The dog saphenous vein: a sensitive and selective preparation for the Y2 receptor of neuropeptide Y

Chronic administration of the Y2 receptor antagonist, JNJ-31020028, induced anti-depressant like-behaviors in olfactory bulbectomized rat

Recent studies from our groups have shown that BIIE0246, a Y2 receptor antagonist, has antidepressant effect in olfactory bulbectomized (OBX) rat. However, its complex structure and high molecular weight limit its usefulness as an in vivo pharmacological tool. Alternatively, the novel and brain penetrant Y2 receptor antagonist, JNJ-31020028 is a useful tool to investigate the in vivo function of the Y2 receptor. In the present study, we evaluated the effect of chronic intracerebroventricular (icv) administration of JNJ-31020028 in a battery of behavioral tests in an animal model that mimics several deficits observed in the human depression, the OBX rat. Chronic administration of JNJ-31020028 induced a decrease in immobility time in the forced swim test in OBX while had no effect in control animals. Additionally, it decreased number of grooming events in OBX animals, but had no effects on some other behavioral deficits observed such as rearing and hyperlocomotion. Furthermore, JNJ-31020028 had no effect on behavior tests that are commonly used to evaluate anxiety, namely the social interaction test in both OBX and control animals. These data indicate that similar to BIIE0246, JNJ-31020028 also has antidepressant like effects in the OBX model.

Neuropeptide Y-induced enhancement of the evoked release of newly synthesized dopamine in rat striatum: Mediation by Y2 receptors

The purpose of the present study was to determine whether or not activation of neuropeptide Y (NPY) receptors resulted in an enhancement or attenuation of the KCl (50 mM) evoked release of [3H]dopamine newly synthesized from [3H]tyrosine in superfused striatal slices and, if so to identify the NPY receptor subtype mediating the effect. Rat striatal slices were prepared and placed in microsuperfusion chambers and continuously superfused with physiological buffer containing 50 microCi/ml of l-3-5-[3H]tyrosine. Superfusate effluents were collected and analyzed for [3H]dopamine by liquid scintillation spectrometry following amberlite CG50 and alumina chromatography. NPY agonists (NPY and PYY3-36) were added 6 min prior to the addition of KCl, while the Y1, Y2, and Y5 antagonist BIBO3304, BIIE0246 and CGP71683A, respectively were added 6 min prior to the agonists. Continuous superfusion with [3H]tyrosine resulted in the production of [3H]dopamine which reached a steady state at approximately 48 min. Depolarization with KCl resulted in a 2- to 3-fold increase in [3H]dopamine overflow. NPY and PYY3-36 produced a concentration dependent enhancement in the KCl induced increase in newly synthesized [3H]dopamine overflow. The Y2 antagonist BIIE0246 produced an attenuation of both the NPY and PYY3-36 induced enhancement while the Y1 antagonist BIBO3304 and theY5 antagonist CGP71683A failed to alter the NPY or PYY3-36 induced enhancement. These results are consistent with the NPY-Y2 receptor subtype mediating the facilitatory effect.

Potentiation by neuropeptide Y of 5HT2A receptor-mediated contraction in porcine coronary artery

Potentiation by neuropeptide Y of serotonin (5-HT)-induced vasoconstriction was investigated in porcine coronary artery. 5-HT caused concentration-dependent contraction through 5-HT2A receptors. Neuropeptide Y (30 nM) significantly increased the 5HT-induced contraction by 16+/-5% in arteries with intact endothelium. Removal of the endothelium abolished the potentiation. A neuropeptide Y1 antagonist, BIBP3226, blocked this neuropeptide Y-induced potentiation. In vessels with intact endothelium, the potentiation by neuropeptide Y was inhibited by in the presence of a cyclo-oxygenase inhibitor, indomethacin (30 microM), but not by the presence of ETA or ETB endothelin receptor antagonists or an NO synthase inhibitor, NG-nitro-L-arginine (L-NNA) (1 mM) at all. A thromboxane A2 (TXA2) synthase inhibitor, ozagrel, and prostanoid TP receptor antagonists, seratrodast and ONO-3708, also inhibited the neuropeptide Y-induced potentiation. In the endothelium-denuded arteries, a prostanoid TP receptor agonist, U-46619 (0.01-0.1 nM), potentiated 5-HT-induced contraction. These results indicate that neuropeptide Y potentiates the 5-HT-induced contraction, due to release of TXA2 from the endothelium via neuropeptide Y1 receptors, in porcine coronary artery.

Common neuropeptide Y2 receptor gene variant is protective against obesity among Swedish men

BACKGROUND

Gut hormones and their receptors are considered important in the control of feeding behavior. The gut hormone peptide-YY (PYY) has anorexic effects via the inhibitory neuropeptide Y2 receptor (Y2R) highly expressed in orexigenic NPY/AGRP neurons within the arcuate nucleus, a major integrator of appetite control in the hypothalamus.

DESIGN

Genetic case-control association study of single nucleotide polymorphisms (SNPs) in Y2R and PYY.

SUBJECTS

Swedish Caucasians comprising 148 lean, 129 overweight/obese and 226 morbidly obese men.

MEASUREMENTS

Genotypes of the common, silent and conserved SNP Y2R 585T>C and the common SNP PYY Arg72Thr, as well as various obesity-related clinical parameters.

RESULTS

Obese men had a lower allele and homozygosity frequency of the common allele 585T>C:T which was particularly evident comparing morbidly obese with lean men (P = 0.002), and analyzing dependence between continuous body mass index (BMI) and genotype (P = 0.002). In agreement, systolic blood pressure tended to be lower in those homozygous for allele T, which was not explained by the BMI - genotype dependence. We found no association to obesity for the PYY Arg72Thr polymorphism, which is located nearby the essential carboxy terminal.

CONCLUSION

A common and conserved variant of the PYY and NPY receptor Y2R is less prevalent among obese compared to among lean Swedish men. This suggests that the common Y2R variant is protective against obesity. Our findings further implicate Y2R in food intake regulation.

Neuropeptide Y selectively potentiates alpha1-adrenoceptor-mediated contraction through Y1 receptor subtype in rat femoral artery

The aim of this study was to investigate the synergism between neuropeptide Y and other vasoconstrictors (phenylephrine and serotonin) and which neuropeptide Y receptor subtype is responsible for the neuropeptide Y-induced potentiation. Exogenous neuropeptide Y (10 nM) potentiated alpha1-adrenoceptor-mediated (PE-induced) contraction in rat femoral artery permissively without its direct action, but not in the thoracic aorta. In contrast, neuropeptide Y produced no change in serotonin-induced contraction in both arteries. Increasing concentrations of neuropeptide Y caused dose-dependent potentiation of the phenylephrine-induced contraction in the femoral artery. This potentiation was blocked by a selective neuropeptide Y-Y1 receptor antagonist, BIBP3226 [(R)-N2-(diphenylacetyl)-N-[4-hydroxyphenyl)methyl]-argininamide] (1 microM). Semiquantitative reverse transcriptase polymerase chain reaction showed the selective expression of neuropeptide Y-Y1 receptor mRNA in the femoral artery. These findings indicated that the neuropeptide Y-induced selective potentiation of alpha1-adrenoceptor-mediated contraction is mediated through neuropeptide Y-Y1 receptor in rat femoral artery.

Marked neuropeptide Y-induced contractions via NPY-Y1 receptor and its desensitization in rat veins

The aim of this study was to investigate neuropeptide Y (NPY)-induced vasoconstrictions in rat blood vessels and which NPY receptor subtype is involved in vasoconstrictions. NPY produced marked contractions in rat common jugular, brachial, portal, femoral and tail veins, and vena cava inferior, whereas it produced little or no contractions in rat common carotid, brachial, femoral and tail arteries, and thoracic and abdominal aortae. The maximal NPY-induced contractions were larger than maximal phenylephrine (PE)-induced contractions in the veins. These NPY-induced contractions were blocked by the Y1 antagonists, SRL-21, and BIBP3226 but not by the Y5 antagonist, L-152804. A Y2 agonist, NPY (13-36), did not produce contractions. RT-PCR showed that NPY-Y1 was the only receptor subtype in the veins indicating that NPY-induced contractions are mediated through the Y1 receptor. Pretreatment with NPY showed a rapid and long-lasting desensitization of these contractions. The marked NPY-induced contractions and its desensitization in the veins suggest the physiological relevance of NPY in the venous circulation.

Neuropeptide Y and its receptors as potential therapeutic drug targets

Neuropeptide Y (NPY) is a 36-amino-acid peptide that exhibits a large number of physiological activities in the central and peripheral nervous systems. NPY mediates its effects through the activation of six G-protein-coupled receptor subtypes named Y(1), Y(2), Y(3), Y(4), Y(5), and y(6). Evidence suggests that NPY is involved in the pathophysiology of several disorders, such as the control of food intake, metabolic disorders, anxiety, seizures, memory, circadian rhythm, drug addiction, pain, cardiovascular diseases, rhinitis, and endothelial cell dysfunctions. The synthesis of agonists and antagonists for these receptors could be useful to treat several of these diseases.

Pharmacology of neuropeptide Y receptor antagonists. Focus on cardiovascular functions

Neuropeptide Y is one of the most abundant mammalian neuropeptides identified to date. The possible actions of neuropeptide Y, that is co-localized and released with noradrenaline, as a sympathetic co-transmitter has attracted much attention during the last decade. In recent years, several non-peptide antagonists with high subtype selectivity for neuropeptide Y receptors have been introduced. With them, the status of neuropeptide Y as a sympathetic transmitter has been established, and so have profound cardiovascular effects mediated by neuropeptide Y Y(1) and Y(2) receptors. Significant release of neuropeptide Y occurs especially upon stronger sympathetic activation, and recent data suggest that the importance of neuropeptide Y seems enhanced in stress-related cardiovascular disorders. The true significance of neuropeptide Y has thus started to unfold, owing to the presence of the first generation of selective neuropeptide Y receptor antagonists. This review concerns the pharmacology of these agents, what we have learnt from them, and might find out in the future.

Neuropeptide Y Y1 receptor mediated mesenteric vasoconstriction in the pig in vivo

The object of the present study was to investigate the effects of the sympathetic cotransmitter neuropeptide Y (NPY), and the closely related gut hormone peptide YY (PYY), on splanchnic blood flow regulation in the anaesthetized pig in vivo. Systemic injections of NPY, PYY and the NPY Y(1) receptor agonist [Leu(31)Pro(34)]NPY (470 pmol kg(-1) each) evoked pressor and mesenteric vasoconstrictor responses that were largely abolished by the selective NPY Y(1) receptor antagonist H 409/22 (60 nmol kg(-1) min(-1)). In contrast, the NPY Y(2) receptor agonist N-acetyl[Leu(28)Leu(31)]NPY(24-36) (1.1 nmol kg(-1)), a dose of which potently evoked splenic NPY Y(2) receptor mediated (not affected by H 409/22) vasoconstriction, did not evoke any mesenteric vascular response. Mesenteric vascular responses to angiotensin II (10 pmol kg(-1)), alpha,beta-methylene ATP (10 nmol kg(-1)) and the alpha(1)-adrenoceptor agonist phenylephrine (15 nmol kg(-1)), were not inhibited by H 409/22. It is concluded that NPY and PYY evokes porcine mesenteric vasoconstriction mediated by the NPY Y(1) receptor subtype, as demonstrated by selective and specific inhibition exerted by the NPY Y(1) receptor antagonist H 409/22, in vivo.

BIIE0246, a potent and highly selective non-peptide neuropeptide Y Y(2) receptor antagonist

1. BIIE0246, a newly synthesized non-peptide neuropeptide Y (NPY) Y(2) receptor antagonist, was able to compete with high affinity (8 to 15 nM) for specific [(125)I]PYY(3 - 36) binding sites in HEK293 cells transfected with the rat Y(2) receptor cDNA, and in rat brain and human frontal cortex membrane homogenates. 2. Interestingly, in rat brain homogenates while NPY, C2-NPY and PYY(3 - 36) inhibited all specific [(125)I]PYY(3 - 36) labelling, BIIE0246 failed to compete for all specific binding suggesting that [(125)I]PYY(3 - 36) recognized, in addition to the Y(2) subtype, another population of specific NPY binding sites, most likely the Y(5) receptor. 3. Quantitative receptor autoradiographic data confirmed the presence of [(125)I]PYY(3 - 36)/BIIE0246-sensitive (Y(2)) and-insensitive (Y(5)) binding sites in the rat brain as well as in the marmoset monkey and human hippocampal formation. 4. In the rat vas deferens and dog saphenous vein (two prototypical Y(2) bioassays), BIIE0246 induced parallel shifts to the right of NPY concentration-response curves with pA(2) values of 8.1 and 8.6, respectively. In the rat colon (a Y(2)/Y(4) bioassay), BIIE0246 (1 microM) completely blocked the contraction induced by PYY(3 - 36), but not that of [Leu(31), Pro(34)]NPY (a Y(1), Y(4) and Y(5) agonist) and hPP (a Y(4) and Y(5) agonist). Additionally, BIIE0246 failed to alter the contractile effects of NPY in prototypical Y(1) in vitro bioassays. 5. Taken together, these results demonstrate that BIIE0246 is a highly potent, high affinity antagonist selective for the Y(2) receptor subtype. It should prove most useful to establish further the functional role of the Y(2) receptor in the organism.

A study of NPY-mediated contractions of the porcine isolated ear artery

Enhanced contractions of the porcine isolated ear artery by the alpha2-adrenoceptor agonist UK14304 are uncovered by pharmacological manipulation. As both neuropeptide Y (NPY) receptors and alpha2-adrenoceptors are negatively-coupled to adenylyl cyclase in this tissue, we determined whether NPY is also able to produce an enhanced contraction in the same tissue, under the same conditions. NPY (0.1 microM) produced a small contraction of porcine isolated ear arteries which was 5.1+/-0.8% of the response to 60 mM KCl (n = 14). An enhanced NPY response was uncovered if the tissue was pre-contracted with 0.1 microM U46619, and relaxed back to baseline with 1-2 microM forskolin before the addition of NPY (49.8+/-5.3%, n = 14). Forskolin (1 microM) stimulated cyclic AMP accumulation in porcine ear artery segments in the presence of 0.1 microM U46619 and 1 mM isobutylmethylxanthine (IBMX), NPY (0.1 microM) inhibited this response by 40%, but had no effect on basal levels of cyclic AMP. An enhanced response to 0.1 microM NPY was also obtained after pre-contraction with 0.1 microM U46619 and relaxation with either SNP (28.9+/-5.7%, n = 14), or dibutyryl cyclic AMP (21.2+/-4.6%, n = 14). This indicates that at least part of the enhanced response to NPY is independent of the agonist's ability to inhibit adenylyl cyclase. In conclusion, an enhanced contraction to NPY in the porcine isolated ear artery can be obtained by prior pharmacological manipulation. The enhanced responses are mediated through adenylyl cyclase-dependent and independent pathways similar to those reported for alpha2-adrenoceptors in this preparation.

Adenosine 5'-triphosphate and neuropeptide Y are co-transmitters in conjunction with noradrenaline in the human saphenous vein

1. Human saphenous veins were used to assess the cooperative participation of adenosine 5-triphosphate (ATP), neuropeptide Y (NPY), and noradrenaline (NA) in the vasomotor responses elicited following electrical depolarization of the perivascular nerve terminals. Rings from recently dissected human biopsies were mounted to record isometric muscular contractions; the motor activity elicited in the circular muscle layer following electrical depolarization (2.5-20 Hz, 50 V, 0.5 msec) were recorded. 2. Incubation of the biopsies with either 100 nM tetrodotoxin (TTX) or 1 microM guanethidine abolished the vasomotor response elicited by electrical nerve depolarization. The independent application of either ATP or NA to vein rings induced concentration-dependent contractions. 3. Tissue incubation with 30 microM suramin or 10 nM prazosin produced 10 fold rightward displacements of the alpha,beta-methylene ATP and NA concentration-response curves respectively. NPY contracted a limited number of biopsies, the vasoconstriction elicited was completely blocked by 1 microM BIBP 3226. A 5 min incubation of the biopsies with 10-100 nM NPY synergized, in a concentration-dependent fashion, both the ATP and the ATP analogue-induced contractions. Likewise, tissue preincubation with 10 nM NPY potentiated the vasomotor responses evoked with 20-60 nM NA. 4. Neither suramin, BIBP 3226, nor prazosin was individually able to significantly modify the derived frequency-tension curves. In contrast, the co-application of 30 microM suramin and 10 nM prazosin or 30 microM suramin and 1 microM BIBP 3226, elicited a significant (P<0.01) downward displacement of the respective frequency-tension curves. 5. The simultaneous application of the three antagonists-30 microM suramin, 1 microM BIBP 3226 and 10 nM prazosin-caused a significantly greater displacement of the frequency-tension curve than that achieved in experiments using two of these antagonists. 6. Electrically-evoked vasomotor activity is blocked to a larger extent by tissue incubation with 2.5 microM chloroethylclonidine and 30 microM suramin rather than with 10 nM 5 methyl urapidil and 30 microM suramin. As a result, the alpha1-adrenoceptor involved in the vasomotor activity has tentatively been associated with the alpha1B adrenoceptor family subtype. 7. Results support the physiological role of ATP in sympathetic neurotransmission. The present results are consistent with the working hypothesis that human sympathetic vasomotor reflexes involve the coordinated motor action of ATP, NPY, and NA acting on vascular smooth muscle cells. The present results support the concept of sympathetic co-transmission in the human saphenous vein.

NPY receptor subtypes involved in the contraction of the proximal colon of the rat

Experiments were designed to determine the receptor subtype(s) involved in the contraction of the rat proximal colon to NPY. In this tissue, mRNA of Y2 and Y4 NPY receptor subtypes were highly expressed, whereas Y5 mRNA levels were very low and Y1 mRNA levels were intermediate. NPY analogues induced contractions with the following order of potency: rPP > hPP = PYY = NPY = [Leu31,Pro34]NPY > NPY(2-36) = [D-Trp32]NPY > NPY(33-36). Responses to NPY, PYY and NPY(13-36) were not or partially affected by tetrodotoxin, in contrast to the responses to [Leu31,Pro34]NPY, rPP, hPP and [D-Trp32]NPY which were fully blocked. Atropine did not inhibit the contractions to NPY, PYY and [Leu31,Pro34]NPY but significantly affected those to NPY(13-36), [D-Trp32]NPY, rPP and hPP. The specific Y1 receptor antagonist BIBP 3226 was ineffective but JCF 104 and JCF 105 (two compounds with preferential affinity toward the hY5 receptor versus the hY1 or hY2 receptor) abolished the contractions provoked by the NPY analogues. These results suggest that NPY activates three receptor subtypes, a Y2 subtype possibly by a direct action on the smooth muscle cells, as well as a Y4 and a Y5 (or 'Y5-like') subtype which, respectively, release acetylcholine and an unknown neurotransmitter.

Characterization of NPY receptors mediating contraction in rat intramyocardial coronary arteries

In vitro experiments in a microvascular myograph were designed in order to characterize the receptor subtypes and the mechanisms underlying the contractions induced by neuropeptide Y (NPY) in rat coronary small arteries. The rank order of potency for NPY-receptor agonist-induced increases in tension in endothelium-intact preparations was polypeptide Y (PYY)> NPY > or = [Leu31Pro34]NPY, while NPY(13-36) only induced small contractions at the highest concentration applied. The selective neuropeptide Y1 receptor antagonist, BIBP 3226, caused rightward shifts in the concentration-response curves for NPY and the slope of the Schild plot was not significantly different from unity. The pA2 value for BIBP 3226 against NPY was 7.88+/-0.15 (n = 6). We have earlier shown that endothelial cell removal does not change the contractile responses induced by NPY, but indomethacin (3 x 10(-6) M) significantly reduced the contractions induced by the peptide. In contrast, the thromboxane receptor antagonist, SQ29548, which abolished the contractions induced by the thromboxane analogue, U46619, did not change the concentration-response curves for NPY. In conclusion, the present study suggests that Y1 receptors mediate NPY-induced contractions in rat coronary resistance arteries, and that a non-thromboxane prostanoid is involved in the contractile mechanism.

Bioassays for NPY receptors: old and new

Classical pharmacology performed on isolated organ preparations is an essential tool for receptor characterization and classification. Basic pharmacological parameters (e.g. ED50, ID50, pD2, pA2 as measures of apparent affinities) obtained by relating the agent concentration with the biological effect are the final results of the various steps required for drug action and necessarily reflect the complex mechanisms of cell function. Results obtained with bioassays are therefore a useful and essential part in the assessment of endogenous systems, in the present case, the NPY family of peptides and their receptors. An attempt has been made, in the present review, to present a choice of isolated organs that may provide a starting point towards the construction of a solid classical pharmacology of receptors for NPY and congeners. Some of these organs appear to be 'monoreceptor systems' (e.g. the rabbit saphenous vein) whose response is contributed by a single receptor type, others (e.g. the rat colon) are 'multiple receptor systems' and their pharmacology is much too complex and requires the use of a variety of compounds from the naturally occuring peptides, to some selective agonists and when available, specific and selective antagonists. Such compounds have been utilised by us and other workers to detect specific biological responses to NPY and congeners in peripheral tissues: such responses have been quantified, carefully analysed in pharmacological terms and characterized as biological effects mediated by Y1 (the rabbit saphenous vein), Y2 (dog saphenous vein, rat vas deferens, rat colon), Y4 (rat colon) and Y5 (rabbit ileum) receptors. Compared to findings obtained with binding assays and molecular biology experiments, the results of the bioassays show very interesting similarities. Much remains however to be done in view of providing the classical pharmacological bases that are needed in the field of NPY.

Neuropeptide Y Y1 receptors in vascular pharmacology

The existence of neurogenic mediator candidates apart from noradrenaline and acetylcholine involved in the control of vascular tone has attracted enormous attention during the past few decades. One such mediator is neuropeptide Y (NPY), which is co-localized with noradrenaline in sympathetic perivascular nerves. Stimulation of sympathetic nerves in vitro and in vivo causes non-adrenergic vasoconstriction which can be blocked by experimental manipulations that inhibit NPY mechanisms. Thus, the vasopressor response to stimulation of sympathetic nerves can be attenuated by chemical or surgical sympathectomy, treatment with reserpine or other pharmacological agents, and tachyphylaxis to NPY or by NPY antagonists. The NPY field was long plagued by a lack of specific antagonists, but with the recently developed, selective, non-peptide and stable NPY antagonists it has now become possible to study subtypes of this receptor family. For instance, it has become clear that the NPY Y1 receptor mediates most of the direct peripheral effects of NPY on vascular tone. These antagonists promise to stimulate NPY research and will likely unravel the true significance of NPY in cardiovascular control under physiological conditions as well as in pathophysiological states.

Increased neuropeptide Y pressor activity in Goldblatt hypertensive rats: in vivo studies with BIBP 3226

Nanomoles of neuropeptide Y (NPY) and noradrenaline (NA), administered i.v. to pentobarbital-anesthetized rats, caused nearly equipotent dose-dependent pressor responses in normotensive rats. However, in renovascular Goldblatt hypertensive rats, the dose-response curves for both NPY and NA were significantly displaced to the left, approximately threefold. Intravenous administration of BIBP 3226 (30-180 microg/kg) did not consistently lower blood pressure, per se, but did evoke competitive antagonism of the NPY pressor response in both rat populations. The magnitude of the NPY antagonism evoked by BIBP 3226 was comparable in normotensive and hypertensive rats. The absence of NA antagonism demonstrates the selectivity of the BIBP 3226 blockade.