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1.
1. Several neural peptides are known to stimulate feeding behaviour in mammalian species. The aim of this study was to elucidate whether central injection of mammalian motilin, melanin-concentrating hormone (MCH) or galanin stimulates feeding in the neonatal chick. 2. None of the peptides applied here enhanced the food intake of the chick. 3. It is suggested that motilin, MCH and galanin, at least those of mammalian origin, may not regulate feeding in neonatal chicks, when administered to the central nervous system.  相似文献   

2.
The acute effect of leptin on the regulation of food intake was investigated in layer and broiler chickens. In an initial study, we observed that a single intraperitoneal injection of recombinant chicken leptin (1 mg/kg BW) dramatically reduced (38%) food intake in 56-day-old layer chickens, more moderately reduced (15%) food intake in 9-day-old layer chicks, and had no significant effect in 9-day-old broiler chicks. In a subsequent study, body weight and plasma concentrations of leptin were measured weekly in layer and broiler chicks from day 1 to 35 of age and brain leptin receptor and neuropeptide Y (NPY) mRNA expression were analyzed at 1, 9, and 35 days of age. At day 1 of age, peripheral concentrations of leptin were significantly greater in layer than broiler chicks. Subsequently, despite increases in body weight and differences in growth rates between layer and broiler chicks from day 8 to day 35 of age, peripheral concentrations of leptin were constant and similar in both genotypes. Leptin receptor and NPY mRNA were expressed in brain from day 1 in chicks of both genotypes and increased significantly to day 35 of age. These observations provide evidence that the inhibitory effect of leptin on the regulation of food intake in growing chicks is an age dependent process. Furthermore, acquisition of the anorectic effect of leptin is likely to be associated with greater expression of the leptin receptor and NPY mRNAs than to changes in blood levels of leptin. Finally, this study provides evidence that chickens selected for high growth rates may be less sensitive or responsive to peripheral concentrations of leptin than chickens with low growth rates (layers), suggesting that the faster growth of broiler chicks may be related to a lessened responsiveness to anorexigenic factors.  相似文献   

3.
Behavioral regulators in the brain of neonatal chicks   总被引：1，自引：0，他引：1  
Domestic chickens are precocial and therefore have relatively well‐developed processes at hatch. As a result, neonatal chicks grow well at hatch with no parental care. The regulation of food intake in animals, including domestic birds, is complicated. Just after hatching, neonatal chicks find their food by themselves and they can control their food intake. Recently, prolactin releasing peptide and gonadotropin‐inhibitory hormone were confirmed as central orexigenic factors in the neonatal chick. Both peptides have a common structure as RFamide peptides. On the other hand, vasoactive intestinal peptide and pituitary adenylate cyclase‐activating polypeptide, both belonging to the glucagon superfamily, were recognized as inhibitory. Broiler chicks have either a greater capability to acclimatize to novel environments, or a blunted hypothalamus‐pituitary‐adrenal axis compared with layer chicks. These differences are explained by higher melatonin concentrations in the pineal gland and other parts of the brain of broiler chicks since melatonin attenuates the stress response. Stressful behavior in chicks can be attenuated by neurotransmitters or by nutrients such as creatine, phosphatidylserine, L‐serine and (‐)‐epigallocatechin gallate. It is suggested that the regulation of behavior is somewhat specific and can be attenuated by some manipulation in neonatal chicks.  相似文献   

4.
This is a test-report of ghrelin levels in plasma and proventriculus, the glandular portion of the avian stomach, by using a specific radioimmunoassay for acylated ghrelin, as well as the expression of the ghrelin gene in the proventriculus after a 12-h fasting period followed by a 6-h feeding period with 6-day-old layer chicks. After fasting, the plasma ghrelin levels increased from 21.3 ± 4.5 to 32.9 ± 5.0 fmol/ml, but once refed it returned to the control value. After fasting, the ghrelin mRNA and the peptide levels in the proventriculus increased, and ghrelin mRNA levels remained high but once refed the ghrelin content returned to the control level. Furthermore, in order to examine the effect of increased circulating ghrelin on food intake, a bolus intravenous injection of 500 pmol of chicken ghrelin was given to 8-day-old chicks. The ghrelin injection did not cause any significant changes in food intake. These results indicate that the levels of ghrelin and its mRNA with layer chicks are altered according to the feeding state and this in a similar manner as has been observed in mammals. Unlike in mammals, an increase in circulating ghrelin does not cause the promotion of food intake in chicks.  相似文献   

5.
Physiology of ghrelin and related peptides   总被引：4，自引：0，他引：4  
Growth hormone (GH) released from pituitary under direct control of hypothalamic releasing (i.e., GHRH) and inhibiting (i.e., sst or SRIF) hormones is an anabolic hormone that regulates metabolism of proteins, fats, sugars and minerals in mammals. Cyril Bowers' discovery of GH-releasing peptide (GHRP-6) was followed by a search for synthetic peptide and nonpeptide GH-secretagogues (GHSs) that stimulate GH release, as well as a receptor(s) unique from GHRH receptor. GHRH and GHSs operate through distinct G protein-coupled receptors to release GH. Signal transduction pathways activated by GHS increase intracellular Ca2+ concentration in somatotrophs, whereas GHRH increases cAMP. Isolation and characterization of ghrelin, the natural ligand for GHS receptor, has opened a new era of understanding to physiology of anabolism, feeding behavior, and nutritional homeostasis for GH secretion and gastrointestinal motility through gut-brain interactions. Other peptide hormones (i.e., motilin, TRH, PACAP, GnRH, leptin, FMRF amide, galanin, NPY, NPW) from gut, brain and other tissues also play a role in modulating GH secretion in livestock and lower vertebrate species. Physiological processes, such as neurotransmission, and secretion of hormones or enzymes, require fusion of secretory vesicles at the cell plasma membrane and expulsion of vesicular contents. This process for GH release from porcine somatotrophs was revealed by atomic force microscopy (AFM), transmission electron microscopy (TEM) and immunohistochemical distribution of the cells in pituitary during stages of development.  相似文献   

6.
Background: Glucocorticoids(GCs) are involved in the control of appetite in birds and mammals. The effect of GCs on feed intake in birds depends on their dietary energy level. But the regulation mechanism of GCs on appetite is still unclear in chickens facing to different energy level. An experiment was conducted to investigate the effect of dexamethasone(DEX) on hypothalamic expression of appetite-related peptides in chickens fed high/low fat diet and under fasting/feeding condition.Results: An interaction between DEX injection and dietary energy level was found on hypothalamic corticotropinreleasing hormone(CRH) gene expression in fasted chickens(P 0.05). The chickens, given a DEX injection and a low fat diet treatment, had the highest CRH m RNA levels than any of the fasted chickens given treatments(P 0.05).Under fasting conditions, the DEX treatment significantly increased hypothalamic neuropeptide Y(NPY) and GC receptors m RNA levels(P 0.05). Under re-feeding conditions, DEX treatment significantly decreased hypothalamic expression levels of NPY and agouti-related peptide(Ag RP) but significantly increased the level of hypothalamic CRH expression(P 0.05).Conclusion: A regulatory network formed by NPY, Ag RP and CRH is associated with the appetite-control by GCs.The result suggests that the regulation of GCs on orexigenic neuropeptides expression is dependent at least partially on dietary energy level and feeding state.  相似文献   

7.
A study was undertaken in Corriedale ewes to test the lipostat theory using data obtained from a model of seasonal change in food intake and body composition. The theory predicts adipose-derived factors signal to the brain and vice versa, to maintain homeostasis. It is held that leptin acts on cells in the brain to regulate food intake and energy expenditure, through “first order” neurons in the arcuate nucleus (ARC). These cells are thought to receive information that is relayed to “second order” neurons, to regulate food intake and other functions. In this study, groups (n = 4–5) of ovariectomized ewes were maintained under natural conditions and sampled at various points across the year. Food intake, body composition and indices of metabolic function were measured prior to collection of brains for in situ hybridization analysis. Expression of genes encoding for neuropeptide Y (NPY), pro-opiomelanocortin (POMC), orexin (ORX), melanin concentrating hormone (MCH) and leptin receptor (ObRb) was quantified. NPY gene expression was high when food intake was also high but, across the year, changes in NPY and POMC gene expression did not correspond predictably to plasma leptin levels or leptin receptor gene expression. Negative correlation was found between adiposity (omental and whole body fat) and gene expression of MCH and ORX, suggesting that changes in expression of genes for “second order” orexigenic peptides are closely linked to changes of metabolic state, even when similar relationships cannot be shown for expression of genes in “first order” neurons. These data provide support for the lipostat theory.  相似文献   

8.
Growing evidence suggests that insulin interacts with both orexigenic and anorexigenic peptides in the brain for the control of feeding behavior in mammals. However, the action of central insulin in chicks has not yet been identified. In the present study, we investigated the effects of central injection of insulin on feeding behavior in chicks. Intracerebroventricular (ICV) administration of insulin, at doses that do not influence peripheral glucose levels, significantly inhibited food intake in chicks. Central injection of insulin in chicks significantly increased expression of pro-opiomelanocortin (POMC) mRNA, and decreased that of neuropeptide Y (NPY) mRNA. Finally, co-injection of the melanocortin antagonist (SHU9119 or HS014) prevented the reduction in food intake caused by ICV administration of insulin. These data suggest that insulin functions in chicks as an appetite-suppressive peptide in the central nervous system, and that the central melanocortin system mediates this anorexic effect of insulin, as in mammals.  相似文献   

9.
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10.
Melanin-concentrating hormone (MCH) stimulates feeding when injected intracerebroventricularly (ICV) in rats. At present it is not clear whether the function of MCH is similar in ruminants, which are species with a continuous delivery of nutrients. Therefore the current investigation sought to determine the role of MCH in sheep. In the first experiment, six, castrate male sheep were satiated and received one of four treatments [saline, 0.1, or 1.0 nmol/kg MCH, and NPY (0.1 nmol/kg)] injected ICV over 30s, then infused ICV for 6 h ( approximately 500 microl/h). Food intake was measured for 2 h before and at 2, 4, 6, 8, 12 and 24 h. In this experiment, feed intake was increased (P相似文献   

11.
Growth hormone (GH) is secreted in a pulsatile manner, but the underlying mechanisms of GH pulse generation remain to be resolved. In the present study, we investigated the relationship between GH pulses in the peripheral circulation and GH-releasing hormone (GHRH) and somatostatin (SRIF) profiles in the cerebrospinal fluid (CSF) of male goats. The effects of an intracerebroventricular (icv) injection of neuropeptide Y (NPY), galanin and ghrelin were also analyzed. Blood and CSF samples were collected every 15 min for 8 hr from the jugular vein and third ventricle, respectively. GH pulsatility in the goat was found to consist of distinct large pulses of 5 hr periodicity and small pulses of 1 hr periodicity. GHRH and SRIF in the CSF fluctuated in a pulsatile manner with 1 hr periodicity, and most of the descending phase of SRIF pulses were associated with the initiation of GH pulses. Icv injections of NPY, galanin and ghrelin stimulated GHRH release without affecting SRIF release. In addition, NPY suppressed, and galanin and ghrelin induced large GH pulses, although ghrelin was much more effective than galanin. These results suggest that an hourly fall in SRIF is involved in generating intrinsic circhoral rhythm of GH pulsatility. The mechanisms underlying the generation of large GH pulses of 5 hr periodicity remain unknown, while direct action of NPY and/or ghrelin on the pituitary might be involved.  相似文献   

12.
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13.
Ghrelin, neuropeptide Y (NPY) and cholecystokinin (CCK) all have important roles in the regulation of feeding in fish and mammals. To better understand the role of the three peptides in appetite regulation in the early developmental stages of blunt snout bream (Megalobrama amblycephala), partial cDNA sequences of ghrelin, NPY and CCK genes were cloned. And then, real‐time quantitative PCR and RT‐PCR were used to detect and quantify the mRNA expressions of these genes from zygotes to larvae of 50 days after hatching (DAH). Ghrelin, NPY and CCK were all expressed throughout the embryonic and larval development stages, and the expression levels were higher in larval stages than in embryonic stages. Ghrelin and NPY mRNA expressions were upregulated at 1, 3, 5 DAH, while CCK mRNA expression was reduced significantly at 3 DAH. The mRNA expression levels of three genes in larvae varied significantly until 30 DAH. In adult fish, all three peptides were detected to be expressed in brain and several peripheral tissues. Ghrelin mRNA was mainly expressed in the intestine, whereas NPY and CCK mRNAs were mainly expressed in the brain. Taken together, these results indicate that ghrelin, NPY and CCK may have roles in early development and participate in the regulation of feeding of larvae in blunt snout bream and will be helpful for further investigation into feed intake regulation in adults of this species.  相似文献   

14.
The regulatory mechanisms underlying food intake in chickens have been a focus of research in recent decades to improve production efficiency when raising chickens. Lines of evidence have revealed that a number of brain‐gut peptides function as a neurotransmitter or peripheral satiety hormone in the regulation of food intake both in mammals and chickens. Glucagon, a 29 amino acid peptide hormone, has long been known to play important roles in maintaining glucose homeostasis in mammals and birds. However, the glucagon gene encodes various peptides that are produced by tissue‐specific proglucagon processing: glucagon is produced in the pancreas, whereas oxyntomodulin (OXM), glucagon‐like peptide (GLP)‐1 and GLP‐2 are produced in the intestine and brain. Better understanding of the roles of these peptides in the regulation of energy homeostasis has led to various physiological roles being proposed in mammals. For example, GLP‐1 functions as an anorexigenic neurotransmitter in the brain and as a postprandial satiety hormone in the peripheral circulation. There is evidence that OXM and GLP‐2 also induce anorexia in mammals. Therefore, it is possible that the brain‐gut peptides OXM, GLP‐1 and GLP‐2 play physiological roles in the regulation of food intake in chickens. More recently, a novel GLP and its specific receptor were identified in the chicken brain. This review summarizes current knowledge about the role of glucagon‐related peptides in the regulation of food intake in chickens.  相似文献   

15.
1. Fatty acid oxidation is known to be involved in the control of food intake in mammals. The effect of fatty acid oxidation on food intake in chickens was studied using a ketone body (beta-hydroxybutyrate (beta-HB)) and mercaptoacetate (MA) (an inhibitor of fatty acid oxidation). 2. Central and peripheral injection of beta-HB decreased food intake in a dose-dependent manner, while low doses of MA had no effect. Higher doses of MA inhibited feeding but also caused mortality. 3. These results indicate that ketone bodies act as an inhibitory signal for food intake in both the central and peripheral nervous systems but that inhibition of fatty acid oxidation may not be associated with feeding behaviour in chicks.  相似文献   

16.
1. Four experiments were carried out to study the effect of offering a 91.5 g/l solution of glucose, compared to tap water, on fluid intake, food intake and growth of individually-caged immature chickens of both layer and broiler strains. 2. Male chicks of an egg-laying strain were offered glucose solution or tap water from 27 to 62 d after hatching. There was no effect of glucose on fluid intake but it depressed food intake (P less than 0.01) to give equal total energy intakes for each treatment. Body weight gain was reduced (P less than 0.001) and carcase fat content increased (P less than 0.001) by the glucose to yield no difference to total carcase energy. 3. When birds were placed in a respiration chamber for two 23-h periods there was no effect of treatment on outputs of energy as faeces + urine or as heat. 4. Male broilers were offered glucose solution or tap water with diets containing either 150 or 195 g protein/kg from 20 to 55 d after hatching. With the low-protein diet glucose depressed food intake (P less than 0.01) but total energy intake and carcase energy were not significantly affected. With the high-protein diet glucose did not depress food intake but increased total energy intake and total body fat. 5. Layer and broiler chicks were offered either a choice of the low- and high-protein diets or a single diet intermediate in protein content, with glucose solution or tap water. With broilers total food intake was depressed by glucose, mainly by a reduced intake of the low-protein diet. Intake of neither diet by the layer chicks was significantly affected by glucose. 6. It is concluded that provision of extra energy in glucose solution depresses food intake when the resultant energy:protein ratio becomes limiting. With a higher protein diet, or with birds having lower protein requirements, glucose solution does not depress food intake and increased fat deposition occurs.  相似文献   

17.
1. An experiment was conducted to study changes in the expression of the hypothalamic leptin receptor, neuropeptide Y (NPY) and proopiomelanocortin (POMC) with age during the early neonatal period in two different strains of chickens: Beijing-You (BY) and Arbor Acres (AA). 2. Compared with BY chickens, AA chickens ate more, and grew faster. Hypothalamic NPY concentrations of both strains increased with age until d 7 followed by a decline. Hypothalamic NPY of BY chickens on d 7 was lower than in AA chickens at the same age. 3. No difference with age was observed in hypothalamic α-melanocyte-stimulating hormone (α-MSH) of BY chickens, while hypothalamic α-MSH in AA chickens on d 0 was higher than on the other days. Compared with AA chickens, BY chickens showed lower hypothalamic α-MSH on d 0. 4. Similar developmental changes between two strains were observed in the expression of leptin receptor, NPY or POMC genes in the hypothalamus. Hypothalamic mRNA of leptin receptor on d 0 was higher than on d 1 and 7. Unlike NPY, hypothalamic NPY mRNA on d 0 was higher than on the other days. 5. Hypothalamic POMC mRNA decreased gradually with age until 7 d followed by a slight increase. 6. The results showed that the developmental changes of hypothalamic signal molecules varied with age and strain. NPY, α-MSH and leptin receptor might be involved in the early programming of feed intake in newly hatched chickens.  相似文献   

18.
It is well known that after a stressor, levels of plasma cortisol rise, inducing physiological changes within the animal that are directed toward maintaining homeostasis. Less well understood is the role of cortisol in regulating food intake in teleosts. This study investigated the effect of cortisol on food intake and regulation of the neuroendocrine appetite-stimulating hormones, neuropeptide Y (NPY) and ghrelin, in tilapia (Oreochromis mossambicus). Male and female tilapia were randomly assigned to one of the following treatments: unhandled control, vehicle-injected control, or cortisol (2 μg/g BW). Food intake was determined 24 h after injection during a 1-h feeding trial. Cortisol reduced food intake (P < 0.001). An identical study was conducted to measure the effects of 24-h cortisol treatment on the endocrine regulators of food intake. Cortisol reduced stomach expression of ghrelin mRNA (P < 0.05) and plasma concentrations of ghrelin (P < 0.05). In the hypothalamus/optic tectum cortisol reduced levels of GHSR1a-LR (biologically active ghrelin receptor) mRNA. In the telencephalon/preoptic area cortisol significantly reduced levels of NPY and GHSR1b-LR (biologically inactive ghrelin receptor) mRNA. These findings suggest that anorexigenic actions of cortisol may be mediated via two separate pathways: (1) reducing circulating ghrelin levels as well as GHSR1a-LR expression in the hypothalamus/optic tectum and/or (2) suppressing NPY expression in the telencephalon/preoptic area.  相似文献   

19.
Role of leptin in farm animals: a review   总被引：2，自引：0，他引：2  
The discovery of hormone leptin has led to better understanding of the energy balance control. In addition to its effects on food intake and energy expenditure, leptin has now been implicated as a mediator of diverse physiological functions. Recently, leptin has been cloned in several domestic species. The sequence similarity suggests a common function or mechanism of this peptide hormone across species. Leptin receptors are expressed in most of tissues, which is consistent with the multiplicity of leptin functions. The main goal of this review was to summarize knowledge about effect of leptin on physiology of farm animals. Experiments point to a stimulatory action of leptin on growth hormone (GH) secretion, normal growth and development of the brain. Surprisingly, leptin is synthesized at a high rate in placenta and may function as a growth factor for fetus, signalling the nutritional status from the mother to her offspring. Maturation of reproductive system can be stimulated by leptin administration. Morphological and hormonal changes, consistent with a major role of leptin in the reproductive system, have also been described, including the stimulation of the release of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin. Leptin has a substantial effect on food intake and feeding behaviour in animals. Administration of leptin reduces food intake. Its level decrease within hours after initiation of fasting. Leptin also serves as a mediator of the adaptation to fasting, and this role may be the primary function for which was the molecule evolved.  相似文献   

20.
Peripheral ghrelin reduces food intake and respiratory quotient in chicken   总被引：7，自引：0，他引：7  
Ghrelin injection, either centrally or peripherally strongly stimulates feeding in human and rodents. In contrast, centrally injected ghrelin inhibits food intake in neonatal chickens. No information is available about the mechanism and its relationship with energy homeostasis in chicken. Since ghrelin is predominantly produced in the stomach, we investigated the effect of peripherally injected ghrelin (1 nmol/100g body weight) on food intake and energy expenditure as measured in respiratory cells by indirect calorimetry for 24h in one-week-old chickens. Plasma glucose, triglycerides, free fatty acids, total protein and T(3) were measured in a separate experiment until 60 min after injection. Food intake decreased until at least 1h after intravenous ghrelin administration. The respiratory quotient (RQ) in ghrelin-injected chickens was reduced until 14 h after administration whereas plasma glucose and triglycerides concentrations were not altered. Free fatty acids and total protein levels also remained unchanged. Ghrelin did not influence heat production and this was supported by the absence of changes in plasma T(3) levels when compared to the control values. In conclusion, peripheral ghrelin reduces food intake as well as RQ and might influence the type of substrate (macronutrient) that is used as metabolic fuel.  相似文献   

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