Elucidating the central anorexigenic mechanism of glucagon-like peptide 1 in Japanese quail (Coturnix japonica).

Glucagon-like peptide 1 (GLP-1) elicits a potent reduction in food intake, although the central mechanism mediating this appetite-suppressive effect is not fully understood in all species. To begin to elucidate the molecular mechanisms in quail, we administered GLP-1 via intracerebroventricular (ICV) injection to 7-day-old Japanese quail (Coturnix japonica) and determined effects on food and water intake, behavior, and brain nucleus activation. We observed a reduction in food and water intake, with the lowest effective dose being 0.01 nmol. Quail injected with GLP-1 displayed fewer steps, feeding pecks, exploratory pecks, and jumps, while time spent sitting increased. We quantified c-Fos immunoreactivity at 60 min post-injection in hypothalamic and brainstem nuclei that mediate food intake and determined that the hypothalamic paraventricular nucleus (PVN), and nucleus of the solitary tract and area postrema of the brainstem were activated in response to GLP-1. In conclusion, these results suggest that GLP-1 induces anorexigenic effects that are likely mediated at the level of the PVN and brainstem.

Ferulic acid, a phytochemical with transient anorexigenic effects in birds.

Ferulic acid (FA) is a phenolic acid found within the plant cell wall that has physiological benefits as an antioxidant. Although metabolic benefits of FA supplementation are described, lacking are reports of effects on appetite regulation. Thus, our objective was to determine if FA affects food or water intake, using chicks as a model. At 4 days post-hatch, broiler chicks were intraperitoneally injected with 0 (vehicle), 12.5, 25, or 50 mg/kg of FA. Chicks treated with 50 mg/kg of FA consumed 70% less food than controls at 30 min post-injection, and the effect dissipated thereafter. Water intake was not affected at any time. In a behavior analysis, FA-treated chicks defecated fewer times than vehicle-injected chicks, while other behaviors were not affected. There was an increase in c-Fos immunoreactivity within the hypothalamic arcuate nucleus (ARC) of FA-treated chicks, and no differences were detected in other nuclei. mRNA abundance was measured in the whole hypothalamus and the ARC. There was decreased hypothalamic galanin, ghrelin, melanocortin receptor 3, and pro-opiomelanocortin (POMC) mRNA in FA-treated chicks. Within the ARC, there was an increase in c-Fos mRNA and a decrease in POMC mRNA in response to FA. It is likely that the mechanism responsible for mediating FA's transient effects on food intake originates within the ARC, possibly involving POMC. A greater understanding of the short-term, mild appetite-suppressive effects of FA may have applications to treating eating disorders and modulating food intake in animal models of obesity.

The anorexigenic effect of neuropeptide AF in Japanese quail, Coturnix japonica, is associated with activation of the melanocortin system.

Neuropeptide AF (NPAF) decreases food and water intake in birds and food intake in mammals. In this study, the objective was to determine the effects of centrally administered NPAF on food and water intake, hypothalamic c-Fos immunoreactivity and hypothalamic mRNA abundance of appetite-regulating factors in Japanese quail (Coturnix japonica). Seven days post hatch, 6 h fasted quail were intracerebroventricularly (ICV) injected with 0 (vehicle), 4, 8, or 16 nmol of NPAF and food and water intake were measured at 30 min intervals for 180 min. In Experiment 1, chicks which received 4, 8, and 16 nmol ICV NPAF had reduced food intake for 120, 60 and 180 min following injection, respectively, and reduced water intake during the entire 180 min observation. In Experiment 2, there was increased c-Fos immunoreactivity in the paraventricular nucleus, the ventromedial nucleus of the hypothalamus, and the dorsomedial hypothalamic nucleus in NPAF-injected quail. In Experiment 3, ICV NPAF was associated with decreased corticotropin-releasing factor mRNA, and an increase in hypothalamic proopiomelanocortin and melanocortin receptor 4 mRNA. These results demonstrate that central NPAF suppresses food and water intake in quail, effects that are likely mediated via the melanocortin system in the hypothalamus.

The anorexigenic effect of beta-melanocyte-stimulating hormone involves corticotrophin-releasing factor and mesotocin in birds.

Beta-melanocyte-stimulating hormone (ß-MSH), when centrally injected, induces anorexigenic effects in rodents and chickens but its mechanism remains unclear. Thus, the primary goal of this research was to elucidate the hypothalamic mechanism using chickens. Intracerebroventricular injection of 0.3, 1.0 and 3.0 nmol of ß-MSH decreased food intake for 540 min. Expression of hypothalamic mRNAs were affected by ß-MSH injection, including corticotrophin-releasing factor (CRF) and its receptor subtype 1 (CRFR1), mesotocin (MT) and its receptor (MTR), pro-opiomelanocortin, cocaine- and amphetamine-regulated transcript (CART), growth hormone secretagogue receptor (GHSR) and neuropeptide Y (NPY) receptor subtype 5 (NPYR5). Within the arcuate nucleus, expressions of NPY, agouti-related peptide, MT and MTR were increased by ß-MSH injection. ß-MSH-treated chicks had more CRF, CRFR1, CRF receptor subtype 2, GHSR, NPY receptor subtype 1 (NPYR1) and NPYR5 mRNA but lower levels of CART and ghrelin, in the paraventricular nucleus. Greater amounts of mRNA for MTR, GHSR, NPYR1 and NPYR5 and less CRF expression were observed in the ventromedial hypothalamus. In conclusion, central injection of ß-MSH potently reduced food intake and was associated with changes in mRNA expression of some anorexigenic factors in a hypothalamic nucleus-specific manner.

Anorexigenic effects of substance P in Coturnix japonica.

Substance P (SP) is an 11-amino acid tachykinin-related peptide that has anorexigenic effects in birds and mammals although the central mechanism is not well understood. Hence, the objective was to identify appetite-associated hypothalamic mechanisms in Japanese quail (Coturnix japonica). Seven days post-hatch, quail were intracerebroventricularly injected with 0, 0.25, 0.5 or 1.0 nmol of SP and monitored for 180 min. On a cumulative basis, quail that received 0.5 and 1.0 nmol of SP consumed less food for 90 min post-injection. On a non-cumulative basis, food intake was reduced in 0.5 nmol-injected birds at 30 min post-injection. Water intake was not affected. A comprehensive behavior analysis was performed, revealing that SP-injected chicks displayed less feeding pecks and reduced locomotion compared to vehicle-injected birds. To identify molecular mechanisms, the hypothalamus was isolated at 1 h post-injection and real-time PCR was performed to measure mRNA. Agouti-related peptide (AgRP) mRNA was reduced in SP-injected chicks. Immunohistochemistry was used to quantify c-Fos-expressing cells in appetite-associated hypothalamic nuclei. There were more reactive cells in the lateral hypothalamus (LH) and the paraventricular nucleus (PVN) of SP- than vehicle-injected chicks. The LH and PVN were collected for gene expression analysis. Corticotropin-releasing factor (CRF) and urotensin 2 (UTS2) mRNAs were greater in SP- than vehicle-injected chicks in the PVN. In the LH, CRF receptor sub-type 2 (CRFR2) mRNA was greater and kappa opioid receptor mRNA was reduced in SP- compared to vehicle-injected quail. Thus, SP induces a potent anorexia in quail that coincides with increased LH-specific CRFR2 mRNA and increased UTS2 mRNA in the PVN. Future studies will evaluate whether SP-induced anorexigenic effects are mediated through CRF receptors.

Gastrin releasing peptide-induced satiety is associated with hypothalamic and brainstem changes in chicks.

Gastrin releasing peptide (GRP) is involved in the stimulation of gastric acid release from the stomach. It also mediates effects on feeding behavior. It is associated with anorexigenic effects in both mammalian and avian species, but the mechanism of action is unknown in any species. The aim of the present study was thus to investigate the hypothalamic and brainstem mechanisms mediating GRP-induced satiety in chicks. In Experiment 1, chicks that received intracerebroventricular (ICV) injection of GRP reduced food intake for up to 150 min following injection and reduced water intake up to 120 min following injection. In Experiment 2, chicks that were food restricted following GRP injection did not reduce water intake. Alimentary canal transit time was not affected by GRP in Experiment 3. A behavior analysis was conducted in Experiment 4, revealing that GRP-treated chicks reduced feeding pecks. In Experiment 5, GRP-treated chicks had increased c-Fos immunoreactivity in the lateral hypothalamus, paraventricular nucleus, and arcuate nucleus of the hypothalamus, and the nucleus of the solitary tract. Collectively, these results demonstrate that central GRP causes anorexigenic effects that are associated with hypothalamic changes without affecting other behaviors.

The anorexigenic effect of neuropeptide K in chicks involves the paraventricular nucleus and arcuate nucleus of the hypothalamus.

Neuropeptide K (NPK) induces satiety in birds and mammals. We demonstrated that in birds this effect was associated with the hypothalamus, but beyond this little is known in any species regarding the central mechanism of action. Thus, this study was designed to identify hypothalamic molecular mechanisms associated with the food intake-inhibiting effects of NPK in chicks. In Experiment 1, intracerebroventricular (ICV) injection of 1.0 and 3.0 nmol of NPK reduced food intake and we identified an effective dose for microinjection. In Experiment 2, food intake was reduced when NPK was microinjected into the PVN. In Experiment 3, whole hypothalamus was collected from chicks at 1 h post-ICV NPK injection. The abundance of corticotropin-releasing factor (CRF) and agouti-related peptide (AgRP) mRNA was reduced in NPK-injected chicks. In Experiment 4, within the isolated paraventricular nucleus (PVN) there was less CRF mRNA, and within the arcuate nucleus (ARC) there was less AgRP mRNA, in NPK- than vehicle-treated chicks at 1 h post-injection. We conclude that there are first order neurons for NPK that reside within the PVN, and the anorexigenic effect of NPK is associated with a decrease in AgRP in the ARC.

Hypothalamic mechanisms associated with neuropeptide K-induced anorexia in Japanese quail (Coturnix japonica).

Central administration of neuropeptide K (NPK), a 36-amino acid peptide, is associated with anorexigenic effects in rodents and chickens. The mechanisms underlying the potent anorexigenic effects of NPK are still poorly understood. Thus, the aim of the present study was to identify the hypothalamic nuclei and neuropeptides that mediate anorexic effects of NPK in 7 day-old Japanese quail (Coturnix japonica). After a 6 h fast, intracerebroventricular (ICV) injection of NPK decreased food and water intake for 180 min post-injection. Quail injected with NPK had more c-Fos immunoreactive cells in the arcuate nucleus (ARC), lateral hypothalamus, and paraventricular nucleus (PVN) compared to the birds that were injected with the vehicle. In the ARC of NPK-injected quail, there was decreased neuropeptide Y (NPY), NPY receptor sub-type 1, and agouti-related peptide mRNA, and increased CART, POMC, and neurokinin receptor 1 mRNA. NPK-injected quail expressed greater amounts of corticotropin-releasing factor (CRF), CRF receptor sub-type 2, melanocortin receptors 3 and 4, and urocortin 3 mRNA in the PVN. In conclusion, results provide insights into understanding NPK-induced changes in hypothalamic physiology and feeding behavior, and suggest that the anorexigenic effects of NPK involve the ARC and PVN, with increased CRF and melanocortin and reduced NPY signaling.

Fasting differentially alters the hypothalamic proteome of chickens from lines with the propensity to be anorexic or obese.

BACKGROUND: The hypothalamus is the ultimate modulator of appetite and energy balance and therefore sensitive to changes in nutritional state. Chicks from lines selected for low (LWS) and high (HWS) body weight are hypophagic and compulsive eaters, respectively, and differ in their propensity to become obese and in their hypothalamic mRNA response to fasting. METHODS: As fasting-induced changes in hypothalamic proteins are unknown, we investigated the hypothalamic proteomes of 5-day old LWS and HWS chicks in the fed and fasted states using a label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach. RESULTS: A total of 744 proteins were identified in the chicken hypothalamus, and 268 differentially abundant proteins were identified among four pairwise comparisons. Ninety-five proteins were associated with the response to fasting in HWS chicks, and 23 proteins were associated with the response to fasting in LWS chicks. Fasting-responsive proteins in HWS chicks were significantly enriched in ATP metabolic processes, glyoxylate/dicarboxylate metabolism, and ribosome function. There was no enrichment for any pathways in LWS chicks in response to fasting. In the fasted and fed states, 159 and 119 proteins differed between HWS and LWS, respectively. Oxidative phosphorylation, citric acid cycle, and carbon metabolism were the main pathways associated with differences between the two lines of chicks. Enzymes associated with metabolic pathways differed between HWS and LWS in both nutritional states, including fumarase, aspartate aminotransferase, mitochondrial GOT2, 3-hydroxyisobutyrate dehydrogenase, chondrogenesis associated lipocalin, sialic acid synthase, arylamine N-acetyltransferase, pineal gland isozyme NAT-3, and succinate dehydrogenase [ubiquinone] flavoprotein subunit, mitochondrial. CONCLUSIONS: These results provide insights into the hypothalamic metabolic pathways that are affected by nutritional status and the regulation of appetite and eating behavior.

Hypothalamic mechanisms associated with corticotropin-releasing factor-induced anorexia in chicks.

Central administration of corticotropin-releasing factor (CRF), a 41-amino acid peptide, is associated with potent anorexigenic effects in rodents and chickens. However, the mechanism underlying this effect remains unclear. Hence, the objective of the current study was to elucidate the hypothalamic mechanisms that mediate CRF-induced anorexia in 4 day-old Cobb-500 chicks. After intracerebroventricular (ICV) injection of 0.02 nmol of CRF, CRF-injected chicks ate less than vehicle chicks while no effect on water intake was observed at 30 min post-injection. In subsequent experiments, the hypothalamus samples were processed at 60 min post-injection. The CRF-injected chicks had more c-Fos immunoreactive cells in the arcuate nucleus (ARC), dorsomedial nucleus (DMN), ventromedial hypothalamus (VMH), and paraventricular nucleus (PVN) of the hypothalamus than vehicle-treated chicks. CRF injection was associated with decreased whole hypothalamic mRNA abundance of neuropeptide Y receptor sub-type 1 (NPYR1). In the ARC, CRF-injected chicks expressed more CRF and CRF receptor sub-type 2 (CRFR2) mRNA but less agouti-related peptide (AgRP), NPY, and NPYR1 mRNA than vehicle-injected chicks. CRF-treated chicks expressed greater amounts of CRFR2 and mesotocin mRNA than vehicle chicks in the PVN and VMH, respectively. In the DMN, CRF injection was associated with reduced NPYR1 mRNA. In conclusion, the results provide insights into understanding CRF-induced hypothalamic actions and suggest that the anorexigenic effect of CRF involves increased CRFR2-mediated signaling in the ARC and PVN that overrides the effects of NPY and other orexigenic factors.

Hypothalamic mechanism of corticotropin-releasing factor's anorexigenic effect in Japanese quail (Coturnix japonica).

Central administration of corticotropin-releasing factor (CRF), a 41-amino acid peptide, is associated with anorexigenic effects across various species, with particularly potent reductions in food intake in rodents and chickens (Gallus gallus domesticus), a species for which the most is known. The purpose of the current study was to determine the hypothalamic mechanism of CRF-induced anorexigenic effects in 7 day-old Japanese quail (Coturnix japonica), a less-intensely-selected gallinaceous relative to the chicken that can provide more evolutionary perspective. After intracerebroventricular (ICV) injection of 2, 22, or 222 pmol of CRF, a dose-dependent decrease in food intake was observed that lasted for 3 and 24 h for the 22 and 222 pmol doses, respectively. The 2 pmol dose had no effect on food or water intake. The numbers of c-Fos immunoreactive cells were increased in the paraventricular nucleus (PVN) and lateral hypothalamic area (LHA) at 1 h post-injection in quail injected with 22 pmol of CRF. The hypothalamic mRNA abundance of proopiomelanocortin, melanocortin receptor subtype 4, CRF, and CRF receptor sub-type 2 was increased at 1 h in quail treated with 22 pmol of CRF. Behavior analyses demonstrated that CRF injection reduced feeding pecks and jumps and increased the time spent standing. In conclusion, results demonstrate that the anorexigenic effects of CRF in Japanese quail are likely influenced by the interaction between CRF and melanocortin systems and that injection of CRF results in species-specific behavioral changes.

Central injection of oxytocin reduces food intake and affects hypothalamic and adipose tissue gene expression in chickens.

Oxytocin (OT) is a well-characterized neurotransmitter that participates in a wide range of physiological processes including the inhibition of food intake. The avian ortholog, mesotocin (MT), differs from OT by a single amino acid. Little is known regarding the function of OT in regulating energy balance in birds; thus, this study was designed to determine the effects of central OT injection on food intake and adipose tissue physiology in chicks. At 4-d post-hatch, broiler chicks were fasted for 3 h and injected intracerebroventricularly with 0 (vehicle), 0.63, 2.5, 5.0, or 10 nmol OT. Oxytocin decreased food and water intake during the entire 180-min observation period. The reduction in water intake was likely not prandial because chicks that were food restricted after OT injection also drank less. There was increased c-Fos immunoreactivity in several appetite-associated hypothalamic nuclei in OT-injected chicks at 1 h, including the arcuate (ARC), dorsomedial nucleus (DMN), lateral hypothalamus (LH), paraventricular nucleus (PVN), and ventromedial hypothalamus (VMH). OT treatment was associated with reduced hypothalamic corticotropin-releasing factor (CRF) mRNA and increased cloacal temperature at 1 h post-injection. We then investigated appetite- and adipose tissue-associated effects of OT in chicks from lines that have undergone long-term selection for either low (LWS) or high (HWS) juvenile body weight. Central injection of OT decreased food intake in both lines with the magnitude of response greater in the HWS than LWS chicks. Adipose tissue abundance of fatty acid-binding protein 4, monoglyceride lipase (MGLL), MT, and perilipin-1 mRNA was greater in LWS than HWS chicks. Lipoprotein lipase, MGLL, and MT mRNAs increased in response to OT injection in LWS but not HWS chicks. In conclusion, central injection of OT induced anorexia, reduced water intake, increased body temperature, and was associated with activation of the ARC, DMN, LH, PVN, and VMH in the hypothalamus. The effects on appetite and body temperature may involve CRF signaling in the hypothalamus and lipolysis in the adipose tissue, respectively. There were differences in the appetite, and adipose tissue response to OT in body weight-selected lines of chicks supports that MT plays a role in energy balance regulation in chickens.

Fasting and refeeding induce differential changes in hypothalamic mRNA abundance of appetite-associated factors in 7 day-old Japanese quail, Coturnix japonica.

There is little information regarding effects of fasting on feeding behavior and hypothalamic physiology in young Japanese quail. The aim was thus to measure food intake and hypothalamic mRNA in response to fasting and refeeding. Five d-old quail ate little during the dark cycle. Food intake was greatest during the first 2 h of the light cycle. Six day-old quail fasted for 6 h ate the most during the first 15 min of refeeding. In 7 d-old quail, 3 h of fasting up-regulated hypothalamic neuropeptide Y (NPY), NPY receptor sub-type 2 (NPYR2), agouti-related peptide (AgRP), orexin receptor 2 (ORXR2), melanocortin receptors 3 and 4 (MC3R and MC4R, respectively), and neuropeptide S (NPS) and decreased corticotropin-releasing factor receptor sub-type 1 (CRFR1) mRNA. Quail fasted for 3 h and refed for 1 h had greater NPY, AgRP, POMC, and MC3R but less CRFR1 mRNA than fed quail. Quail fasted for 6 h expressed more NPY, NPYR1, NPYR2, and MC3R and less ORXR2, prolactin releasing peptide (PrRP), cocaine- and amphetamine-regulated transcript (CART), and calcitonin (CAL) mRNA than fed quail. Quail fasted for 6 h and refed for 1 h expressed more NPY, NPYR1, NPYR2, AgRP, MC3R, MC4R, and NPS and less galanin, ORXR2, PrRP, CART, and CAL mRNA than fed birds. Hence, fasting induced changes in hypothalamic mRNA, with the largest changes occurring in genes associated with NPY and melanocortin signaling. Most genes remained elevated or downregulated after refeeding, suggesting that there was a time lag for transcription to respond to compensatory feeding.

Appetite-associated responses to central neuropeptide Y injection in quail.

The appetite-associated effects of neuropeptide Y (NPY) have been extensively studied in mammalian models. Less knowledge exists for other vertebrate species including birds. The aim of this study was to determine the effects of central injection of NPY on feeding behavior and hypothalamic physiology in 7 day-old Japanese quail (Coturnix japonica). During the light cycle, intracerebroventricular injection of 1.9 pmol, 0.5, and 1.0 nmol doses of NPY did not affect food intake, 0.031 to 0.13 nmol increased food intake, and 2.0 nmol NPY decreased food intake, in comparison to vehicle injection. Multiple doses of NPY stimulated water intake, but when food was not available, water intake was not affected. When injected during the dark cycle, NPY did not influence food intake. NPY-injected chicks had more c-Fos immunoreactive cells in the arcuate nucleus of the hypothalamus (ARC) and greater hypothalamic agouti-related peptide and neuropeptide Y receptors 1 and 2 (NPYR1 and NPYR2, respectively) mRNA than vehicle-injected chicks. Within the ventromedial hypothalamus, NPY-treated chicks expressed less NPYR1 mRNA, within the dorsomedial hypothalamus less NPY mRNA, and in the ARC greater NPYR2 mRNA than vehicle-injected chicks. Lastly, quail injected with NPY increased feeding pecks, escape attempts, and time spent preening, while locomotion, the number of steps, and time spent perching decreased compared to chicks injected with the vehicle. Results demonstrate that NPY stimulates food intake in quail, consistent with mammals and other avian species, but with some unique responses at the molecular level that are not documented in other species.

Dietary macronutrient composition and central neuropeptide Y injection affect dietary preference and hypothalamic gene expression in chicks.

OBJECTIVE: The objective of this study was to determine the influence of dietary macronutrient composition on central NPY's orexigenic effect in chicks. METHODS: Day-of-hatch chicks were fed one of three diets (3000 kcal ME/kg) ad libitum from hatch: high carbohydrate (HC), high fat (HF; 30% ME derived from soybean oil), and high protein (HP; 25 vs. 22% CP). In Experiment 1, chicks received intracerebroventricular injections of 0 (vehicle), 0.2, or 2.0 nmol NPY on day 4 and food intake was recorded for 6 hours. In Experiment 2, chicks were given all three diets before and after injection. In Experiment 3, hypothalamus was collected at 1-hour post-injection for gene expression analysis. RESULTS: The HC diet-fed chicks responded with a greater increase, while the chicks fed the HF diet had a lower threshold response in food intake to NPY. Neuropeptide Y dose-dependently increased food intake in chicks fed the HC and HP diets. Chicks administered 0.2 nmol NPY preferred the HC and HP diets over the HF diet. Relative quantities of hypothalamic NPYR1 and MC4R mRNA were reduced by NPY in chicks that consumed the HP and HC diets, respectively. DISCUSSION: Consumption of the HC diet was associated with the most robust NPY-induced increase in food intake. Injection of NPY accentuated differences among dietary groups in hypothalamic gene expression of several appetite-associated factors, results suggesting that the NPY/agouti-related peptide and melanocortin pathways are associated with some of the diet- and NPY-induced differences observed in this study.

Dietary macronutrient composition affects hypothalamic appetite regulation in chicks.

OBJECTIVE: The objective was to determine the effects of high-protein and high-fat diets, and fasting and refeeding, on appetite regulation in chicks. METHODS: Day of hatch chicks were fed one of four diets: basal, high protein (25% crude protein), and 15 and 30% high fat (15 and 30% metabolizable energy derived from soybean oil, respectively), and assigned to one of three treatments at 4 days: (1) access to feed, (2) 3 hours of fasting, or (3) fasting followed by 1 hour of refeeding. The hypothalamus was collected, total RNA isolated, and mRNA abundance measured. RESULTS: Food intake was reduced in chicks fed the high-protein and high-fat diets. Agouti-related peptide, neuropeptide Y (NPY), NPY receptors 1, 2, and 5, melanocortin receptors 3 and 4 (MC3R and 4R, respectively), mesotocin, corticotropin-releasing factor (CRF), and CRF receptor sub-type 2 (CRFR2) mRNAs were greatest in chicks that consumed the basal diet. Refeeding was associated with increased MC3R mRNA in the high-protein diet group. CRFR2 mRNA was increased by fasting and refeeding in chicks that consumed the high-protein diet. DISCUSSION: Food intake and hypothalamic gene expression of some important appetite-associated factors were reduced in chicks fed the high-protein or high-fat diets. Fasting and refeeding accentuated several differences and results suggest that the CRF and melanocortin pathways are involved.

The central effects of alpha-melanocyte stimulating hormone (α-MSH) in chicks involve changes in gene expression of neuropeptide Y and other factors in distinct hypothalamic nuclei.

Alpha-melanocyte stimulating hormone (α-MSH) is a satiety-inducing factor in birds and mammals although central mechanisms mediating its effects on appetite in birds are poorly understood. Thus, the objective of the present study was to determine effects of centrally-injected α-MSH on c-Fos and gene expression in chick appetite-associated hypothalamic nuclei. At 4days post-hatch, 3h-fasted chicks were intracerebroventricularly (ICV) injected with 0 (vehicle) or 0.12nmol α-MSH and 1h later, hypothalamus samples were collected for measuring c-Fos immunoreactivity and mRNA abundance of appetite-associated factors in hypothalamic nuclei. There were more c-Fos immunoreactive cells in the arcuate nucleus (ARC), dorsomedial nucleus (DMN), lateral hypothalamus (LH), and paraventricular nucleus (PVN) of α-MSH- than vehicle-injected chicks. Neuropeptide Y (NPY), oxytocin receptor (OXTR), and agouti-related peptide (AgRP) mRNAs were greater in α-MSH- than vehicle-injected chicks in the ARC. In the PVN, NPY receptor sub-type 1 (NPYR1) mRNA was reduced while c-Fos mRNA was increased in response to treatment with α-MSH. NPY, c-Fos, and DOPA decarboxylase (DDC) mRNAs were greater in treated than vehicle-injected chicks in the DMN. Results suggest that during the first hour post-injection, the appetite-inhibiting effects of α-MSH involve activation of the ARC, DMN, PVN, and LH, and corresponding changes in transcriptional regulation of factors involved with NPY, AgRP and mesotocin signaling, and monoamine synthesis. The effects of these changes may include an inhibition of NPY signaling in the PVN to induce satiety and stimulation of NPY/AgRP neurons in the ARC in an attempt to restore homeostatic levels of food intake.

The central anorexigenic mechanism of amylin in Japanese quail (Coturnix japonica) involves pro-opiomelanocortin, calcitonin receptor, and the arcuate nucleus of the hypothalamus.

Amylin is a 37-amino acid peptide hormone that exerts anorexigenic effects in humans and animals. We demonstrated that central injection of amylin into chicks affected feeding and related behaviors via the hypothalamus and brainstem, although the molecular mechanisms remained elusive. Thus, the objective of this study was to investigate the molecular mechanisms underlying anorexigenic effects of amylin in 7 day-old Japanese quail. Food but not water intake was reduced after intracerebroventricular amylin injection, and the behavior analysis indicated that this was associated with decreased food pecks and preening. Whole hypothalamus and hypothalamic nuclei including the arcuate nucleus (ARC), paraventricular nucleus (PVN), ventromedial hypothalamus (VMH), dorsomedial nucleus (DMN) and lateral hypothalamic area (LH) were extracted from quail at 1h post-injection for total RNA isolation. Real time PCR was performed to quantify mRNA abundance of amylin receptors, appetite-associated neuropeptides and monoamine-synthesis-related enzymes. Central amylin injection increased the mRNA abundance of calcitonin receptor (CALCR), receptor activity modifying protein 1 (RAMP1), pro-opiomelanocortin (POMC), and aromatic l-amino acid decarboxylase (AADC) in the hypothalamus and individual hypothalamic nuclei. Relative quantities of CALCR and POMC mRNA were greater in the ARC of the amylin- than vehicle-treated group. Thus, amylin-mediated effects on food intake may involve POMC, monoamine synthesis, and amylin receptor 1 (a complex of CALCR and RAMP1) in the ARC. Together, these data provide novel insights on the hypothalamic-specific molecular mechanisms of amylin-induced food intake.

Effects of intracerebroventricular injection of rosiglitazone on appetite-associated parameters in chicks.

Rosiglitazone, a thiazolidinedione, is a peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist that increases insulin sensitivity. A documented side effect of this diabetes drug is increased appetite, although the mechanism mediating this response is unknown. To better understand effects on food intake regulation, we evaluated the appetite-associated effects of rosiglitazone in an alternative vertebrate and agriculturally-relevant model, the domesticated chick. Four day-old chicks received intracerebroventricular (ICV) injections of 0, 5, 10 or 20nmol rosiglitazone and food and water intake were measured. Chicks that received 5 and 10nmol rosiglitazone increased food intake during the 2h observation period, with no effect on water intake. In the next experiment, chicks were ICV-injected with 10nmol rosiglitazone and hypothalamus was collected at 1h post-injection for total RNA isolation. Real-time PCR was performed to measure mRNA abundance of appetite- and glucose regulation-associated factors. Neuropeptide Y (NPY) and proopiomelanocortin (POMC) mRNA decreased while NPY receptor 1 (NPYr1) mRNA increased in rosiglitazone-injected chicks compared to the controls. Results show that central effects of rosiglitazone on appetite are conserved between birds and mammals, and that increases in food intake might be mediated through NPY and POMC neurons in the hypothalamus.

Anorexigenic effect of serotonin is associated with changes in hypothalamic nuclei activity in an avian model.

The anorexigenic effect of serotonin (5HT) has been documented for decades; however, its central mechanism has not been fully elucidated, especially so in non-mammalian vertebrates. Therefore, we centrally injected 5HT to chicks and measured several appetite-associated parameters. Chicks that received central 5HT dose- and time-dependently decreased food intake while water intake was not affected. To determine which hypothalamic nuclei were associated with this effect c-Fos immunoreactivity was measured in appetite-associated nuclei. Only the ventromedial hypothalamus and arcuate nucleus were activated. Whole blood glucose was measured after 5HT injection but was not affected. From the hypothalamus, several appetite-associated mRNAs were measured by real-time PCR after 5HT injection but not one of these showed any difference in expression. Lastly, a comprehensive behavior analysis demonstrated that 5HT caused reducing pecking and increased deep rest. Together we interpret these results as exogenous 5HT injection causes short term satiety that is likely a secondary effect to an increase in the amount of time spent in deep rest.