Inhibition of SNL-induced upregulation of CGRP and NPY in the spinal cord and dorsal root ganglia by the 5-HT(2A) receptor antagonist ketanserin in rats

Our previous study has demonstrated that topical and systemic administration of the 5-HT_2A receptor antagonist ketanserin attenuates neuropathic pain. To explore the mechanisms involved, we examined whether ketanserin reversed the plasticity changes associated with calcitonin gene-related peptides (CGRP) and neuropeptide Y (NPY) which may reflect distinct mechanisms: involvement and compensatory protection. Behavioral responses to thermal and tactile stimuli after spinal nerve ligation (SNL) at L5 demonstrated neuropathic pain and its attenuation in the vehicle- and ketanserin-treated groups, respectively. SNL surgery induced an increase in CGRP and NPY immunoreactivity (IR) in laminae I-II of the spinal cord. L5 SNL produced an expression of NPY-IR in large, medium and small diameter neurons in dorsal root ganglion (DRG) only at L5, but not adjacent L4 and L6. Daily injection of ketanserin (0.3 mg/kg, s.c.) for two weeks suppressed the increase in CGRP-IR and NPY-IR in the spinal cord or DRG. The present study demonstrated that: (1) the expression of CGRP was enhanced in the spinal dorsal horn and NPY was expressed in the DRG containing injured neurons, but not in the adjacent DRG containing intact neurons, following L5 SNL; (2) the maladaptive changes in CGRP and NPY expression in the spinal cord and DRG mediated the bioactivity of 5-HT/5-HT_2A receptors in neuropathic pain and (3) the blockade of 5-HT_2A receptors by ketanserin reversed the evoked upregulation of both CGRP and NPY in the spinal cord and DRG contributing to the inhibition of neuropathic pain.     

Neuropeptide Y modulates effects of bradykinin and prostaglandin E2 on trigeminal nociceptors via activation of the Y1 and Y2 receptors

BACKGROUND AND PURPOSE: Although previous studies have demonstrated that neuropeptide Y (NPY) modulates nociceptors, the relative contributions of the Y1 and Y2 receptors are unknown. Therefore, we evaluated the effect of Y1 and Y2 receptor activation on nociceptors stimulated by bradykinin (BK) and prostaglandin E2 (PGE2). EXPERIMENTAL APPROACH: Combined immunohistochemistry (IHC) with in situ hybridization (ISH) demonstrated that Y1- and Y2-receptors are collocated with bradykinin (2) (B2)-receptors in rat trigeminal ganglia (TG). The relative functions of the Y1 and Y2 receptors in modulating BK/PGE2-evoked CGRP release and increased intracellular calcium levels in cultured TG neurons were evaluated. KEY RESULTS: The Y1 and Y2 receptors are co-expressed with B2 in TG neurons, suggesting the potential for direct NPY modulation of BK responses. Pretreatment with the Y1 agonist [Leu31,Pro34]-NPY, inhibited BK/PGE2-evoked CGRP release. Conversely, pretreatment with PYY(3-36), a Y2 agonist, increased BK/PGE2 evoked CGRP release. Treatment with NPY evoked an overall inhibitory effect, although of lesser magnitude. Similarly, [Leu31,Pro34]-NPY inhibited BK/PGE2-evoked increases in intracellular calcium levels whereas PYY(3-36) increased responses. NPY inhibition of BK/PGE2-evoked release of CGRP was reversed by the Y1 receptor antagonist, BIBO3304, and higher concentrations of BIBO3304 significantly facilitated CGRP release. The Y2 receptor antagonist, BIIE0246, enhanced the inhibitory NPY effects. CONCLUSIONS AND IMPLICATIONS: These results demonstrate that NPY modulation of peptidergic neurons is due to net activation of inhibitory Y1 and excitatory Y2 receptor systems. The relative expression or activity of these opposing receptor systems may mediate dynamic responses to injury and pain.     

Functional interaction between neuropeptide Y receptors and modulation of calcium channels in the rat hippocampus

We investigated the functional interaction between neuropeptide Y (NPY) receptors using nerve terminals and cultured rat hippocampal neurons, and we evaluated the involvement of voltage-gated Ca(2+) channels (VGCCs) in NPY receptors-induced inhibition of Ca(2+) influx and glutamate release. The KCl-evoked release of glutamate from hippocampal synaptosomes was inhibited by 1 microM NPY and this effect was insensitive to either BIBP3226 (Y1 receptor antagonist) or L-152,804 (Y5 receptor antagonist), but was sensitive to BIIE0246 (Y2 receptor antagonist). We could also pharmacologically dissect the NPY receptors activity by using Y1, Y2 and Y5 receptor agonists ([Leu(31),Pro(34)]NPY, NPY13-36, NPY (19-23)-(Gly(1),Ser(3),Gln(4),Thr(6),Ala(31),Aib(32),Gln(34))-pancreatic polypeptide (PP), respectively), and in all the cases we observed that these agonists could inhibited the KCl-induced release of glutamate. However, the selective and specific co-activation of both Y1 and Y2 or Y2 and Y5 receptors resulted in non-additive inhibition, and this effect was prevented in the presence of the Y2 antagonist, but was insensitive to the Y1 or Y5 receptor antagonist. Moreover, as we previously showed for Y1 receptors, we also observed that the activation of Y5 receptors inhibited the glutamate release in the dentate gyrus and CA3 subregion, without significant effect in the CA1 subregion of the hippocampus. The same qualitative results were obtained when we investigated the role of NPY Y1 and Y2 receptors in modulating the changes in [Ca(2+)](i) due to KCl depolarisation in cultured hippocampal neurons. The inhibitory effect of nitrendipine (L-type VGCC blocker) or omega-conotoxin GVIA (omega-CgTx; N-type VGCC blocker) was not potentiated by the simultaneous activation of Y1 or Y2 receptors. Moreover, the exocytotic release of glutamate was inhibited by omega-agatoxin IVA (omega-Aga; P-/Q-type VGCC blocker), and this VGCC blocker did not potentiate Y1, Y2 or Y5 receptor-mediated inhibition of glutamate release. Also, the effect of ionomycin in inducing the exocytotic release of glutamate from hippocampal synaptosomes was insensitive to the activation of NPY receptors. In the present paper, we identified a role for NPY Y1, Y2 and Y5 receptors in modulating the exocytotic release of glutamate and the [Ca(2+)](i) changes in the rat hippocampus. In conditions of co-activation, there appears to exist a physiological cross-talk between Y1 and Y2 and also between Y2 and Y5 receptors, in which Y2 receptors play a predominant role. Moreover, we also show that Y1 and Y2 receptors exert their inhibitory action by directly modulating L-, N-, and P-/Q-type VGCCs, whereas the inhibition of glutamate release mediated by the Y5 receptors seems to involve P-/Q-type VGCCs.     

Neuropeptide Y expression in mouse hippocampus and its role in neuronal excitotoxicity

Aim: To investigate neuropeptide Y (NPY) expression in mouse hippocampus within early stages of kainic acid (KA) treatment and to understand its role in neuronal excitotoxicity. Methods: NPY expression in the hippocampus within early stages of KA intraperitoneal (ip) treatment was detected by immunohistochemistry (IHC) and in situ hybridization (ISH) methods. The role of NPY and Y5, Y2 receptors in excitotoxicity was analyzed by terminal deoxynucleotidyl transferase-mediated UTP nick end-labeling (TUNEL) assay. Results: Using IHC assay, in granule cell layer of the dentate gyrus (DG), NPY positive signals appeared 4 h after KA injection, reached the peak at 8 h and leveled off at 16 and 24 h. In CA3, no positive signal was found within the first 4 h after KA injection, but strong signal appeared at 16 and 24 h. No noticeable signal was detected in CA1 at all time points after KA injection. Using the ISH method, positive signals were detected at 4, 8, and 16 h in CA3, CA1, and hilus. In DG, much stronger ISH signals were detected at 4 h, but leveled off at 8 and 16 h. TUNEL analysis showed that intracerebroventricularly (icv) infusion of NPY and Y5, Y2 receptor agonists within 8 h after KA insult with proper dose could remarkably rescue pyramidal neurons in CA3 and CAI from apoptosis. Conclusion: NPY is an important anti-epileptic agent. The preceding elevated expression of NPY in granule cell layer of DG after KA injection might partially explain its different excitotoxicity-induced apoptotic responses in comparison with the pyramidal neurons from CA3 and CA1 regions. NPY can not only reduce neuronal excitability but also prevent excitotoxicity-induced neuronal apoptosis in a time-and doserelated way by activation of Y5 and Y2 receptors.     

Neuropeptide Y receptor subtypes in the basolateral nucleus of the amygdala modulate anxiogenic responses in rats

The behavioral effects induced by intra-amygdala stimulation of the neuropeptide Y (NPY) Y(2) and the NPY Y(5) receptor subtypes were assessed in the social interaction (SI) test. Microinjections of NPY(3-36), an NPY Y(2) preferring agonist, into the basolateral nucleus of the amygdala (BLA) produced bi-directional dose-response curve. At low doses NPY(3-36) has an anxiogenic effect while at higher doses it produced an anxiolytic effect. Pretreatment with the NPY Y(5) receptor antagonist Novartis 1(1 nmol), an analog of CGP71683A synthesized by Eli Lilly and Company, IN, blocked the anxiolytic effects of NPY(3-36) (80 pmol), while pretreatment with BIBO 3304 (200 pmol), a Y(1) antagonist, had no effect, suggesting that the Y(5), but not the Y(1) receptor was involved in the anxiolytic behavior produced following intra-amygdalar NPY(3-36) administration. In addition, the Y(5) antagonist had no behavioral effect when given alone at 1.0 nmol. These findings support the hypothesis that amygdalar Y(2) receptors may play a role in mediating anxiogenic effects, while Y(5) receptors may be involved in the anxiolytic behaviors of NPY.     

Relevance of the neuropeptide Y system in the biology of cancer progression

The peptides pancreatic polypeptide (PP), peptide YY (PYY), and neuropeptide Y (NPY) share a similar structure, known as PP-fold. Within this family of peptides, NPY, a highly conserved 36-aminoacid residue peptide, is involved in the regulation of a wide range of physiological functions, such as food intake and energy metabolism, as well as in the promotion of some remarkable aspects of tumor progression, including cell proliferation, matrix invasion, metastatization, and angiogenesis. NPY exerts its biological effects through five G-protein coupled receptors, named Y1-, Y2-, Y4-, Y5-, and y6-R, which appear associated with different aspects of oncogenesis. Y1-R seems involved in the modulation of cancer cell proliferation, whereas Y2-R activation appears to promote angiogenesis. The development of NPY receptor subtype selective analogs has helped to elucidate the physiological and pathophysiological role and localization of each receptor and may contribute to a better understanding of the receptor-ligand interaction. The NPY system appears to be variously associated with specific tumors, including neural crest-derived tumors, breast and prostate cancers. In addition to NPY, PYY is also able to affect cancer cell growth in a dose-dependent manner and through Y-Rs. In conclusion, peptides of the NPY family and the related receptors play an important role in the progression of different cancer types, with some molecular specificity according to each step of this process. On this basis, future studies may be directed to the implementation of novel diagnostic and therapeutic approaches targeting this system.     

Neuropeptide Y: multiple receptors and multiple roles in cardiovascular diseases

Neuropeptide Y (NPY), a sympathetic co-transmitter, acts through multiple G protein-coupled receptors (Y1 to y6) to elicit its vast range of effects in the cardiovascular, immune, and central and peripheral nervous systems. Initially, the focus of the function of NPY in the cardiovascular system involved its acute actions, such as vasoconstriction via the Y1 receptor. However, recent studies have shown that NPY is a potent growth and angiogenic factor, which acts on multiple receptor subtypes. To be more specific, NPY-mediated vascular smooth muscle cell growth, leading to neointima formation, involves Y1 and Y1 receptors, while the angiogenic effects of NPY include Y2 and Y5 receptor activation. The presence of dipeptidyl peptidase IV also influences the cardiovascular responses of NPY by acting as a converting enzyme, shifting NPY activities away from Y1. Thus, agonists and antagonists aimed at the NPY system represent a new avenue for drug treatment, which may help alleviate several cardiovascular disorders in which vascular remodeling plays a major role, such as atherosclerosis, restenosis following balloon angioplasty, hypertension and peripheral vascular disease.     

Receptor subtypes Y1 and Y5 mediate neuropeptide Y induced feeding in the guinea-pig

1. Neuropeptide Y (NPY) is one of the most potent stimulants of food intake. It has been debated which receptor subtype mediates this response. Initially Y(1) was proposed, but later Y(5) was announced as a 'feeding' receptor in rats and mice. Very little is known regarding other mammals. The present study attempts to characterize the role of NPY in feeding behaviour in the distantly related guinea-pig. When infused intracerebroventricularly, NPY dose-dependently increased food intake. 2. PYY, (Leu(31),Pro(34))NPY and NPY(2 - 36) stimulated feeding, whereas NPY(13 - 36) had no effect. These data suggest that either Y(1) or Y(5) receptors or both may mediate NPY induced food intake in guinea-pigs. 3. The Y(1) receptor antagonists, BIBO 3304 and H 409/22 displayed nanomolar affinity for the Y(1) receptor (K(i) values 1.1+/-0.2 nM and 5.6+/-0.9 nM, respectively), but low affinity for the Y(2) or Y(5) receptors. When guinea-pigs were pretreated with BIBO 3304 and H 409/22, the response to NPY was inhibited. 4. The Y(5) antagonist, CGP 71683A had high affinity for the Y(5) receptor (K(i) 1.3+/-0.05 nM) without having any significant activities at the Y(1) and Y(2) receptors. When CGP 71683A was infused into brain ventricles, the feeding response to NPY was attenuated. 5. The present study shows that NPY stimulates feeding in guinea-pigs through Y(1) and Y(5) receptors. As the guinea-pig is very distantly related to the rat and mouse, this suggests that both Y(1) and Y(5) receptors may mediate NPY-induced hyperphagia also in other orders of mammals.     

The therapeutic potential of neuropeptide Y in central nervous system disorders with special reference to pain and sympathetically maintained pain

Neuropeptide Y (NPY), a widely distributed peptide, has been shown to have numerous effects in both the central and peripheral nervous systems. In particular, NPY has an important role in mediating analgesia and hyperalgesia by distinct central and peripheral mechanisms. At least six NPY receptor subtypes are known to exist and the development of subtype-specific ligands targeted at NPY receptors will offer novel therapeutic agents. This article will review the involvement of NPY in diverse pathologies of the nervous system, including pain, and will propose a role for NPY in the maintenance of sympathetically maintained pain.     

Changes of brain neuropeptide Y and its receptors in rats with flurazepam tolerance and dependence

AIM: Anticonvulsant tolerance and dependence are two obstacles that restrict the clinical use of benzodiazepines (BDZ). In order to explore the mechanism of these two adverse reactions, changes of neuropeptide Y (NPY) and its receptors in the hippocampus of rat models, in relation to flurazepam (FZP, a member of BDZ) tolerance and dependence, were investigated. METHODS: The mRNA of preproNPY and its receptors (Y1, Y2, and Y5) in the hippocampus were determined by competitive RT-PCR, and the distribution of NPY in the hippocampus was examined by immunohistochemistry. RESULTS: A decrease of preproNPY mRNA in the hippocampus was found in tolerant and dependent rats. The level of preproNPY mRNA in the hippocampus was reversely correlated with the degree of tolerance and dependence, measured by the threshold of pentylenetetrazol-induced seizures. Immunohistochemistry indicated a decrease of NPY-immunoreactive material in neurons of the CA1, CA3, and dentate gyrus regions of both tolerant and dependent rats. The mRNA of NPY receptors Y1 and Y5 decreased in tolerant rats but did not change in dependent rats. The mRNA of NPY receptor Y2 increased in tolerant rats but decreased in dependent rats. CONCLUSION: A decrease of NPY in the hippocampus might be involved in anticonvulsant tolerance and dependence following long-term treatment with FZP. Y1, Y2, and Y5 mRNA were also altered in FZP tolerance and dependence.     

Neuropeptide Y2 receptors as drug targets for the central regulation of body weight

During the past decade, a detailed understanding has emerged of the aminergic and peptidergic neural pathways present within the brain that regulate appetite. Central among the peptide regulators is neuropeptide Y (NPY), a potent orexigenic agent that acts through five different receptor subtypes. Efforts to find novel appetite suppressant drugs that inhibit the interaction of NPY with either the NPY Y1 or NPY Y5 receptor subtypes have proven disappointing. Attempts have now been made to identify an NPY Y2 stimulator that will suppress appetite. Within the hypothalamus, NPY Y2 receptors have a predominantly presynaptic location where they act to inhibit NPY release. Stimulation of NPY Y2 receptors with synthetic peptide ligands or the gut derived peptide PY3-36 has been shown to reduce food intake. The NPY Y2 receptor has a wide distribution both within the brain and in the periphery. Stimulation of the NPY Y2 subtype at these sites produces a wide array of effects unrelated to changes in food intake. In consequence, the administration of both endogenous and exogenous agonists of the NPY Y2 receptor is likely to cause side effects, particularly regarding pituitary hormone release, as well as on the cardiovascular and gastrointestinal systems. The possibility that long-term NPY Y2 agonism could cause bone thinning and retinal angiogenesis are of particular concern and will need to be investigated as drug discovery moves forward.     

Modulation of neuropeptide Y receptors for the treatment of obesity

Background: Neuropeptide Y (NPY) has been demonstrated to have critical roles in the physiological control of appetite and energy homeostasis through NPY Y1, Y2, Y4 and Y5 receptors. A number of synthetic ligands for NPY receptor subtypes have been developed to date, with Y5 receptor antagonists and Y2 and Y4 receptor agonists advancing into clinical trials. Methods: A survey of the scientific and patent literature since mid-2006 is presented. Conclusion: In addition to the specific modulation of respective NPY receptor subtypes, recent investigations have revealed that modulation of multiple NPY receptor subtypes produces additive or even synergistic anti-obesity effects. Development of reliable small molecule Y1, Y2 and Y4 receptor ligands would greatly accelerate investigations and drug discovery.     

Influence of endogenous neuropeptide Y (NPY) on the sympathetic-parasympathetic interaction in the canine heart

The purpose of this study was to examine the sympathetic-parasympathetic interactions on heart rate through release of neuropeptide Y (NPY) and its action on prejunctional NPY Y2 receptors on vagal and sympathetic nerve fibers. In other studies on various preparations and in various organs, attenuation of transmitter release has in fact been demonstrated through activation of the NPY Y2 receptor. In the present study on anesthetized dogs we examine, however, for the first time if vagal bradycardia is attenuated by endogenous NPY released during intense cardiac sympathetic stimulation. In addition, we explore if sympathetic transmitter release and heart rate, during moderate sympathetic stimulation, are affected through this receptor system. The significance of the NPY Y2 receptor was revealed by performing experiments before and after administration of its specific receptor antagonist BIIE0246. We found that attenuation of the bradycardia during vagal nerve stimulation was dose-dependently counteracted by BIIE0246 and that the tachycardia elicited by sympathetic stimulation remained unaffected after NPY Y2 receptor blockade. Thus, endogenous NPY appears to attenuate vagal bradycardia by stimulating prejunctional NPY Y2 receptors on cardiac vagal nerve terminals and, less efficiently, to attenuate transmitter release and tachycardia through a feedback loop on the cardiac sympathetic nerve fibers.     

Neuropeptide Y1 subtype pharmacology of a recombinantly expressed neuropeptide receptor.

Neuropeptide Y (NPY) is an important central and peripheral modulator of neural and endocrine functions. This neuropeptide interacts with at least two pharmacologically distinct receptors, termed Y1 and Y2. At Y1 receptors, the NPY analog [Leu31,Pro34] NPY, but not the carboxyl-terminal fragment NPY-(18-36), displaces radiolabeled NPY and the sequence-related peptide YY, whereas Y2 receptors exhibit the opposite selectivity. We have used cultured mammalian 293 cells for the high level transient expression of a previously cloned putative neuropeptide receptor of rat brain. We report that this receptor displays the ligand binding properties and selectivity of a Y1 receptor, with a single high affinity site for 125I-NPY (Kd, 0.7 +/- 0.2 nM). The functionality of the recombinantly expressed receptor was demonstrated by an inhibition of adenylyl cyclase and a concomitant mobilization of intracellular Ca2+.     

The putative neuroprotective role of neuropeptide Y in the central nervous system

Neuropeptide Y (NPY) is one of the most abundant and widely distributed neuropeptides in the mammalian central nervous system (CNS). An overview of the distribution of the G-protein coupled NPY receptor family (Y(1), Y(2), Y(4), Y(5) receptors) in the brain is described. The coexistence of NPY with other neurotransmitters and its wide distribution in several brain areas predict the high importance of NPY as a neuromodulator. Thus, the effect of NPY on the release of several neurotransmitters such as glutamate, gamma-aminobutyric acid (GABA), norepinephrine (NE), dopamine, somastotatin (SOM), serotonin (5-HT), nitric oxide (NO), growth hormone (GH) and corticotropin releasing factor (CRF) is reviewed. A neuroprotective role for NPY under physiological conditions and during hyperactivity such as epileptic-seizures has been suggested. We have shown previously that NPY inhibits glutamate release evoked from hippocampal nerve terminals and has a neuroprotective effect in rat organotypic hippocampal cultures exposed to an excitotoxic insult. Moreover, changes in NPY levels have been observed in different pathological conditions such as brain ischemia and neurodegenerative diseases (Huntington's, Alzheimer's and Parkinson's diseases). Taken together, these studies suggest that NPY and NPY receptors may represent pharmacological targets in different pathophysiological conditions in the CNS.     

Neuropeptide Y receptors as targets of obesity treatment

The prevalence of obesity continues to increase throughout the world and the burden of obesity and related co-morbidities is large. However, existing drug therapies for obesity are limited, and agents with high efficacy, safety and tolerability are expected to better meet patient needs and lead to more substantial commercial success. Neuropeptide Y (NPY) is thought to have a major role in the physiological control of energy homeostasis. Multiple receptor subtypes mediate the effects of NPY on energy homeostasis and many pharmacological studies indicate the involvement of Y1 and Y5 receptor subtypes in NPY-induced feeding and obesity. In addition, recent observations with gut-derived peptides suggest a role for Y2 and Y4 receptor subtypes as catabolic receptors. This article highlights and reviews recent observations and patents regarding NPY receptor ligands for drug discovery as antiobesity agents.     

Neuropeptide Y (NPY): functions and biosynthesis as a peptidergic neurotransmitter and the regulation of neuron-specific expression of NPY gene

Neuropeptide Y (NPY) is widely distributed in the central and sympathetic nervous systems and has a variety of central actions including regulation of blood pressure and peripheral actions; e.g., continuous vasoconstriction and inhibition of catecholamine release. The NPY receptor can be divided into 2 subclasses (Y1, Y2), and these subclasses are coupled to GTP binding proteins (Gi, Go, Gp ......). Recently, human and rat prepro-NPY mRNA and NPY gene structures have been determined by cDNA and genomic cloning and sequencing. The strong evolutionary conservation of these structures suggested that NPY is an essential peptidergic neurotransmitter. Little is known about the biosynthesis, processing, degradation of NPY and NPY gene expression. We showed that NPY gene expression and NPY biosynthesis are regulated by neural activity, hormone, and intracellular second messengers via neurotransmitter receptors. The change of NPY gene expression by these neural factors is considered to be a good model for a synaptic plasticity, because these changes cause the changes of synaptic transmission. Furthermore, because NPY is expressed in sympathetic neurons and its gene expression increased markedly on the differentiation of adrenergic cells, this study about NPY gene expression could provide good clues for elucidating the differentiation of sympathetic neurons.     

Neuropeptide Y2 receptors are involved in enhanced neurogenic vasoconstriction in spontaneously hypertensive rats

1. The present study addressed the role of neuropeptide (NPY) Y2 receptors in neurogenic contraction of mesenteric resistance arteries from female spontaneously hypertensive rats (SHR). Arteries were suspended in microvascular myographs, electrical field stimulation (EFS) was performed, and protein evaluated by Western blotting and immunohistochemistry. 2. In vasopressin-activated endothelium-intact arteries, NPY and fragments with selectivity for Y1 receptors, [Leu31,Pro34]NPY, Y2 receptors, NPY(13-36), and rat pancreatic polypeptide evoked more pronounced contractions in segments from SHR than in Wistar Kyoto (WKY) arteries, even in the presence of the Y1 receptor antagonist, BIBP3226 (0.3 microM, (R)-N(2)-(diphenacetyl)-N-[(4-hydroxyphenyl)methyl]D-arginineamide). 3. In the presence of prazosin and during vasopressin activation, EFS-evoked contractions were larger in arteries from SHR compared to WKY. EFS contractions were enhanced by the Y2 receptor selective antagonist BIIE0246TF (0.5 microM, (S)-N2-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6h)-oxodibenz[b,e]azepin-11-y1]-1-piperazinyl]-2-oxoethyl]cyclo-pentyl-N-[2-[1,2-dihydro-3,5 (4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamide), reduced by BIBP3226, and abolished by the combination of BIBP3226 and BIIE0246TF. 4. Immunoblotting showed NPY Y1 and Y2 receptor expression to be similar in arteries from WKY and SHR, although a specific Y2 receptor band at 80 kDa was detected only in arteries from WKY. 5. Immunoreaction for NPY was enhanced in arteries from SHR. In contrast to arteries from WKY, BIIE0246TF increased NPY immunoreactivity in EFS-stimulated arteries from SHR. 6. The present results suggest that postjunctional neuropeptide Y1 and Y2 receptors contribute to neurogenic contraction of mesenteric small arteries. Moreover, both enhanced NPY content and altered neuropeptide Y1 and Y2 receptor activation apparently contribute to the enhanced neurogenic contraction of arteries from SHR.     

The effect of intrahippocampal injection of group II and III metobotropic glutamate receptor agonists on anxiety; the role of neuropeptide Y.

Earlier studies conducted by our group and by other authors indicated that metabotropic glutamatergic receptor (mGluR) ligands might have anxiolytic activity and that amygdalar neuropeptide Y (NPY) neurons were engaged in that effect. Apart from the amygdala, the hippocampus, another limbic structure, also seems to be engaged in regulation of anxiety. It is rich in mGluRs and contains numerous NPY interneurons. In the present study, we investigated the anxiolytic activity of group II and III mGluR agonists after injection into the hippocampus, and attempted to establish whether hippocampal NPY neurons and receptors were engaged in the observed effects. Male Wistar rats were bilaterally microinjected with the group II mGluR agonist (2S,1'S,2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I), group III mGluR agonist O-Phospho-L-serine (L-SOP), NPY, the Y1 receptor antagonist BIBO 3304, and the Y2 receptor antagonist BIIE 0246 into the CA1 or dentate area (DG). The effect of those compounds on anxiety was tested in the elevated plus-maze. Moreover, the effects of L-CCG-I and L-SOP on the expression of NPYmRNA in the hippocampus were studied using in situ hybridization method. It was found that a significant anxiolytic effect was induced by L-SOP injection into the CA1 region or by L-CCG-I injection into the DG. The former effect was inhibited by BIBO 3304, the latter by BIIE 0246. NPY itself showed antianxiety action after injection into both structures. In the CA1 area, the effect of NPY was prevented by BIBO 3304, whereas in the DG by BIIE 0246. Both the mGluR agonists L-CCG-I and L-SOP induced a potent increase in NPYmRNA expression in the DG region of the hippocampal formation. The obtained results indicate that group II and III mGluR agonists, L-CCG-I and L-SOP, as well as NPY display anxiolytic activity in the hippocampus, but act differently in the CA1 and DG. It was observed that group III mGluRs and Y1 receptors were engaged in the response in the CA1 area, whereas group II mGluRs and Y2 receptors played a pivotal role in the DG region.     

Binding properties of three neuropeptide Y receptor subtypes from zebrafish: comparison with mammalian Y1 receptors

Neuropeptide Y (NPY) and peptide YY (PYY) are two related 36-amino-acid peptides found in all vertebrates and are involved in many physiological processes. Five receptor subtypes have been cloned in mammals (Y1, Y2, Y4, Y5, and y6). We have recently cloned three NPY/PYY receptor subtypes in zebrafish, called Ya, Yb, and Yc. Here we report on a direct comparison of the pharmacological properties of these three receptors in vitro using porcine NPY with alanine substitutions in positions 33–36 as ligands and three analogues with internal deletions: [Ahx^8–20]NPY, [Ahx^8–20, Pro³⁴]NPY, and [Ahx^5–24]NPY. In all cases, the zYc receptor was the most sensitive to the modifications of the NPY molecule and zYa was the least sensitive (except for the Arg → Ala replacement at position 33). Our data identified zYa as a receptor that can bind ligands specific for Y1, Y2, and Y4 receptors, while zYb and zYc were more Y1-like. All peptides with internal deletions bound to the zYa receptor with affinities similar to that of intact pNPY. Neither the Y1-selective antagonists BIBP3226 and SR120819A nor the Y2-selective BIIE0246 bound to any of the zebrafish receptors, although the amino acids identified as important for BIBP3226 binding were almost completely conserved. These results may prove helpful in molecular modeling of the three-dimensional receptor structure.