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.

Administration of neuropeptide Y into the rat nucleus accumbens shell, but not core, attenuates the motivational impairment from systemic dopamine receptor antagonism by α-flupenthixol.

Previous research has demonstrated that dopamine and Neuropeptide Y (NPY) promote motivated behavior, and there is evidence to suggest that they interact within neural circuitry involved in motivation. NPY and dopamine both modulate appetitive motivation towards food through direct actions in the nucleus accumbens (NAc), although how they interact in this region to promote motivation is presently unclear. In this study, we sought to further elucidate the relationship between NAc NPY and dopamine and their effects on motivated behavior. Specifically, we examined whether NAc injections of NPY might reverse behavioral deficits caused by reduced dopamine signaling due to systemic dopamine receptor antagonism. Appetitive motivation was measured using a progressive ratio-2 paradigm. Male Sprague Dawley rats were treated with systemic injections of the dopamine antagonist, α-flupenthixol or a saline vehicle. Two hours following injections, they were administered infusions of NPY (at 0, 156, or 235 pmol) into either the NAc shell (n = 12) or the NAc core (n = 10) and were placed in operant chambers. In both groups, α-flupenthixol impaired performance on the PR-2 task. NPY receptor stimulation of the NAc shell significantly increased both breakpoint and active lever presses during the PR-2 task, and dose-dependently increased responding following systemic dopamine receptor blockade. NPY did not affect appetitive motivation when injected into the NAc core. These data demonstrate that NPY in the NAc shell can improve motivational impairments that result from dopamine antagonism, and that these effects are site specific. These results also suggest that upregulation of NPY in neurodegenerative diseases may possibly buffer early motivational deficits caused by dopamine depletion in Parkinson's and Huntington's disease patients, both of which show increased NPY expression after disease onset.

Central nucleus of the amygdala projections onto the nucleus accumbens core regulate binge-like alcohol drinking in a CRF-dependent manner.

RATIONALE: The nucleus accumbens (NAc) is important for regulating a number of behaviors, including alcohol and substance use. We previously found that chemogenetically manipulating neuronal activity in the NAc core regulates binge-like drinking in mice. The central amygdala (CeA) is also an important regulator of alcohol drinking, and projects to the NAc core. We tested whether neuronal projections from the CeA to the NAc core, or neuropeptides released by the CeA in the NAc core, could regulate binge drinking. METHODS: For experiment 1, mice were administered AAV2 Cre-GFP into the NAc core and a Cre-inducible DREADD [AAV2 DIO- hM3Dq, -hM4Di, or -mCherry control] into the CeA. We tested the effects of altering CeA to NAc core activity on binge-like ethanol intake (via "Drinking in the Dark", DID). For experiment 2, we bilaterally microinfused corticotropin releasing factor (CRF), neuropeptide Y (NPY), or somatostatin (SST) into the NAc core prior to DID. For experiment 3, we tested whether intra-NAc CRF antagonism prevented reductions in drinking induced by CNO/hM3Dq stimulation of CeA->NAc projections. RESULTS: Chemogenetically increasing activity in neurons projecting from the CeA to NAc core decreased binge-like ethanol drinking (p < 0.01). Intra-NAc core CRF mimicked chemogenetic stimulation of this pathway (p < 0.05). Binge-like drinking was unaffected by the doses of NPY and SST tested. Lastly, we found that intra-NAc CRF antagonism prevented reductions in drinking induced by chemogenetic stimulation of CeA->NAc projections. These findings demonstrate that neurons projecting from the CeA to NAc core that release CRF are capable of regulating binge-like drinking in mice.

Investigation of the effect of a modified fragment of neuropeptide Y on memory phases and extrapolation escape of animals.

The article presents a study of the effect of a modified fragment of neuropeptide Y (H-L-Ile-L-Asn-L-Leu-L-Nle-L-Ser- L-Arg-L-Asn-L-Arg-L-Tyr-NH2) named nonapeptide NP9 on the memory phases and extrapolation escape of animals. The study was performed in the passive avoidance test with intact animals, scopolamine-treated animals, and the extrapolation escape task. NP9 was investigated in the dose range of 0.04-0.4 mg/kg with a single intranasal administration. The comparison drug used peptide nootropic medicine Semax® (Met-Glu-His-Phe-Pro-Gly-Pro) at a dose of 0.1 mg/kg. Efficiency was assessed by the retention latency, the percentage of animals that have reached the learning criterion, the number of incomplete attempts to enter, the antiamnestic activity index calculated by Butlers formula, and the number of animals that successfully performed the extrapolation escape task. Peptide NP9 was superior to Semax® in most indicators. It demonstrated the ability to improve memorization due to its effect on I phase of memory and facilitated extinction of negative experiences when administered after a stress stimulus. NP9 also increased the cognitive ability of animals in the conditions an aversive environment in the extrapolation escape test. Thus, peptide NP9 is promising for a further study as a potential drug for the treatment of cognitive impairment and therapy of post-traumatic stress disorder.

Brain Region-Dependent Effects of Neuropeptide Y on Conditioned Social Fear and Anxiety-Like Behavior in Male Mice.

Neuropeptide Y (NPY) has anxiolytic-like effects and facilitates the extinction of cued and contextual fear in rodents. We have previously shown that the intracerebroventricular administration of NPY reduces the expression of social fear in a mouse model of social fear conditioning (SFC). In the present study, we aimed to identify the brain regions that mediate these effects of NPY. We show that NPY (0.1 nmol/0.2 µL/side) reduces the expression of SFC-induced social fear in a brain-region-dependent manner. In more detail, NPY reduced the expression of social fear when administered into the dorsolateral septum (DLS) and central amygdala (CeA), but not when administered into the dorsal hippocampus (DH), medial amygdala (MeA) and basolateral amygdala (BLA). We also investigated whether the reduced expression of social fear might partly be due to a reduced anxiety-like behavior, and showed that NPY exerted anxiolytic-like effects when administered into the DH, DLS, CeA and BLA, but not when administered into the MeA. This study identifies the DLS and the CeA as brain regions mediating the effects of NPY on the expression of social fear and suggests that partly distinct neural circuitries mediate the effects of NPY on the expression of social fear and on anxiety-like behavior.

Central injection of neuropeptide Y modulates sexual behavior in male rats: interaction with GnRH and kisspeptin/neurokinin B/dynorphin.

AIMS: A number of studies have shown that neuropeptide Y (NPY) is considered to be one of the key regulators of hypothalamic-pituitary-gonadal (HPG) axis in the mammals. In addition, kisspeptin (encode by Kiss1 gene), neurokinin B (encode by Tac3 gene) and dynorphin (encode by Pdyn gene) (commonly known as KNDy secreting neurons) are a powerful upstream regulators of GnRH neuron in hypothalamus. MATERIALS AND METHODS: The present study aims to investigate the effects of the intracerebroventricular (icv) injection of NPY and BIBP3226 (NPY receptor antagonist (NPYRA)) on the male sexual behavioral. Additionally, in order to see whether NPY signals can be relayed through the pathway of kisspeptin/neurokinin B/dynorphin, the gene expression of these peptides along with Gnrh1 gene in the hypothalamus were measured. RESULTS: The icv injection of NPY decreased the latencies and increase the frequencies of sexual parameters of the male rats in a significant way. In this line, NPYRA antagonized the stimulative effects of NPY. Moreover, data from real-time quantitative PCR indicated that injection of NPY significantly increased the gene expression of Gnrh1, Kiss1 and Tac3 and decrease the Pdyn while treatment with NPYRA controlled the modulative effects of NPY on these gene expression. CONCLUSIONS: In conclusion based on the results of this study, NPY can exert its impacts on the sexual behavior of male rats via modulation of the KNDy secreting neurons as an interneural pathway to GnRH neurons.

A Randomized Controlled Trial of Intranasal Neuropeptide Y in Patients With Major Depressive Disorder.

BACKGROUND: Since about one-third of patients with major depressive disorder (MDD) do not respond adequately to available antidepressants, there is a need for treatments based on novel mechanisms of action. Neuropeptide Y (NPY), a normal brain constituent, is reduced in cerebrospinal fluid of patients with MDD and post-traumatic stress disorder and in corresponding rodent models. Moreover, NPY administered centrally or intranasally rescues pathophysiology in these models. Consequently, we conducted the first, to our knowledge, controlled trial of NPY as a treatment for MDD. METHODS: Thirty MDD patients on a stable dose of a conventional antidepressant insufflated 6.8 mg NPY (n = 12) or placebo (n = 18) in a double blind randomized fashion. Effects were assessed at baseline, +1 hour, +5 hours, +24 hours, and +48 hours. The primary outcome was change in depression severity measured with the Montgomery-Åsberg Depression Rating Scale (MADRS). RESULTS: NPY was superior to placebo at +24 hours (change -10.3 [95% CI: -13.8; -6.8]) vs -5.6 (95% CI: -8.4; -2.7); group*time F = 3.26, DF = (1,28), P = .04; Cohen's d = 0.67). At +5 hours MADRS decreased -7.1 ([95% CI: -10.0; -4.2] vs -3.5 [95% CI: -5.8; -1.2]; group*time F = 2.69, DF = (1,28), P = .05; Cohen's d = 0.61). MADRS reduction at +48 hours was not significant. CONCLUSIONS: Since no results regarding the trajectory of NPY effects existed prior to this study we extrapolated from the known NPY biology and predicted the effects will occur 5-48 hours post insufflation. We chose +48 hours as the primary endpoint and +1, +5, and +24 hours as secondary endpoints. The results, the first of their kind, indicate that insufflated NPY is antidepressant, despite not meeting the primary outcome, and call for dose ranging and repeated NPY insufflation trials. CLINICAL TRIAL REGISTRATION: EudraCT Number: 2014-000129-19.

Effect of intranasal administration of neuropeptide Y and single prolonged stress on food consumption and body weight in male rats.

Emerging evidence indicates that intranasal delivery of neuropeptide Y (NPY) to the brain has therapeutic potential for management of stress-triggered neuropsychiatric disorders. Here we aimed to determine how intranasal administration of NPY, either before or immediately after, traumatic stress in single prolonged stress (SPS) rodent model of Post-traumatic stress disorder (PTSD) impacts food consumption and body weight. SPS stressors suppressed food consumption for at least two days in the vehicle-treated animals. When given prior to SPS stressors, intranasal NPY prevented the SPS-elicited reduction in food intake only for several hours afterwards. When given after the SPS stressors, under conditions shown to prevent behavioral and biochemical impairments, intranasal NPY had no effect on food intake. Although all groups showed circadian variation, the SPS-exposed rats ate less than unstressed animals during the dark (active) phase. Seven days after exposure to SPS stressors, there were no differences in food intake, although body weight was still lower than unstressed controls in all the experimental groups. Thus, traumatic stress has pronounced effect on food consumption during the rodent's active phase, and a prolonged effect on body weight. Single intranasal infusion of NPY, which was previously shown to prevent development of several PTSD associated behavioral and neuroendocrine impairments, did not elicit prolonged changes in stress triggered food consumption nor regulation of body weight.

Neuropeptide Y3-36 incorporated into PVAX nanoparticle improves angiogenesis in a murine model of myocardial ischemia.

Neuropeptide-Y (NPY) leads to angiogenesis and remodeling of the ischemic myocardium. The objective of this study is to assess the therapeutic potential of NPY in a model of acute myocardial ischemia using a nanoparticles delivery system targeted to tissue with oxidative stress. NPY3-36 was loaded onto copolyoxalate containing vanillyl alcohol (PVAX) using a double emulsification strategy. Adult C57BL/J6 mice (n = 49) were randomly divided into PVAX-NPY3-36 (n = 22), Vehicle (Saline) (n = 16), and Sham (n = 11) groups. The ischemia to left anterior descending artery was induced in PVAX-NPY3-36 or vehicle groups. The tissue was collected at the end of two weeks after assessing the functional and echocardiographic data. There was a significant decrease in infarction size and mortality in PVAX-NPY3-36 group compared to the Vehicle group (P = 0.01 and P = 0.05). On echocardiography, there was significant improvement in contractility and diastolic parameters (P = 0.01). On pressure-volume loop there was significant increase in stroke volume (P = 0.01), cardiac output (P = 0.01) and ventricular stroke work (P = 0.01) in the PVAX-NPY3-36 group. On Western blot analysis, there was a significant increase in pro-angiogenic factors Ang-1, TGF-ß, PDGF- ß and its receptors and VEGF in the ischemic tissue treated with PVAX-NPY3-36 as compared to Vehicle ischemic tissue (P = 0.01, P = 0.0003, and P < 0.05 respectively). It may be possible to have targeted delivery of labile neurotransmitters NPY3-36 to the ischemic myocardium using nanoparticle PVAX and achieving angiogenesis and significant functional improvement.

Neuropeptide Y prolongs non-social memory in a brain region- and receptor-specific way in male mice.

Neuropeptide Y (NPY) and its receptors are highly expressed in brain regions involved in learning and memory processes. We have previously shown that intracerebroventricular administration of NPY prolongs the retention of non-social memory in the object discrimination test. Here, we aimed to identify the brain regions which mediate these memory-enhancing effects of NPY. We show that NPY (0.1 nmol/0.2 µl/side) prolongs retention of non-social memory when administered into the dorsolateral septum (DLS) and medial amygdala (MeA), but not when administered into the dorsal hippocampus, central amygdala and basolateral amygdala. In the DLS, the effects of NPY were blocked by the Y1 receptor antagonist BIBO3304 trifluoroacetate (0.2 nmol/0.2 µl/side), but not by the Y2 receptor antagonist BIIE0246 (0.2 nmol/0.2 µl/side). In the MeA, on the other hand, BIIE0246, but not BIBO3304 trifluoroacetate blocked the effects of NPY. This study demonstrates that NPY exerts Y1 receptor-mediated memory-enhancing effects in the DLS and Y2 receptor-mediated memory-enhancing effects in the MeA, and suggests that distinct brain regions and receptor subtypes are recruited to mediate the effects of NPY on non-social memory.

Intra-articular injection of 2-pyridylethylamine produces spinal NPY-mediated antinociception in the formalin-induced rat knee-joint pain model.

Low doses of histamine or H1R agonist 2-pyridylethylamine (2-PEA) into the knee-joint were found to decrease formalin-induced articular nociception in rats. In this study, we evaluated the participation of spinal NPY in the antinociceptive effect produced by 2-PEA. Injection of formalin (1.5%) into one of the knee-joints causes the limping of the respective limb due to nociception, which was registered each 5 min over 60 min. Neuropeptide Y1 receptor (Y1R) content in the spinal cord was evaluated by western-blotting. Intrathecal (i.t.) injection of Y1R agonist Leu31, Pro34-NPY (0.7-7 µmol) decreased nociception, while injection of the antagonist BIBO 3304 (4 µmol), increased nociception. Antinociception produced by 2-PEA was reversed by a sub-effective i.t. dose of the Y1R antagonist. Similarly, this antinociceptive effect was prevented by i.t. pretreatment with the neurotoxin NPY-saporin (750 ng), which also reduced immunoblotting for Y1R in spinal cord homogenates. These data support the idea that antinociception induced by H1R agonists in the knee-joint of rats may be mediated by the spinal release of NPY, and this peptide seems to be acting via Y1R.

Development and characterization of a 99m Tc-labeled Neuropeptide Y short analog with potential application in breast cancer imaging.

The aim of this work was to develop and evaluate a 99m Tc-labeled neuropeptide Y derivative with affinity toward Y1-receptor. The selected amino acid sequence included nine amino acids derived from the C-terminal portion of the NPY complemented with the addition of one cysteine-mercaptoacetic acid moiety to bind the radiometal. Labeling was achieved through the preparation of a 3 + 1 nitrido complex. Physicochemical evaluation, cell uptake, internalization and externalization studies, and competitive assays were performed. Biodistribution experiments were carried out in normal and tumor-bearing mice. A single product with radiochemical purity >90% and high stability was obtained. In vitro analysis showed specific cellular uptake, IC50 of 73.2 nM, and a high internalization rate (80%). Biodistribution studies showed low blood and renal uptake and combined hepatobiliary and urinary elimination. Preliminary studies in mice bearing induced breast tumors rendered promising uptake values.

Inhibition of epileptiform activity by neuropeptide Y in brain tissue from drug-resistant temporal lobe epilepsy patients.

In epilepsy patients, drug-resistant seizures often originate in one of the temporal lobes. In selected cases, when certain requirements are met, this area is surgically resected for therapeutic reasons. We kept the resected tissue slices alive in vitro for 48 h to create a platform for testing a novel treatment strategy based on neuropeptide Y (NPY) against drug-resistant epilepsy. We demonstrate that NPY exerts a significant inhibitory effect on epileptiform activity, recorded with whole-cell patch-clamp, in human hippocampal dentate gyrus. Application of NPY reduced overall number of paroxysmal depolarising shifts and action potentials. This effect was mediated by Y2 receptors, since application of selective Y2-receptor antagonist blocked the effect of NPY. This proof-of-concept finding is an important translational milestone for validating NPY-based gene therapy for targeting focal drug-resistant epilepsies, and increasing the prospects for positive outcome in potential clinical trials.

Intranasal Neuropeptide Y Blunts Lipopolysaccharide-Evoked Sickness Behavior but Not the Immune Response in Mice.

Neuropeptide Y (NPY) has been demonstrated to exert stress buffering effects and promote resilience. Non-invasive intranasal (IN) application of NPY to rodents is able to mitigate traumatic stress-induced behavioral changes as well as dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis. However, it is unknown whether IN NPY could prevent the behavioral, pro-inflammatory and neurochemical responses to peripheral immune activation by the Toll-like receptor 4 (TLR4) stimulant lipopolysaccharide (LPS). Therefore, we analyzed the effects of IN NPY (100 µg) on the behavioral sickness response (reduced locomotion and exploration) and the underlying molecular mechanisms, 3 h and 21 h after intraperitoneal injections of LPS (0.03 mg/kg) in male C57BL/6N mice. The acute behavioral sickness response was significantly dampened by pretreatment with IN NPY 3 h after LPS injection. This effect was accompanied by diminished weight loss and lowered plasma corticosterone (CORT) levels 21 h after LPS injection. In contrast, acute circulating cytokine levels and hypothalamic cytokine mRNA expression remained unaltered by IN NPY, which indicates that the peripheral and cerebral immune response to LPS was left undisturbed. Our findings are in agreement with the reported activity of NPY to dampen the response of the HPA axis to stress. We propose that IN NPY ablates sickness behavior at a site beyond the peripheral and cerebral cytokine response, an action that is associated with reduced activity of the HPA axis as determined by decreased plasma CORT.These results indicate that IN NPY administration may be relevant to the management of neuropsychiatric disorders arising from immune-induced neuroendocrine dysfunction.

Neuropeptide Y reduces expression of social fear via simultaneous activation of Y1 and Y2 receptors.

BACKGROUND: Neuropeptide Y (NPY) has anxiolytic effects and facilitates extinction of cued and contextual fear in rodents, thereby acting as a resilience factor against exaggerated fear responses after adverse events. We investigated whether NPY influences acquisition, expression and extinction of social fear in a mouse model of social fear conditioning (SFC). METHODS: NPY was administered intracerebroventricularly before SFC or before social fear extinction with or without prior administration of Y1 and/or Y2 receptor antagonists. RESULTS: We show that NPY affects SFC-induced social fear in a time point-dependent manner. When administered before SFC, NPY did not affect acquisition, expression and extinction of social fear. However, when administered before social fear extinction, NPY reduced expression of social fear via simultaneous activation of Y1 and Y2 receptors. As such, neither the Y1 receptor antagonist BIBO3304 trifluoroacetate nor the Y2 receptor antagonist BIIE0246 was able to block the effects of NPY completely. However, when administered in combination, they completely blocked the effects of NPY on social fear expression. CONCLUSIONS: These findings have important clinical implications, as they suggest that although medication strategies aimed at increasing brain NPY activity are unlikely to prevent the formation of aversive memories after a traumatic social experience, they might improve the recovery from a traumatic social experience by reducing the expression of social fear.

Preclinical findings on the potential of intranasal neuropeptide Y for treating hyperarousal features of PTSD.

Acoustic startle response (ASR) assesses hyperarousal, a core symptom of posttraumatic stress disorder (PTSD). Intranasal neuropeptide Y (NPY) administration was shown to prevent hyperarousal in single prolonged stress (SPS) rodent PTSD model. However, it is unclear how ASR itself alters responses to stress. Rats (A-S-A) were exposed to acoustic startle (AS) 1 day before SPS (ASR1) and 2 weeks afterward (ASR2). Other groups were exposed in parallel to either AS (A-A) or SPS or neither. SPS enhanced ASR2. In relevant brain areas, mRNA levels were determined by qRT-PCR. In mediobasal hypothalamus, AS or SPS each increased CRH mRNA levels without an additive effect. Exposure to AS appeared to dampen some responses to SPS. The SPS-triggered reduction of GR and FKBP5 gene expression was not observed in A-S-A group. In locus coeruleus, SPS increased CRHR1 and reduced Y2R mRNAs, but not in A-S-A group. In both regions, AS altered NPY receptor gene expression, which may mediate dampening responses to SPS. In second experiment, intranasal NPY administered 2 weeks after SPS reversed hyperarousal symptoms for at least 7 days. This study reveals important effects of AS on the NPY system and demonstrates that intranasal NPY elicits long-lasting reversal of traumatic stress-triggered hyperarousal.

Neuropeptide Y impairs the acquisition of conditioned defeat in Syrian hamsters.

Recent evidence indicates that Neuropeptide Y (NPY) may function as a potent anxiolytic as well as a resilience factor that can insulate the brain from the effects of stress. However, most of these studies have utilized physical stressors such as shock or restraint. In the present study, we use an ethologically-based model in Syrian hamsters (Mesocricetus auratus) called Conditioned Defeat (CD) to investigate whether NPY can ameliorate the effect of social defeat stress. In the CD model, a male Syrian hamster is socially defeated by a larger, more aggressive conspecific. Subsequently, when paired with a smaller, non-aggressive intruder (NAI) in its own home cage, changes in its behavioral repertoire occur, including a reduction in aggression and chemosensory (social) investigation, and a concomitant increase in submissive behaviors. In Experiment 1, hamsters were infused intracerebroventricularly (icv) with NPY prior to social defeat, and 24-hours later, hamsters were exposed to a NAI. Results indicate that NPY significantly reduced submissive/defensive behaviors in socially defeated hamsters compared to control animals. In Experiment 2, we examined whether this effect was mediated by the NPY Y1 receptor. Subjects were first pre-treated with the Y1 receptor antagonist BIBP 3226 or vehicle, followed by NPY and then socially defeated. Upon testing with a NAI 24-hours later, pretreatment with BIBP 3226 failed to block the NPY effect compared to controls. These results demonstrate that NPY may function as an important resilience factor in socially defeated hamsters, but that these effects are not mediated by the Y1 receptor.

Single stimulation of Y2 receptors in BNSTav facilitates extinction and dampens reinstatement of fear.

RATIONALE: Return of fear by re-exposure to an aversive event is a major obstacle in the treatment of fear-related disorders. Recently, we demonstrated that local pharmacological stimulation of neuropeptide Y type 2 receptors (Y2R) in anteroventral bed nucleus of stria terminalis (BNSTav) facilitates fear extinction and attenuates retrieval of remote fear with or without concomitant extinction training. Whether Y2R activation could also protect against re-exposure to traumatic events is still unknown. OBJECTIVE: Therefore, we investigated reinstatement of remote fear following early Y2R manipulation in BNSTav in relation to concomitant extinction training in mice. METHODS: We combined local pharmacological manipulation of Y2Rs in BNSTav with or without extinction training and tested for reinstatement of remote fear 15 days later. Furthermore, we employed immediate early gene mapping to monitor related local brain activation. RESULTS: Y2R stimulation by local injection of NPY3-36 into BNSTav facilitated extinction, reduced fear reinstatement at remote stages, and mimicked the influence of extinction in groups without prior extinction training. In contrast, Y2R antagonism (JNJ-5207787) delayed extinction and increased reinstatement. Y2R treatment immediately before remote fear tests had no effect. Concomitantly, Y2R activation at early time points reduced the number of c-Fos positive neurons in BNSTav during testing of reinstated remote fear. CONCLUSION: Local Y2R stimulation in BNSTav promotes fear extinction and stabilizes suppression of reinstated fear through a long-term influence, even without extinction training. Thus, Y2Rs in BNST are crucial pharmacological targets for extinction-based remote fear suppression.

Neuropeptide Y treatment induces retinal vasoconstriction and causes functional and histological retinal damage in a porcine ischaemia model.

PURPOSE: To investigate the effects of intravitreal neuropeptide Y (NPY) treatment following acute retinal ischaemia in an in vivo porcine model. In addition, we evaluated the vasoconstrictive potential of NPY on porcine retinal arteries ex vivo. METHODS: Twelve pigs underwent induced retinal ischaemia by elevated intraocular pressure clamping the ocular perfusion pressure at 5 mmHg for 2 hr followed by intravitreal injection of NPY or vehicle. After 4 weeks, retinas were evaluated functionally by standard and global-flash multifocal electroretinogram (mfERG) and histologically by thickness of retinal layers and number of ganglion cells. Additionally, the vasoconstrictive effects of NPY and its involved receptors were tested using wire myographs and NPY receptor antagonists on porcine retinal arteries. RESULTS: Intravitreal injection of NPY after induced ischaemia caused a significant reduction in the mean induced component (IC) amplitude ratio (treated/normal eye) compared to vehicle-treated eyes. This reduction was accompanied by histological damage, where NPY treatment reduced the mean thickness of inner retinal layers and number of ganglion cells. In retinal arteries, NPY-induced vasoconstriction to a plateau of approximately 65% of potassium-induced constriction. This effect appeared to be mediated via Y1 and Y2, but not Y5. CONCLUSION: In seeming contrast to previous in vitro studies, intravitreal NPY treatment caused functional and histological damage compared to vehicle after a retinal ischaemic insult. Furthermore, we showed for the first time that NPY induces Y1- and Y2- but not Y5-mediated vasoconstriction in retinal arteries. This constriction could explain the worsening in vivo effect induced by NPY treatment following an ischaemic insult and suggests that future studies on exploring the neuroprotective effects of NPY might focus on other receptors than Y1 and Y2.

Potential of Intranasal Neuropeptide Y (NPY) and/or Melanocortin 4 Receptor (MC4R) Antagonists for Preventing or Treating PTSD.

There is a great need for effective treatment options for post-traumatic stress disorder (PTSD). Neuropeptide Y (NPY) is associated with resilience to traumatic stress. MC4R antagonists, such as HS014, also reduce response to stress. Both regulate stress-responsive systems - the hypothalamic-pituitary-axis (HPA) and the noradrenergic nervous system and their associated behaviors. Therefore, we examined if their intranasal delivery to brain could attenuate development of PTSD-related symptoms in single prolonged stress (SPS) rodent PTSD model. Three regimens were used: (1) prophylactic treatment 30 min before SPS stressors, (2) early intervention right after SPS stressors, (3) therapeutic treatment when PTSD behaviors are manifested 1 wk or more after the traumatic stress. NPY delivered by regimen 1 or 2 prevented SPS-triggered elevation in anxiety, depressive-like behavior, and hyperarousal and reduced dysregulation of HPA axis. Hypothalamic CRH mRNA and GR in ventral hippocampus were significantly induced in vehicle- but not NPY-treated group. NPY also prevented hypersensitivity of LC/NE system to novel mild stressor and induction of CRH in amygdala. Some of these impairments were also reduced with HS014, alone or together with NPY. When given after symptoms were manifested (regiment 3), NPY attenuated anxiety and depressive behaviors. This demonstrates strong preclinical proof of concept for intranasal NPY, and perhaps MC4R antagonists, for non-invasive early pharmacological interventions for PTSD and comorbid disorders and possibly also as therapeutic strategy.