Neuropeptide Y (NPY) is an abundant neurotransmitter in the nervous system and forms a family of evolutionarily related peptides together with peptide YY (PYY), pancreatic polypeptide (PP) and polypeptide Y (PY). These peptides are ligands to a family of receptors that mediate a wide range of physiological effects including stimulation of appetite. This work describes the molecular cloning of four novel NPY receptors. In rat a receptor called PP1, later renamed Y4, was cloned and characterized. It displays the highest amino acid sequence identity to the Y1 receptor. Rat Y4 differs extensively from human Y4, cloned subsequently, in both pharmacological properties, tissue distribution, and amino acid sequence with only 75% identity. Rat and human Y4 are the most diverged orthologues in the NPY receptor family. In guinea pig, the y6 receptor gene was found to be a pseudogene with several frameshift mutations. The gene is a pseudogene in human and pig too, but seems to give rise to a functional receptor in mouse and rabbit. This unusual evolutionary situa- tion may be due to inactivation of the gene in a mammalian ancestor and then restoration of expression in mouse and rabbit, but perhaps more likely due to independent inactivations in guinea pig, human and pig. In zebrafish, two new intronless receptor genes were cloned. Sequence comparisons suggest that both receptors are distinct from the mammalian receptors Y1, Y4 and y6, hence they were named Ya and Yb. Chromosomal localization provides further support that Ya and Yb may be distinct subtypes. The discoveries of the rat Y4 and zebrafish Ya and Yb receptors were unexpected and show that the NPY receptor family is larger than previously thought.

<p>Neuropeptide Y (NPY) is known to influence a vast number of physiological and behavioral processes such as vasoconstriction, circadian rhythms, feeding, anxiety and memory. Peptides of the NPY family bind to five different cloned G-protein coupled receptor subtypes (Y1, 2, 4-6). The studies compiled in this thesis present inter-species comparisons of sequence similarities, binding properties and expression patterns among receptors of the NPY family.</p><p>Cloning of Y1 and Y2 receptor subtypes from guinea pigs revealed strong binding profile similarity to the corresponding human receptors. Previously demonstrated atypical binding profiles in the caval vein of guinea pigs were concluded to result from other receptors than the cloned Y1 and Y2 receptors, or possibly combinations of distinct receptor subtypes.</p><p>The guinea pig Y5 receptor was found to be expressed in regions of the brain that have been indicated as important for regulation of food intake. Expression in the hypothalamus, amygdala and brain stem was noticed, similar to studies in rats and humans. In other brain regions, such as the striatum and hippocampus, some species differences were observed.</p><p>Mutagenesis studies of the human Y1 receptor indicated sites important for binding both of endogenous agonists and synthetic antagonists. Putative new sites of interaction with the Y1 antagonists BIBP3226 and/or SR120819A were recognized. The data were used to construct a three-dimensional structure model, based on a high-resolution bovine rhodopsin model.</p><p>Cloning of the chicken (<i>Gallus gallus</i>) Y1, Y2 and Y5 receptors revealed high sequence similarities with mammalian receptors. Most endogenous ligands bound with similar affinities as to mammalian receptors. The strongest exception was the discovery of high-affinity binding to chicken Y2 of [Leu³¹, Pro³⁴]NPY, which was previously considered to bind non-Y2 receptors only. </p><p>The new human Y1 receptor model provides a basis for further investigations of ligand-receptor interactions which will be aided by information on NPY receptors from other taxa. Guinea pigs are concluded to be a good complement to rats and mice for studying NPY signaling. These results demonstrate the benefits of species comparisons for pharmacological studies.</p>

Neuropeptide Y (NPY) is known to influence a vast number of physiological and behavioral processes such as vasoconstriction, circadian rhythms, feeding, anxiety and memory. Peptides of the NPY family bind to five different cloned G-protein coupled receptor subtypes (Y1, 2, 4-6). The studies compiled in this thesis present inter-species comparisons of sequence similarities, binding properties and expression patterns among receptors of the NPY family. Cloning of Y1 and Y2 receptor subtypes from guinea pigs revealed strong binding profile similarity to the corresponding human receptors. Previously demonstrated atypical binding profiles in the caval vein of guinea pigs were concluded to result from other receptors than the cloned Y1 and Y2 receptors, or possibly combinations of distinct receptor subtypes. The guinea pig Y5 receptor was found to be expressed in regions of the brain that have been indicated as important for regulation of food intake. Expression in the hypothalamus, amygdala and brain stem was noticed, similar to studies in rats and humans. In other brain regions, such as the striatum and hippocampus, some species differences were observed. Mutagenesis studies of the human Y1 receptor indicated sites important for binding both of endogenous agonists and synthetic antagonists. Putative new sites of interaction with the Y1 antagonists BIBP3226 and/or SR120819A were recognized. The data were used to construct a three-dimensional structure model, based on a high-resolution bovine rhodopsin model. Cloning of the chicken (Gallus gallus) Y1, Y2 and Y5 receptors revealed high sequence similarities with mammalian receptors. Most endogenous ligands bound with similar affinities as to mammalian receptors. The strongest exception was the discovery of high-affinity binding to chicken Y2 of [Leu31, Pro34]NPY, which was previously considered to bind non-Y2 receptors only. The new human Y1 receptor model provides a basis for further investigations of ligand-receptor interactions which will be aided by information on NPY receptors from other taxa. Guinea pigs are concluded to be a good complement to rats and mice for studying NPY signaling. These results demonstrate the benefits of species comparisons for pharmacological studies.

Investigou-se o efeito da leptina exógena e do maior consumo de energia, sobre o padrão da expressão de genes no hipotálamo de novilhas zebuínas; de modo a elucidar o mecanismo de sinalização da leptina no hipotálamo e os genes responsáveis pela obtenção da puberdade. Trinta e seis novilhas não púberes, e com idade entre 18 e 20 meses, foram divididas em três grupos experimentais: baixa energia (BAIXA), alta energia (ALTA), baixa energia com administração de leptina recombinante ovina (BAIXA+LEP), totalizando 56 dias de tratamento. Vinte e quatro novilhas foram abatidas ao apresentar sinais de puberdade, sendo eles: concentração de progesterona no soro superior a 1 ng/mL por duas amostras seguidas e presença de corpo lúteo detectável por ultra-sonografia. O hipotálamo foi colhido e armazenado a -80ºC. As amostras foram submetidas à extração do RNA total, tratadas com DNAse I e submetidas à síntese de cDNA. A quantificação relativa de quatro genes candidatos reconhecidamente envolvidos com a sinalização hipotalâmica da leptina em bovinos: NPY, NPY-Y1, NPY-Y4 e SOCS-3, foi feita através de PCR quantitativo (tempo real). Não houve efeito da administração de leptina sobre a expressão do NPY (P=0,70), ou de seus receptores: NPY-Y1 (P=0,27) e NPY-Y4 (P=0,92) no início da puberdade. A expressão de SOCS-3 foi reduzida (P=0,05) no hipotálamo de novilhas tratadas com leptina, o que sugere menor ação inibitória sobre a leptina. Em novilhas alimentadas com dieta de alta energia, a expressão do NPY-Y1 foi reduzida (P=0,04), o que indica que o hipotálamo estaria menos sensível à ação do NPY, permitindo a entrada precoce em puberdade. Nos demais genes estudados, NPY (P=0,75), NPY-Y4 (P=0,92) e SOCS-3 (P=0,24), a dieta não alterou significativamente suas expressões hipotalâmicas. Estudo mais abrangente do efeito da nutrição e da administração de leptina foi realizado através de hibridização em microarranjos de DNA, objetivando a identificação de possíveis genes candidatos, expressos no hipotálamo, que influenciam na obtenção da puberdade em novilhas Nelore tratadas com leptina ou submetidas à dieta de alta energia. Foram encontrados 78 genes cuja expressão foi alterada pela densidade energética da dieta (P=0,05) no hipotálamo das novilhas Nelore, destes foram selecionados os que apresentaram razões de expressão da ordem de 1,4 ou mais, totalizando 20 genes. Entre esses se destaca o gene da &beta;-arrestina 1 (ARRB1), que foi 1,40 vezes mais expresso (P=0,04) em novilhas submetidas à dieta de alta energia, pois atua na mediação da dessensibilização dos receptores acoplados à proteína-G-(GPCRs)1, como os receptores de NPY. Foram encontrados 134 genes diferencialmente expressos (P=0,05) devido a aplicação de leptina. Dentre os 80 genes que apresentaram razões superiores a 1,4, 18 genes tiveram a expressão reduzida, e 62 tiveram a expressão aumentada pela aplicação de leptina. Destes, alguns estão envolvidos na regulação da sinalização da leptina. O gene SRC foi menos expresso (1,64 vezes; P=0,04) em novilhas tratadas com leptina, o que sugere menor ação inibitória pela SHP-2. A proteína SOCS-2 foi 1,43 vezes (P=0,01) mais expressa no hipotálamo de novilhas tratadas com leptina. Sabe-se que, ao contrário de SOCS-1 e SOCS-3, CIS e SOCS-2 não se ligam, ou inibem, as janus kinases. O STAT-3 foi 2,14 vezes (P=0,03) mais expresso em novilhas tratadas com leptina, e sua ativação possibilita a ligação hipotalâmica da leptina com seu receptor (Ob-Rb). As IGFPB-1 e -2 foram mais expressas no hipotálamo de novilhas tratadas com leptina que em novilhas não tratadas, sendo IGFPB-1 1,78 vezes (P=0,04) mais expressa e IGFPB-2 1,89 vezes (P=0,05). As IGFPBs podem desempenhar função de potencialização da ação do IGF-1, ou exercer ação inibitória. Conclui-se que tanto o consumo de energia quanto a aplicação com leptina influenciaram o padrão de expressão gênica no hipotálamo de novilhas Nelore. A modulação da quantidade do receptor do NPY, NPY-Y1, no hipotálamo pode ser uma via importante pela qual a nutrição afeta o início da puberdade em novilhas. E ainda que estudos mais aprofundados de expressão dos genes encontrados nas hibridizações por microarranjo poderão revelar interações mais concisas entre os genes, a nutrição e a leptina na obtenção da puberdade. / It was investigated the effect of exogenous leptin and the high energy intake on gene expression pattern in the hypothalamus of zebuine heifers; in a way to elucidate the mechanism of leptin signaling in hypothalamus and the responsible genes for puberty. Thirty six heifers not in puberty at 18 and 20 months of age were divided in three experimental groups: low energy diet (LOW), high energy diet (HIGH), low energy diet with administration of recombinant ovine leptin (LOW+LEP), totalizing 56 days of treatment. Twenty four heifers were slaughtered when presented the signals of puberty: progesterone serum concentration above 1 ng/mL for two followed weeks and the presence of detectable corpus luteum by ultrasonography. The hypothalamus was collected and stored at -80ºC. Samples were submitted to total RNA extraction, treated with DNAse I and submitted to cDNA synthesis. The relative quantification of four candidate genes admittedly involved with hypothalamic leptin signaling in bovine: NPY, NPY-Y1, NPY-Y4 and SOCS-3, was evaluated through quantitative PCR (real time). There was no effect of leptin administration on NPY expression (P=0.70), or on its receptors: NPY-Y1 (P=0.27) and NPY-Y4 (P=0.92) in the onset of puberty. The expression of SOCS-3 was reduced (P=0.05) in the hypothalamus of heifers treated with leptin, what suggests lower inhibitory action over leptin. In heifers fed high energy diets, the expression of NPY-Y1 was reduced (P=0.04), which indicates that the hypothalamus would be less sensitive to the action of NPY, allowing the precocious onset of puberty. In other studied genes, NPY (P=0.75), NPY-Y4 (P=0.92) and SOCS-3 (P=0.24), the diet did not significantly altered their hypothalamic expressions. A more comprehensive study regarding the effect of nutrition and leptin administration was performed through the hybridization in DNA microarrangements, aiming the identification of possible candidate genes, expressed in hypothalamus that influence in the onset of puberty in Nelore heifers treated with leptin or submitted to high energy diets. It was found 78 genes whose expression was altered by the energy density of the diet (P<0.05) in the hypothalamus of Nelore heifers. From them, it was selected those genes which presented rates of expression in the order of 1.4 or more, totalizing 20 genes. From them, the highlight gene was &beta;-arrestin 1 (ARRB1) which was 1.40 more expressed (P=0.04) in heifers fed high energy diet due to its action in the mediation of receptors desensibilization coupled to protein-G-(GPCRs)1, as the receptors of NPY. It was found 134 genes differently expressed (P<0.05) due to leptin administration. From the 80 genes that presented rates of expression higher than 1.4, 18 genes had their expression reduced and 62 had their expression increased by leptin administration. Some of these 62 genes are involved in the regulation of leptin signaling. The gene SRC was the less expressed (1.64 times; P=0.04) in heifers treated with leptin what suggests lower inhibitory action by SHP-2. The protein SOCS-2 was 1.43 times (P=0.01) more expressed in the hypothalamus of heifers treated with leptin. It is known that on the contrary of SOCS-1 and SOCS-3, CIS and SOCS-2 do not bind or inhibit, as janus kinases. The STAT-3 was 2.14 times (P=0.03) more expressed in heifers treated with leptin and its activation enables the hypothalamic binding of leptin and its receptor (Ob-Rb). The IGFPB-1 and -2 were more expressed in the hypothalamus of heifers treated with leptin than the animals not treated, being the IGFPB-1 1.78 times (P=0.04) more expressed and the IGFPB-2 1.89 times (P=0.05). The IGFPBs could play a function of IGF-1 action enhancer or exert an inhibitory action. It is concluded that both energy intake and leptin administration influenced gene expression pattern in the hypothalamus of Nelore heifers. The modulation of the receptor quantity of NPY, NPY-Y1 in hypothalamus could be an important route in which nutrition affects the onset of puberty in heifers. Moreover, more detailed studies regarding gene expression in hybridization by microarrangement could reveal more concise interactions between genes, nutrition and leptin in the onset of puberty.

A elucidação dos mecanismos moleculares pelos quais tratamentos hormonais alteram o início da puberdade é de fundamental importância para o desenvolvimento de estratégias que reduzam a idade ao primeiro parto, e consequentemente a taxa de desfrute do rebanho Nelore. Foram investigados os efeitos do uso de dispositivos de progesterona, e do estradiol endógeno, sobre mecanismos moleculares controlando a obtenção da puberdade de novilhas Nelore peripúberes. Especificamente, como as diferenças na expressão de genes relativos à reprodução em duas áreas do hipotálamo. Trinta e cinco novilhas Nelores não púberes, e com idade entre 13 e 14 meses, foram divididas em quatro tratamentos experimentais (nove ou oito por tratamento): dispositivo de P4 sem estradiol (SP); dispositivo de P4 com estradiol (PE); sem dispositivo de P4 e sem estradiol (SS); e sem dispositivo de P4 e com estradiol (SE). As novilhas foram alimentadas no cocho pós desmame até atingirem 295 ± 11 kg, com fornecimento de água à vontade. Ao término do tratamento hormonal as novilhas foram abatidas e as porções de hipotálamo colhidas para processamento e armazenagem a -80 ºC. O RNA total do tecido hipotalâmico foi extraído, tratado com DNAse I e submetido à síntese de cDNA para estudo da expressão gênica por PCR em tempo real (qRT-PCR). Foram formados pools de RNA para a realização de um estudo abrangente da administração de progesterona e do efeito do estradiol endógeno e das diferenças entre áreas do hipotálamo, realizado por sequenciamento de nova geração (RNA-Seq), de forma a identificar possíveis genes candidatos no hipotálamo. Foram encontrados genes diferencialmente expressos alterados pelos tratamentos e entre as áreas do hipotálamo relativos à obtenção da puberdade. / The understanding of the molecular mechanisms by which nutrition, genetics and hormonal treatments affect the beginning of puberty is of great importance for developing strategies aiming to reduce the age at first calving, and therefore increase the slaughter rate in Nellore cattle. The effects of progesterone device and of endogenous estradiol on the molecular mechanisms controlling the attainment of puberty in Nellore heifers were investigated. Specifically, the molecular pathways of progesterone and estradiol were studied in the hypothalamus. Thirty five non-pubertal heifers, between 13 and 14 months of age, were divided into four treatment (nine or eight per treatment): P4 device without estradiol (SP), P4 device with estradiol (PE), without P4 device and without estradiol (SS), and without P4 device and with estradiol (SE). The heifers were fed after weaning until reach 295 ± 11 Kg, with water access. At the end of the hormonal treatments all heifers were slaughtered and the hypothalamus areas were harvested, processed and then also stored at -80°C. Total RNA of hypothalamus were extracted, treated with DNase I and submitted to cDNA synthesis for gene expression quantification by real time PCR (qRT-PCR). RNA samples were pooling to realize a comprehensive study of the effects of progesterone administration and endogenous estrogen on attainment of puberty by next-generation sequencing (RNA-Seq), in order to identify possible candidate genes in the hypothalamus. Genes diffentially expressed between hypothalamic areas and affected by treatments were found.

<p>Gene families in vertebrates often contain more dulicates (paralogs) than in invertebrates. This has been attributed to genome duplications, i.e., tetraploidizations. Two of the gene families that have expanded in vertebrate evolution are the neuropeptide Y (NPY) family of peptides and the neuropeptide Y receptors (NPYR) that are involved in many brain functions including appetite regulation.</p><p>Two NPYR genes, Y2 and Y7, were cloned in the rainbow trout. Although they arose from a common ancestral gene in early vertebrate evolution, their ligand-binding properties are very similar. Two NPYR genes were cloned in the coelacanth <i>Latimeria chalumnae</i> and found to be orthologs of Y5 and Y6 discovered in mammals.</p><p>Analyses of gene families close to the NPYR genes in the pufferfishes <i>T. nigroviridis</i> and <i>T. rubripes</i> showed that at least 25 additional gene families had an evolutionary history similar to the NPYR family, thereby providing evidence for fish specific-duplications of these chromosomes. Cloning and phylogenetic analysis of 22 NPYR gene fragments from several ray-finned fishes showed that basal species seem to have the same repertoire as tetrapods. Despite the tetraploidization in the teleost fish lineage, many teleosts seem to have fever genes than the gnathostome ancestor due to gene loss. Only one duplicate seems to have survived.</p><p>The NPY peptide family was found to have expanded in the teleost tetraploidization with duplicates of both NPY and PYY (peptide YY) in some teleosts. Fourteen neighboring gene families were found to have evolved in a similar manner as the NPY-family genes. Positional information fascilitated orthology assignment of peptide genes in teleost fishes and allowed correction of previously misidentified genes.</p><p>In summary, the evolutionary history of the NPY and NPYR gene families involve large-scale duplication events coinciding with the proposed tetraploidizations. The appearance of new genes in early vertebrates and in teleost fishes probably had important implications for the evolution of new functions in this system.</p>

Gene families in vertebrates often contain more dulicates (paralogs) than in invertebrates. This has been attributed to genome duplications, i.e., tetraploidizations. Two of the gene families that have expanded in vertebrate evolution are the neuropeptide Y (NPY) family of peptides and the neuropeptide Y receptors (NPYR) that are involved in many brain functions including appetite regulation. Two NPYR genes, Y2 and Y7, were cloned in the rainbow trout. Although they arose from a common ancestral gene in early vertebrate evolution, their ligand-binding properties are very similar. Two NPYR genes were cloned in the coelacanth Latimeria chalumnae and found to be orthologs of Y5 and Y6 discovered in mammals. Analyses of gene families close to the NPYR genes in the pufferfishes T. nigroviridis and T. rubripes showed that at least 25 additional gene families had an evolutionary history similar to the NPYR family, thereby providing evidence for fish specific-duplications of these chromosomes. Cloning and phylogenetic analysis of 22 NPYR gene fragments from several ray-finned fishes showed that basal species seem to have the same repertoire as tetrapods. Despite the tetraploidization in the teleost fish lineage, many teleosts seem to have fever genes than the gnathostome ancestor due to gene loss. Only one duplicate seems to have survived. The NPY peptide family was found to have expanded in the teleost tetraploidization with duplicates of both NPY and PYY (peptide YY) in some teleosts. Fourteen neighboring gene families were found to have evolved in a similar manner as the NPY-family genes. Positional information fascilitated orthology assignment of peptide genes in teleost fishes and allowed correction of previously misidentified genes. In summary, the evolutionary history of the NPY and NPYR gene families involve large-scale duplication events coinciding with the proposed tetraploidizations. The appearance of new genes in early vertebrates and in teleost fishes probably had important implications for the evolution of new functions in this system.

Two whole genome duplications (2R) occurred early in vertebrate evolution. By using combined information from phylogenetic analyses and chromosomal location of genes, this thesis delineates the evolutionary history of two receptor-ligand systems that expanded by these large scale events. A third whole genome duplication (3R) took place in the teleost fish lineage and has also contributed to the complexity of the gene families. New members of neuropeptide Y (NPY) peptide and receptor families were generated in 2R and 3R. Evolutionary comparisons show that the ancestral teleost fish had four peptides; subsequently, differential losses of the peptide genes occurred. In zebrafish the peptides and receptors display differences in tissue distribution and have  evolved binding preferences. In the frog Silurana tropicalis three peptides and six receptors werev identified, also displaying some differences in tissue distribution and receptor-ligand preferences. The findings in these experimental animals highlight both evolutionary conservation and lineage-specific features of the NPY system. The opioid system consists of four receptors and several peptides originating from four precursors. These results show that the receptor family was formed in 2R and 3R and that 2R together with one local duplication gave rise to the peptide family. The ancestral receptor and peptide genes were located on the same chromosome, suggesting coevolution. The Hox gene clusters, important in early development, provided the first strong evidence for 2R. Several neighboring gene families were analyzed and found to have expanded in 2R and 3R. In depth analyses of insulin-like growth factor binding protein (IGFBP) and voltage-gated sodium channel (SCN) gene families illustrates the importance of local duplications in combination with whole genome duplications in the formation of gene families. These findings provide additional strong evidence for two genome duplications in early vertebrate evolution and show that these events generated many new genes that could evolve new or more specialized functions.

During the past few decades, obesity has risen significantly in the United States with recent estimates showing that 65% of Americans are overweight and 30% are obese. This increase is a major cause for concern because obesity is linked to many secondary health consequences that include type II diabetes, heart disease, and cancer. Current approaches to the obesity problem primarily have focused on controls of food intake and have been largely unsuccessful. Food, however, almost always has to be acquired (foraging) and frequently is stored for later consumption (hoarding). Therefore, a more comprehensive approach that includes studying the underlying mechanisms in human foraging and food hoarding behaviors could provide an additional target for pharmaceutical or behavioral manipulations in the treatment and possibly prevention of obesity. Neuropeptide Y (NPY) is a particular peptide that provides a potent orexigenic drive to alter foraging, food hoarding (appetitive ingestive behaviors) and food intake (consummatory ingestive behaviors) in variety of species. NPY is predominantly produced in the arcuate nucleus of the hypothalamus (ARC) and has extensive efferent projections throughout the brain. Two target nuclei of ARC-NPY, the paraventricular nucleus of the hypothalamus (PVH) and perifornical area (PFA), have been shown to mediate the effect of NPY on food intake in laboratory rats and mice, but nothing is known about the effect of ARC-NPY on foraging and food hoarding. In addition, the action of specific NPY receptor subtypes within these two nuclei for these behaviors is unknown. Even though ARC-NPY is one of the main sources of input into the PVH and PFA, it is not known if this NPY fiber projection mediates alterations in appetitive and consummatory ingestive behaviors. Therefore, the purpose of this dissertation is to test 1) if NPY within the PVH or PFA controls appetitive, as well as, consummatory ingestive behaviors, 2) if NPY Y1 receptors within the PVH or PFA differentially control appetitive or consummatory ingestive behaviors, and 3) if NPY from the ARC is necessary for the control of appetitive and consummatory ingestive behaviors.

The mechanism of weight gain due to treatment with olanzapine, a serotonin receptor antagonist, has not been fully understood. Weight gain and food intake are under the control of neuropeptides/hormones, POMC (proopiomelanocortin), CART (cocaine and amphetamine regulated transcript), AgRP (Agouti-related peptide) and NPY (neuropeptide Y) that are synthesized and secreted from the arcuate nucleus (ARC) of hypothalamus. In this study, the altereration of the ARC neuropeptide/hormone levels both in humans and rats were determined as one of the weight gain mechanism. To examine olanzapine&rsquo / s weight gain effects, male first attack psychotic patients (pre-treatment), were hospitalized and treated for 4 -weeks (post-treatment), (n = 22), and healthy control group (n = 26) were included to the study. Case-control association design was used to analyze the changes in body mass index (BMI), peripheral leptin and the ARC neuropeptides levels. In patients, after 4-weeks of the olanzapine treatment / BMI and the waist circumference were significantly increased with average weight gain of 4.33 kg. In pre-treatment group, NPY levels were significantly lower while &alpha / -MSH, the anorexigenic product of POMC levels were significantly higher vs. control. At post-treatment, both leptin and NPY levels were significantly increased but the CART levels did not change. To further understand the underlying mechanism of olanzapine induced weight gain, the drug was orally administrated to 10 healthy male Wistar rats to analyze both the hypotalamic gene expression and peripheral levels of those candidate neuropeptides. In rats food consumption was increased and hypotalamic mRNA levels of NPY, AgRP and POMC were decreased while CART levels did not show any alteration. Consistent with the expression data, circulating levels of NPY, AgRP and &alpha / -MSH decreased significantly but CART levels were also reduced unexpectedly. In conclusion, it may be presumed that the antagonistic effect of olanzapine on the ARC neurons might be the basis for a disregulation of the neurohormones secretion which may cause weight gain in the treated psychotic patients.