Dipeptidyl Peptidase (DPP)-4 Inhibitors and Pituitary Adenylate Cyclase-Activating Polypeptide, a DPP-4 Substrate, Extend Neurite Outgrowth of Mouse Dorsal Root Ganglia Neurons: A Promising Approach in Diabetic Polyneuropathy Treatment.

Individuals suffering from diabetic polyneuropathy (DPN) experience debilitating symptoms such as pain, paranesthesia, and sensory disturbances, prompting a quest for effective treatments. Dipeptidyl-peptidase (DPP)-4 inhibitors, recognized for their potential in ameliorating DPN, have sparked interest, yet the precise mechanism underlying their neurotrophic impact on the peripheral nerve system (PNS) remains elusive. Our study delves into the neurotrophic effects of DPP-4 inhibitors, including Diprotin A, linagliptin, and sitagliptin, alongside pituitary adenylate cyclase-activating polypeptide (PACAP), Neuropeptide Y (NPY), and Stromal cell-derived factor (SDF)-1a-known DPP-4 substrates with neurotrophic properties. Utilizing primary culture dorsal root ganglia (DRG) neurons, we meticulously evaluated neurite outgrowth in response to these agents. Remarkably, all DPP-4 inhibitors and PACAP demonstrated a significant elongation of neurite length in DRG neurons (PACAP 0.1 µM: 2221 ± 466 µm, control: 1379 ± 420, p < 0.0001), underscoring their potential in nerve regeneration. Conversely, NPY and SDF-1a failed to induce neurite elongation, accentuating the unique neurotrophic properties of DPP-4 inhibition and PACAP. Our findings suggest that the upregulation of PACAP, facilitated by DPP-4 inhibition, plays a pivotal role in promoting neurite elongation within the PNS, presenting a promising avenue for the development of novel DPN therapies with enhanced neurodegenerative capabilities.

Activation of NPY Receptors in the BLA Inhibits Projections to the Bed Nucleus of the Stria Terminalis and Buffers Stress-Induced Decreases in Social Interaction in Male Rats.

Neuropeptide Y (NPY) increases resilience and buffers behavioral stress responses in male rats in part through decreasing the excitability of principal output neurons in the basolateral amygdala (BLA). Intra-BLA administration of NPY acutely increases social interaction (SI) through activation of either Y1 or Y5 receptors, whereas repeated NPY (rpNPY) injections (once daily for 5 d) produce persistent increases in SI through Y5 receptor-mediated neuroplasticity in the BLA. In this series of studies, we characterized the neural circuits from the BLA that underlie these behavioral responses to NPY. Using neuronal tract tracing, NPY Y1 and Y5 receptor immunoreactivity was identified on subpopulations of BLA neurons projecting to the bed nucleus of the stria terminalis (BNST) and the central nucleus of the amygdala (CeA). Inhibition of BLA→BNST, but not BLA→CeA, neurons using projection-restricted, cre-driven designer receptors exclusively activated by designer drug-Gi expression increased SI and prevented stress-induced decreases in SI produced by a 30 min restraint stress. This behavioral profile was similar to that seen after both acute and rpNPY injections into the BLA. Intracellular recordings of BLA→BNST neurons demonstrated NPY-mediated inhibition via suppression of H currents, as seen previously. Repeated intra-BLA injections of NPY, which are associated with the induction of BLA neuroplasticity, decreased the activity of BLA→BNST neurons and decreased their dendritic complexity. These results demonstrate that NPY modulates the activity of BNST-projecting BLA neurons, suggesting that this pathway contributes to the stress-buffering actions of NPY and provides a novel substrate for the proresilient effects of NPY.

Effect of intracerebroventricular (ICV) injection of adrenomedullin and its interaction with NPY and CCK pathways on food intake regulation in neonatal layer-type chicks.

Adrenomedullin has various physiological roles including appetite regulation. The objective of present study was to determine the effects of ICV injection of adrenomedullin and its interaction with NPY and CCK receptors on food intake regulation. In experiment 1, chickens received ICV injection of saline and adrenomedullin (1, 2, and 3 nmol). In experiment 2, birds injected with saline, B5063 (NPY1 receptor antagonist, 1.25 µg), adrenomedullin (3 nmol) and co-injection of B5063+adrenomedullin. Experiments 3 to 5 were similar to experiment 2 and only SF22 (NPY2 receptor antagonist, 1.25 µg), SML0891 (NPY5 receptor antagonist, 1.25 µg) and CCK4 (1 nmol) were injected instead of B5063. In experiment 6, ICV injection of saline and CCK8s (0.125, 0.25, and 0.5 nmol) were done. In experiment 7, chickens injected with saline, CCK8s (0.125 nmol), adrenomedullin (3 nmol) and co-injection of CCK8s+adrenomedullin. After ICV injection, birds were returned to their individual cages immediately and cumulative food intake was measured at 30, 60, and 120 min after injection. Adrenomedullin (2 and 3 nmol) decreased food intake compared to control group (P < 0.05). Coinjection of B5063+adrenomedullin amplified hypophagic effect of adrenomedullin (P < 0.05). The ICV injection of the CCK8s (0.25 and 0.5 nmol) reduced food intake (P < 0.05). Co-injection of the CCK8s+adrenomedullin significantly potentiated adrenomedullin-induced hypophagia (P < 0.05). Administration of the SF22, SML0891 and CCK4 had no effect on the anorexigenic response evoked by adrenomedullin (P > 0.05). These results suggested that the hypophagic effect of the adrenomedullin is mediated by NPY1 and CCK8s receptors. However, our novel results should form the basis for future experiments.

A new invertebrate NPY-like polypeptide, ZoaNPY, from the Zoanthus sociatus, as a novel ligand of human NPY Y2 receptor rescues vascular insufficiency via PLC/PKC and Src- FAK-dependent signaling pathways.

Our recent multi-omics studies have revealed rich sources of novel bioactive proteins and polypeptides from marine organisms including cnidarians. In the present study, we initially conducted a transcriptomic analysis to review the composition profile of polypeptides from Zoanthus sociatus. Then, a newly discovered NPY-like polypeptide-ZoaNPY was selected for further in silico structural, binding and virtually pharmacological studies. To evaluate the pro-angiogenic effects of ZoaNPY, we employed an in vitro HUVECs model and an in vivo zebrafish model. Our results indicate that ZoaNPY, at 1-100 pmol, enhances cell survival, migration and tube formation in the endothelial cells. Besides, treatment with ZoaNPY could restore a chemically-induced vascular insufficiency in zebrafish embryos. Western blot results demonstrated the application of ZoaNPY could increase the phosphorylation of proteins related to angiogenesis signaling including PKC, PLC, FAK, Src, Akt, mTOR, MEK, and ERK1/2. Furthermore, through molecular docking and surface plasmon resonance (SPR) verification, ZoaNPY was shown to directly and physically interact with NPY Y2 receptor. In view of this, all evidence showed that the pro-angiogenic effects of ZoaNPY involve the activation of NPY Y2 receptor, thereby activating the Akt/mTOR, PLC/PKC, ERK/MEK and Src- FAK-dependent signaling pathways. Furthermore, in an excision wound model, the treatment with ZoaNPY was shown to accelerate the wound healing process in mice. Our findings provide new insights into the discovery and development of novel pro-angiogenic drugs derived from NPY-like polypeptides in the future.

Topical Neuropeptide Y for Ischemic Skin Wounds.

Our objective was to investigate the effects of topically applied neuropeptide Y (NPY) on ischemic wounds. Initially, the animal model for ischemic wound healing was validated using 16 male Sprague Dawley albino rats. In the intervention study, an additional 28 rats were divided into three groups: NPY (0.025%), the positive control insulin-like growth factor-I (IGF-I, 0.0025%), and the hydrogel carrier alone (control). The hydrogel was selected due to its capacity to prolong NPY release (p < 0.001), as demonstrated in a Franz diffusion cell. In the animals, an 8 mm full-thickness wound was made in a pedunculated dorsal ischemic skin flap. Wounds were then treated and assessed for 14 days and collected at the end of the experiment for in situ hybridization analysis (RNAscope®) targeting NPY receptor Y2R and for meticulous histologic examination. Wound healing rates, specifically the percentage changes in wound area, did not show an increase with NPY (p = 0.907), but there was an increase with rhIGF-I (p = 0.039) compared to the control. Y2R mRNA was not detected in the wounds or adjacent skin but was identified in the rat brain (used as a positive control). Light microscopic examination revealed trends of increased angiogenesis and enhanced inflammatory cell infiltration with NPY compared to control. An interesting secondary discovery was the presence of melanophages in the wounds. Our findings suggest the potential of NPY to enhance neovascularization under ischemic wound healing conditions, but further optimization of the carrier and dosage is necessary. The mechanism remains elusive but likely involves NPY receptor subtypes other than Y2R.

Role of the intracerebroventricular injection of the visfatin and its interaction with neuropeptide Y and nitric systems on food intake in neonatal chicken.

Visfatin play an essential role in the central regulation of appetite in birds. This study aimed to determine role of intracerebroventricular (ICV) injection of the visfatin on food intake and its possible interaction with neuropeptide Y (NPY) and nitric oxide system in neonatal broiler chicken. In experiment 1, neonatal chicken received ICV injection visfatin (1, 2 and 4 µg). In experiment 2, chicken received ICV injection of B5063 (NPY1 receptor antagonist 1.25 µg), visfatin (4 µg) and co-injection of the B5063 + Visfatin. In experiments 3-6, SF22 (NPY2 receptor antagonist 1.25 µg), SML0891 (NPY5 receptor antagonist 1.25 µg), L-NAME (nitric oxide synthase inhibitor, 100 nmol) and L-arginine (Precursor of nitric oxide, 200 nmol) were injected instead of B5063. Then the amount of cumulative food was measured at 30, 60 and 120 min after injection. Obtained data showed, injection visfatin (2 and 4 µg) increased food intake compared to control group (P < 0.05). Co-injection of the B5063 + Visfatin decreased visfatin-induced hyperphagia compared to control group (P < 0.05). Co-injection of the L-NAME + Visfatin amplified visfatin-induced hyperphagia compared to control group (P < 0.05). The result showed that visfatin has hyperphagic role and this effect mediates via NPY1 and nitric oxide system in neonatal chicken.

Effects of neuropeptide Y on the immune-protection and intestinal tract of juvenile Micropterus salmoides.

Neuropeptide Y is known to be directly or indirectly involved in immune regulation. The immune effects of NPY include immune cell transport, helper T cell differentiation, cytokine secretion, staining and killer cell activity, phagocytosis and production of reactive oxygen species. In this study, we investigated the immunoprotective effect of synthetic NPY on largemouth bass larvae. For the first time, the dose and time effects of NPY injection on largemouth bass was explored, and then Poly I:C and LPS infection was carried out in juvenile largemouth bass, respectively, after the injection of NPY. The results showed that NPY could reduce the inflammatory response by inhibiting the expression of il-1ß, tgf-ß, ifn-γ and other immune factors in head kidney, spleen and brain, and alleviate the immune stress caused by strong inflammatory response in the early stage of infection. Meanwhile, NPY injection ameliorated the intestinal tissue damage caused by infection. This study provides a new way to protect juvenile fish and improve its innate immunity.

Lesion of NPY Receptor-expressing Neurons in Perifornical Lateral Hypothalamus Attenuates Glucoprivic Feeding.

Glucoprivic feeding is one of several counterregulatory responses (CRRs) that facilitates restoration of euglycemia following acute glucose deficit (glucoprivation). Our previous work established that glucoprivic feeding requires ventrolateral medullary (VLM) catecholamine (CA) neurons that coexpress neuropeptide Y (NPY). However, the connections by which VLM CA/NPY neurons trigger increased feeding are uncertain. We have previously shown that glucoprivation, induced by an anti-glycolygic agent 2-deoxy-D-glucose (2DG), activates perifornical lateral hypothalamus (PeFLH) neurons and that expression of NPY in the VLM CA/NPY neurons is required for glucoprivic feeding. We therefore hypothesized that glucoprivic feeding and possibly other CRRs require NPY-sensitive PeFLH neurons. To test this, we used the ribosomal toxin conjugate NPY-saporin (NPY-SAP) to selectively lesion NPY receptor-expressing neurons in the PeFLH of male rats. We found that NPY-SAP destroyed a significant number of PeFLH neurons, including those expressing orexin, but not those expressing melanin-concentrating hormone. The PeFLH NPY-SAP lesions attenuated 2DG-induced feeding but did not affect 2DG-induced increase in locomotor activity, sympathoadrenal hyperglycemia, or corticosterone release. The 2DG-induced feeding response was also significantly attenuated in NPY-SAP-treated female rats. Interestingly, PeFLH NPY-SAP lesioned male rats had reduced body weights and decreased dark cycle feeding, but this effect was not seen in female rats. We conclude that a NPY projection to the PeFLH is necessary for glucoprivic feeding, but not locomotor activity, hyperglycemia, or corticosterone release, in both male and female rats.

Putative identification of proopiomelanocortin and neuropeptide-Y neurons of the arcuate nucleus by their response to leptin: in vivo electrophysiology study in male and female rats.

The arcuate nucleus (ARN) of the hypothalamus is involved in multiple biological functions, such as feeding, sexual activity, and the regulation of the cardiovascular system. It was reported that leptin increased c-Fos expression in the proopiomelanocortin (POMC)- and decreased it in the neuropeptide-Y (NPY)-positive neurons of the ARN, suggesting that it stimulates the former, and inhibits the later. This study aimed at the direct electrophysiological examination of the effect of leptin on ARN neurons and to investigate potential sex-dimorphic changes. Wistar rats were anesthetized with urethane and the electrodes were inserted into the ARN. After a spontaneous active neuron was recorded for at least one minute, leptin was administered intravenously, and the firing activity of the same neuron was recorded for two additional minutes. It was found that approximately half of the ARN neurons had an excitatory, and another half an inhibitory response to the leptin administration. The excitability of the neurons with excitatory response to leptin was not different between the sexes. The average firing rate of the neurons with inhibitory response to leptin in females was, however, significantly lower comparing to the males. The obtained results demonstrate that the ARN neurons with stimulatory response to leptin are POMC and those with inhibitory response are NPY neurons. NPY Y1 receptor be might responsible, at least in part, for the sex differences in the excitability of the neurons putatively identified as NPY neurons.

The plasticity of neuropeptide Y-Y1 receptor system on Tac2 neurons contributes to mechanical hyperknesis during chronic itch.

Rationale: In the physiological states, the act of scratching protects the person from harmful substances, while in certain pathological conditions, the patient suffers from chronic itch, both physically and mentally. Chronic itch sufferers are more sensitive to mechanical stimuli, and mechanical hyperknesis relief is essential for chronic itch treatment. While neuropeptide Y-Y1 receptor (NPY-Y1R) system is known to play a crucial role in modulating mechanical itch in physiological conditions, it is elusive how they are altered during chronic itch. We hypothesize that the negative regulatory effect of Y1Rs on Tac2 neurons, the key neurons that transmit mechanical itch, declines during chronic itch. Methods: We combined transgenic mice, chemogenetic manipulation, immunofluorescence, rabies virus circuit tracing, and electrophysiology to investigate the plasticity of Y1Rs on Tac2 neurons during chronic itch. Results: We found that Tac2 neurons receive direct input from Npy neurons and that inhibition of Npy neurons induces activation of Tac2 neurons. Moreover, the expression of Y1Rs on Tac2 neurons is reduced, and the regulatory effect is also reduced during chronic itch. Conclusion: Our study clarifies the plasticity of Y1Rs on Tac2 neurons during chronic itch and further elucidates the mechanism by which NPY-Y1R system is responsible for modulating mechanical itch. We highlight Y1Rs as a promising therapeutic target for mechanical hyperknesis during chronic itch.

Valence-dependent effects of neuropeptide Y on the expression of conditioned fear and anxiety-like behavior: Involvement of the bed nucleus of the stria terminalis.

Neuropeptide Y (NPY) has anxiolytic-like effects and facilitates the extinction of cued and contextual fear in rodents. We have previously shown that intracerebroventricular administration of NPY reduces the expression of social fear via simultaneous activation of Y1 and Y2 receptors in a mouse model of social fear conditioning (SFC). In the present study, we investigated whether the anteroventral bed nucleus of the stria terminalis (BNSTav) mediates these effects of NPY, given the important role of BNSTav in regulating anxiety- and fear-related behaviors. We show that while NPY (0.1 nmol/0.2 µl/side) did not reduce the expression of SFC-induced social fear in male CD1 mice, it reduced the expression of both cued and contextual fear by acting on Y2 but not on Y1 receptors within the BNSTav. Prior administration of the Y2 receptor antagonist BIIE0246 (0.2 nmol/0.2 µl/side) but not of the Y1 receptor antagonist BIBO3304 trifluoroacetate (0.2 nmol/0.2 µl/side) blocked the effects of NPY on the expression of cued and contextual fear. Similarly, NPY exerted non-social anxiolytic-like effects in the elevated plus maze test but not social anxiolytic-like effects in the social approach avoidance test by acting on Y2 receptors and not on Y1 receptors within the BNSTav. These results suggest that administration of NPY within the BNSTav exerts robust Y2 receptor-mediated fear-reducing and anxiolytic-like effects specifically in non-social contexts and add a novel piece of evidence regarding the neural underpinnings underlying the effects of NPY on conditioned fear and anxiety-like behavior.

The vasoactive effects of bradykinin, vasoactive intestinal peptide, calcitonin gene-related peptide and neuropeptide Y depend on the perivascular tissue in porcine retinal arterioles in vitro.

PURPOSE: The retina contains a number of vasoactive neuropeptides and corresponding receptors, but the role of these neuropeptides for tone regulation of retinal arterioles has not been studied in detail. METHODS: Porcine arterioles with preserved perivascular retinal tissue were mounted in a wire myograph, and the tone was measured after the addition of increasing concentrations of bradykinin, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP) and brain natriuretic peptide (BNP). The experiments were performed during inhibition of the synthesis of nitric oxide (NO), prostaglandins and dopamine and were repeated after removal of the perivascular retinal tissue. RESULTS: Bradykinin, VIP and CGRP induced significant concentration-dependent dilatation and NPY significant concentration-dependent contraction of the arterioles in the presence of perivascular retinal tissue (p < 0.03 for all comparisons) but not on isolated arterioles. BNP and SP had no effect on vascular tone. The NOS inhibitor L-NAME reduced bradykinin- and VIP-induced relaxation (p < 0.001 for both comparisons), whereas none of the other inhibitors influenced the vasoactive effects of the studied neuropeptides. CONCLUSION: The effects of neuropeptides on the tone of retinal arterioles depend on the perivascular retinal tissue and may involve effects other than those mediated by nitric oxide, prostaglandins and adrenergic compounds. Investigation of the mechanisms underlying the vasoactive effect of neuropeptides may be important for understanding and treating retinal diseases where disturbances in retinal flow regulation are involved in the disease pathogenesis.

Effect of Adrenoreceptor Stimulation on Peptidergic Regulation of Cardiac Activity in Newborn Rats.

We studied the effect of adrenoreceptor stimulation on the frequency of spontaneous activity and amplitude-time parameters of isometric contraction of the atrial myocardial strips from newborn rats, as well as the effect of Y receptor stimulation against the background of adrenoreceptor activation. After addition of Y1,5 receptor agonist [Leu31, Pro34] NPY (10-7 M), a tendency to a decrease in the effect of ß1,2-adrenoreceptor agonist isoproterenol (10-5 M) on the frequency of spontaneous activity and atrial myocardial contractility was observed. The age-related features of the effect of NPY on the frequency of spontaneous activity and contractility of myocardial strips from newborn and adult rats were revealed.

Neuropeptide Y: Direct vasoconstrictor and facilitatory effects on P2X1 receptor-dependent vasoconstriction in human small abdominal arteries.

Neuropeptide Y (NPY) is co-released with norepinephrine and ATP by sympathetic nerves innervating arteries. Circulating NPY is elevated during exercise and cardiovascular disease, though information regarding the vasomotor function of NPY in human blood vessels is limited. Wire myography revealed NPY directly stimulated vasoconstriction (EC50 10.3 ± 0.4 nM; N = 5) in human small abdominal arteries. Maximum vasoconstriction was antagonised by both BIBO03304 (60.7 ± 6%; N = 6) and BIIE0246 (54.6 ± 5%; N = 6), suggesting contributions of both Y1 and Y2 receptor activation, respectively. Y1 and Y2 receptor expression in arterial smooth muscle cells was confirmed by immunocytochemistry, and western blotting of artery lysates. α,ß-meATP evoked vasoconstrictions (EC50 282 ± 32 nM; N = 6) were abolished by suramin (IC50 825 ± 45 nM; N = 5) and NF449 (IC50 24 ± 5 nM; N = 5), suggesting P2X1 mediates vasoconstriction in these arteries. P2X1, P2X4 and P2X7 were detectable by RT-PCR. Significant facilitation (1.6-fold) of α,ß-meATP-evoked vasoconstrictions was observed when submaximal NPY (10 nM) was applied between α,ß-meATP applications. Facilitation was antagonised by either BIBO03304 or BIIE0246. These data reveal NPY causes direct vasoconstriction in human arteries which is dependent upon both Y1 and Y2 receptor activation. NPY also acts as a modulator, facilitating P2X1-dependent vasoconstriction. Though in contrast to the direct vasoconstrictor effects of NPY, there is redundancy between Y1 and Y2 receptor activation to achieve the facilitatory effect.

Gßγ subunit signalling underlies neuropeptide Y-stimulated vasoconstriction in rat mesenteric and coronary arteries.

BACKGROUND AND PURPOSE: Raised serum concentrations of the sympathetic co-transmitter neuropeptide Y (NPY) are linked to cardiovascular diseases. However, the signalling mechanism for vascular smooth muscle (VSM) constriction to NPY is poorly understood. Therefore, the present study investigated the mechanisms of NPY-induced vasoconstriction in rat small mesenteric (RMA) and coronary (RCA) arteries. EXPERIMENTAL APPROACH: Third-order mesenteric or intra-septal arteries from male Wistar rats were assessed in wire myographs for isometric tension, VSM membrane potential and VSM intracellular Ca2+ events. KEY RESULTS: NPY stimulated concentration-dependent vasoconstriction in both RMA and RCA, which was augmented by blocking NO synthase or endothelial denudation in RMA. NPY-mediated vasoconstriction was blocked by the selective Y1 receptor antagonist BIBO 3304 and Y1 receptor protein expression was detected in both the VSM and endothelial cells in RMA and RCA. The selective Gßγ subunit inhibitor gallein and the PLC inhibitor U-73122 attenuated NPY-induced vasoconstriction. Signalling via the Gßγ-PLC pathway stimulated VSM Ca2+ waves and whole-field synchronised Ca2+ flashes in RMA and increased the frequency of Ca2+ flashes in myogenically active RCA. Furthermore, in RMA, the Gßγ pathway linked NPY to VSM depolarization and generation of action potential-like spikes associated with intense vasoconstriction. This depolarization activated L-type voltage-gated Ca2+ channels, as nifedipine abolished NPY-mediated vasoconstriction. CONCLUSIONS AND IMPLICATIONS: These data suggest that the Gßγ subunit, which dissociates upon Y1 receptor activation, initiates VSM membrane depolarization and Ca2+ mobilisation to cause vasoconstriction. This model may help explain the development of microvascular vasospasm during raised sympathetic nerve activity.

Self-Assembly of Organelle-Localized Neuropeptides Triggers Intrinsic Apoptosis Against Breast Cancer.

Biosynthesis has become a diverse toolbox for the development of bioactive molecules and materials, particularly for enzyme-induced modification and assembly of peptides. However, intracellular spatiotemporal regulation of artificial biomolecular aggregates based on neuropeptide remains challenging. Here, an enzyme responsive precursor (Y1 L-KGRR-FF-IR) is developed based on the neuropeptide Y Y1 receptor ligand, which self-assembles into nanoscale assemblies in the lysosomes and subsequently has an appreciable destructive effect on the mitochondria and cytoskeleton, resulting in breast cancer cell apoptosis. More importantly, in vivo studies reveal that Y1 L-KGRR-FF-IR has a good therapeutic effect, reduces breast cancer tumor volume and generates excellent tracer efficacy in lung metastasis models. This study provides a novel strategy for stepwise targeting and precise regulation of tumor growth inhibition through functional neuropeptide Y-based artificial aggregates for intracellular spatiotemporal regulation.

Neuropeptide Y in the medial habenula alleviates migraine-like behaviors through the Y1 receptor.

BACKGROUND: Migraine is a highly disabling health burden with multiple symptoms; however, it remains undertreated because of an inadequate understanding of its neural mechanisms. Neuropeptide Y (NPY) has been demonstrated to be involved in the modulation of pain and emotion, and may play a role in migraine pathophysiology. Changes in NPY levels have been found in patients with migraine, but whether and how these changes contribute to migraine is unknown. Therefore, the purpose of this study was to investigate the role of NPY in migraine-like phenotypes. METHODS: Here, we used intraperitoneal injection of glyceryl trinitrate (GTN, 10 mg/kg) as a migraine mouse model, which was verified by light-aversive test, von Frey test, and elevated plus maze test. We then performed whole-brain imaging with NPY-GFP mice to explore the critical regions where NPY was changed by GTN treatment. Next, we microinjected NPY into the medial habenula (MHb), and further infused Y1 or Y2 receptor agonists into the MHb, respectively, to detect the effects of NPY in GTN-induced migraine-like behaviors. RESULTS: GTN effectively triggered allodynia, photophobia, and anxiety-like behaviors in mice. After that, we found a decreased level of GFP+ cells in the MHb of GTN-treated mice. Microinjection of NPY attenuated GTN-induced allodynia and anxiety without affecting photophobia. Furthermore, we found that activation of Y1-but not Y2-receptors attenuated GTN-induced allodynia and anxiety. CONCLUSIONS: Taken together, our data support that the NPY signaling in the MHb produces analgesic and anxiolytic effects through the Y1 receptor. These findings may provide new insights into novel therapeutic targets for the treatment of migraine.

Evidence for a feeding related association between melanocortin in the NTS and Neuropeptide-Y in the PVN.

Melanocortin and neuropeptide-Y (NPY) are both involved in feeding and energy regulation, and they have opposite effects in the paraventricular nucleus of the hypothalamus (PVN). The present study examined an interaction between melanocortin in the nucleus of the solitary tract (NTS) and NPY in the PVN. Male Sprague-Dawley rats were implanted with cannulae in the injection sites of interest. In Experiment 1, subjects received either the melanocortin 3/4-receptor (MC3/4) antagonist SHU9119 (0, 10, 50 and 100 pmol/0.5 µl) or the MC3/4 agonist MTII (0, 10, 50, 100 and 200 pmol/0.5 µl) into the NTS. Food intake was measured at 1, 2, 4, 6 and 24-h post-injection. Administration of SHU9119 into the NTS significantly and dose-dependently increased food intake at 1, 2, 4, 6 and 6-24-h, and administration of MTII into the NTS significantly and dose-dependently decreased 24-h free feeding. In Experiment 2, subjects received the MC3/4 agonist MTII (0, 10, 50, 100 and 200 pmol/0.5 µl) into the NTS just prior to NPY (0 and 1µg/0.5 µl) in the PVN. PVN injection of NPY stimulated feeding, and administration of MTII (50, 100 and 200 pmol) into the NTS significantly and dose-dependently decreased NPY-induced feeding at 2, 4, 6 and 6-24-h. These data suggest that there could be a neuronal association between melanocortin in the NTS and NPY in the PVN, and that the melanocortin system in the NTS has an antagonistic effect on NPY-induced feeding in the PVN.

Potential benefits of intranasal neuropeptide Y include sustained extinction of fear memory.

Compelling evidence in animals and humans from a variety of approaches demonstrate that neuropeptide Y (NPY) in the brain can provide resilience to development of many stress-elicited symptoms. Preclinical experiments demonstrated that delivery of NPY by intranasal infusion to rats shortly after single exposure to traumatic stress in the single prolonged stress (SPS) rodent model of post-traumatic stress disorder (PTSD) can prevent development of many relevant behavioral alterations weeks later, including heightened anxiety and depressive-like behavior. Here, we examined responses to intranasal NPY in the absence of stress to evaluate the safety profile. Rats were administered intranasal NPY (150 µg/rat) or equal volume of vehicle (distilled water), and 7 days later they were tested on the elevated plus maze (EPM) and forced swim test (FST). There was no significant difference in the number of entries or duration in the open or closed arms, or in their anxiety index. Defecation on the EPM and immobility on the FST, measures of anxiety and depressive-like behavior respectively, were similar in both groups. To further characterize potential benefits of intranasal NPY, its effect on fear memory and extinction, important features of PTSD, were examined. Intranasal administration of NPY at the time of the traumatic stress had a profound effect on fear conditioning a week later. It prevented the SPS-triggered impairment in the retention of extinguished behavior, both contextual and cued. The findings support the translation of non-invasive intranasal NPY delivery to the brain for PTSD-behaviors including impairments in sustained extinction of fear memories.

Mechanisms of Modulation of Adrenergic Regulation of Spontaneous Activity Rate and Atrial Myocardial Contractility in Early Postnatal Ontogeny in Rats.

We studied combined effect of the ß1,2-adrenoreceptor agonist isoproterenol and the Y1,5 receptor agonist [Leu31, Pro34]neuropeptide Y on the frequency of spontaneous activity and myocardial contractility in 21- and 100-day-old rats. Isoproterenol increased the frequency of spontaneous activity and reduced the main parameters of isometric contraction of the atrial myocardium. When [Leu31, Pro34]neuropeptide Y was added, the frequency of spontaneous activity and the negative inotropic and the positive chronotropic effects of isoproterenol were reduced in 100-day-old rats. In 21-day-olds rats, a tendency to a decrease in the effect of isoproterenol was observed.