Comparative developmental profile of the neuropeptide Y Y1 receptor gene and protein in the rat brain

Distribution of a Y1 receptor mRNA in the brain of two Lamprey species, the sea lamprey (Petromyzon marinus) and the river Lamprey (Lampetra fluviatilis)

The neuropeptide Y system consists of several neuropeptides acting through a broad number of receptor subtypes, the NPY family of receptors. NPY receptors are divided into three subfamilies (Y1, Y2, and Y5) that display a complex evolutionary history due to local and large-scale gene duplication events and gene losses. Lampreys emerged from a basal branch of the tree of vertebrates and they are in a key position to shed light on the evolutionary history of the NPY system. One member of the Y1 subfamily has been reported in agnathans, but the phylogenetic tree of the Y1 subfamily is not yet clear. We cloned the sequences of the Y1-subtype receptor of Petromyzon marinus and Lampetra fluviatilis to study the expression pattern of this receptor in lampreys by in situ hybridization and to analyze the phylogeny of the Y1-subfamily receptors in vertebrates. The phylogenetic study showed that the Y1 receptor of lampreys is basal to the Y1/6 branch of the Y1-subfamily receptors. In situ hybridization showed that the Y1 receptor is widely expressed throughout the brain of lampreys, with some regions showing numerous positive neurons, as well as the presence of numerous cerebrospinal fluid-contacting cells in the spinal cord. This broad distribution of the lamprey Y1 receptor is more similar to that found in other vertebrates for the Y1 receptor than that of the other members of the Y1 subfamily: Y4, Y8, and Y6 receptors. Both phylogenetic relationship and expression pattern suggest that this receptor is a Y1 receptor.

Effects of maternal deprivation on the somatotrophic axis and neuropeptide Y in the hypothalamus and pituitary in female lambs. The histomorphometric study

The effects of maternal deprivation on the somatotrophic axis and neuropeptide Y (NPY) neuronal system in the hypothalamus of female lambs were evaluated. Twelve-week-old lambs were divided into two groups: the control (lambs stayed with mothers) and maternally deprived (MD; lambs separated for 3 days from mothers). The expression of immunoreactive (ir) somatostatin in the neurons of the periventricular nucleus (PEV) and in nerve terminals of the median eminence (ME), growth hormone (GH) in the adenohypophyseal cells and NPY in the neurons of the PEV and arcuate (ARC) nuclei of the hypothalamus using immunohistochemistry followed by the image analysis were estimated. Concentrations of GH in the blood plasma were determined by radioimmunoassay. The expression of ir somatostatin in the PEV and ME, ir NPY in the ARC and PEV, ir GH in adenohypophyseal cells, and blood plasma GH concentrations were greater (p<0.05) in MD than in the control lambs. In conclusion, MD affects the somatotrophic axis by enhancement of GH secretion via restraining of somatostatin output. The simultaneous increase of expression of hypothalamic ir NPY suggests NPY involvement in the regulation of psychoemotional stress through the somatotrophic axis in the female lambs.

Neuropeptide Y directly inhibits neuronal activity in a subpopulation of gonadotropin-releasing hormone-1 neurons via Y1 receptors

Neuropeptide Y (NPY), a member of the pancreatic polypeptide family, is an orexigenic hormone. GnRH-1 neurons express NPY receptors. This suggests a direct link between metabolic function and reproduction. However, the effect of NPY on GnRH-1 cells has been variable, dependent on metabolic and reproductive status of the animal. This study circumvents these issues by examining the role of NPY on GnRH-1 neuronal activity in an explant model that is based on the extra-central nervous system origin of GnRH-1 neurons. These prenatal GnRH-1 neurons express many receptors found in GnRH-1 neurons in the brain and use similar transduction pathways. In addition, these GnRH-1 cells exhibit spontaneous and ligand-induced oscillations in intracellular calcium as well as pulsatile calcium-controlled GnRH-1 release. Single-cell PCR determined that prenatal GnRH-1 neurons express the G protein-coupled Y1 receptor (Y1R). To address the influence of NPY on GnRH-1 neuronal activity, calcium imaging was used to monitor individual and population dynamics. NPY treatment, mimicked with Y1R agonist, significantly decreased the number of calcium peaks per minute in GnRH-1 neurons and was prevented by a Y1R antagonist. Pertussis toxin blocked the effect of NPY on GnRH-1 neuronal activity, indicating the coupling of Y1R to inhibitory G protein. The NPY-induced inhibition was independent of the adenylate cyclase pathway but mediated by the activation of G protein-coupled inwardly rectifying potassium channels. These results indicate that at an early developmental stage, GnRH-1 neuronal activity can be directly inhibited by NPY via its Y1R.

Reduced expression of neuropeptide genes in a genome-wide screen of a secretion-deficient mouse

Activity-dependent changes in synapses rely on functional changes in resident proteins and on gene expression. We addressed the relationship between synapse activity and the expression of synaptic genes by comparing RNA levels in the neocortex of normal mice versus secretion-deficient and therefore synaptically silent munc18-1 (mammalian homologue of Caenorhabditis elegans uncoordinated locomotion-18) null mutants, using microarray expression analysis, real-time quantitative PCR and northern blotting. We hypothesized that genes under the control of synaptic activity would be differentially expressed between mutants and controls. We found that few synaptic genes were differentially expressed. However, most neuropeptide genes with detectable expression on the microarray were differentially expressed, being expressed 3-20-fold higher in control cortex. Several other secreted proteins were also differentially expressed, but genes encoding their receptors and many other synaptic components were not. Differential expression was confirmed by real-time quantitative PCR analysis. In situ hybridization indicated that the difference in neuropeptide expression was uniform and not due to the loss of specific cells in the mutant. In primary sensory neurons, which do not depend on synaptic activity for their input, the differential expression of neuropeptides was not observed. These data argue against a general relationship between the activity of synapses and the expression of their resident proteins, but suggest a link between secretion and the expression of genes encoding the secreted products.

Neuropeptide Y modulates excitatory synaptic transmission in the olfactory bulb

Although the olfactory bulb contains one of the highest concentrations of neuropeptide Y in the CNS, its function in the bulb remains unclear. In this study, we used whole-cell electrophysiological, molecular, and primary culture techniques to investigate neuropeptide Y gene expression and neuromodulatory actions of neuropeptide Y on rat olfactory bulb neurons. Northern analysis showed that neuropeptide Y mRNA increases with animal age or time in culture, in a parallel manner. In electrophysiology experiments, agonists that activate neuropeptide Y receptors (whole neuropeptide Y) and the Y2 receptor subtype (neuropeptide Y 13-36) reduced spontaneous excitatory activity in bulb interneurons. In investigating potential presynaptic effects, both agonists reduced the amplitude of calcium channel currents in the presynaptic (mitral/tufted) cell. Also consistent with a presynaptic effect, both agonists reduced the frequency but not the amplitude of miniature excitatory postsynaptic currents (or "minis") in interneurons. In examining potential postsynaptic effects, both agonists slightly increased membrane resistance but had no effect on currents evoked by glutamate. Together, these data suggest that neuropeptide Y inhibits excitatory neurotransmission between olfactory bulb neurons via a presynaptic effect on transmitter (glutamate) release.

cDNA cloning and mRNA expression of neuropeptide Y in orange spotted grouper, Epinephelus coioides

A full-length cDNA encoding the neuropeptide Y (NPY) was cloned from the hypothalamus of orange spotted grouper (Epinephelus coioides) by rapid amplification of cDNA ends approaches. The NPY cDNA sequence is 688 bp long and has an open reading frame of 300 bp encoding prepro-NPY with 99 amino acids. The deduced amino acid sequences contain a 28-amino-acids signal peptide followed by a 36-amino-acids mature NPY peptide. mRNA expression of NPY was determined using semi-quantitative RT-PCR followed by Southern blot analysis. NPY mRNA was expressed in olfactory bulb, telencephalon, pituitary, hypothalamus, optic tectum-thalamus, medulla oblongata, cerebellum and spinal cord. Low levels of NPY mRNA expression were found in retina, ovary and stomach, while much lower levels of expression were detected in liver, heart, gill, skin, anterior intestine, thymus and blood. No NPY mRNA expression was observed in unfertilized eggs, newly fertilized eggs, 16-cells stage and morula stage of the embryo and lower levels of expression were detected in the blastula, gastrula and neurula stages. It was highly expressed from lens formation stage to 52-day-old larval stage. NPY might be involved in the late embryonic and larval development of the orange spotted grouper.

A deletion causing spontaneous fracture identified from a candidate region of mouse Chromosome 14

Map-based cloning is an iterative approach that identifies the underlying genetic cause of a mutant phenotype. However, the classic protocol of positional cloning is time-consuming and labor-intensive. We now describe a genome sequence-based cloning approach that has led to localizing the underlying genetic cause of spontaneous fractures (sfx) in a mouse model. The sfx/sfx mouse is characterized by a spontaneous femoral fracture seen around 6 weeks of age, which represents a new mouse model for bone fragility. Genetic studies indicate that the phenotype of sfx/sfx mice is caused by an alteration at a single locus that is roughly mapped onto the central region of mouse Chromosome 14. Using our strategy of combining mouse genome resources and high-throughput technology, we discovered a deletion of all 12 exons in the gene for L-gulonolactone oxidase (LGO), a key enzyme in the synthesis of ascorbic acid. We have also examined the expression of LGO and found no expression of LGO in sfx mice while the LGO expresses in several tissues of normal mice. Our data demonstrated the feasibility to positionally clone the mutated gene from a non-fine-mapped locus, which has applicability to the positional cloning of genes from many other animal models, as their genome sequences are sequenced or will be sequenced soon.

Distribution of NPY receptors in the hypothalamus

Neuropeptide Y (NPY) neurons abundantly innervate the hypothalamus, where NPY is involved in the regulation and integration of a broad range of homeostatic functions. In order to understand NPY-mediated behavioral, autonomic and neuroendocrine effects, it is important to characterize in detail the distribution of the hypothalamic NPY receptors. In this review, we briefly summarize the origin of NPY and its two related peptides, peptide YY and pancreatic polypeptide in the hypothalamus. Moreover, based on the results obtained with histological techniques such as in situ hybridization, immunohistochemistry and ligand binding, we summarize data on the hypothalamic distribution of the known NPY receptors, the Y1 Y2, Y4 and Y5 receptors as best characterized to date. These NPY receptors are found with individual distribution patterns in many hypothalamic neurons including neuroendocrine motoneurons, magnocellular neurosecretory neurons and numerous neurons connecting the hypothalamus with the limbic and the autonomic nervous systems. The histochemical analyses allow characterization of coexisting molecules and in this way definition of the neurochemistry of NPY circuitries. By showing coexistence of various NPY receptors they provide a morphological basis for in vitro studies showing heterodimerization of NPY receptors. The NPY neurons and their circuitries underlie the integrative role of NPY as a pleiotropic neuropeptide in the regulation of homeostasis.

Insulin-like growth factor-1 and post-ischemic brain injury

Insulin-like growth factor-1 (IGF-1) is a naturally occurring neurotrophic factor that plays an important role in promoting cell proliferation and differentiation during normal brain development and maturation. The present review examines recent evidence that endogenous IGF-1 also plays a significant role in recovery from insults such as hypoxia-ischemia and that giving additional exogenous IGF-1 can actively ameliorate damage. It is now well established that neurons and other cell types die many hours or even days after initial injury due to activation of programmed cell death pathways. IGF-1 and its binding proteins and receptors are intensely induced within damaged brain regions following brain injury, suggesting a possible a role for IGF-1 in brain recovery. Exogenous administration of IGF-1 within a few hours after brain injury is now known to be protective in both gray and white matter and leads to improved somatic function. In contrast, pre-treatment is ineffective, likely reflecting limited intracerebral penetration of IGF-1 into the uninjured brain. The neuroprotective effects of IGF-1 are mediated by IGF-1 receptors and its binding proteins and are specific to particular cellular phenotypes and brain regions. The window of opportunity for treatment with IGF-1 is limited to a few hours after normothermic brain injury, reflecting its specific actions on early, intracellular events in the apoptotic cascade. However, injury-associated mild post-hypoxic hypothermia, which delays the development of cell death, can shift and dramatically extend the window of opportunity for delayed treatment with IGF-1. Such a combined approach is likely to be essential for any clinical treatment.

Ontogeny of the hypothalamic neuropeptide Y system

Early onset obesity and type II diabetes is rapidly becoming an epidemic, especially within the United States. This dramatic increase is likely due to many factors including both prenatal and postnatal environmental cues. The purpose of this review is to highlight some of the recent advances in our knowledge of the development of the hypothalamic circuits involved in the regulation of energy balance, with a focus on the neuropeptide Y (NPY) system. Unlike the adult rat, during the postnatal period NPY is transiently expressed in several hypothalamic regions, along with the expected expression within the arcuate nucleus (ARH). These transient populations of NPY neurons during the postnatal period may provide local NPY production to sustain the necessary energy intake during this critical growth phase. This may be physiologically important since ARH-NPY projections do not fully develop until the 3rd postnatal week. The significance of this ontogeny is that many peripheral metabolic signals have little effect of feeding prior to the development of the ARH projections. The essential questions now are whether prenatal and/or postnatal exposure to high levels of insulin or leptin during development can cause permanent changes in the function of hypothalamic circuits. It is vital to understand not only the natural development of the hypothalamic circuits that regulate energy homeostasis, but also their abnormal development caused by maternal and postnatal environmental cues. This will be pivotal for designing intervention and therapeutics to treat early onset obesity/type II diabetes, which may very well need to be different from those designed to prevent/treat adult onset obesity/type II diabetes.

Unopposed orexic pathways in the developing fetus

Fetal swallowing has important roles in fetal gastrointestinal development, and perhaps fetal somatic growth and maturation. Ingestive behavioral responses must develop in utero to provide for acquisition of water and food intake during the neonatal period. At birth, the rat, ovine and human fetus have developed mechanisms to acquire food via intact mechanisms of taste, suckling and swallowing. Our preliminary studies suggest that in sheep and likely in human fetuses, putative orexic-mediated ingestive responses are present near term gestation. We hypothesize that both orexic (appetite) and satiety mechanisms develop during the last third of gestation and the related neurotransmitters involved in this process are functional. The potential in utero imprinting of orexic mechanisms may influence infant, childhood and ultimately adult appetite "set-points". Thus, dysfunctional appetite, and perhaps obesity, may result from maternal environmental influences during critical stages of development.

Neuron-specific aminopeptidase and puromycin-sensitive aminopeptidase in rat brain development

Neuron-specific aminopeptidase (NAP) and the ubiquitous puromycin-sensitive aminopeptidase (PSA) were compared in the rat hippocampus during early development. Hippocampus contains the highest amount of NAP determined by a fast-protein liquid chromatography-aminopeptidase analyzer using Leu beta-naphthylamide as substrate. Both enzymes were found in the hippocampus in all ages. NAP was lower in immature rat; the 19th embryonic-day fetus contained the least. It increased steeply during the prenatal through the early postnatal period, 9-fold by the first month. The rate of increase diminished subsequently, increasing 20% in the second month and 13% in the third. The age-dependent increase in NAP activity was parallel to its protein expression as determined by Western blot. The specific molecular activity (hydrolytic activity/ NAP antigenicity) in newborn, 15-day-old, and 30-day-old rats were 1.00, 0.88, and 1.00, respectively. The PSA developmental profile without linear increase in activity was distinct from NAP. PSA activity was higher than NAP in decreasing order, 100-4 times, during the same development span. Similarly, different growth profiles for NAP and PSA were also found in the primary culture of developing cerebellar granule cells. Puromycin (1-5 microM) blocked neurite outgrowth and caused apoptosis by nonantibiotic effects. Our data suggest that the synaptosome-enriched NAP plays a role in neuron growth, differentiation, and information programming.

Postnatal development of the hypothalamic neuropeptide Y system

In the adult rat, arcuate-neuropeptide Y/agouti-related protein neurons have efferent projections throughout the hypothalamus and provide a potent orexigenic stimulus. At birth neuropeptide Y fibers are also present throughout the hypothalamus; however, the source of these fibers has been unknown. The present studies determined the postnatal ontogeny of arcuate-neuropeptide Y fibers into the paraventricular nucleus and dorsomedial hypothalamic nucleus, as well as the ontogeny of neuropeptide Y1 receptor expression within these areas. Agouti-related protein messenger RNA and protein expression was present exclusively in cell bodies in the arcuate throughout postnatal development, starting at P2, and was colocalized in the vast majority of arcuate-neuropeptide Y neurons. This exclusive colocalization of agouti-related protein with arcuate-neuropeptide Y neurons makes it an excellent marker for these neurons and their projections. Even though single-label neuropeptide Y fibers were abundant in the dorsomedial hypothalamic nucleus and paraventricular nucleus as early as P2, arcuate-neuropeptide Y/agouti-related protein fibers did not significantly innervate these areas until P5-6 and P10-11, respectively. In contrast, a portion of the neuropeptide Y fibers within the paraventricular nucleus as early as P2 originated from the brainstem, as indicated by their colocalization with dopamine beta hydroxylase. It remains to be determined if local sources of neuropeptide Y-expressing cells within the dorsomedial hypothalamic nucleus and paraventricular nucleus also contribute to the neuropeptide Y-immunoreactive fibers within these regions prior to the development of arcuate-neuropeptide Y/agouti-related protein projections. In addition to the dramatic change in arcuate-neuropeptide Y/agouti-related protein projections, there is also a striking change in Y1 protein expression in the hypothalamus during the first two postnatal weeks. Taken together these data suggest that the early postnatal period, during which there is a dynamic change in the hypothalamic neuropeptide Y system, may constitute a critical period in the development of this important feeding circuit.

The neuropeptide Y receptors, Y1 and Y2, are transiently and differentially expressed in the developing cerebellum

Neuropeptide Y (NPY), a peptide widely expressed in the brain, acts through the protein G-coupled receptors Y1, Y2 and Y5. In the adult rat, this peptide modulates many important functions such as the control of energy balance and anxiety. Its involvement in brain development has been less investigated. In the present study, we have analysed the expression of Y1 and Y2 in the developing rat cerebellum using RNase protection assay. Both receptors were detected in the embryo but at very low levels. Their expression then increased, reaching a peak at postnatal day 10. At later stages, we observed a down-regulation of both Y1 and Y2 mRNA levels. This pattern of expression was delayed in hypothyroid rats, suggesting that the regulation of NPY receptors was strictly related to cerebellar development stages. In situ hybridisation and immunohistochemistry analyses revealed specific localisations of the receptors. Y1 was exclusively expressed by Purkinje cells while Y2 was found mostly in granule cells of the internal granule cell layer. These observations argue in favour of specific roles for Y1 and Y2 in the developing cerebellum. In an initial attempt to characterise these roles, we have determined the number of apoptotic cells in the developing cerebellum of Y2(-/-) mice and analysed the effects of NPY on primary cultures of cerebellar granule neurones. Our data showed that the absence of Y2 did not increase cell death in the internal granule cell layer of the developing cerebellum, and that NPY by itself did not prevent the death of differentiated granule cells cultured in serum-free medium. However, we found that co-treatment of the cells by NPY and neuromediators such as NMDA or GABA strongly promoted the survival of granule neurones. Taken together, these observations suggest an involvement of the NPY receptors in cerebellar ontogenesis that remains to be demonstrated in vivo.

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.

Appetite suppression based on selective inhibition of NPY receptors

AIM

The aim of this review is to critically assess available evidence that blockade of the actions of NPY at one of the five NPY receptor subtypes represents an attractive new drug discovery target for the development of an appetite suppressant drug.

RESULTS

Blockade of the central actions of NPY using anti-NPY antibodies, antisense oligodeoxynucleotides against NPY and NPY receptor antagonists results in a decrease in food intake in energy-deprived animals. These results appear to show that endogenous NPY plays a role in the control of appetite. The fact that NPY receptors exist as at least five different subtypes raises the possibility that the actions of endogenous NPY on food intake can be adequately dissociated from other effects of the peptide. Current drug discovery has produced a number of highly selective NPY receptor antagonists which have been used to establish the NPY Y(1) receptor subtype as the most critical in regulating short-term food intake. However, additional studies are now needed to more clearly define the relative contribution of NPY acting through the NPY Y2 and NPY Y5 receptors in the complex sequence of physiological and behavioral events that underlie the long-term control of appetite.

CONCLUSIONS

Blockade of the NPY receptor may produce appetite-suppressing drugs. However, it is too early to state with certainty whether a single subtype selective drug used alone or a combination of NPY receptor selective antagonists used in combination will be necessary to adequately influence appetite regulation.

Localization and characterization of NPY/PYY receptors in rat frontoparietal cortex during development

Neuropeptide Y (NPY) is present in most cerebrocortical areas during fetal and postnatal development. In the rat frontal cortex, a dense radial fiber network containing NPY immunoreactivity is observed transiently as early as embryonic day 17 (E17) and disappears at the end of the first postnatal week. We have investigated the distribution of NPY receptors in the frontoparietal cortex at 13 stages of development, from E15 fetuses to adults, by in vitro autoradiography, using (125)I-pPYY as a radioligand. Quantitative receptor density was measured through all cortical layers at each developmental stage. Pharmacological identification of (125)I-pPPY binding sites was made by competition experiments using pNPY or [Leu(31),Pro(34)]pNPY and pNPY(13-36), as selective competitors for Y1 and Y2 receptors, respectively. NPY receptors were first detected in the cerebral cortex at low densities at E19 in a thin layer of tissue corresponding to the inner half of the intermediate zone (IZ) and the upper ventricular zone (VZ). The neuroepithelium did not contain binding sites. High densities of sites were observed by E21 onward to P10 in the deep cortical layers corresponding to the IZ and layers V-VI. A decreasing gradient of receptor density was observed from layer VI to the marginal zone (layer I). The distribution of NPY receptors does not match with the perikarya of transient NPY-immunoreactive neurons located in the cortical plate but does coincide with their axonal extension. The receptor density decreased abruptly between P10 and P12 in deep layers, whereas a moderate expression of binding sites is detected from P10 to P12 in layers I-III. By P14, the binding level was the lowest observed in the postnatal period. From P21 onward, receptors were observed in superficial layers I-III, and their density rose by two- to threefold up to adulthood. Competition studies indicated that the NPY receptors located in the deep cortical layers of the E21 or P1 rat cortex exhibit Y2 receptor type characteristics. The binding sites detected in the superficial layers from P10 to P12 rats also show Y2 receptors characteristics, unlike the NPY receptors in layers II-III of the adult, which behave like Y1 receptors. These data show that different NPY receptor types are successively expressed in specific layers during late gestation and early postnatal life in the rat frontoparietal cortex.

Neurobiological mechanisms of the onset of puberty in primates

An increase in pulsatile release of LHRH is essential for the onset of puberty. However, the mechanism controlling the pubertal increase in LHRH release is still unclear. In primates the LHRH neurosecretory system is already active during the neonatal period but subsequently enters a dormant state in the juvenile/prepubertal period. Neither gonadal steroid hormones nor the absence of facilitatory neuronal inputs to LHRH neurons is responsible for the low levels of LHRH release before the onset of puberty in primates. Recent studies suggest that during the prepubertal period an inhibitory neuronal system suppresses LHRH release and that during the subsequent maturation of the hypothalamus this prepubertal inhibition is removed, allowing the adult pattern of pulsatile LHRH release. In fact, y-aminobutyric acid (GABA) appears to be an inhibitory neurotransmitter responsible for restricting LHRH release before the onset of puberty in female rhesus monkeys. In addition, it appears that the reduction in tonic GABA inhibition allows an increase in the release of glutamate as well as other neurotransmitters, which contributes to the increase in pubertal LHRH release. In this review, developmental changes in several neurotransmitter systems controlling pulsatile LHRH release are extensively reviewed.

Dietary composition during fetal and neonatal life affects neuropeptide Y functioning in adult offspring

The aim of this study was to examine the impact of maternal diet during the gestation and lactation periods on the neuropeptide Y (NPY) system in adult offspring. Male Long-Evans rats were obtained from dams fed either on a well-balanced diet (C), a high carbohydrate diet (HC) or a high-fat diet (HF) and fed themselves on the well-balanced diet for their whole life. At 6 months of age, their feeding response to various doses of NPY injected in the lateral brain ventricle was measured in one group and NPY concentrations in microdissected nuclei of the hypothalamic were measured in a second group. The HF rats were lighter than the two other groups (P<0.001). The control rats showed a typical dose-dependent feeding response to NPY. The HC rats showed a continuous increase in the response, starting at the intermediate dose (1.0 microg) only while the HF rats had a maximal response at the lowest dose (0.5 microg). The HF rats ate twice as much as the HC rats at the lowest dose tested 1 h after injection (4.4+/-0.6 vs. 2.7+/-0.4 g; P<0.05), showing therefore the greatest sensitivity to NPY. This change in the sensitivity was not related to hypothalamic NPY concentration as it was not modified in the arcuate and paraventricular nuclei. The diet imposed on the mother could have long-lasting effects on body weight regulation of the offsprings and alter the NPY system likely through modifications at the receptor level.

Selective neuroprotective effects with insulin-like growth factor-1 in phenotypic striatal neurons following ischemic brain injury in fetal sheep

Severe perinatal asphyxia can lead to injury and dysfunction of the basal ganglia. Post insult administration of insulin-like growth factor-1 is neuroprotective, particularly in the striatum. Insulin-like growth factor-1 is also known to be a neuromodulator of several types of striatal neurons. The striatum comprises various phenotypic neurons with a complex neurochemical anatomy and physiology. In the present study, we examined the specificity of neuronal rescue with insulin-like growth factor-1 on different striatal neurons. Bilateral brain injury was induced in near term fetal sheep by 30 min of reversible carotid artery occlusion. A single dose of 3 microg of insulin-like growth factor-1 was infused over 1 h into the lateral ventricle 90 min following ischemia. The histological and immunohistochemical outcome were examined after 4 days recovery using paraffin tissue preparations. Insulin-like growth factor-1 treatment (n = 11) significantly reduced the percentage of neuronal loss in the striatum compared with the vehicle treated group (n = 10, 28.3+/-5.1% vs 55.5+/-17.3%, P < 0.005). Immunohistochemical studies showed that ischemia resulted in a significant loss of calbindin-28kd, choline acetyltransferase, parvalbumin, glutamate acid decarboxylase, neuronal nitric oxide synthase and neuropeptide Y immunopositive neurons, compared with sham controls. Insulin-like growth factor-1 markedly prevented the loss of calbindin-28kd (n = 7, P < 0.05), choline acetyltransferase (n = 7, P < 0.05), neuropeptide Y (n = 7, P < 0.05), neuronal nitric oxide synthase (n = 8, P < 0.05) and glutamate acid decarboxylase (n = 9, P < 0.05) immunopositive neurons, but failed to protect parvalbumin (n = 6) immunopositive neurons. The present study indicates that the therapeutic effect of insulin-like growth factor-1 in the basal ganglia is selectively associated with cholinergic and some phenotypic GABAergic neurons. These data suggest a potential role for insulin-like growth factor-1 in preventing cerebral palsy due to perinatal asphyxia.

[(125)I]-GR231118: a high affinity radioligand to investigate neuropeptide Y Y(1) and Y(4) receptors

GR231118 (also known as 1229U91 and GW1229), a purported Y(1) antagonist and Y(4) agonist was radiolabelled using the chloramine T method. [(125)I]-GR231118 binding reached equilibrium within 10 min at room temperature and remained stable for at least 4 h. Saturation binding experiments showed that [(125)I]-GR231118 binds with very high affinity (K(d) of 0.09 - 0.24 nM) in transfected HEK293 cells with the rat Y(1) and Y(4) receptor cDNA and in rat brain membrane homogenates. No specific binding sites could be detected in HEK293 cells transfected with the rat Y(2) or Y(5) receptor cDNA demonstrating the absence of significant affinity of GR231118 for these two receptor classes. Competition binding experiments revealed that specific [(125)I]-GR231118 binding in rat brain homogenates is most similar to that observed in HEK293 cells transfected with the rat Y(1), but not rat Y(4), receptor cDNA. Autoradiographic studies demonstrated that [(125)I]-GR231118 binding sites were fully inhibited by the Y(1) antagonist BIBO3304 in most areas of the rat brain. Interestingly, high percentage of [(125)I]-GR231118/BIBO3304-insensitive binding sites were detected in few areas. These [(125)I]-GR231118/BIBO3304-insensitive binding sites likely represent labelling to the Y(4) receptor subtype. In summary, [(125)I]-GR231118 is a new radiolabelled probe to investigate the Y(1) and Y(4) receptors; its major advantage being its high affinity. Using highly selective Y(1) antagonists such as BIBO3304 or BIBP3226 it is possible to block the binding of [(125)I]-GR231118 to the Y(1) receptor allowing for the characterization and visualization of the purported Y(4) subtype. British Journal of Pharmacology (2000) 129, 37 - 46

The murine Y1 receptor 5' upstream sequence directs cell-specific and developmentally regulated LacZ expression in transgenic mice CNS

The Y1 receptor for neuropeptide Y (NPY) is highly expressed in mammalian CNS where it mediates the activation of several neurobiological functions. We have previously demonstrated that a 1.3-kb fragment upstream of the transcription initiation sites of the murine Y1 receptor gene is able to direct specific expression of reporter genes in neuronal cell cultures. In the present study transgenic mice harbouring this putative promoter region linked to the LacZ reporter gene were generated and analysed for temporal and spatial distribution. Ten transgenic lines expressed beta-galactosidase in the CNS but not in other organs such as heart, liver and kidney. Histochemical analysis of brain from adult transgenic mice showed specific expression of the transgene in specific brain regions with little variation. Four transgenic lines showed characteristic patterns of beta-galactosidase activity in the brain that are consistent with the expression of the endogenous gene. Prominent LacZ activity was present in several telencephalic and diencephalic structures, including deeper layers of cerebral cortex, amygdaloid complex, hippocampus, preoptic area, several thalamic and hypothalamic nuclei and habenula. The ontogeny analysis indicates that the LacZ expression agrees with the temporal expression pattern of rat Y1 receptor mRNA. These data demonstrate that the 1.3-kb upstream region of the murine Y1 receptor gene contains the cis acting elements required for establishing a CNS-restricted and developmental stage-specific pattern of expression in vivo. Moreover they provide further information on the distribution of this NPY subtype receptor in mammalian brain.

Hypothalamic neuropeptide Y content and mRNA expression in weanling rats subjected to dietary manipulations during fetal and neonatal life

Hypothalamic neuropeptide Y (NPY) is present very early during the fetal life and is rapidly functional in the regulation of feeding behavior after birth. In the present experiment, we tried to determine the influence that the diet type ingested by dams during gestation and lactation would have on the growth and hypothalamic and pancreatic peptides of their progeny immediately after weaning. The dams were fed on either a high-carbohydrate (HC), a high-fat (HF) or a control diet ad libitum. At 3 days of age, the HC pups weighed significantly more than the two other groups (P < 0.02 vs. C and P < 0.002 vs. HF). At weaning, the HF rats were significantly lighter than the two other groups (P < 0.001). Food intake was significantly lower in the HF rats than in the two other groups 3 days (P < 0.002) and 5 days after weaning (P < 0.02). Plasma glucose of the HF rats was significantly lower than that of the control rats (P < 0.05) and of the HC rats (P < 0.01). Immunoreactive insulin in the HF rats was also significantly lower than that in the control rats (-53%; P < 0.001) and in the HC rats (-47%; P < 0.001). NPY content and mRNA expression in the arcuate nucleus were not significantly different between the three groups. NPY concentration only varied in the ventromedian nucleus. In the control rats, it was significantly lower than that of the HC rats (-35%; P < 0.01) and that of the HF rats (-32%; P < 0.002). These data demonstrated that the regulatory mechanisms of feeding behavior in offspring are completely and differentially modified by the macronutrient content of the diets ingested by their mother. Both peripheral and central mediators were strongly implicated. These modifications could have long-term repercussions on body weight and composition.

Preferential expression of the neuropeptide Y Y1 over the Y2 receptor subtype in cultured hippocampal neurons and cloning of the rat Y2 receptor

1 Neuropeptide Y (NPY) and NPY receptors are most abundant in the hippocampal formation where they modulate cognitive functions. Expression of NPY receptors in rat cultured primary hippocampal cells was investigated in the present study by use of combined molecular, pharmacological and immunohistochemical approaches, including the cloning of the rat Y2 receptor described here for the first time. 2 More than 70% of the hippocampal neurones were endowed with [125I]-[Leu31,Pro34]PYY Y1-like receptor silver grain accumulations and Y1 receptor immunostaining. These radio- and immuno-labelling signals were distributed over cell bodies and processes of bipolar, stellate and pyramidal-like neuronal cells, as confirmed by neurone-specific enolase and MAP-2 staining. 3 Competition binding profiles revealed that specific [125I]-[Leu31,Pro34]PYY binding was competitively displaced according to a ligand selectivity pattern prototypical of the Y1 receptor sub-type with [Leu31,Pro34]substituted NPY/PYY analogues >> C-terminal fragments = pancreatic polypeptides, with the non-peptide antagonist BIBP3226 being most potent. This profile excludes the possible labelling by [125I]-[Leu31,Pro34]PYY of the newly cloned Y4, Y5 and Y6 receptors. 4 The expression of the genuine Y1 receptor was confirmed by RT-PCR in hippocampal cultures. In contrast, negligible levels of Y2-like/[125I]-PYY3-36 binding were detected in these cultures in spite of the presence of its mRNA, as characterized by RT-PCR. The expression of both the Y1 and the Y2 receptor mRNAs was also noted in normal embryonic hippocampal tissues showing that signals expressed in cultured neurones were also present in utero. 5 Taken together, these results suggest that the Y1 receptor subtype may be of critical importance in the normal functioning of the rat hippocampus, especially during brain development and maturation.