Different Regulation of Atrial ANP Release through Neuropeptide Y2 and Y4 Receptors

Neuropeptide Y (NPY) receptors are present in cardiac membranes. However, its physiological roles in the heart are not clear. The aim of this study was to define the direct effects of pancreatic polypeptide (PP) on atrial dynamics and atrial natriuretic peptide (ANP) release in perfused beating atria. Pancreatic polypeptides, a NPY Y₄ receptor agonist, decreased atrial contractility but was not dose-dependent. The ANP release was stimulated by PP in a dose-dependent manner. GR 23118, a NPY Y₄ receptor agonist, also increased the ANP release and the potency was greater than PP. In contrast, peptide YY (3-36) (PYY), an NPY Y₂ receptor agonist, suppressed the release of ANP with positive inotropy. NPY, an agonist for Y_{1, 2, 5} receptor, did not cause any significant changes. The pretreatment of NPY (18-36), an antagonist for NPY Y₃ receptor, markedly attenuated the stimulation of ANP release by PP but did not affect the suppression of ANP release by PYY. BIIE0246, an antagonist for NPY Y₂ receptor, attenuated the suppression of ANP release by PYY. The responsiveness of atrial contractility to PP or PYY was not affected by either of the antagonists. These results suggest that NPY Y₄ and Y₂ receptor differently regulate the release of atrial ANP.     

Inhibition of vasoconstriction and Ca2+ currents mediated by neuropeptide Y Y2 receptors.

The effects of neuropeptide Y (NPY) and agonists selective for NPY Y1 and Y2 receptors were studied on contraction and Ca2+ currents in arterial smooth muscle. In isolated arterioles from the guinea pig small intestine, small brief constrictions were evoked by depolarising the arteriolar smooth muscle using high K+ solution applied from a micropipette. The constrictions were reduced in amplitude by the Y2-selective agonists PYY(13-36) and N-acetyl[Leu28, Leu31]NPY-(24-36) in concentrations from 20-100 nM. NPY or the Y1 selective agonist [Leu31 Pro34]NPY in concentrations from 50 pM to 100 nM increased the amplitude of the constrictions, with a maximum effect at 10 nM. Smooth muscle cells were isolated from rat small mesenteric arteries, and voltage-activated Ca2+ currents measured by whole cell patch clamping. The peak amplitude of the Ca2+ currents was decreased by N-acetyl[Leu28, Leu31]NPY-(24-36), and by NPY (100 nM). [Leu31, Pro34]NPY either had no effect or slightly increased the Ca2+ currents. We conclude that Y2 receptors on vascular smooth muscle can reduce Ca2+ currents induced by depolarisation, and thus oppose constriction caused by smooth muscle depolarisation.     

N-methyl-D-aspartate receptor complex modulation by neuropeptide Y and peptide YY in rat hippocampus in vitro

Neuropeptide Y (NPY) and peptide YY (PYY) are known to bind with high affinity to sigma (sigma) and phencyclidine (PCP) binding sites in rat brain. The functional significance of these results was assessed by testing both peptides in an in vitro bioassay system used for studying the N-methyl-D-aspartate (NMDA) receptor and consisting of rat hippocampal slices preloaded with [3H]noradrenaline (NA) and maintained under superfusion. The addition of NMDA in the superfusion medium induced an efflux of [3H]NA from the slices and the presence of NPY and PYY produced an enhancement of the stimulating effect. These results suggest that NPY and PYY could have a modulatory role at the NMDA receptor complex through an interaction with the sigma and/or PCP receptor.     

Production and characterization of four anti-neuropeptide Y monoclonal antibodies.

Human neuropeptide Y (hNPY) is a potent vasoconstrictor peptide of 36 aminoacid residues. We isolated hybridomas secreting four monoclonal antibodies directed against various epitopes of neuropeptide Y and studied their cross-reactivity with peptide YY (PYY) and the pancreatic polypeptide (PP), two peptides sharing sequence homologies with hNPY (respectively 70% and 50%). The antibody NPY02 is an IgG1 with a Ka of 5.5 x 10(10) liters/mol. It binds to the 11-24 region of NPY (IC50 = 2 x 10(-7)M), does not recognize PP but cross-reacts weakly with PYY. Antibodies NPY03 and NPY05 are IgG2 with respective Ka's of 6.7 x 10(9) and 2.5 x 10(10) liters/mol. They interact with a C-terminal epitope on NPY (NPY 27-34, IC50 = 2 x 10(-9) M for NPY03 and NPY 32-36, IC50 = 1 x 10(-9) M for NPY05). These two antibodies cross-react with PYY whereas only NPY05 binds PP. NPY05 is unable to bind the free acid form of neuropeptide Y. The 32-36 COOH free subpeptide is recognized 50,000 less efficiently by NPY05 than its amidated form. Antibody NPY04 is an IgG3 with a Ka of 3.8 x 10(8) liters/mol. It recognizes a N-terminal epitope between aminoacids 1 and 12 (IC50 = 2.5 x 10(-6) M). NPY04 interacts weakly with PYY but not detectably with PP. These results obtained with 4 different monoclonal antibodies demonstrate the presence of at least four epitopes on hNPY, two of them being continuous. These antibodies will be used to study the interaction of NPY with its receptor and to develop sensitive and specific assays for determination of NPY concentrations in biological fluids.     

Functional autoradiography of neuropeptide Y Y1 and Y2 receptor subtypes in rat brain using agonist stimulated [35S]GTPgammaS binding

Neuropeptide Y, one of the most abundant brain peptides, has been found to modulate several important biological functions via a family of G-protein coupled receptors. To investigate the localization of functional NPY receptor subtypes in the rat brain, we performed agonist-induced [35S]GTPgammaS autoradiography. The Y1/Y4/Y5 agonist Leu(31), Pro(34)-NPY increased [35S]GTPgammaS binding in several brain areas with a regional distribution consistent with that produced when labeling adjacent sections with [125I]-Leu(31), Pro(34)-PYY. The Y1 selective antagonist BIBP3226 antagonized the Leu(31), Pro(34)-NPY stimulated increase in [35S]GTPgammaS binding in all areas examined. The Y2 agonist C2-NPY stimulated [35S]GTPgamma binding in numerous brain areas with a regional distribution similar to the binding observed with [125I]-PYY 3-36. No increase in [35S]GTPgammaS binding above basal was observed in any brain area evaluated using Y4 and Y5 selective agonists. This study demonstrates abundant Y1 and Y2 receptor activation in the rat brain, while evidence for functional Y4 and Y5 receptors was not observed.     

Neuropeptide Y suppresses epileptiform activity in rat frontal cortex and hippocampus in vitro via different NPY receptor subtypes.

Neuropeptide Y (NPY) and different NPY receptor (Y) subtype-selective agonists were tested for their effects on spontaneous epileptiform discharges which developed in rat cortical and hippocampal slices in Mg(2+)-free medium. Epileptiform activity, recorded extracellularly, was attenuated by NPY (0.5-1 microM) in both the frontal cortex and hippocampal CA3/CA1 pyramidal cell layers. In the cortex the Y1/5 selective agonist [Leu31 Pro34] NPY was more effective than the Y2 preferring agonist NPY13-36 and the Y2/5 preferring agonist NPY3-36. The suppression of epileptiform discharges induced by NPY in cortical slices was blocked by the selective Y1 receptor antagonist (R)-N2-(diphenylacetyl)-N-((4-hydroxyphenyl)methyl] argininamide (BIBP 3226). In the hippocampus, NPY13-36 and NPY3-36 were more effective than [Leu31 Pro34] NPY. In conclusion, the antiepileptic activity of NPY is mediated predominantly by the Y1 receptor subtype in the frontal cortex and by Y2 and probably Y5 receptors in the hippocampal CA3/CA1 areas.     

Neuropeptide Y stimulates food consumption through multiple receptors in goldfish

In this study, the acute effects of brain intracerebroventricular (icv) injections of mammalian neuropeptide Y (NPY) Y1 ([31Leu,34Pro]NPY), Y2 (NPY2-36) and Y5 ([D-32Trp]NPY) receptor subtype agonists on food intake in goldfish were examined. Icv injection of Y1 and Y5 receptor agonists in dosages of 1 and 5 ng/g exhibited dose-dependent effects on food intake; however, higher dosages of both receptor subtypes had desensitising effects on food intake, and caused a decrease in food intake in comparison to the lower dosages. At 10 and 20 ng/g, Y1 receptor agonist-treated fish exhibited feeding significantly lower than intact and saline-injected fish; fish treated with the same dosages of Y5 agonist exhibited food intake similar to intact and saline-injected fish. Y2 agonist had no effects on food intake. Co-icv administration of Y1 and Y5 agonists in dosages of 1 and 5 ng/g caused enhanced food intake that was additive of the individual doses alone. However, desensitising one receptor did not influence the responsiveness of the other. Co-icv injection of Y1 receptor agonist in desensitizing high dosages (10 and 15 ng/g) with Y5 receptor agonist in lower doses (1 and 5 ng/g, respectively) or vice versa, resulted in a food intake similar to the dosages of Y1 and Y5 receptor agonists at 1 and 5 ng/g given alone. Overall, this study demonstrates that NPY acts centrally through Y1 and Y5 receptors to stimulate food intake in goldfish. The Y1 and Y5 receptors appear to act independently in the stimulation of food intake in goldfish.     

Structure-function analysis of stimulation of food intake by neuropeptide Y: effects of receptor agonists.

Neuropeptide Y (NPY) is a potent natural orexigenic signal in the rat. In this study, we have compared the effects of several COOH-terminal fragments of NPY and NPY receptor agonists on cumulative food intake in male rats. Rats were implanted with permanent cannulae either into the third cerebroventricle or paraventricular nucleus (PVN). NPY1-36 and various COOH-terminal fragments of NPY, two agonist analogues [Leu31, Pro34]NPY and NPY 1-4-Aca (epsilon-amino-caproic acid)-25-36, were administered intracerebroventricularly (ICV) or directly into the PVN, and the cumulative 2-h food intake response was compared. We observed that peptides that were effective by ICV were also effective when administered into the PVN, but smaller amounts of the peptides were required after PVN injection to evoke an equivalent food intake response. Injection of NPY1-36 induced a dose-dependent increment in food intake. Surprisingly, deletion of NH2-terminal tyrosine residue did not adversely affect feeding behavior. In fact, NPY2-36 was consistently more effective than NPY1-36; the enhancement in feeding by NPY2-36 was dose-related and was higher than evoked by NPY1-36 at each dose tested. Further serial deletion of aminoacids at NH2-terminal resulted in complete loss of activity. In addition, NPY agonist analogue, NPY 1-4-Aca-25-36, failed to stimulate feeding. However, NPY Y1 receptor agonist, [Leu31, Pro34]NPY, but not Y2 receptor agonist, NPY13-36, stimulated feeding.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuropeptide Y(5) receptors reduce synaptic excitation in proximal subiculum, but not epileptiform activity in rat hippocampal slices

Neuropeptide Y (NPY) potently inhibits excitatory synaptic transmission in the hippocampus, acting predominantly via a presynaptic Y(2) receptor. Recent reports that the Y(5) receptor may mediate the anticonvulsant actions of NPY in vivo prompted us to test the hypothesis that Y(5) receptors inhibit synaptic excitation in the hippocampal slice and, furthermore, that they are effective in an in vitro model of anticonvulsant action. Two putative Y(5) receptor-preferring agonists inhibited excitatory postsynaptic currents (EPSCs) evoked by stimulation of stratum radiatum in pyramidal cells. We recorded initially from area CA1 pyramidal cells, but subsequently switched to cells from the subiculum, where a much greater frequency of response was observed to Y(5) agonist application. Both D-Trp(32)NPY (1 microM) and [ahx(8-20)]Pro(34)NPY (3 microM), a centrally truncated, Y(1)/Y(5) agonist we synthesized, inhibited stimulus-evoked EPSCs in subicular pyramidal cells by 44.0 +/- 5.7% and 51.3 +/- 3.5% (mean +/- SE), in 37 and 58% of cells, respectively. By contrast, the less selective centrally truncated agonist, [ahx(8-20)] NPY (1 microM), was more potent (66.4 +/- 4.1% inhibition) and more widely effective, suppressing the EPSC in 86% of subicular neurons. The site of action of all NPY agonists tested was most probably presynaptic, because agonist application caused no changes in postsynaptic membrane properties. The selective Y(1) antagonist, BIBP3226 (1 microM), did not reduce the effect of either more selective agonist, indicating that they activated presynaptic Y(5) receptors. Y(5) receptor-mediated synaptic inhibition was more frequently observed in slices from younger animals, whereas the nonselective agonist appeared equally effective at all ages tested. Because of the similarity with the previously reported actions of Y(2) receptors, we tested the ability of Y(5) receptor agonists to suppress stimulus train-induced bursting (STIB), an in vitro model of ictaform activity, in both area CA3 and the subiculum. Neither [ahx(8-20)]Pro(34)NPY nor D-Trp(32)NPY were significantly effective in suppressing or shortening STIB-induced afterdischarge, with <20% of slices responding to these agonists in recordings from CA3 and none in subiculum. By contrast, 1 microM each of [ahx(8-20)]NPY, the Y(2) agonist, [ahx(5-24)]NPY, and particularly NPY itself suppressed the afterdischarge in area CA3 and the subiculum, as reported earlier. We conclude that Y(5) receptors appear to regulate excitability to some degree in the subiculum of young rats, but their contribution is relatively small compared with those of Y(2) receptors, declines with age, and is insufficient to block or significantly attenuate STIB-induced afterdischarges.     

Forebrain sites of NPY action on estrous behavior in Syrian hamsters

Food deprivation and similar metabolic challenges inhibit estrous behavior in female Syrian hamsters. The relevant metabolic cues appear to be detected in the hindbrain, and this information is then relayed synaptically to the forebrain circuits controlling estrous behavior. Neuropeptide Y (NPY) may be one of the neuropeptides/neurotransmitters serving this function. Infusion of NPY or the Y2/Y5 agonist, peptide YY3-36 (PYY3-36), into the lateral ventricles rapidly inhibits estrous behavior in ovariectomized, steroid-primed hamsters. This experiment sought to determine the neural loci where NPY acts to inhibit estrous behavior. Steroid-primed animals received infusions of artificial cerebrospinal fluid (aCSF) vehicle, 0.024 nmol PYY3-36 and 0.24 nmol PYY3-36 in separate tests 30 min prior to testing for sexual receptivity. Infusion of 0.24 nmol, but not 0.024 nmol, of PYY3-36 reduced lordosis duration when infused into the paraventricular nucleus of the hypothalamus (PVN), the caudal part of the medial preoptic area (MPO), the anterior hypothalamus (AH) or the lateral ventricles. Placements in the ventromedial hypothalamus (VMH), the arcuate nucleus (ARC) and the fourth ventricle were generally without effect. These data suggest that increased endogenous release of NPY into the caudal MPO-AH-PVN continuum during food deprivation could contribute to the observed inhibition of sexual receptivity. The possible contributions of other neuropeptides and neural estrogen receptors to this action of NPY are discussed.     

Decreased levels of neuropeptide Y(5) receptor binding sites in two experimental models of epilepsy

It has been suggested that the anticonvulsant effects of neuropeptide Y (NPY) could be mediated by the activation of Y(2) and/or Y(5) receptors. NPY Y(1) receptor levels are known to decrease and Y(2) to increase in rat models of epilepsy. By using an autoradiographic approach, we investigated whether epilepsy models (kainic acid and kindling) are also associated with changes in Y(5) receptors. Compared with naive controls, [125I][Leu(31), Pro(34)]PYY/BIBP3226-insensitive (Y(5)) binding sites in the hippocampus (strata oriens and radiatum of CA3 and CA1) and in the neocortex (superficial layers) were unchanged in sham-stimulated rats, but reduced by approximately 50% in kindled rats (seven days after the last stimulus evokes seizure), and further reduced (to approximately -90%) 1h after a kindled seizure. Additionally, Y(5) receptor binding sites in the hippocampus and in the neocortex were unchanged 6h after kainic acid injection, but were highly reduced at 12 and 24h. No changes in Y(5) binding levels were found in the dentate gyrus and the pyramidal cell layer of the hippocampus.The present data suggest that changes in Y(5) receptor levels occur in epilepsy models. These changes may play a role in seizure expression and/or in the maintenance of kindling hyperexcitability.     

Neuropeptide Y and peptide YY inhibit adenylate cyclase activity in the rat striatum

The equilibrium binding of [3H]propionyl neuropeptide Y ([ 3H]pNPY) to receptors in a crude synaptic membrane preparation from the rat striatum was influenced by GTP, which caused an apparent loss of high-affinity binding sites for [3H]pNPY. In the presence of GTP (10(-5) M), NPY and peptide YY (PYY) inhibited basal and forskolin-stimulated adenylate cyclase activity in a concentration-dependent manner in a cell-free preparation from rat striatum. The IC50 values for NPY and PYY were 1 X 10(-8) M and 1.4 x 10(-8) M respectively. The inhibitory action of NPY (10(-6) M) or of PYY (10(-6) M) was additive to that of acetylcholine (10(-4) M). The two peptides together also showed additivity (P less than 0.05) in inhibiting adenylate cyclase.     

Regional differences in the effect of guanine nucleotides on agonist and antagonist binding to adenosine A1-receptors in rat brain, as revealed by autoradiography

The effect of increasing doses of GTP on agonist and antagonist binding to adenosine A1-receptors in different regions of rat brain was studied by autoradiography. A high concentration of GTP (100 microM) practically eliminated the binding of the agonist [3H]N6-cyclohexyladenosine in all regions. However, there were regional differences in the effects of low concentrations of GTP (0.1-10 microM). In some regions, for example the hippocampus, all concentrations of GTP decreased [3H]N6-cyclohexyladenosine binding, by decreasing the Bmax. In other structures, e.g. the superior colliculus, there was a biphasic response to GTP. Concentrations of 0.1-3 microM increased agonist binding, apparently due to a decrease in KD, whereas higher concentrations also decreased binding in these regions. The effects of GTP were mimicked by the stable GTP analogue guanosine-5'-O-(3-thiotriphosphate). GTP (0.5-100 microM) increased the binding of the antagonist [3H]8-cyclopentyl-1,3-dipropylxanthine in all regions, but most markedly in those where GTP had a biphasic effect on agonist binding. Decreasing the levels of endogenous adenosine by increasing the concentration of adenosine deaminase and adding the 5'-nucleotidase inhibitor alpha-beta-methylene adenosine-5'-diphosphate gave an increase in [3H]8-cyclopentyl-1,3-dipropylxanthine binding and diminished the response to GTP. In sections treated with adenosine deaminase and alpha-beta-methylene adenosine-5'-diphosphate, GTP steadily decreased [3H]N6-cyclohexyladenosine binding in all regions. Thus, the GTP-induced increase in both agonist and antagonist binding may be due to a displacement of endogenous adenosine. In the presence of 1 mM EDTA, GTP had a monophasic effect on the binding of [3H]N6-cyclohexyladenosine in all regions. In the presence of 2 mM MgCl2 a biphasic response to GTP was seen in all regions. In EDTA washed sections, the effect of MgCl2 on [3H]N6-cyclohexyladenosine binding was more pronounced in the superior colliculus, where we had observed a biphasic response to GTP. The results suggest that there are regional differences in the effects of GTP on adenosine A1-receptor binding in rat brain, that reflect regional differences in the magnesium-dependent binding of endogenous adenosine, which is bound to the receptor by tight binding, is very difficult to remove, and easily interferes with radioligand binding in in vitro experiments. There may be regional differences in the sensitivity of A1-receptor-G-protein complexes to magnesium, that reflect a heterogeneity of the G-proteins to which the A1-receptors are coupled.     

Neuropeptide Y promotes neurogenesis in murine subventricular zone

Stem cells of the subventricular zone (SVZ) represent a reliable source of neurons for cell replacement. Neuropeptide Y (NPY) promotes neurogenesis in the hippocampal subgranular layer and the olfactory epithelium and may be useful for the stimulation of SVZ dynamic in brain repair purposes. We describe that NPY promotes SVZ neurogenesis. NPY (1 microM) treatments increased proliferation at 48 hours and neuronal differentiation at 7 days in SVZ cell cultures. NPY proneurogenic properties are mediated via the Y1 receptor. Accordingly, Y1 receptor is a major active NPY receptor in the mouse SVZ, as shown by functional autoradiography. Moreover, short exposure to NPY increased immunoreactivity for the phosphorylated form of extracellular signal-regulated kinase 1/2 in the nucleus, compatible with a trigger for proliferation, whereas 6 hours of treatment amplified the phosphorylated form of c-Jun-NH(2)-terminal kinase signal in growing axons, consistent with axonogenesis. NPY, as a promoter of SVZ neurogenesis, is a crucial factor for future development of cell-based brain therapy. Disclosure of potential conflicts of interest is found at the end of this article.     

Characterization of NPY mRNA-expressing cells in the human brain: co-localization with Y2 but not Y1 mRNA in the cerebral cortex, hippocampus, amygdala, and striatum

Neuropeptide Y (NPY) is one of the most abundant peptides in the central nervous system. Its effects on, for example, cognition, memory and motor functions are thought to be mediated mainly via its interactions with the NPY Y1 and Y2 receptor subtypes. We had previously described the neuroanatomical organization of the Y1 and Y2 mRNA expression in humans. However, in view of the lack of information regarding the overall detailed distribution of NPY mRNA expression in the human brain, a complete picture of the anatomical organization of the NPY-related genes was still missing. Thus, in the present study, the regional distribution of NPY mRNA-expressing cells was analyzed in the post-mortem human brain. In addition, double labeling in situ hybridization was performed to characterize the NPY neuronal populations in relation to the Y1 and/or Y2 receptor mRNA localization in the human cerebral cortex, striatum, and amygdala. NPY mRNA was found to be abundant in layers II and VI of the neocortex, polymorphic layer of the dentate gyrus, basal ganglia, and amygdala. Double labeling in situ hybridization showed the co-expression of NPY mRNA with the Y2, but not with the Y1, mRNA in the human cerebral cortex, hippocampus, amygdala, striatum, and nucleus accumbens, and the existence of co-expression of the Y1 and Y2 mRNAs in the cerebral cortex and amygdala. Overall, these results suggest a role for the Y2, but not Y1, as an autoreceptor in the NPY neuronal populations of the human brain.     

Involvement of peripheral neuropeptide Y receptors in sympathetic modulation of acute cutaneous flare induced by intradermal capsaicin

In a recent study, we have demonstrated that the dorsal root reflex (DRR)-mediated acute cutaneous neurogenic inflammation following intradermal injection of capsaicin (CAP) is sympathetically dependent and subject to modulation by peripheral alpha(1)-adrenoceptors. Postganglionic sympathetic neurons contain not only adrenergic neurotransmitters, but also non-adrenergic substances, including neuropeptide Y (NPY). In this study, we examined if peripheral NPY receptors participate in the flare following CAP injection. Different NPY receptor subtypes were studied by using relatively specific agonists and antagonists for the Y(1) and Y(2) subtypes. Changes in cutaneous blood flow on the plantar surface of the foot were measured using a laser Doppler flowmeter. Following CAP injection, cutaneous flare spread more than 20 mm away from the site of CAP injection. Removal of the postganglionic sympathetic nerves by surgical sympathectomy reduced dramatically the CAP-evoked flare. If the foot of sympathectomized rats was pretreated with either NPY or Y(2) receptor agonists by intra-arterial injection, the spread of flare induced by CAP injection could be restored and prolonged. However, if the spinal cord was pretreated with a GABA(A) receptor antagonist, bicuculline, to prevent DRRs, NPY or an Y(2) receptor agonist no longer restored the CAP-evoked flare. A Y(1) receptor agonist did not affect the CAP-evoked flare in sympathectomized rats. In sympathetically intact rats, blockade of either peripheral NPY or Y(2) receptors with [D-Trp(32)]-NPY or BIIE0246 markedly reduced the flare induced by CAP injection, whereas blockade of peripheral Y(1) receptors by BIBP3226 did not obviously affect the flare. It is suggested that NPY is co-released with NE from the postganglionic sympathetic terminals to activate NPY Y(2) and alpha(1) receptors following CAP injection. Both substances are involved, at least in part, in modulation of the responses of CAP sensitive afferents thereby affecting their ability to evoke the release of inflammatory agents from primary afferents.     

Distinct effects of NPY13-36, a specific NPY Y2 agonist, in a model of rodent endotoxemia on leukocyte subsets and cytokine levels

Even now, sepsis remains a major problem in modern clinical medicine, leading to systemic inflammatory response including altered leukocyte subset distribution and increased cytokine release. As immune cells are known to express NPY receptors, we investigated the effects of a specific NPY Y(2) receptor agonist (NPY(13-36)) and/or the corresponding Y(2) receptor antagonist BIIE0246 treatment on blood (by FACS analyses) and tissue (by immunohistochemistry) leukocyte subsets as well as on levels of IL-4, IL-6, IL-10, TNF-α, INF-γ (by Cytometric Bead Array) in healthy and acutely endotoxemic rats. Results show a significant decrease in blood monocytes after LPS challenge in endotoxemic control animals (by 93%), in endotoxemic NPY(13-36) treated animals (by 83%) and in endotoxemic BIIE0246 treated animals (by 88%) as compared to the corresponding healthy controls. Endotoxemic control animals showed a significant increase of TNF-α (by 98%) as compared to the healthy control group. A treatment with NPY(13-36) significantly stabilized TNF-α level in endotoxemic animals. This study indicates distinct subset- and cytokine-specific in vivo effects induced by an NPY Y(2) receptor specific treatment after a short-term LPS challenge.     

Y5 receptors mediate neuropeptide Y actions at excitatory synapses in area CA3 of the mouse hippocampus.

Neuropeptide Y (NPY) is a potent modulator of excitatory synaptic transmission and limbic seizures. NPY is abundantly expressed in the dentate gyrus and is thought to modulate hippocampal excitability via activation of presynaptic Y2 receptors (Y2R). Here we demonstrate that NPY, and commonly used Y2R-preferring (NPY(13-36)) and Y5 receptor (Y5R)-preferring ([D-Trp(32)]NPY and hPP) peptide agonists, evoke similar levels of inhibition at excitatory CA3 synapses in hippocampal slices from wild-type control mice (WT). In contrast, NPYergic inhibition of excitatory CA3 synaptic transmission is absent in mice lacking the Y5R subtype (Y5R KO). In both analyses of evoked population spike activity and spontaneous excitatory postsynaptic synaptic currents (EPSCs), NPY agonists induced powerful inhibitory effects in all hippocampal slices from WT mice, whereas these peptides had no effect in slices from Y5R KO mice. In slices from WT mice, NPY (and NPY receptor-preferring agonists) reduced the frequency of spontaneous EPSCs but had no effect on sEPSC amplitude, rise time, or decay time. Furthermore, NPYergic modulation of spontaneous EPSCs in WT mice was mimicked by bath application of a novel Y5R-selective peptide agonist ([cpp]hPP) but not the selective Y2R agonist ([ahx(5-24)]NPY). In situ hybridization was used to confirm the presence of NPY, Y2, and Y5 mRNA in the hippocampus of WT mice and the absence of Y5R in knockout mice. These results suggest that the Y5 receptor subtype, previously believed to mediate food intake, plays a critical role in modulation of hippocampal excitatory transmission at the hilar-to-CA3 synapse in the mouse.     

Adrenoceptors mediating contraction in the human uterine artery

Pharmacological characterization of adrenoceptors mediating smooth muscle contraction was performed in isolated preparations from the human uterine artery. The mixed alpha 1- and alpha 2-adrenergic agonist, noradrenaline (NA) and the selective alpha 1-agonists, phenylephrine and methoxamine, all contracted the smooth muscle preparations in a concentration-dependent manner. The responses were antagonized competitively by the selective alpha 1-antagonist, prazosin, yielding pA2 values for the three agonists (8.33-9.08) typical for an interaction with alpha 1-receptors. The alpha 2-selective receptor agonists, clonidine and BHT 920, did not exert any contractile effects in the isolated uterine arteries, and the alpha 2-adrenergic antagonist, yohimbine, counteracted the contractile effect of NA only at high concentrations. The concentration-response curve for NA was unaffected by the alpha 2-selective antagonists, rauwolscine and idazoxan. The results suggest that the postjunctional contractile receptors in the human uterine artery primarily are of the alpha 1 type, and give no evidence for any substantial involvement of alpha 2-receptors in this important tributary vessel of the human female reproductive tract.