Neuropeptide Y (NPY)-induced feeding behavior in female rats: comparison with human NPY ([Met17]NPY), NPY analog ([norLeu4]NPY) and peptide YY

Porcine neuropeptide Y (pNPY) administered into the third ventricle of the brain is known to elicit a powerful feeding response in steroid-treated ovariectomized and intact male rats. The present study compared the effects of pNPY and 3 structurally related peptides, human NPY (hNPY), an analog of NPY (NPY-A, [norLeu4]NPY) and peptide YY (PYY) on feeding behavior in intact female rats. Intraventricular administration of pNPY, hNPY, NPY-A and PYY over a dose range of 0.5 to 10 micrograms evoked feeding behavior to a varying extent. Cumulative food intake during 60 and 120 min was increased in a dose-related fashion at 0.5 and 2.0 microgram for the 4 peptides. Whereas the 10-micrograms dose of pNPY evoked a feeding response smaller than that seen after 2 micrograms, the responses to either 10 micrograms hNPY or 10 micrograms PYY were similar to that seen after 2 micrograms. The effects of these peptides on the time spent eating were quite different: while pNPY increased the time spent eating, this effect was not dose-related, whereas hNPY, NPY-A and PYY produced dose-related increments in the time spent eating. The most dramatic increment in local eating rate was observed after 2.0 micrograms pNPY, with lesser increments seen after 2.0 microgram hNPY and NPY-A. This increased local eating was apparently responsible for the highest cumulative food intake observed. These results demonstrate that (a) 2 micrograms pNPY is equally effective in stimulating feeding behavior in intact female rats as it is in steroid-primed ovariectomized female and intact male rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuropeptide Y (NPY) in alcohol intake and dependence

Neuropeptide Y has a role in alcohol intake and dependence. NPY's effect on alcohol intake appears to be in part dependent on the individual's history of alcohol dependence. In models of high intake such as alcohol-preferring, selectively bred rat lines (e.g., the P-line and the HAD line), as well as in ethanol-vapor-exposed subjects, NPY modulates alcohol intake while leaving it unaffected during baseline conditions. The primary receptor subtype mediating NPY's effect on ethanol intake remains in question. The Y2-antagonist BIIE0246 significantly suppresses ethanol intake in an operant paradigm with a sensitization to the effect of BIIE0246 in vapor-exposed subjects. We propose the NPY system to be one of the most interesting target systems for the development of treatments for alcohol abuse and dependence.     

Neuropeptide Y (NPY) immunoreactive neurons in the retina of different species

Summary Neurons displaying Neuropeptide Y (NPY) immunoreactivity were found among amacrine cells in the retina of baboon, pig, cat, pigeon, chicken, frog, trout, carp and goldfish. The immunoreactive cell bodies were located in the middle and the innermost cell rows of the inner nuclear layer with processes forming one, two or three more or less well-defined sublayers in the inner plexiform layer. The location and the density of the sublayers varied with the species investigated. In the frog retina, bipolar-like cell bodies were found in the middle of the inner nuclear layer as well as sparsely occurring ovoid cell bodies in the ganglion cell layer. Like the amacrine cells, these cells emitted processes ramifying in three sublayers in the inner plexiform layer.     

Neuropeptide Y (NPY) immunoreactive neurons in the retina of different species

Neurons displaying Neuropeptide Y (NPY) immunoreactivity were found among amacrine cells in the retina of baboon, pig, cat, pigeon, chicken, frog, trout, carp and goldfish. The immunoreactive cell bodies were located in the middle and the innermost cell rows of the inner nuclear layer with processes forming one, two or three more or less well-defined sublayers in the inner plexiform layer. The location and the density of the sublayers varied with the species investigated. In the frog retina, bipolar-like cell bodies were found in the middle of the inner nuclear layer as well as sparsely occurring ovoid cell bodies in the ganglion cell layer. Like the amacrine cells, these cells emitted processes ramifying in three sublayers in the inner plexiform layer.     

Neuropeptide Y (NPY) and NPY receptors in the cardiovascular system: implication in the regulation of intracellular calcium

The 3-dimensional confocal microscopy technique has allowed us to identify the presence of yet another cardioactive factor and its receptor, namely neuropeptide Y (NPY) and its Y1 receptor, at the level of vascular smooth muscle cells and heart cells including endocardial endothelial cells (EECs). Using this technique, we also demonstrated that NPY is able to induce an increase in both cytosolic and nuclear calcium in all these cell types. Furthermore, besides being expressed at the level of EECs, NPY is also released from these cells following a sustained increase of intracellular Ca2+. This suggests the ability of NPY to contribute to the regulation of the excitation-secretion coupling of EECs and the excitation-contraction coupling of cardiomyocytes and vascular smooth muscle cells.     

Neuropeptide Y (NPY) and peptide YY (PYY) receptors in rat brain

1. Specific binding sites for neuropeptide Y (NPY) and peptide YY (PYY) were investigated in rat brain areas using quantitative receptor autoradiography with 125I-Bolton-Hunter NPY (125I-BH-NPY) and 125I-PYY, radioligands for PP-fold family peptides receptors. 2. There were no differences between localization of 125I-BH-NPY and 125I-PYY binding sites in the rat brain. High densities of the binding sites were present in the anterior olfactory nucleus, lateral septal nucleus, stratum radiatum of the hippocampus, posteromedial cortical amygdaloid nucleus, and area postrema. 3. In cold ligand-saturation experiments done in the presence of increasing concentrations of unlabeled NPY and PYY, 125I-BH-NPY and 125I-PYY binding to the stratum radiatum of the hippocampus, layer I of the somatosensory frontoparietal cortex, molecular layer of the cerebellum, and area postrema was single and of a high affinity. There was a significant difference between the affinities of 125I-BH-NPY (Kd = 0.96 nM) and 125I-PYY binding (Kd = 0.05 nM) to the molecular layer of the cerebellum. The binding of the two radioligands to the other areas examined had the same affinities. 4. When comparing the potency of unlabeled rat pancreatic polypeptide (rPP), a family peptide of NPY and PYY, to inhibit the binding to the areas examined, rPP displaced 125I-BH-NPY and 125I-PYY binding to the area postrema more potently than it did the binding to the stratum radiatum of the hippocampus, layer I of the somatosensory frontoparietal cortex, and molecular layer of the cerebellum. 5. Thus, the quantitative receptor autoradiographic method with 125I-BH-NPY and 125I-PYY revealed differences in binding characteristics of specific NPY and PYY binding sites in different areas of the rat brain. The results provide further evidence for the existence of multiple NPY-PYY receptors in the central nervous system.     

Respiratory effects of pressor and depressor agents in conscious rats

We hypothesized that the respiratory baroreflex in conscious rats is either more transient, or has a higher pressure threshold than in other species. To characterize the effect of arterial pressure changes on respiration in conscious rats, ventilation (V) was measured by the plethysmographic technique during injections, or infusions, of pressor and depressor agents. Bolus injections of angiotensin II (Ang II) or arginine vasopressin (AVP), transiently increased mean arterial pressure (MAP; mean +/- SE) 43+/-6 and 28+/-5 mm Hg (1 mm Hg = 133.3 Pa), respectively, and immediately reduced tidal volume (Vt) and, in the case of AVP, V. In contrast, by 10 min of a sustained elevation of MAP (40+/-3 mm Hg) with infusion of Ang II, Vt, f, and V were not different from control levels. Bolus injection of sodium nitroprusside (SNP) to lower MAP (-28+/-3 mm Hg) immediately increased breathing frequency (f) and V, whereas sustained infusion of SNP to lower MAP (-21+/-3 mm Hg) did not change for V at 10 and 20 min. In conscious rats, both injection and infusion of the pressor agent PE (+40 to 50 mm Hg) stimulated f and V; this contrasted with anesthetized rats where PE inhibited f and V, as reported by others. In conscious rats, respiratory responses associated with baroreflexes adapt rapidly and, in the case of PE, can be overridden by some other mechanism.     

Localization and identification of Neuropeptide Y (NPY)-like immunoreactivity in the frog brain

The distribution of neuropeptide Y (NPY) in the central nervous system of the frog Rana ridibunda was determined by immunofluorescence using a highly specific antiserum. NPY-like containing perikarya were localized in the infundibulum, mainly in the ventral and dorsal nuclei of the infundibulum, in the preoptic nucleus, in the posterocentral nucleus of the thalamus, in the anteroventral nucleus of the mesencephalic tegmentum, in the part posterior to the torus semicircularis, and in the mesencephalic cerebellar nucleus. Numerous perikarya were also distributed in all cerebral cortex. Important tracts of immunoreactive fibers were found in the infundibulum, in the preoptic area, in the lateral amygdala, in the habenular region, and in the tectum. The cerebral cortex was also densely innervated by NPY-like immunoreactive fibers. A rich network of fibers was observed in the median eminence coursing towards the pituitary stalk. Scattered fibers were found in all other parts of the brain except in the cerebellum, the nucleus isthmi and the torus semicircularis, where no immunoreactivity could be detected. NPY-immunoreactive fibers were observed at all levels of the spinal cord, with particularly distinct plexus around the ependymal canal and in the distal region of the dorsal horn. At the electron microscope level, NPY containing perikarya and fibers were visualized in the ventral nuclei of the infundibulum, using the peroxidase-antiperoxidase and the immunogold techniques. NPY-like material was stored in dense core vesicles of 100 nm in diameter. A sensitive and specific radioimmunoassay was developed. The detection limit of the assay was 20 fmole/tube. The standard curves of synthetic NPY and the dilution curves for acetic acid extracts of cerebral cortex, infundibulum, preoptic region, and mesencephalon plus thalamus were strictly parallel. The NPY concentrations measured in these regions were (pmole/mg proteins) 163±8, 233±16, 151±12 and 60±13, respectively. NPY was not detectable in cerebellar extracts. After Sephadex G-50 gel filtration of acetic acid extracts from whole frog brain, NPY-like immunoreactivity eluted in a single peak. Reverse phase high performance liquid chromatography (HPLC) and radioimmunoassay were used to characterize NPY-like peptides in the frog brain. HPLC analysis revealed that infundibulum, preoptic area and telencephalon extracts contained a major peptide bearing NPY-like immunoreactivity. The retention times of frog NPY and synthetic porcine NPY were markedly different. HPLC analysis revealed also the existence, in brain extracts, of several other minor components cross-reacting with NPY antibodies. These results provide the first evidence for the presence of NPY in the brain of a non-mammalian chordate and indicate that the structure of NPY is preserved among the vertebrate phylum. The abundance of NPY producing neurons in the hypothalamus and telencephalon suggests that this peptide may play both neuroendocrine and neurotransmitter functions in amphibians.     

Neuropeptide Y (NPY) in neuroblastoma: effect on growth and vascularization

Neuroblastomas are pediatric tumors of sympathetic origin, expressing neuronal markers, such as NPY and its receptors. Due to this, neuroblastomas are often associated with elevated plasma levels of NPY, which correlates with poor clinical outcome of the disease. This clinical data corroborates the recent discovery of growth-promoting actions of NPY in neuroblastomas. The peptide has been shown to stimulate proliferation of neuroblastoma cells in an autocrine manner and induce tumor vascularization. Since both processes are mediated by the same Y2 and Y5 receptors, targeting this pathway may be a potential bidirectional therapy for these children's tumors.     

Neuropeptide Y induces fasted pattern of duodenal motility via Y(2) receptors in conscious fed rats

Neuropeptide Y (NPY), a 36-amino acid peptide abundantly expressed in the brain, has been implicated in the regulation of feeding and visceral functions. The present study was designed to investigate whether or not NPY specifically regulates duodenal motility. The manometric method was used to measure duodenal motility in conscious, freely moving rats. The rat duodenum showed phasic contractions mimicking the migrating motor complex in the fasted state that were replaced by irregular contractions after the ingestion of food. NPY powerfully affected the contractile activity after intracerebroventricular (i.c.v.) administration, changing fed (postprandial) patterns into phasic contractions characterized as fasted (interdigestive) patterns. This effect was mediated via receptors with pharmacological profiles similar to rat Y(2) and Y(4) receptors, although neither Y(1) nor Y(5) agonists had any effects on motility despite potent feeding-stimulatory effects. Immunoneutralization with anti-NPY antiserum administered i.c.v. abolished fasted patterns and induced fed-like motor activities. An i.c.v. dose of peptide YY produced a different effect from NPY, with increase in the motor activities of both fed and fasted patterns. These results indicate that fasted and fed motor activities are regulated processes and that NPY induces fasted activity through Y(2), and possibly Y(4), receptors, which may represent an integrated mechanism linked to the onset of feeding behavior.     

Effects of Neuropeptide Y (NPY) on the release of anterior pituitary hormones in the rat

Neuropeptide Y (NPY) has been recently localized in several hypothalamic nuclei in the mammalian brain. In order to investigate the possible role of NPY on neuroendocrine function, we have investigated the effects of the peptide on the release of anterior pituitary hormones in the rat. Both intravenous (300 μg) or intraventricular (2 to 15 μg) injection of NPY produced in gonadectomized male rats a significant and long-lasting decrease of plasma LH levels. A short duration stimulating effect on prolactin plasma levels was also observed after the intravenous but not after the intraventricular injection of NPY. Plasma levels of the other pituitary hormones were not significantly modified after NPY injection. When incubated in vitro with anterior pituitary cells in monolayer culture, NPY produced no significant change in release of pituitary hormones. Thus NPY seems to exert a selective effect on LH release. Since this effect can be observed after both intravenous and intraventricular injection, it might be hypothesized that NPY could affect LHRH release in two areas which lack blood-brain barrier: the organum vasculosum of the lamina terminalis (OVLT) which contains LHRH cell bodies and NPY fibers and the median eminence which contains both LHRH and NPY fibers. The effect on prolactin release needs to be carefully evaluated in different experimental conditions.     

Fine-structural localization of neuropeptide tyrosine (NPY)-like immunoreactivity in the neuronal somata of colchicine-pretreated celiac ganglia of rats

Summary In colchicine-pretreated cells of sympathetic ganglia, intensely NPY-immunoreactive material was localized within vacuoles and vesicles of the disorganized, widely dispersed Golgi apparatus. Intensely positive large granular vesicles, which are known to be one of major storage sites of various peptides in the autonomic nerve endings, were essentially unobserved in the perikaryal cytoplasm. The present finding provides evidence that one pool of NPY-like immunoreactivity is localized in the Golgi apparatus of colchicine-pretreated as well as normal sympathetic ganglion cells. It is also clear that visualization of NPY-immunoreactive somata by colchicine-pretreatment in the sympathetic ganglia is due to the accumulation of the neuropeptide in the disorganized Golgi stacks instead of increased amount of the large granular vesicles containing NPY.     

Neuropeptide Y (NPY) and depression: from animal studies to the human condition

Neuropeptide Y (NPY) is widely distributed throughout the central nervous system (CNS) and is one of the most conserved peptides in evolution, suggesting an important role in the regulation of basic physiological functions. In addition, both pre-clinical and clinical evidence have suggested that NPY, together with its receptors, may have a direct implication in several psychiatric disorders, including depression and related illnesses. NPY-like immunoreactivity and NPY receptors are expressed throughout the brain, with varying concentrations being found throughout the limbic system. Such brain structures have been repeatedly implicated in the modulation of emotional processing, as well as in the pathogenesis of depressive disorders. This review will concentrate on the distribution of NPY, its receptors, and the putative role played by this peptide in depressive illness based on both pre-clinical and clinical evidence.     

Neuropeptide Y (NPY)-like immunoreactive amacrine cells in retinas of frog and goldfish

Summary The distribution of neuropeptide Y (NPY)-like immunoreactivity in rat, rabbit, chick, frog and goldfish retinas was investigated by immunohistochemistry. Positive results were observed only in the frog and goldfish retinas. NPY immunoreactivity was associated with a small population of amacrine cell bodies in the inner nuclear layer and cell processes in the inner plexiform layer of both retinas. In the frog retina, three distinct layers containing immunoreactivity were observed in the inner plexiform layer. In contrast, the immunoreactivity in the same area of the goldfish retina was more or less separated into two layers. Convincing evidence could not be found for the co-existence of NPY-like material with other putative transmitter-like substances in the two retinas.Radioimmunoassay revealed the presence of small amounts of NPY-like immunoreactivity in the rabbit retina; the goldfish and frog retinas contained significantly more immunoreactive material. High performance liquid chromatography of the immunoreactive material in frog and goldfish retinas showed each retina containing different molecular forms of NPY-like proteins, neither of which resembled porcine NPY or PYY.The endogenous NPY-like material of the frog retina can be released by potassium depolarisation in a calciumdependent way. In view of all these data an NPY-like protein must now be considered a potential retinal transmitter.     

Neuropeptide Y (NPY) functional group mimetics: design, synthesis, and characterization as NPY receptor antagonists

N,N′-bis-[2-N-(O-2,6-dichlorobenzyl-L-tyrosyl)aminoethylguanyl]cystamine 3 and N,N′-bis-[2-N-(O-2,6-dichlorobenzyl-L-tyrosyl)aminoethyl]-1,6-hexanediguanidine 4 have been designed as neuropeptide Y (NPY) functional group mimetics. Both 3 and 4 displace N-[propionyl-³H]-NPY from rat brain binding sites, and are NPY receptor antagonists in rat femoral artery ring segments.     

Neuropeptide Y (NPY) and the pig heart: release and coronary vasoconstrictor effects

The effects of electrical stimulation of the stellate ganglia on the arterio-venous concentration differences of neuropeptide Y (NPY)-like immunoreactivity (LI) over the pig heart were studied in vivo in relation to changes in heart rate and left ventricular pressure. Furthermore, the effects of NPY on coronary vascular tone were analysed in vivo and in vitro. Stellate ganglion stimulation at a high frequency (10 Hz) caused a clear-cut, long lasting increase in plasma levels of NPY-LI in the coronary sinus compared to the aorta, suggesting release of this peptide from sympathetic terminals within the heart. The stimulation-evoked overflow of NPY-LI from the heart was enhanced about 3-fold by alpha-adrenoceptor blockade using phenoxybenzamine, suggesting that NPY release is under prejunctional inhibitory control by noradrenaline (NA). Combined alpha- and beta-adrenoceptor blockade abolished most of the positive inotropic response of the heart upon stellate ganglion stimulation, while a considerable positive chronotropic effect remained. After guanethidine treatment, stellate ganglion stimulation still produced a small positive inotropic and chronotropic effect on the heart. The stimulation evoked NPY overflow was markedly reduced by guanethidine indicating an origin from sympathetic nerve terminals. Injection of NPY into the constantly perfused left anterior descending artery in vivo caused a long lasting, adrenoceptor antagonist resistant increase in perfusion pressure, suggesting coronary vasoconstriction. NPY contracted coronary arteries in vitro via a nifedipine-sensitive mechanism. NA dilated coronary vessels both in vivo and in vitro via beta-adrenoceptor activation. It is concluded that sympathetic nerve stimulation increases overflow of NPY-LI from the heart suggesting release from cardiac nerves in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuropeptide Y (NPY) suppresses experimental autoimmune encephalomyelitis: NPY1 receptor-specific inhibition of autoreactive Th1 responses in vivo

Prior studies have revealed that the sympathetic nervous system regulates the clinical and pathological manifestations of experimental autoimmune encephalomyelitis (EAE), an autoimmune disease model mediated by Th1 T cells. Although the regulatory role of catecholamines has been indicated in the previous works, it remained possible that other sympathetic neurotransmitters like neuropeptide Y (NPY) may also be involved in the regulation of EAE. Here we examined the effect of NPY and NPY receptor subtype-specific compounds on EAE, actively induced with myelin oligodendrocyte glycoprotein 35-55 in C57BL/6 mice. Our results revealed that exogenous NPY as well as NPY Y(1) receptor agonists significantly inhibited the induction of EAE, whereas a Y(5) receptor agonist or a combined treatment of NPY with a Y(1) receptor antagonist did not inhibit signs of EAE. These results indicate that the suppression of EAE by NPY is mediated via Y(1) receptors. Furthermore, treatment with the Y(1) receptor antagonist induced a significantly earlier onset of EAE, indicating a protective role of endogenous NPY in the induction phase of EAE. We also revealed a significant inhibition of myelin oligodendrocyte glycoprotein 35-55-specific Th1 response as well as a Th2 bias of the autoimmune T cells in mice treated with the Y(1) receptor agonist. Ex vivo analysis further demonstrated that autoimmune T cells are directly affected by NPY via Y(1) receptors. Taken together, we conclude that NPY is a potent immunomodulator involved in the regulation of the Th1-mediated autoimmune disease EAE.