Effects Of Neuropeptide Y Research Articles

Neuropeptide Y in the rostral ventromedial medulla reverses inflammatory and nerve injury hyperalgesia in rats via non-selective excitation of local neurons

Chronic pain reflects not only sensitization of the ascending nociceptive pathways, but also changes in descending modulation. The rostral ventromedial medulla (RVM) is a key structure in a well-studied descending pathway, and contains two classes of modulatory neurons, the ON-cells and the OFF-cells. Disinhibition of OFF-cells depresses nociception; increased ON-cell activity facilitates nociception. Multiple lines of evidence show that sensitization of ON-cells contributes to chronic pain, and reversing or blocking this sensitization is of interest as a treatment of persistent pain. Neuropeptide Y (NPY) acting via the Y1 receptor has been shown to attenuate hypersensitivity in nerve-injured animals without affecting normal nociception when microinjected into the RVM, but the neural basis for this effect was unknown. We hypothesized that behavioral anti-hyperalgesia was due to selective inhibition of ON-cells by NPY at the Y1 receptor. To explore the possibility of Y1 selectivity on ON-cells, we stained for the NPY-Y1 receptor in the RVM, and found it broadly expressed on both serotonergic and non-serotonergic neurons. In subsequent behavioral experiments, NPY microinjected into the RVM in lightly anesthetized animals reversed signs of mechanical hyperalgesia following either nerve injury or chronic hindpaw inflammation. Unexpectedly, rather than decreasing ON-cell activity, NPY increased spontaneous activity of both ON- and OFF-cells without altering noxious-evoked changes in firing. Based on these results, we conclude that the anti-hyperalgesic effects of NPY in the RVM are not explained by selective inhibition of ON-cells, but rather by increased spontaneous activity of OFF-cells. Although ON-cells undoubtedly facilitate nociception and contribute to hypersensitivity, the present results highlight the importance of parallel OFF-cell-mediated descending inhibition in limiting the expression of chronic pain.

Involvement of hypothalamic neuropeptide Y in pentazocine induced suppression of food intake in rats

The potent orexigenic peptide neuropeptide Y (NPY) has been considered as a possible endogenous ligand for a subpopulation of sigma receptors (SigR). However, their mutual interaction with reference to feeding behavior remains poorly understood. In the present study, we explored the possible interaction between sigma1 receptors (Sig1R) agonist, pentazocine, and NPY on food intake in satiated rats. While pentazocine dose-dependently reduced the food intake, NPY significantly increased it at 2, 4 and 6h post injection time points. In combination studies, pretreatment with NPY (0.1nmol/rat, intra-PVN) normalized the inhibitory effect of pentazocine (60μg/rat, intra-PVN) on food intake. Similarly, pre-treatment with pentazocine (30μg/rat, intra-PVN) significantly antagonized the orexigenic effect of NPY (0.5 and 1.0nmol/rat, intra-PVN). Moreover, pentazocine treatment decreased NPY immunoreactivity in arcuate (ARC), paraventricular (PVN), dorsomedial (DMH) and ventromedial (VMH) nuclei of hypothalamus. However, no change was observed in lateral hypothalamus (LH). Study implicates the reduced NPY immunoreactivity for the anorectic effect observed following pentazocine injections. Therefore, the concomitant activation of the NPYergic system along with the Sig1R agonist treatment may serve a useful purpose in the management of the unwanted side effects related to energy homeostasis.

Limbic substrates of the effects of neuropeptide Y on intake of and motivation for palatable food

Neuropeptide Y (NPY), given centrally augments food intake and the motivation to work for palatable food. Here, the brain regions were identified through which NPY increases food intake and motivation. NPY was infused into three brain regions implicated in food intake and motivation: the lateral hypothalamus (LH), nucleus accumbens shell (NAc), and ventral tegmental area (VTA). Motivation for sucrose was assessed using a progressive-ratio schedule of reinforcement in which the effort to obtain successive rewards increased incrementally. To disentangle the effects of NPY on motivation for palatable food from food consumption, free-feeding experiments were performed in which animals had ad libitum access to sucrose pellets. Infusion of NPY into either VTA or NAc increased the motivation to respond for sucrose, whereas infusion of NPY in either NAc or LH increased sucrose consumption. In addition, the effect of intra-VTA NPY on motivation for food was attenuated after pretreatment with the dopamine receptor antagonist alpha-flupenthixol. Specific limbic substrates through which NPY influences consumption of and motivation for palatable food were identified by these data. The motivational effects of NPY are exerted through the VTA, its consummatory effects through the LH, and the NAc is involved in both.

Effect of neuropeptide Y on norepinephrine-induced constriction in the rabbit facial artery after carotid artery occlusion

Atherosclerotic-occlusive changes could be observed in orofacial branches of the external carotid artery. Atherosclerosis-induced ischemia caused alteration in production and release of endothelial factors. The aim of this study was to investigate the influence of carotid artery occlusion (10, 30 and 60 min) on vascular effects of norepinephrine (NOR) and neuropeptide Y (NPY) in the isolated glandular branch of the rabbit facial artery, the main feeding artery for the submandibular gland. Changes in isometric tension were recorded in organ bath studies with arterial rings, before and after carotid artery occlusion. Concentration-dependent vasocontractile effect of NOR was significantly augmented after 30 and 60 min of carotid occlusion, but only in the rings with intact endothelium. Given alone, NPY showed no effect in isolated glandular branch of the rabbit facial artery, but enhanced NOR vasoconstriction in all the investigated rings. NOR vasocontractile effect enhancement in the presence of NPY was attenuated after 30 and 60 min of carotid occlusion. Also, enhancement of NOR vasoconstriction by NPY was significantly higher in endothelium-intact rings compared to endothelium-denuded rings obtained after 30 and 60 min of carotid occlusion. The present investigation provides results of increased vasocontractile effect of NOR and decreased enhancing effect of NPY on NOR vasoconstriction in the rabbit facial artery after carotid occlusion that is related to altered endothelium function.

Inflammation enhances Y1 receptor signaling, neuropeptide Y-mediated inhibition of hyperalgesia, and substance P release from primary afferent neurons

Neuropeptide Y (NPY) is present in the superficial laminae of the dorsal horn and inhibits spinal nociceptive processing, but the mechanisms underlying its anti-hyperalgesic actions are unclear. We hypothesized that NPY acts at neuropeptide Y1 receptors in the dorsal horn to decrease nociception by inhibiting substance P (SP) release, and that these effects are enhanced by inflammation. To evaluate SP release, we used microdialysis and neurokinin 1 receptor (NK1R) internalization in rat. NPY decreased capsaicin-evoked SP-like immunoreactivity in the microdialysate of the dorsal horn. NPY also decreased non-noxious stimulus (paw brush)-evoked NK1R internalization (as well as mechanical hyperalgesia and mechanical and cold allodynia) after intraplantar injection of carrageenan. Similarly, in rat spinal cord slices with dorsal root attached, [Leu31, Pro34]-NPY inhibited dorsal root stimulus-evoked NK1R internalization. In rat dorsal root ganglion neurons, Y1 receptors colocalized extensively with calcitonin gene-related peptide (CGRP). In dorsal horn neurons, Y1 receptors were extensively expressed and this may have masked the detection of terminal co-localization with CGRP or SP. To determine whether the pain inhibitory actions of Y1 receptors are enhanced by inflammation, we administered [Leu31, Pro34]-NPY after intraplantar injection of complete Freund’s adjuvant (CFA) in rat. We found that [Leu31, Pro34]-NPY reduced paw clamp-induced NK1R internalization in CFA rats but not uninjured controls. To determine the contribution of increased Y1 receptor-G protein coupling, we measured [35S]GTPγS binding simulated by [Leu31, Pro34]-NPY in mouse dorsal horn. CFA inflammation increased the affinity of Y1 receptor G-protein coupling. We conclude that Y1 receptors contribute to the anti-hyperalgesic effects of NPY by mediating the inhibition of SP release, and that Y1 receptor signaling in the dorsal horn is enhanced during inflammatory nociception.

Therapeutic concentrations of valproate but not amitriptyline increase neuropeptide Y (NPY) expression in the human SH-SY5Y neuroblastoma cell line

Neuropeptide Y (NPY) is a peptide found in the brain and autonomic nervous system, which is associated with anxiety, depression, epilepsy, learning and memory, sleep, obesity and circadian rhythms. NPY has recently gained much attention as an endogenous antiepileptic and antidepressant agent, as drugs with antiepileptic and/or mood-stabilizing properties may exert their action by increasing NPY concentrations, which in turn can reduce anxiety and depression levels, dampen seizures or increase seizure threshold.We have used human neuroblastoma SH-SY5Y cells to investigate the effect of valproate (VPA) and amitriptyline (AMI) on NPY expression at therapeutic plasma concentrations of 0.6mM and 630nM, respectively. In addition, 12-O-tetradecanoylphorbol-13-acetate (TPA) known to differentiate SH-SY5Y cells into a neuronal phenotype and to increase NPY expression through activation of protein kinase C (PKC) was applied as a positive control (16nM). Cell viability after drug treatment was tested with a 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. NPY expression was measured using immunofluorescence and quantitative RT-PCR (qRT-PCR). Results from immunocytochemistry have shown NPY levels to be significantly increased following a 72h but not 24h VPA treatment. A further increase in expression was observed with simultaneous VPA and TPA treatment, suggesting that the two agents may increase NPY expression through different mechanisms. The increase in NPY mRNA by VPA and TPA was confirmed with qRT-PCR after 72h. In contrast, AMI had no effect on NPY expression in SH-SY5Y cells.Together, the data point to an elevation of human NPY mRNA and peptide levels by therapeutic concentrations of VPA following chronic treatment. Thus, upregulation of NPY may have an impact in anti-cancer treatment of neuroblastomas with VPA, and antagonizing hypothalamic NPY effects may help to ameliorate VPA-induced weight gain and obesity without interfering with the desired central effects of VPA.

Modulation of Distal Calcium Electrogenesis by Neuropeptide Y1 Receptors Inhibits Neocortical Long-Term Depression

In layer 5 neocortical pyramidal neurons, backpropagating action potentials (bAPs) firing at rates above a critical frequency (CF) induce supralinear Ca²⁺ influx and regenerative potentials in apical dendrites. Paired temporally with an EPSP, this Ca²⁺ influx can result in synaptic plasticity. We studied the actions of neuropeptide Y (NPY), an abundant neocortical neuropeptide, on Ca²⁺ influx in layer 5 pyramidal neurons of somatosensory neocortex in Sprague Dawley and Wistar rats, using a combination of somatic and dendritic intracellular recordings and simultaneous Ca²⁺ imaging. Ca²⁺ influx induced by trains of bAPs above a neuron's CF was inhibited by NPY, acting only at the distal dendrite, via Y₁ receptors. NPY does not affect evoked synaptic glutamate release, paired synaptic facilitation, or synaptic rundown in longer trains. Extracellular Cs⁺ did not prevent NPY's postsynaptic effects, suggesting it does not act via either G-protein-activated inwardly rectifying K⁺ conductance (G(IRK)) or hyperpolarization-activated, cyclic nucleotide-gated channels. NPY application suppresses the induction of the long-term depression (LTD) normally caused by pairing 100 EPSPs with bursts of 2 bAPs evoked at a supracritical frequency. These findings suggest that distal dendritic Ca²⁺ influx is necessary for LTD induction, and selective inhibition of this distal dendritic Ca²⁺ influx by NPY can thus regulate synaptic plasticity in layer 5 pyramidal neurons.

Genes involved in fatty acid metabolism: Molecular characterization and hypothalamic mRNA response to energy status and neuropeptide Y treatment in the orange-spotted grouper Epinephelus coioides

As in mammals, fatty acid (FA) metabolism plays diverse and vital roles in regulating food intake in fish. Multiple lines of evidence suggest that the effect of FA metabolism on food intake is linked to changes in the level of neuropeptide Y (NPY) in the hypothalamus of the rainbow trout. In mammals, the evidence suggests that FA metabolism regulates feeding via hypothalamic NPY. NPY is therefore considered an important factor that mediates the modulation of food intake by FA metabolism in vertebrates. The stimulatory effect of NPY on food intake is well known. However, to the best of our knowledge, the effect of NPY on FA metabolism in the hypothalamus has not been examined. In this study, we cloned the cDNA of four key enzymes involved in FA metabolism and assessed the effect of energy status and NPY on their mRNA expression in the hypothalamus of grouper. The full-length cDNAs of UCP2 and CPT1a and the partial coding sequence (CDS) of ACC1 and FAS were isolated from the grouper hypothalamus. These genes are expressed in the hypothalamus and during the organogenetic stage of embryogenesis. A feeding rhythm study showed that the hypothalamic expression level of NPY and CPT1a was highly correlated with feeding rhythm. Long-term fasting was found to significantly induce the hypothalamic mRNA expression of NPY, CPT1a and UCP2. An in vitro study demonstrated that NPY strongly stimulated CPT1a and UCP2 mRNA expression in a time- and dose-dependent manner. Collectively, these results suggest that these four genes related to FA metabolism may play a role in regulating food intake in grouper and, that NPY modulates FA metabolism in the grouper hypothalamus. This study showed, for the first time in vertebrates, the effect of NPY on the gene expression of FA metabolism-related enzymes.

Neuropeptide Y inhibits biliary hyperplasia of cholestatic rats by paracrine and autocrine mechanisms

Neuropeptide Y (NPY) exerts its functions through six subtypes of receptors (Y₁-Y₆). Biliary homeostasis is regulated by several factors through autocrine/paracrine signaling. NPY inhibits cholangiocarcinoma growth; however, no information exists regarding the autocrine/paracrine role of NPY on biliary hyperplasia during cholestasis. The aims of this study were to determine: 1) the expression of NPY and Y₁-Y₅ in cholangiocytes and 2) the paracrine/autocrine effects of NPY on cholangiocyte proliferation. Normal or bile duct ligation (BDL) rats were treated with NPY, neutralizing anti-NPY antibody, or vehicle for 7 days. NPY and NPY receptor (NPYR) expression was assessed in liver sections and isolated cholangiocytes. NPY secretion was assessed in serum and bile from normal and BDL rats, as well as supernatants from normal and BDL cholangiocytes and normal rat cholangiocyte cell line [intrahepatic normal cholangiocyte culture (NRICC)]. We evaluated intrahepatic bile ductal mass (IBDM) in liver sections and proliferation in cholangiocytes. With the use of NRICC, the effects of NPY or anti-NPY antibody on cholangiocyte proliferation were determined. The expression of NPY and all NPYR were increased after BDL. NPY levels were lower in serum and cholangiocyte supernatant from BDL compared with normal rats. NPY secretion from NRICC was detected at both the basolateral and apical domains. Chronic NPY treatment decreased proliferating cellular nuclear antigen (PCNA) expression and IBDM in BDL rats. Administration of anti-NPY antibody to BDL rats increased cholangiocyte proliferation and IBDM. NPY treatment of NRICC decreased PCNA expression and increased the cell cycle arrest, whereas treatment with anti-NPY antibody increased proliferation. Therapies targeting NPY-mediated signaling may prove beneficial for the treatment of cholangiopathies.

Opposing roles of corticotropin-releasing factor and neuropeptide Y within the dorsolateral bed nucleus of the stria terminalis in the negative affective component of pain in rats.

Pain is a complex experience composed of sensory and affective components. Although the neural systems of the sensory component of pain have been studied extensively, those of its affective component remain to be determined. In the present study, we examined the effects of corticotropin-releasing factor (CRF) and neuropeptide Y (NPY) injected into the dorsolateral bed nucleus of the stria terminalis (dlBNST) on pain-induced aversion and nociceptive behaviors in rats to examine the roles of these peptides in affective and sensory components of pain, respectively. In vivo microdialysis showed that formalin-evoked pain enhanced the release of CRF in this brain region. Using a conditioned place aversion (CPA) test, we found that intra-dlBNST injection of a CRF1 or CRF2 receptor antagonist suppressed pain-induced aversion. Intra-dlBNST CRF injection induced CPA even in the absence of pain stimulation. On the other hand, intra-dlBNST NPY injection suppressed pain-induced aversion. Coadministration of NPY inhibited CRF-induced CPA. This inhibitory effect of NPY was blocked by coadministration of a Y1 or Y5 receptor antagonist. Furthermore, whole-cell patch-clamp electrophysiology in dlBNST slices revealed that CRF increased neuronal excitability specifically in type II dlBNST neurons, whereas NPY decreased it in these neurons. Excitatory effects of CRF on type II dlBNST neurons were suppressed by NPY. These results have uncovered some of the neuronal mechanisms underlying the affective component of pain by showing opposing roles of intra-dlBNST CRF and NPY in pain-induced aversion and opposing actions of these peptides on neuronal excitability converging on the same target, type II neurons, within the dlBNST.

Acute Central Neuropeptide Y Administration Increases Food Intake but Does Not Affect Hepatic Very Low-Density Lipoprotein (Vldl) Production in Mice

ObjectiveCentral neuropeptide Y (NPY) administration stimulates food intake in rodents. In addition, acute modulation of central NPY signaling increases hepatic production of very low-density lipoprotein (VLDL)-triglyceride (TG) in rats. As hypertriglyceridemia is an important risk factor for atherosclerosis, for which well-established mouse models are available, we set out to validate the effect of NPY on hepatic VLDL-TG production in mice, to ultimately investigate whether NPY, by increasing VLDL production, contributes to the development of atherosclerosis.Research Design and MethodsMale C57Bl/6J mice received an intracerebroventricular (i.c.v.) cannula into the lateral (LV) or third (3V) ventricle of the brain. One week later, after a 4 h fast, the animals received an intravenous (i.v.) injection of Tran35S (100 µCi) followed by tyloxapol (500 mg/kg body weight; BW), enabling the study of hepatic VLDL-apoB and VLDL-TG production, respectively. Immediately after the i.v. injection of tyloxapol, the animals received either an i.c.v. injection of NPY (0.2 mg/kg BW in artificial cerebrospinal fluid; aCSF), synthetic Y1 receptor antagonist GR231118 (0.5 mg/kg BW in aCSF) or vehicle (aCSF), or an i.v. injection of PYY3–36 (0.5 mg/kg BW in PBS) or vehicle (PBS).ResultsAdministration of NPY into both the LV and 3V increased food intake within one hour after injection (+164%, p<0.001 and +367%, p<0.001, respectively). NPY administration neither in the LV nor in the 3V affected hepatic VLDL-TG or VLDL-apoB production. Likewise, antagonizing central NPY signaling by either PYY3–36 or GR231118 administration did not affect hepatic VLDL production.ConclusionIn mice, as opposed to rats, acute central administration of NPY increases food intake without affecting hepatic VLDL production. These results are of great significance when extrapolating findings on the central regulation of hepatic VLDL production between species.

Neuropeptide Y (NPY) prevents depressive-like behavior, spatial memory deficits and oxidative stress following amyloid-β (Aβ1–40) administration in mice

Neuropeptide Y (NPY) is a 36-amino acid peptide widely distributed in the central nervous system (CNS) that has been associated with the modulation of several functions including food intake, learning and memory, mood and neuroprotection. There is great interest in understanding the role of NPY in the deleterious effects induced by the central accumulation of amyloid-β (Aβ) peptides, a pathological hallmark of Alzheimer's disease (AD). Herein, we evaluated the effects of a single intracerebroventricular (i.c.v.) administration of NPY (0.0234μmol/μL) 15min prior to the i.c.v. injection of aggregated Aβ1–40 peptide (400pmol/mouse) in behavioral and neurochemical parameters related to oxidative stress in mice. Pretreatment with NPY prevented Aβ1–40-induced depressive-like responses and spatial memory impairments evaluated in the tail suspension and object location tasks, respectively. The protective effects of NPY on spatial memory of Aβ1–40-treated mice were abolished by the pretreatment with the selective Y2 receptor antagonist BIIE0246. On the other hand, the administration of NPY and Aβ1–40 did not alter the performance of the animals in the elevated plus-maze and open field arena, indicating lack of effects on anxiety state and locomotor function. Although Aβ1–40 infusion did not change hippocampal and cortical glutathione peroxidase (GPx) activity and glutathione (GSH) levels, Aβ1–40-infused animals showed an increased lipid peroxidation in hippocampus and prefrontal cortex that were blunted by NPY administration. These findings indicate that central administration of NPY prevents Aβ1–40-induced depressive-like behavior and spatial memory deficits in mice and that this response is mediated, at least in part, by the activation of Y2 receptors and prevention of oxidative stress.

NPY modulates miR-30a-5p and BDNF in opposite direction in an in vitro model of Alzheimer disease: a possible role in neuroprotection?

Using in vitro models of Alzheimer's disease (AD), we found that the toxic effects of amyloid beta 25-35 (Aβ(25-35)) on the neurotrophin brain-derived neurotrophic factor (BDNF) were counteracted by pre-incubation with neuropeptide Y (NPY), a neuropeptide expressed within the central nervous system. Nonetheless, the mechanism of action of NPY on BDNF neuronal production in the presence of Aβ is not known. BDNF expression might be directly regulated by microRNA (miRs), small non-coding DNA fragments that regulate the expression of target genes. Thus, there is the possibility that miRs alterations are present in AD-affected neurons and that NPY influences miR expression. To test this hypothesis, we exposed NPY-pretreated primary rat cortical neurons to Aβ(25-35) and measured miR-30a-5p (a member of the miR-30a family involved in BDNF tuning expression) and BDNF mRNA and protein expression after 24 and 48 h. Our results demonstrated that pre-treatment with NPY decreased miR-30a-5p expression and increased BDNF mRNA and protein expression at 24 and 48 h of incubation with Aβ. Therefore, this study demonstrates that NPY modulates BDNF and its regulating microRNA miR-30a-5p in opposite direction with a mechanism that possibly contributes to the neuroprotective effect of NPY in rat cortical neurons exposed to Aβ.

Novel Role of Neuropeptide Y in the Modulation of Microglia Activity

Microglia are the smallest member of the glia family but greatly responsible for vital physiological responses to brain injury and/or infection. The resulting inflammatory process includes the recruitment of microglial cells to the site of injury, the release of both toxic and trophic molecules and the clearance of invading pathogens or dead cells. The purpose of this review is to detail the role of neuropeptide Y (NPY) over microglia principal activities. In addition, we also summarize the main effects of other neuropeptides, such as galanin, somatostatin, substance P, pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP). Recently, we showed that NPY downregulates the innate immune response, by decreasing the release of interleukin-1 and nitric oxide, migration and phagocytosis by activated microglia cells. A huge body of evidence has also showed that the reduction of microglia inflammatory responses supports regenerative mechanisms aiming at the protection of susceptible neurons in several brain diseases. Therefore, the neuroprotective and immunosuppressive effects of NPY in microglia cells suggest that it can be a key therapeutic target against Central Nervous System injury or disease.

Reversed synaptic effects of hypocretin and NPY mediated by excitatory GABA-dependent synaptic activity in developing MCH neurons

In mature neurons, GABA is the primary inhibitory neurotransmitter. In contrast, in developing neurons, GABA exerts excitatory actions, and in some neurons GABA-mediated excitatory synaptic activity is more prevalent than glutamate-mediated excitation. Hypothalamic neuropeptides that modulate cognitive arousal and energy homeostasis, hypocretin/orexin and neuropeptide Y (NPY), evoked reversed effects on synaptic actions that were dependent on presynaptic GABA release onto melanin-concentrating hormone (MCH) neurons. MCH neurons were identified by selective green fluorescent protein (GFP) expression in transgenic mice. In adults, hypocretin increased GABA release leading to reduced excitation. In contrast, in the developing brain as studied here with analysis of miniature excitatory postsynaptic currents, paired-pulse ratios, and evoked potentials, hypocretin acted presynaptically to enhance the excitatory actions of GABA. The ability of hypocretin to enhance GABA release increases inhibition in adult neurons but paradoxically enhances excitation in developing MCH neurons. In contrast, NPY attenuation of GABA release reduced inhibition in mature neurons but enhanced inhibition during development by attenuating GABA excitation. Both hypocretin and NPY also evoked direct actions on developing MCH neurons. Hypocretin excited MCH cells by activating a sodium-calcium exchanger and by reducing potassium currents; NPY reduced activity by increasing an inwardly rectifying potassium current. These data for the first time show that both hypocretin and NPY receptors are functional presynaptically during early postnatal hypothalamic development and that both neuropeptides modulate GABA actions during development with a valence of enhanced excitation or inhibition opposite to that of the adult state, potentially allowing neuropeptide modulation of use-dependent synapse stabilization.

Neuropeptide Y stimulates food intake and regulates metabolism in grass carp, Ctenopharyngodon idellus

Neuropeptide Y (NPY) has been established as an important regulator of food intake in mammals. However, the involvement of NPY in the feeding behavior of fish has not yet been fully understood. The present study investigated the role of NPY in food intake in grass carp. The full-length cDNA sequence of gc-NPY was 797bp, and an ORF of 96 amino acids, including the 28-residue signal peptide and 36-residue mature peptide, which had high identities to the NPY of cyprinid fishes. Two receptors Y1 and Y5 which mediate the appetite-stimulating effects of NPY in mammals lost from some of the euteleost genomes. However, sequences of other NPY receptors Y8a and Y8b were obtained from the ESTs library of grass carp in our previous studies. NPY and both Y8 receptors were predominantly expressed in the brain. Cumulative food intake was significantly increased by intracerebroventricular administration of NPY during a 72-h observation period. For better understanding of NPY's action in grass carp, the mRNA levels of appetite regulators, energy metabolism genes and key digestive enzymes were assessed. The results showed that the mRNA levels of Y8b were significantly increased, while the expressions of cholecystokinin (CCK), cocaine and amphetamine regulated transcript (CART), pituitary adenylate cyclase-activating peptide (PACAP), leptin, leptin receptor (leptinR) and leptin receptor overlapping transcript protein (LEPROT) were significantly decreased after NPY injection. In addition, the marked stimulation of insulin-like growth factor1 (IGF1), insulin-like growth factor 1 receptor (IGF1R), lipoprotein lipase (LPL), Stearoyl-CoA desaturase 1 (SCD1), amylase and trypsin mRNA levels in liver were caused by NPY administration, and the mRNA level of uncoupling protein 1(UCP 1) tended to decrease but not significantly. These results indicate that NPY acts as an orexigenic factor in the grass carp, and Y8b may involve in the feeding regulation. NPY not only affects food intake, but also has marked effects on energy metabolism in grass carp. Moreover, NPY seems to closely interact with other appetite regulators, and the present results provide novel insight into these complex interactions. Further understandings of appetite regulation in fish ultimately have the potential to yield methods for improving feed efficiency in aquaculture.

Differences in neuropeptide Y-induced secretion of endothelin-1 in left and right human endocardial endothelial cells

The aim of the study was to test the hypothesis that neuropeptide Y (NPY) may induce endothelin-1 (ET-1) secretion in left (hLEECs) and right (hREECs) human endocardial endothelial cells. Furthermore, the type of NPY receptor implicated could be different in NPY-induced secretion in hLEECs and hREECs. Using immunofluorescence coupled to real 3D confocal microscopy and ELISA, our results showed that stimulation of secretion by NPY induced the release of ET-1 from both right and left human ventricular endocardial endothelial cells (hEECs) in a time-dependent manner. Furthermore, the secretory capacity of hREECs was higher than that of hLEECs. In addition, our results showed that the effect of NPY on ET-1 secretion in hLEECs was only due to activation of Y5 receptors. However, the effect of NPY on ET-1 secretion in hREECs was due to mainly Y2 and partially Y5 receptors activation. In conclusion, our results suggest that differences in excitation–secretion coupling exist between hREECS and hLEECs which may contribute to the functional differences between right and left ventricular muscle. Furthermore, high NPY level contributes to ET-1 release by hEECs and Y2 and Y5 receptors antagonists may be used for regulation of ET-1 secretion in the heart.

Central nervous system neuropeptide Y signaling via the Y1 receptor partially dissociates feeding behavior from lipoprotein metabolism in lean rats

Elevated plasma triglyceride (TG) levels contribute to an atherogenic dyslipidemia that is associated with obesity, diabetes, and metabolic syndrome. Numerous models of obesity are characterized by increased central nervous system (CNS) neuropeptide Y (NPY) tone that contributes to excess food intake and obesity. Previously, we demonstrated that intracerebroventricular (icv) administration of NPY in lean fasted rats also elevates hepatic production of very low-density lipoprotein (VLDL)-TG. Thus, we hypothesize that elevated CNS NPY action contributes to not only the pathogenesis of obesity but also dyslipidemia. Here, we sought to determine whether the effects of NPY on feeding and/or obesity are dissociable from effects on hepatic VLDL-TG secretion. Pair-fed, icv NPY-treated, chow-fed Long-Evans rats develop hypertriglyceridemia in the absence of increased food intake and body fat accumulation compared with vehicle-treated controls. We then modulated CNS NPY signaling by icv injection of selective NPY receptor agonists and found that Y1, Y2, Y4, and Y5 receptor agonists all induced hyperphagia in lean, ad libitum chow-fed Long-Evans rats, with the Y2 receptor agonist having the most pronounced effect. Next, we found that at equipotent doses for food intake NPY Y1 receptor agonist had the most robust effect on VLDL-TG secretion, a Y2 receptor agonist had a modest effect, and no effect was observed for Y4 and Y5 receptor agonists. These findings, using selective agonists, suggest the possibility that the effect of CNS NPY signaling on hepatic VLDL-TG secretion may be relatively dissociable from effects on feeding behavior via the Y1 receptor.

Dysbalance in sympathetic neurotransmitter release and action in cirrhotic rats: Impact of exogenous neuropeptide Y

Splanchnic vasodilation is an essential disturbance in portal hypertension. Increased systemic sympathetic nerve activity is well known, but potential corresponding vascular desensitization is incompletely characterized. Release of splanchnic sympathetic neurotransmitters noradrenaline (NA) and co-transmitter neuropeptide Y (NPY) remains to be elucidated. Finally, the effects of exogenous NPY on these mechanisms are unexplored. Portal vein ligated cirrhotic, and control rats were used for in vitro perfusion of mesenteric arteries. Depletion of vascular pressure response was induced by repetitive electric sympathetic perivascular nerve stimulation (PNS) and performed in the absence and presence of exogenous NPY. Additionally, PNS-induced release of NA and NPY was measured. Mesenteric PNS-induced pressure response was lower in portal hypertension. Depletion of the pressure response to PNS, representing the degree of desensitization, was enhanced in portal hypertension. NA release was elevated, whereas NPY release was attenuated in cirrhosis. Administration of exogenous NPY led to marked recovery from desensitization and vasoconstrictive improvement in cirrhotic rats, being associated with more pronounced decrease of NA release. Pronounced depletion of splanchnic arterial pressure-response to repetitive sympathetic nerve stimulation in cirrhosis is partly attributable to altered NA release as well as to deficient NPY release. External NPY restores vascular contractility and attenuates pathologically elevated NA release in the portal hypertensive mesenteric vasculature, revealing post-, and prejunctional effects at the vascular smooth muscle motor endplate; therefore outlining encouraging therapeutic strategies.

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.