPY expression. We immunohistochemically quantified NPY expression in four different seasons, including pre-breeding (June), breeding (September), post-breeding (December), and regressed (March) in the brain of Spotted Munia. We evaluated changes in the expression levels of the peptide throughout the year, by determining the expression at four different periods throughout the year. Peptide expression levels were projected to fluctuate within photoperiod-induced seasons. It was discovered that the parts of the brain related to vision (RoT, HA, and HP) have a higher number of immunoreactive cells during their mating season, i.e., during the summer. The appearance of NPY, a non-photic marker, in brain areas linked with light perception, was fascinating. Indirectly, NPY aids avian reproduction in a variety of ways. These findings demonstrate the importance of these nuclei in the process of reproduction, as well as the involvement of NPY in the visual brain areas of Spotted Munia.

Neurosecretory Protein GL Promotes Normotopic Fat Accumulation in Male ICR Mice

Neurosecretory protein GL (NPGL) is a small secretory protein identified in the hypothalamus of birds and mammals. We recently reported that NPGL exerts obesogenic effects in obesity-prone C57BL6/J mice. However, whether NPGL elicits adiposity in different mouse strains is poorly understood. In this study, we generated transgenic mice overexpressing Npgl using the ICR strain (Npgl Tg mice) to elucidate the obesogenic effects of NPGL in different strains. Npgl Tg mice showed increased white adipose tissue (WAT) mass. Although the mass of brown adipose tissue (BAT) was slightly altered in Npgl Tg mice, hypertrophy of lipid droplets was also observed in BAT. In contrast, fat accumulation was not induced in the liver, with the upregulation of mRNAs related to hepatic lipolysis. These results support the hypothesis that NPGL causes obesity in several strains and species. This report highlights the pivotal role of NPGL in fat accumulation in adipose tissues and contributes to the elucidation of the biological mechanisms underlying obesity and metabolic diseases in heterogeneous populations.

Rutland C. Equine Stress: Neuroendocrine Physiology and Pathophysiology

This review presents new aspects to understanding the neuroendocrine regulation of equine stress responses, and their influences on the physiological, pathophysiological, and behavioral processes. Horse management, in essence, is more frequently confirmed by external and internal stress factors, than in other domestic animals. Regardless of the nature of the stimulus, the equine stress response is an effective and highly conservative set of interconnected relationships designed to maintain physiological integrity even in the most challenging circumstances (e.g., orthopedic injuries, abdominal pain, transport, competitions, weaning, surgery, and inflammation). The equine stress response is commonly a complementary homeostatic mechanism that provides protection (not an adaptation) when the body is disturbed or threatened. It activates numerous neural and hormonal networks to optimize metabolic, cardiovascular, musculoskeletal, and immunological functions. This review looks into the various mechanisms involved in stress responses, stress-related diseases, and assessment, prevention or control, and management of these diseases and stress. Stress-related diseases can not only be identified and assessed better, given the latest research and techniques but also prevented or controlled.

The short neuropeptide F regulates appetitive but not aversive responsiveness in a social insect

The neuropeptide F (NPF) and its short version (sNPF) mediate food- and stress-related responses in solitary insects. In the honeybee, a social insect where food collection and defensive responses are socially regulated, only sNPF has an identified receptor. Here we increased artificially sNPF levels in honeybee foragers and studied the consequences of this manipulation in various forms of appetitive and aversive responsiveness. Increasing sNPF in partially fed bees turned them into the equivalent of starved animals, enhancing both their food consumption and responsiveness to appetitive gustatory and olfactory stimuli. Neural activity in the olfactory circuits of fed animals was reduced and could be rescued by sNPF treatment to the level of starved bees. In contrast, sNPF had no effect on responsiveness to nociceptive stimuli. Our results thus identify sNPF as a key modulator of hunger and food-related responses in bees, which are at the core of their foraging activities.

Organization of Neuropeptide Y-Immunoreactive Cells in the Mongolian gerbil (Meriones unguiculatus) Visual Cortex

Neuropeptide Y (NPY) is found throughout the central nervous system where it appears to be involved in the regulation of a wide range of physiological effects. The Mongolian gerbil, a member of the rodent family Muridae, is a diurnal animal and has been widely used in various aspects of biomedical research. This study was conducted to investigate the organization of NPY-immunoreactive (IR) neurons in the gerbil visual cortex using NPY immunocytochemistry. The highest density of NPY-IR neurons was located in layer V (50.58%). The major type of NPY-IR neuron was a multipolar round/oval cell type (44.57%). Double-color immunofluorescence revealed that 89.55% and 89.95% of NPY-IR neurons contained gamma-aminobutyric acid (GABA) or somatostatin, respectively. Several processes of the NPY-IR neurons surrounded GABAergic interneurons. Although 30.81% of the NPY-IR neurons contained calretinin, NPY and calbindin-D28K-IR neurons were co-expressed rarely (3.75%) and NPY did not co-express parvalbumin. Triple-color immunofluorescence with anti-GluR2 or CaMKII antibodies suggested that some non-GABAergic NPY-IR neurons may make excitatory synaptic contacts. This study indicates that NPY-IR neurons have a notable architecture and are unique subpopulations of the interneurons of the gerbil visual cortex, which could provide additional valuable data for elucidating the role of NPY in the visual process in diurnal animals.

Metaplastic contribution of neuropeptide Y receptors to spatial memory acquisition

Neuropeptide Y (NPY) is highly abundant in the brain and is released as a co-transmitter with plasticity-related neurotransmitters such as glutamate, GABA and noradrenaline. Functionally, its release is associated with appetite, anxiety, and stress regulation. NPY acting on Y2 receptors (Y₂R), facilitates fear extinction, suggesting a role in associative memory. Here, we explored to what extent NPY action at Y₂R contributes to hippocampus-dependent spatial memory and found that dorsal intrahippocampal receptor antagonism improved spatial reference memory acquired in a water maze in rats, without affecting anxiety levels, or spontaneous motor activity. Water maze training resulted in an increase of Y₂R, but not Y₁R expression in the hippocampus. By contrast, in the prefrontal cortex there was a decrease in Y₂R, and an increase of Y₁R expression. Our results indicate that neuropeptide Y₂R are significantly involved in hippocampus-dependent spatial memory and that receptor expression is dynamically regulated by this learning experience. Effects are consistent with a metaplastic contribution of NPY receptors to cumulative spatial learning.

Mapping of neuropeptide Y expression in Octopus brains

Neuropeptide Y (NPY) is an evolutionarily conserved neurosecretory molecule implicated in a diverse complement of functions across taxa and in regulating feeding behavior and reproductive maturation in Octopus. However, little is known about the precise molecular circuitry of NPY-mediated behaviors and physiological processes, which likely involve a complex interaction of multiple signal molecules in specific brain regions. Here, we examined the expression of NPY throughout the Octopus central nervous system. The sequence analysis of Octopus NPY precursor confirmed the presence of both, signal peptide and putative active peptides, which are highly conserved across bilaterians. In situ hybridization revealed distinct expression of NPY in specialized compartments, including potential "integration centers," where visual, tactile, and other behavioral circuitries converge. These centers integrating separate circuits may maintain and modulate learning and memory or other behaviors not yet attributed to NPY-dependent modulation in Octopus. Extrasomatic localization of NPY mRNA in the neurites of specific neuron populations in the brain suggests a potential demand for immediate translation at synapses and a crucial temporal role for NPY in these cell populations. We also documented the presence of NPY mRNA in a small cell population in the olfactory lobe, which is a component of the Octopus feeding and reproductive control centers. However, the molecular mapping of NPY expression only partially overlapped with that produced by immunohistochemistry in previous studies. Our study provides a precise molecular map of NPY mRNA expression that can be used to design and test future hypotheses about molecular signaling in various Octopus behaviors.

A potential and novel type transgenic corn plant for control of the Corn Borer

The corn borer is a world-wide agricultural pest. In this study, a full-length neuropeptide F (npf) gene in Ostrinia furnacalis was sequenced and cloned from a cDNA library, in which the npf gene produces two splicing mRNA variants - npf1 and npf2 (with a 120 bp segment inserted into the npf1 sequence to generate npf2). A spatio-temporal expression analysis showed that the highest expression level of npf was in the midgut of 5^th instar larvae (the gluttony period), and their npf expression and food consumption were significantly promoted after food deprivation for 6 h. When npf was knocked down by double-stranded RNA for NPF, larval food intake, weight and body size were effectively inhibited through changes of a biosynthesis and metabolism pathway; i.e. gene silencing of NPF causes decreases of total lipid and glycogen and increases of trehalose production. Moreover, we produced transgenic corn plants with stably expressed dsNPF. Results showed that O. furnacalis larvae fed on these transgenic leaves had lower food consumption and smaller body size compared to controls. These results indicate that NPF is important in the feeding control of O. furnacalis and valuable for production of potential transgenic corn.

Neuropeptide Y expression confers benzo[a]pyrene induced anxiolytic like behavioral response during early adolescence period of male Wistar rats

Environmental neurotoxicant like benzo[a]pyrene (B[a]P) is known to induce neurobehavioral changes. Our previous reports address the adverse effect of B[a]P on the neurobehavioral responses and neuromorphology of sensitive brain regions in adolescent rats. Present study was conducted on male Wistar rat neonates at postnatal day 5 (PND5) to ascertain B[a]P induced anxiolytic like behavioral response could be an outcome of neuropeptide Y (NPY) overexpression in brain. Single intracisternal administration of B[a]P was carried out at PND5 to elucidate the role of NPY on neurobehavioral responses at PND30. The behavioral studies showed anxiolytic like effect of B[a]P in both light and dark box and elevated plus maze tests. Antioxidant assay involving glutathione peroxidase activity was significantly decreased where as lipid peroxidation was significantly augmented in both hippocampus and hypothalamus of B[a]P treated group as compared to naive and control. The neurotransmitter estimation by HPLC-ECD showed significant increase in 5-HT level in both hippocampus and hypothalamus of B[a]P treated group. Significant elevation in NPY expression was observed in both hippocampus and hypothalamus of B[a]P group. Intracellular Ca²⁺ estimation using Fura-2AM by fluorometry showed that B[a]P induced increase in Ca²⁺ influx was associated with augmented NPY expression in brain. As NPY has orexigenic effect, our result revealed that there was a significant increase in body weight at PND30 following B[a]P administration to rat neonates at PND5. These findings suggested that NPY overexpression in brain regions might be associated with anxiolytic like behavioral response and orexigenic effect in rats following single intracisternal B[a]P administration. Future research directing towards understanding the signaling cascades of B[a]P induced biochemical and neuromorphological alteration might address the independent pathway which induce neurodegeneration despite NPY overexpression in brain regions of adolescent rats.

Neuropeptides and Microglial Activation in Inflammation, Pain, and Neurodegenerative Diseases

Microglial cells are responsible for immune surveillance within the CNS. They respond to noxious stimuli by releasing inflammatory mediators and mounting an effective inflammatory response. This is followed by release of anti-inflammatory mediators and resolution of the inflammatory response. Alterations to this delicate process may lead to tissue damage, neuroinflammation, and neurodegeneration. Chronic pain, such as inflammatory or neuropathic pain, is accompanied by neuroimmune activation, and the role of glial cells in the initiation and maintenance of chronic pain has been the subject of increasing research over the last two decades. Neuropeptides are small amino acidic molecules with the ability to regulate neuronal activity and thereby affect various functions such as thermoregulation, reproductive behavior, food and water intake, and circadian rhythms. Neuropeptides can also affect inflammatory responses and pain sensitivity by modulating the activity of glial cells. The last decade has witnessed growing interest in the study of microglial activation and its modulation by neuropeptides in the hope of developing new therapeutics for treating neurodegenerative diseases and chronic pain. This review summarizes the current literature on the way in which several neuropeptides modulate microglial activity and response to tissue damage and how this modulation may affect pain sensitivity.

Neuropeptide Y (NPY) in tumor growth and progression: Lessons learned from pediatric oncology

Neuropeptide Y (NPY) is a sympathetic neurotransmitter with pleiotropic actions, many of which are highly relevant to tumor biology. Consequently, the peptide has been implicated as a factor regulating the growth of a variety of tumors. Among them, two pediatric malignancies with high endogenous NPY synthesis and release - neuroblastoma and Ewing sarcoma - became excellent models to investigate the role of NPY in tumor growth and progression. The stimulatory effect on tumor cell proliferation, survival, and migration, as well as angiogenesis in these tumors, is mediated by two NPY receptors, Y2R and Y5R, which are expressed in either a constitutive or inducible manner. Of particular importance are interactions of the NPY system with the tumor microenvironment, as hypoxic conditions commonly occurring in solid tumors strongly activate the NPY/Y2R/Y5R axis. This activation is triggered by hypoxia-induced up-regulation of Y2R/Y5R expression and stimulation of dipeptidyl peptidase IV (DPPIV), which converts NPY to a selective Y2R/Y5R agonist, NPY(3-36). While previous studies focused mainly on the effects of NPY on tumor growth and vascularization, they also provided insight into the potential role of the peptide in tumor progression into a metastatic and chemoresistant phenotype. This review summarizes our current knowledge of the role of NPY in neuroblastoma and Ewing sarcoma and its interactions with the tumor microenvironment in the context of findings in other malignancies, as well as discusses future directions and potential clinical implications of these discoveries.

Hypothalamic Non-AgRP, Non-POMC GABAergic Neurons Are Required for Postweaning Feeding and NPY Hyperphagia

The hypothalamus is critical for feeding and body weight regulation. Prevailing studies focus on hypothalamic neurons that are defined by selectively expressing transcription factors or neuropeptides including those expressing proopiomelanocortin (POMC) and agouti-related peptides (AgRP). The Cre expression driven by the pancreas-duodenum homeobox 1 promoter is abundant in several hypothalamic nuclei but not in AgRP or POMC neurons. Using this line, we generated mice with disruption of GABA release from a major subset of non-POMC, non-AgRP GABAergic neurons in the hypothalamus. These mice exhibited a reduction in postweaning feeding and growth, and disrupted hyperphagic responses to NPY. Disruption of GABA release severely diminished GABAergic input to the paraventricular hypothalamic nucleus (PVH). Furthermore, disruption of GABA-A receptor function in the PVH also reduced postweaning feeding and blunted NPY-induced hyperphagia. Given the limited knowledge on postweaning feeding, our results are significant in identifying GABA release from a major subset of less appreciated hypothalamic neurons as a key mediator for postweaning feeding and NPY hyperphagia, and the PVH as one major downstream site that contributes significantly to the GABA action. Significance statement: Prevalent studies on feeding in the hypothalamus focus on well characterized, selective groups neurons [e.g., proopiomelanocortin (POMC) and agouti-related peptide (AgRP) neurons], and as a result, the role of the majority of other hypothalamic neurons is largely neglected. Here, we demonstrated an important role for GABAergic projections from non-POMC non-AgRP neurons to the paraventricular hypothalamic nucleus in promoting postweaning (mainly nocturnal) feeding and mediating NPY-induced hyperphagia. Thus, these results signify an importance to study those yet to be defined hypothalamic neurons in the regulation of energy balance and reveal a neural basis for postweaning (nocturnal) feeding and NPY-mediated hyperphagia.

Learning context modulates aversive taste strength in honey bees

The capacity of honey bees (Apis mellifera) to detect bitter substances is controversial because they ingest without reluctance different kinds of bitter solutions in the laboratory, whereas free-flying bees avoid them in visual discrimination tasks. Here, we asked whether the gustatory perception of bees changes with the behavioral context so that tastes that are less effective as negative reinforcements in a given context become more effective in a different context. We trained bees to discriminate an odorant paired with 1 mol l(-1) sucrose solution from another odorant paired with either distilled water, 3 mol l(-1) NaCl or 60 mmol l(-1) quinine. Training was either Pavlovian [olfactory conditioning of the proboscis extension reflex (PER) in harnessed bees], or mainly operant (olfactory conditioning of free-walking bees in a Y-maze). PER-trained and maze-trained bees were subsequently tested both in their original context and in the alternative context. Whereas PER-trained bees transferred their choice to the Y-maze situation, Y-maze-trained bees did not respond with a PER to odors when subsequently harnessed. In both conditioning protocols, NaCl and distilled water were the strongest and the weakest aversive reinforcement, respectively. A significant variation was found for quinine, which had an intermediate aversive effect in PER conditioning but a more powerful effect in the Y-maze, similar to that of NaCl. These results thus show that the aversive strength of quinine varies with the learning context, and reveal the plasticity of the bee's gustatory system. We discuss the experimental constraints of both learning contexts and focus on stress as a key modulator of taste in the honey bee. Further explorations of bee taste are proposed to understand the physiology of taste modulation in bees.

Genome-wide association study of vitamin D levels in children: replication in the Western Australian Pregnancy Cohort (Raine) study

This genome-wide association study (GWAS) utilises data from the Western Australian Pregnancy Cohort (Raine) Study for 25-hydroxyvitamin D (25(OH)D) levels measured in blood collected at age 6 years (n=673) and at age 14 years (n=1140). Replication of significantly associated genes from previous GWASs was found for both ages. Genome-wide significant associations were found both at age 6 and 14 with single nucleotide polymorphisms (SNPs) on chromosome 11p15 in PDE3B/CYP2R1 (age 6: rs1007392, P=3.9 × 10(-8); age14: rs11023332, P=2.2 × 10(-10)) and on chromosome 4q13 in GC (age 6: rs17467825, P=4.2 × 10(-9); age14: rs1155563; P=3.9 × 10(-9)). In addition, a novel association was observed at age 6 with SNPs on chromosome 7p15 near NPY (age 6: rs156299, P=1.3 × 10(-6)) that could be of functional interest in highlighting alternative pathways for vitamin D metabolism in this age group and merits further analysis in other cohort studies.

Neuropeptide Y in the central nucleus of amygdala regulates the anxiolytic effect of agmatine in rats

In the present study, modulation of anxiolytic action of agmatine by neuropeptide Y (NPY) in the central nucleus of amygdala (CeA) is evaluated employing Vogel's conflict test (VCT) in rats. The intra-CeA administration of agmatine (0.6 and 1.2µmol/rat), NPY (10 and 20pmol/rat) or NPY Y1/Y5 receptors agonist [Leu(31), Pro(34)]-NPY (30 and 60pmol/rat) significantly increased the number of punished drinking licks following 15min of treatment. Combination treatment of subeffective dose of NPY (5pmol/rat) or [Leu(31), Pro(34)]-NPY (15pmol/rat) and agmatine (0.3µmol/rat) produced synergistic anxiolytic-like effect. However, intra-CeA administration of selective NPY Y1 receptor antagonist, BIBP3226 (0.25 and 0.5mmol/rat) produced anxiogenic effect. In separate set of experiment, pretreatment with BIBP3226 (0.12mmol/rat) reversed the anxiolytic effect of agmatine (0.6µmol/rat). Furthermore, we evaluated the effect of intraperitoneal injection of agmatine (40mg/kg) on NPY-immunoreactivity in the nucleus accumbens shell (AcbSh), lateral part of bed nucleus of stria terminalis (BNSTl) and CeA. While agmatine treatment significantly decreased the fibers density in BNSTl, increase was noticed in AcbSh. In addition, agmatine reduced NPY-immunoreactive cells in the AcbSh and CeA. Immunohistochemical data suggest the enhanced transmission of NPY from the AcbSh and CeA. Taken together, this study suggests that agmatine produced anxiolytic effect which might be regulated via modulation of NPYergic system particularly in the CeA.

Fat mass and obesity-associated (FTO) protein interacts with CaMKII and modulates the activity of CREB signaling pathway

Polymorphisms in the fat mass and obesity-associated (FTO) gene have been associated with obesity in humans. FTO is a nuclear protein and its physiological function remains largely unknown, but alterations in its expression in mice influence energy expenditure, food intake and, ultimately, body weight. To understand the molecular functions of FTO, we performed a yeast two-hybrid screen to identify the protein(s) that could directly interact with human FTO protein. Using multiple assays, we demonstrate that FTO interacts with three isoforms of calcium/calmodulin-dependent protein kinase II: α, β and γ, which are protein kinases that phosphorylate a broad range of substrates. This interaction is functional; overexpression of FTO delays the dephosphorylation of cAMP response element-binding protein (CREB) in human neuroblastoma (SK-N-SH) cells, which in turn leads to a dramatic increase in the expression of the CREB targets neuropeptide receptor 1 (NPY1R) and brain-derived neurotrophic factor (BDNF), which already are known to regulate food intake and energy homeostasis. Thus, our results suggest that FTO could modulate obesity by regulating the activity of the CREB signaling pathway.

Role of neuropeptides in anxiety, stress, and depression: from animals to humans

Major depression, with its strikingly high prevalence, is the most common cause of disability in communities of Western type, according to data of the World Health Organization. Stress-related mood disorders, besides their deleterious effects on the patient itself, also challenge the healthcare systems with their great social and economic impact. Our knowledge on the neurobiology of these conditions is less than sufficient as exemplified by the high proportion of patients who do not respond to currently available medications targeting monoaminergic systems. The search for new therapeutical strategies became therefore a "hot topic" in neuroscience, and there is a large body of evidence suggesting that brain neuropeptides not only participate is stress physiology, but they may also have clinical relevance. Based on data obtained in animal studies, neuropeptides and their receptors might be targeted by new candidate neuropharmacons with the hope that they will become important and effective tools in the management of stress related mood disorders. In this review, we attempt to summarize the latest evidence obtained using animal models for mood disorders, genetically modified rodent models for anxiety and depression, and we will pay some attention to previously published clinical data on corticotropin releasing factor, urocortin 1, urocortin 2, urocortin 3, arginine-vasopressin, neuropeptide Y, pituitary adenylate-cyclase activating polypeptide, neuropeptide S, oxytocin, substance P and galanin fields of stress research.

Regulation of sleep by neuropeptide Y-like system in Drosophila melanogaster

Sleep is important for maintenance of normal physiology in animals. In mammals, neuropeptide Y (NPY), a homolog of Drosophila neuropeptide F (NPF), is involved in sleep regulation, with different effects in human and rat. However, the function of NPF on sleep in Drosophila melanogaster has not yet been described. In this study, we investigated the effects of NPF and its receptor-neuropeptide F receptor (NPFR1) on Drosophila sleep. Male flies over-expressing NPF or NPFR1 exhibited increased sleep during the nighttime. Further analysis demonstrated that sleep episode duration during nighttime was greatly increased and sleep latency was significantly reduced, indicating that NPF and NPFR1 promote sleep quality, and their action on sleep is not because of an impact of the NPF signal system on development. Moreover, the homeostatic regulation of flies after sleep deprivation was disrupted by altered NPF signaling, since sleep deprivation decreased transcription of NPF in control flies, and there were less sleep loss during sleep deprivation and less sleep gain after sleep deprivation in flies overexpressing NPF and NPFR1 than in control flies, suggesting that NPF system auto-regulation plays an important role in sleep homeostasis. However, these effects did not occur in females, suggesting a sex-dependent regulatory function in sleep for NPF and NPFR1. NPF in D1 brain neurons showed male-specific expression, providing the cellular locus for male-specific regulation of sleep by NPF and NPFR1. This study brings a new understanding into sleep studies of a sexually dimorphic regulatory mode in female and male flies.

Regulation of circadian locomotor rhythm by neuropeptide Y-like system in Drosophila melanogaster

Circadian rhythms in behaviour and physiology exist widely in animals, plants, fungi and cyanobacteria. Although much work has been carried out to characterize the endogenous clock circuit, the output signals coupling the circadian pacemaker to behaviour and physiology remain elusive. Here, we show that neuropeptide F (NPF), a homologue of mammalian neuropeptide Y, and its G protein-coupled receptor NPFR1 regulate the locomotor rhythm in Drosophila melanogaster. Flies with loss of function in NPF or NPFR1 were unable to ramp up their activity before lights off under light : dark (LD) cycles, and oscillations in npf/NPF and npfr1/NPFR1 were found to correlate temporally with the locomotor rhythm. Furthermore, NPF is expressed in clock neurones including dorsolateral neurones (LNd s) and ventrolateral neurones (LNv s), whereas NPFR1 is expressed in dorsal neurone 1 (DN1) and LNd s. These results show that NPF signalling is involved in the circadian locomotor rhythm in LD cycles.

Unraveling the central proopiomelanocortin neural circuits

Central proopiomelanocortin (POMC) neurons form a potent anorexigenic network, but our understanding of the integration of this hypothalamic circuit throughout the central nervous system (CNS) remains incomplete. POMC neurons extend projections along the rostrocaudal axis of the brain, and can signal with both POMC-derived peptides and fast amino acid neurotransmitters. Although recent experimental advances in circuit-level manipulation have been applied to POMC neurons, many pivotal questions still remain: how and where do POMC neurons integrate metabolic information? Under what conditions do POMC neurons release bioactive molecules throughout the CNS? Are GABA and glutamate or neuropeptides released from POMC neurons more crucial for modulating feeding and metabolism? Resolving the exact stoichiometry of signals evoked from POMC neurons under different metabolic conditions therefore remains an ongoing endeavor. In this review, we analyze the anatomical atlas of this network juxtaposed to the physiological signaling of POMC neurons both in vitro and in vivo. We also consider novel genetic tools to further characterize the function of the POMC circuit in vivo. Our goal is to synthesize a global view of the POMC network, and to highlight gaps that require further research to expand our knowledge on how these neurons modulate energy balance.

Peptidomic Analysis of the Brain and Corpora Cardiaca-Corpora Allata Complex in the Bombyx mori

The silkworm, Bombyx mori, is an important economic insect for silk production. However, many of the mature peptides relevant to its various life stages remain unknown. Using RP-HPLC, MALDI-TOF MS, and previously identified peptides from B. mori and other insects in the transcriptome database, we created peptide profiles showing a total of 6 ion masses that could be assigned to peptides in eggs, including one previously unidentified peptide. A further 49 peptides were assigned to larval brains. 17 new mature peptides were identified in isolated masses. 39 peptides were found in pupal brains with 8 unidentified peptides. 48 were found in adult brains with 12 unidentified peptides. These new unidentified peptides showed highly significant matches in all MS analysis. These matches were then searched against the National Center for Biotechnology Information (NCBI) database to provide new annotations for these mature peptides. In total, 59 mature peptides in 19 categories were found in the brains of silkworms at the larval, pupal, and adult stages. These results demonstrate that peptidomic variation across different developmental stages can be dramatic. Moreover, the corpora cardiaca-corpora allata (CC-CA) complex was examined during the fifth larval instar. A total of 41 ion masses were assigned to peptides.

Characterization of neuropeptide Y in snakeskin gourami and the change in its expression due to feeding status and melanocortin 4 receptor expression

In this study, we characterized the neuropeptide Y (NPY) mRNA in snakeskin gourami (Trichogaster pectoralis) (TpNPY). TpNPY displayed characteristics typical of previously reported NPYs, and it exhibited a high degree of homology with the NPY proteins of other vertebrates. A phylogenetic analysis demonstrated that TpNPY was closely related to the NPYs found in the acanthomorpha and salmoniformes fish species. TpNPY was found to be ubiquitously expressed in all brain regions when assessed by real-time RT-PCR and in situ hybridization. In addition, a graded expression level of TpNPY was observed in peripheral tissues; for example, a moderate level of TpNPY was found in the gills, liver, kidney, stomach, intestine, spleen and gonads, while a low level of TpNPY was found in the muscle. The change in expression of TpNPY with respect to daily feeding habits was investigated in distinct brain regions, including the telencephalon, mesencephalon, metencephalon, and diencephalon. Fluctuations in the expression level of TpNPY were observed for a 24h post-prandial period. Except for the telencephalon, a reduction in TpNPY expression was found after a meal, while a peak level of TpNPY was observed 1h before the scheduled breakfast. Furthermore, there was a positive correlation between TpNPY and TpMC4R in the telencephalon and diencephalon throughout the circadian feeding cycle, which suggests that there is a connection between the function of NPY and the melanocortin system for the regulation of daily feeding. Fish brains were incubated with an MC4R antagonist (i.e., HS024), and the expression of TpNPY and TpMC4R was measured. Interestingly, there was a significant relationship between the expression of TpNPY and TpMC4R under the effects of HS024, which demonstrates that there are interactions between MC4R and NPY, particularly in a hyperphagic state.

Potential role of neurogenic inflammatory factors in the pathogenesis of vitiligo

BACKGROUND

Vitiligo is a highly complex multifactorial condition of the skin that has an unclear mechanism of pathogenesis.

OBJECTIVE

This review summarizes the role of various neurogenic inflammatory factors significantly upregulated in vitiligo.

METHODS

A literature review was conducted of all pertinent data regarding neuropeptides that are altered in vitiligo and their possible role in the destruction of melanocytes.

RESULTS

The close associations between the skin, immune system, and nervous system, along with specific changes demonstrated in vitiligo patients, support a pathogenic mechanism of vitiligo that involves neuroimmunologic factors, the release of which can be governed by mental stress.

CONCLUSION

Neuropeptides and nerve growth factors are critical regulators of emotional response and may precipitate the onset and development of vitiligo in certain predisposed individuals. More studies are required to investigate whether a direct link exists between genetics, mental stress, and neurogenic factors in vitiligo.

Structural and functional characterization of neuropeptide Y in a primitive teleost, the Japanese eel (Anguilla japonica)

In the present study, the first full-length cDNA encoding Neuropeptide Y (NPY) was cloned from the brain of Japanese eel (Anguilla japonica). The open reading frame of Japanese eel NPY gene is 294 bp in length, encoding a precursor protein of 97 amino acids, which contains a 36-amino-acid mature peptide. Sequence analysis showed that the Japanese eel NPY peptide is similar to that of other species. Real-time PCR revealed that NPY in Japanese eel is mainly expressed in the brain, especially in the hypothalamus and the optic tectum thalamus. The effect of a negative energy balance on NPY gene expression was examined subsequently. The mRNA level of NPY in the hypothalamus and the optic tectum thalamus showed a pronounced increase after 4 days of food deprivation. The biological activities of Japanese eel NPY were further investigated in vivo and in vitro. Intraperitoneal injection of the NPY peptide into Japanese eel could potently elevate the expression of the mammalian gonadotropin-releasing hormone (mGnRH) in hypothalamus and the follicle-stimulating hormone beta (FSHβ), the luteinizing hormone beta (LHβ) and growth hormone (GH) in pituitary. In static incubation studies, the stimulatory effects of NPY on mGnRH expression in hypothalamic fragments and on FSHβ, LHβ and GH expression in pituitary cells were also observed. However, in vivo and in vitro studies showed that NPY exhibits an inhibitory action on the expression of thyroid-stimulating hormone beta (TSHβ) in pituitary. The results indicate that NPY is involved in the regulation of multiple physiological processes in Japanese eel.

Neuropeptide Y enhances olfactory mucosa responses to odorant in hungry rats

Neuropeptide Y (NPY) plays an important role in regulating appetite and hunger in vertebrates. In the hypothalamus, NPY stimulates food intake under the control of the nutritional status. Previous studies have shown the presence of NPY and receptors in rodent olfactory system, and suggested a neuroproliferative role. Interestingly, NPY was also shown to directly modulate olfactory responses evoked by a food-related odorant in hungry axolotls. We have recently demonstrated that another nutritional cue, insulin, modulates the odorant responses of the rat olfactory mucosa (OM). Therefore, the aim of the present study was to investigate the potential effect of NPY on rat OM responses to odorants, in relation to the animal's nutritional state. We measured the potential NPY modulation of OM responses to odorant, using electro-olfactogram (EOG) recordings, in fed and fasted adult rats. NPY application significantly and transiently increased EOG amplitudes in fasted but not in fed rats. The effects of specific NPY-receptor agonists were similarly quantified, showing that NPY operated mainly through Y1 receptors. These receptors appeared as heterogeneously expressed by olfactory neurons in the OM, and western blot analysis showed that they were overexpressed in fasted rats. These data provide the first evidence that NPY modulates the initial events of odorant detection in the rat OM. Because this modulation depends on the nutritional status of the animal, and is ascribed to NPY, the most potent orexigenic peptide in the central nervous system, it evidences a strong supplementary physiological link between olfaction and nutritional processes.

Developmental reversal in neuropeptide Y action on feeding in an amphibian

Neuropeptide Y (NPY) is expressed in the hypothalamus where it exerts orexigenic actions within the feeding control circuit. While NPY stimulates feeding in juvenile and adult animals, it is not known whether NPY influences food intake at earlier life stages. We investigated a role for NPY in regulating feeding at two stages of the life cycle of an amphibian, the Western spadefoot toad Spea hammondii. We administered NPY by intracerebroventricular (i.c.v.) injection to juvenile toads or prometamorphic tadpoles, and monitored locomotion, feeding behavior and/or food intake. Injection of NPY (20 or 200 ng/g BW) into juvenile toads decreased the latency to, and increased the number of strikes at prey, and the number of crickets eaten compared to uninjected or vehicle-injected controls. By contrast, injection of NPY (0.02-20 ng/g BW) into prometamorphic tadpoles caused a dose-dependent decrease in time spent foraging compared to controls. Blocking NPY signaling in the prometamorphic tadpole brain by i.c.v. injection of a general NPY receptor antagonist increased foraging, and partly blocked the action of exogenous NPY on foraging. Taken together, our findings show a developmental reversal in NPY actions on feeding in an amphibian, with the peptide having a characteristic orexigenic action in the juvenile toad, but an inhibitory action on foraging in the prometamorphic tadpole. The anorexigenic action of NPY in the tadpole correlates with a decrease in feeding that occurs at metamorphic climax when the tadpole's gut and cranium remodels for the transition to a carnivorous diet.

Neuropeptide Y modulates calcium channels in hamster submandibular ganglion neurons

It is established that neuropeptide Y (NPY) is a transmitter of parasympathetic secretory impulses in submandibular gland. The neuropeptides substance P, vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP) are likely mediators of secretory parasympathetic responses of the gland. Previously, we have shown that substance P, VIP and CGRP modulate voltage-dependent Ca(2+) channels (VDCCs) in hamster submandibular ganglion (SMG) neurons. In this study, we attempt to characterize the effect of NPY on VDCCs current using Ba(2+) (I(Ba)) in SMG neurons. Application of NPY caused both facilitation and inhibition of L-type and N/P/Q-type I(Ba), respectively. Intracellular dialysis of the Gα(s)-protein antibody attenuated the NPY-induced facilitation of I(Ba). The adenylate cyclase (AC) inhibitor, as well as protein kinase A (PKA) inhibitor attenuated the NPY-induced facilitation of I(Ba). Intracellular dialysis of the Gα(i)-protein antibody attenuated the NPY-induced inhibition of I(Ba). Application of a strong depolarizing voltage prepulse attenuated the NPY-induced inhibition of I(Ba). These results indicate that NPY facilitates L-type VDCCs via Gα(s)-protein involving AC and PKA. On the other hand, NPY also inhibits N/P/Q-type VDCCs via Gα(i)-protein βγ subunits in the SMG neurons.

Tobacco addiction and the dysregulation of brain stress systems

Tobacco is a highly addictive drug and is one of the most widely abused drugs in the world. The first part of this review explores the role of stressors and stress-associated psychiatric disorders in the initiation of smoking, the maintenance of smoking, and relapse after a period of abstinence. The reviewed studies indicate that stressors facilitate the initiation of smoking, decrease the motivation to quit, and increase the risk for relapse. Furthermore, people with depression or an anxiety disorder are more likely to smoke than people without these disorders. The second part of this review describes animal studies that investigated the role of brain stress systems in nicotine addiction. These studies indicate that corticotropin-releasing factor, Neuropeptide Y, the hypocretins, and norepinephrine play a pivotal role in nicotine addiction. In conclusion, the reviewed studies indicate that smoking briefly decreases subjective stress levels but also leads to a further dysregulation of brain stress systems. Drugs that decrease the activity of brain stress systems may diminish nicotine withdrawal and improve smoking cessation rates.

Y5 neuropeptide Y receptor overexpression in mice neither affects anxiety- and depression-like behaviours nor seizures but confers moderate hyperactivity

Neuropeptide Y (NPY) has been implicated in anxiolytic- and antidepressant-like behaviour as well as seizure-suppressant effects in rodents. Although these effects appear to be predominantly mediated via other NPY receptors (Y1 and/or Y2), several studies have also indicated a role for Y5 receptors. Gene therapy using recombinant viral vectors to induce overexpression of NPY, Y1 or Y2 receptors in the hippocampus or amygdala has previously been shown to modulate emotional behaviour and seizures in rodents. The present study explored the potential effects of gene therapy with the Y5 receptor, by testing effects of recombinant adeno-associated viral vector (rAAV) encoding Y5 (rAAV-Y5) in anxiety- and depression-like behaviour as well as in kainate-induced seizures in adult mice. The rAAV-Y5 vector injected into the hippocampus and amygdala induced a pronounced and sustained increase in Y5 receptor mRNA expression and functional Y5 receptor binding, but no significant effects were found with regard to anxiety- and depression-like behaviours or seizure susceptibility. Instead, rAAV-mediated Y5 receptor transgene overexpression resulted in moderate hyperactivity in the open field test. These results do not support a potential role for single transgene overexpression of Y5 receptors for modulating anxiety-/depression-like behaviours or seizures in adult mice. Whether the induction of hyperactivity by rAAV-Y5 could be relevant for other conditions remains to be studied.

Acupuncture at ST36 prevents chronic stress-induced increases in neuropeptide Y in rat

Chronic stress, as seen in post-traumatic stress disorder, can exacerbate existing diseases. Electroacupuncture (EA) has been proposed to treat chronic stress, although information on its efficacy or mechanism(s) of action is limited. While many factors contribute to the chronic stress response, the sympathetic peptide, neuropeptide Y (NPY), has been shown to be elevated in chronic stress and is hypothesized to contribute to the physiological stress response. Our objective was to determine if EA at acupuncture point stomach 36 (ST36) is effective in mitigating cold stress-induced increase in NPY in rats. Both pretreatment and concomitant treatment with EA ST36 effectively suppressed peripheral and central NPY after 14 d of cold stress ( P < 0.05). The effect was specific, as NPY in Sham-EA rats was not different than observed in stress-only rats. Additionally, the effect of EA ST36 was long-lasting, as NPY levels remained suppressed despite early cessation of EA ST36, while exposure to cold stress was continued. In the paraventricular nucleus (PVN), it was notable that changes in NPY mirrored plasma NPY levels, and that the significant elevation in PVN Y1 receptor observed with stress was also prevented with EA ST36. The findings indicate that EA ST36 is effective in preventing one of the sympathetic pathways stimulated during chronic stress, and thus may be a useful adjunct therapy in stress-related disorders.

Select Neuropeptides and their G-Protein Coupled Receptors in Caenorhabditis Elegans and Drosophila Melanogaster

The G-protein coupled receptor (GPCR) family is comprised of seven transmembrane domain proteins and play important roles in nerve transmission, locomotion, proliferation and development, sensory perception, metabolism, and neuromodulation. GPCR research has been targeted by drug developers as a consequence of the wide variety of critical physiological functions regulated by this protein family. Neuropeptide GPCRs are the least characterized of the GPCR family as genetic systems to characterize their functions have lagged behind GPCR gene discovery. Drosophila melanogaster and Caenorhabditis elegans are genetic model organisms that have proved useful in characterizing neuropeptide GPCRs. The strength of a genetic approach leads to an appreciation of the behavioral plasticity that can result from subtle alterations in GPCRs or regulatory proteins in the pathways that GPCRs control. Many of these invertebrate neuropeptides, GPCRs, and signaling pathway components serve as models for mammalian counterparts as they have conserved sequences and function. This review provides an overview of the methods to match neuropeptides to their cognate receptor and a state of the art account of neuropeptide GPCRs that have been characterized in D. melanogaster and C. elegans and the behaviors that have been uncovered through genetic manipulation.

GABAergic signaling by AgRP neurons prevents anorexia via a melanocortin-independent mechanism

The hypothalamic arcuate nucleus contains two anatomically and functionally distinct populations of neurons-the agouti-related peptide (AgRP)- and pro-opiomelanocortin (POMC)-expressing neurons that integrate various nutritional, hormonal, and neuronal signals to regulate food intake and energy expenditure, and thereby help achieve energy homeostasis. AgRP neurons, also co-release neuropeptide Y (NPY) and γ-aminobutyric acid (GABA) to promote feeding and inhibit metabolism through at least three possible mechanisms: (1) suppression of the melanocortin signaling system through competitive binding of AgRP with the melanocortin 4 receptors; (2) NPY-mediated inhibition of post-synaptic neurons that reside in hypothalamic nuclei; (3) GABAergic inhibition of POMC neurons in their post-synaptic targets including the parabrachial nucleus (PBN), a brainstem structure that relays gustatory and visceral sensory information. Acute ablation of AgRP neurons in adult mice by the action of diphtheria toxin (DT) results in precipitous reduction of food intake, and eventually leads to starvation within 6days of DT treatment. Chronic delivery of bretazenil, a GABA(A) receptor partial agonist, into the PBN is sufficient to restore feeding and body weight when AgRP neurons are ablated, whereas chronic blockade of melanocortin 4 receptor signaling is inadequate. This review summarizes the physiological roles of a neural circuitry regulated by AgRP neurons in control of feeding behavior with particular emphasis of the GABA output to the parabrachial nucleus. We also describe a compensatory mechanism that is gradually engaged after ablation of AgRP neurons that allows mice to continue eating without them.

Neuropeptide Y modulation of interleukin-1{beta} (IL-1{beta})-induced nitric oxide production in microglia

Given the modulatory role of neuropeptide Y (NPY) in the immune system, we investigated the effect of NPY on the production of NO and IL-1β in microglia. Upon LPS stimulation, NPY treatment inhibited NO production as well as the expression of inducible nitric-oxide synthase (iNOS). Pharmacological studies with a selective Y(1) receptor agonist and selective antagonists for Y(1), Y(2), and Y(5) receptors demonstrated that inhibition of NO production and iNOS expression was mediated exclusively through Y(1) receptor activation. Microglial cells stimulated with LPS and ATP responded with a massive release of IL-1β, as measured by ELISA. NPY inhibited this effect, suggesting that it can strongly impair the release of IL-1β. Furthermore, we observed that IL-1β stimulation induced NO production and that the use of a selective IL-1 receptor antagonist prevented NO production upon LPS stimulation. Moreover, NPY acting through Y(1) receptor inhibited LPS-stimulated release of IL-1β, inhibiting NO synthesis. IL-1β activation of NF-κB was inhibited by NPY treatment, as observed by confocal microscopy and Western blotting analysis of nuclear translocation of NF-κB p65 subunit, leading to the decrease of NO synthesis. Our results showed that upon LPS challenge, microglial cells release IL-1β, promoting the production of NO through a NF-κB-dependent pathway. Also, NPY was able to strongly inhibit NO synthesis through Y(1) receptor activation, which prevents IL-1β release and thus inhibits nuclear translocation of NF-κB. The role of NPY in key inflammatory events may contribute to unravel novel gateways to modulate inflammation associated with brain pathology.

A G-protein-coupled neuropeptide Y-like receptor suppresses behavioral and sensory response to multiple stressful stimuli in Drosophila

Recent studies suggest that human neuropeptide Y (NPY) plays a prominent role in management of stress response and emotion, and higher NPY levels observed in combat-exposed veterans may help coping with posttraumatic stress. Neuropeptide F (NPF), the counterpart of NPY in Drosophila melanogaster, also displays parallel activities, including promotion of resilience to diverse stressors and prevention of uncontrolled aggressive behavior. However, it remains unclear how NPY family peptides modulate physical and emotional responses to various stressors. Here we show that NPFR1, a G-protein-coupled NPF receptor, exerts an inhibitory effect on larval aversion to diverse stressful stimuli mediated by different subtypes of fly and mammalian transient receptor potential (TRP) family channels. Imaging analysis in larval sensory neurons and cultured human cells showed that NPFR1 attenuates Ca(2+) influx mediated by fly TRPA and rat TRPV1 channels. Our findings suggest that suppression of TRP channel-mediated neural excitation by the conserved NPF/NPFR1 system may be a major mechanism for attaining its broad anti-stress function.

Neuropeptide Y signaling in the central nucleus of amygdala regulates alcohol-drinking and anxiety-like behaviors of alcohol-preferring rats

BACKGROUND

The neuropeptide Y (NPY) system of the central nucleus of amygdala (CeA) has been shown to be involved in anxiety and alcoholism. In this study, we investigated the molecular mechanisms by which NPY in the CeA regulates anxiety and alcohol drinking behaviors using alcohol-preferring (P) rats as an animal model.

METHODS

Alcohol-preferring rats were bilaterally cannulated targeting the CeA and infused with artificial cerebrospinal fluid (aCSF) or NPY. Alcohol drinking and anxiety-like behaviors were assessed by the 2-bottle free-choice paradigm and light/dark box (LDB) exploration test, respectively. The levels of NPY and related signaling proteins were determined by the gold immunolabeling procedure. The mRNA levels of NPY were measured by in situ RT-PCR. Double-immunofluorescence labeling was performed to observe the colocalization of NPY and Ca(2+)/calmodulin-dependent protein kinase IV (CaMK IV).

RESULTS

We found that NPY infusion into the CeA produced anxiolytic effects, as measured by the LDB exploration test, and also decreased alcohol intake in P rats. NPY infusion into the CeA significantly increased levels of CaMK IV and phosphorylated cAMP responsive element-binding (pCREB) protein and increased mRNA and protein levels of NPY, but produced no changes in protein levels of CREB or the catalytic alpha-subunit of protein kinase A (PKA-Calpha) in the CeA. We also observed that alcohol intake produced anxiolytic effects in P rats in the LDB test and also increased NPY expression and protein levels of pCREB and PKA-Calpha without modulating protein levels of CREB or CaMK IV, in both the CeA and medial nucleus of amygdala. In addition, we found that CaMK IV-positive cells were co-localized with NPY in amygdaloid structures of P rats.

CONCLUSIONS

These results suggest that NPY infusion may increase the expression of endogenous NPY in the CeA, which is most likely attributable to an increase in CaMK IV-dependent CREB phosphorylation and this molecular mechanism may be involved in regulating anxiety and alcohol drinking behaviors of P rats.

Excitatory and inhibitory synapses in neuropeptide Y-expressing striatal interneurons

Although rare, interneurons are pivotal in governing striatal output by extensive axonal arborizations synapsing on medium spiny neurons. Using a genetically modified mouse strain in which a green fluorescent protein (GFP) is driven to be expressed under control of the neuropeptide Y (NPY) promoter, we identified NPY interneurons and compared them with striatal principal neurons. We found that the bacteria artificial chromosome (BAC)-npy mouse expresses GFP with high fidelity in the striatum to the endogenous expression of NPY. Patch-clamp analysis from NPY neurons showed a heterogeneous population of striatal interneurons. In the majority of cells, we observed spontaneous firing of action potentials in extracellular recordings. On membrane rupture, most NPY interneurons could be classified as low-threshold spiking interneurons and had high-input resistance. Voltage-clamp recordings showed that both GABA and glutamate gated ion channels mediate synaptic inputs onto these striatal interneurons. AMPA receptor-mediated spontaneous excitatory postsynaptic currents (sEPSCs) were small in amplitude and infrequent in NPY neurons. Evoked EPSCs did not show short-term plasticity but some rectification. Evoked N-methyl-d-aspartate (NMDA) EPSCs had fast decay kinetics and were poorly sensitive to an NR2B subunit containing NMDA receptor blocker. Spontaneous inhibitory postsynaptic currents (sIPSCs) were mediated by GABA(A) receptors and were quite similar among all striatal neurons studied. On the contrary, evoked IPSCs decayed faster in NPY neurons than in other striatal neurons. These data report for the first time specific properties of synaptic transmission to NPY striatal interneurons.

Insight into zinc signaling from dietary zinc deficiency

Zinc is necessary for not only brain development but also brain function. Zinc homeostasis in the brain is tightly regulated by the brain barrier system and is not easily disrupted by dietary zinc deficiency. However, histochemically reactive zinc as revealed by Timm's staining is susceptible to zinc deficiency, suggesting that the pool of Zn(2+) can be reduced by zinc deficiency. The hippocampus is also susceptible to zinc deficiency in the brain. On the other hand, zinc deficiency causes abnormal glucocorticoid secretion from the adrenal cortex, which is observed prior to the decrease in extracellular zinc concentration in the hippocampus. The hippocampus is enriched with glucocorticoid receptors and hippocampal functions are changed by abnormal glucocorticoid secretion. Zinc deficiency elicits neuropsychological symptoms and affects cognitive performance. It may also aggravate glutamate excitotoxicity in neurological diseases. Abnormal glucocorticoid secretion is associated with these symptoms in zinc deficiency. Furthermore, the decrease in Zn(2+) pool may cooperate with glucocorticoid action in zinc deficiency. Judging from susceptibility of Zn(2+) pool in the brain to zinc deficiency, it is possible that the decrease in Zn(2+) pool in the peripheral tissues triggers abnormal glucocorticoid secretion. To understand the importance of zinc as a signaling factor, this paper analyzes the relationship among the changes in hippocampal functions, abnormal behavior and pathophysiological changes in zinc deficiency, based on the data from experimental animals.

Behavior in the forced swim test and neurochemical changes in the hippocampus in young rats after 2-week zinc deprivation

Abnormal behavior in zinc deficiency and its cause are poorly understood. In the present paper, behavior in the forced swim test and neurochemical changes in the brain associated with its behavior were studied focused on abnormal corticosterone secretion in zinc deficiency. The effect of chronic corticosterone treatment was also studied. Immobility time in the forced swim test was increased in young rats fed a zinc-deficient diet for 2 weeks, as well as corticosterone (40mg/kg/dayx14 days)-treated control rats. The basal Ca(2+) levels in the hippocampus, which were determined by fluo-4FF, AM, were increased in both brain slices from zinc-deficient and corticosterone-treated rats. Serum glucose level was decreased in zinc deficiency and hippocampal glucose metabolism, which is determined by [(14)C]2-deoxyglucose uptake, was elevated. Hippocampal ATP level was not decreased, whereas, the concentrations of glutamate, GABA and glutamine in the hippocampus, unlike the whole brain, were decreased in zinc deficiency. However, the decrease in these amino acids was restored by adrenalectomy prior to zinc deficiency. These results suggest that glucose is insufficient for the synthesis of amino acids in the hippocampus of zinc-deficient rats. It is likely that the neurochemical and metabolic changes in the hippocampus, which may be associated with abnormal corticosterone secretion, is the base of abnormal behavior associated with neuropsychological symptoms in zinc deficiency.

Regulation of maternal food intake and mother-pup interactions by the Y5 receptor

Neuropeptide Y (NPY) is increased in the hypothalamus during lactation. To investigate the role of the NPY Y5 receptor during lactation, an antisense oligodeoxynucleotide (ODN) targeted to the NPY Y5 receptor, an equivalent scrambled ODN or vehicle, was chronically infused into the 3rd ventricle of lactating rats from day 8 postpartum. Y5 antisense ODN treatment reduced Y5 positive cell number in the paraventricular nucleus and resulted in significant reductions in food intake and litter growth. Litters from pair-fed vehicle treated dams gained significantly more weight than the litters of Y5 antisense ODN treated dams suggesting that decreased maternal food intake is not the only mechanism involved in suppressing litter weight gain. When mother-litter interaction was examined on day 13 pp, Y5 antisense ODN treated dams spent significantly less time on the nest and had significantly shorter nest bouts. These results suggest that in addition to regulating feeding behaviour, the Y5 receptor subtype may have previously unrecognised roles in the control of nesting behaviour during lactation with subsequent effects on litter growth rates.

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.

The role of neuropeptide Y in the expression and extinction of fear-potentiated startle

Neuropeptides are a promising target for novel treatments for anxiety and other psychiatric disorders and neuropeptide Y (NPY) has emerged as a key component of anxiolytic circuits in the brain. For this reason, we have evaluated the role of NPY in the expression and extinction of conditioned fear. We found that intracerebroventricular administration of NPY inhibits both baseline acoustic startle and the expression of fear-potentiated startle. Infusion of NPY (10 pmol/side) into the basolateral, but not the medial, nucleus of the amygdala reproduced the intracerebroventricular effect. Central administration of NPY (10 microg) also enhanced within-session extinction of fear-potentiated startle. This finding, coupled with the growing body of literature correlating NPY with resilience in humans, led us to the hypothesis that NPY may enhance the extinction of conditioned fear. When NPY (10 microg) is administered intracerebroventricularly before extinction training, extinction retention for both the contextual and cued components of conditioned fear is enhanced when tested 48 h later off drug. Additionally, we found that intra-basolateral amygdala administration of the NPY Y(1) receptor antagonist BIBO 3304 (200 pmol/side) before extinction training led to a profound deficit in extinction retention. This is the first evidence that NPY facilitates and an NPY antagonist blocks the extinction of conditioned fear. We believe that the role of NPY in the extinction of conditioned fear may, at least in part, explain the mechanism underlying the association between NPY and psychobiological resilience in humans.

Neuropeptide Y receptor genes are associated with alcohol dependence, alcohol withdrawal phenotypes, and cocaine dependence

BACKGROUND

Several lines of evidence in both human and animal studies suggest that variation in neuropeptide Y (NPY) or its receptor genes (NPY1R, NPY2R and NPY5R) is associated with alcohol dependence as well as alcohol withdrawal symptoms. Additional studies suggest that cocaine may affect NPY expression.

METHODS

A total of 39 single nucleotide polymorphisms (SNPs) were genotyped across NPY and its 3 receptor genes in a sample of 1,923 subjects from 219 multiplex alcoholic families of European American descent recruited as part of the Collaborative Studies on the Genetics of Alcoholism (COGA) study. Family-based association analysis was performed to test the primary hypothesis that variation in these genes is associated with alcohol dependence. Secondary analyses evaluated whether there was an association of these SNPs with symptoms of alcohol withdrawal, cocaine dependence, or comorbid alcohol and cocaine dependence.

RESULTS

Although variations in NPY itself were not associated with these phenotypes, variations in 2 NPY-receptor genes were. SNPs in NPY2R provided significant evidence of association with alcohol dependence, alcohol withdrawal symptoms, comorbid alcohol and cocaine dependence, and cocaine dependence (all p < 0.03). Haplotype analyses strengthened the evidence for these phenotypes (global 0.0004 < p < 0.005). SNPs in NPY5R demonstrated significant association with alcohol withdrawal characterized by seizures (p < 0.05).

CONCLUSION

These results indicate that sequence variations in NPY receptor genes are associated with alcohol dependence, particularly a severe subtype of alcohol dependence characterized by withdrawal symptoms, comorbid alcohol and cocaine dependence, and cocaine dependence.

Drosophila TRPA channel modulates sugar-stimulated neural excitation, avoidance and social response

Drosophila melanogaster postfeeding larvae show food-averse migration toward food-free habitats before metamorphosis. This developmental switching from food attraction to aversion is regulated by a neuropeptide Y (NPY)-related brain signaling peptide. We used the fly larva model to delineate the neurobiological basis of age-restricted response to environmental stimuli. Here we provide evidence for a fructose-responsive chemosensory pathway that modulates food-averse migratory and social behaviors. We found that fructose potently elicited larval food-averse behaviors, and painless (pain), a transient receptor potential channel that is responsive to noxious stimuli, was required for the fructose response. A subset of pain-expressing sensory neurons have been identified that show pain-dependent excitation by fructose. Although evolutionarily conserved avoidance mechanisms are widely appreciated for their roles in stress coping and survival, their biological importance in animal physiology and development remains unknown. Our findings demonstrate how an avoidance mechanism is recruited to facilitate animal development.

Acute stress differentially affects corticotropin-releasing hormone mRNA expression in the central amygdala of the "depressed" flinders sensitive line and the control flinders resistant line rats

Preclinical and clinical evidence suggests that neuropeptides play a role in the pathophysiology of mood disorders. In the present study, we investigated the involvement of the peptides corticotropin-releasing hormone (CRH), neuropeptide Y (NPY) and nociceptin/orphanin FQ (N/OFQ) and of their receptors in the regulation of emotional behaviours. In situ hybridization experiments were performed in order to evaluate the mRNA expression levels of these neuropeptidergic systems in limbic and limbic-related brain regions of the Flinders Sensitive Line (FSL) rats, a putative genetic animal model of depression. The FSL and their controls, the Flinders Resistant Line (FRL) rats, were subjected to one hour acute restraint and the effects of the stress exposure, including possible strain specific changes on these neuropeptidergic systems, were studied. In basal conditions, no significant differences between FSL and FRL rats in the CRH mRNA expression were found, however an upregulation of the CRH mRNA hybridization signal was detected in the central amygdala of the stressed FRL, compared to the non stressed FRL rats, but not in the FSL, suggesting a hypoactive mechanism of response to stressful stimuli in the "depressed" FSL rats. Baseline levels of NPY and N/OFQ mRNA were lower in the FSL rats compared to the FRL in the dentate gyrus of hippocampus and in the medial amygdala, respectively. However, the exposure to stress induced a significant upregulation of the N/OFQ mRNA levels in the paraventricular thalamic nucleus, while in the same nucleus the N/OFQ receptor mRNA expression was higher in the FSL rats. In conclusion, selective alterations of the NPY and N/OFQ mRNA in limbic and limbic-related regions of the FSL rats, a putative animal model of depression, provide further support for the involvement of these neuropeptides in depressive disorders. Moreover, the lack of CRH activation following stress in the "depressed" FSL rats suggests a form of allostatic load, that could alter their interpretation of environmental stimuli and influence their behavioural response to stressful situations.