Differential thresholds of neuromedins B-, C-, and bombesin-induced anorexia and crop-emptying rate in chicks

Effect of platelet-activating factor on food intake, cloacal temperature, voluntary activity and crop emptying rate in chicks

Platelet-activating factor (PAF) plays a significant role in several leucocyte functions, including platelet aggregation and inflammation. Additionally, PAF has a role in the behavioral and physiological changes in mammals. However, the effect of PAF has not been well studied in birds. Therefore, the study aimed to determine if PAF affects feeding behavior, voluntary activity, cloacal temperature, and feed passage through the digestive tract in chicks (Gallus gallus). We also studied the involvement of PAF in the innate immune system induced by lipopolysaccharide (LPS), a cell wall component of gram-negative bacteria. Both intraperitoneal (IP) and intracerebroventricular (ICV) injections of PAF significantly decreased food intake. IP injection of PAF significantly decreased voluntary activity and slowed the feed passage from the crop, whereas ICV injection had no effect. Conversely, ICV injection of PAF significantly increased the cloacal temperature, but IP injection had no effect. The IP injection of LPS significantly reduced the mRNA expression of lysophosphatidylcholine acyltransferase 2, an enzyme responsible for PAF production in the heart and pancreas. On the other hand, LPS significantly increased the mRNA expression of the PAF receptor in the peripheral organs. The present study shows that PAF influences behavioral and physiological responses and is related to the response against bacterial infections in chicks.

Zymosan and lipopolysaccharide decrease gene expression of neuronal nitric oxide synthase in peripheral organs in chicks

Nitric oxide (NO) is gaseous bioactive molecule that is synthesized by NO synthase (NOS). Inducible NOS (iNOS) expression occurs in response to pathogenic challenges, resulting in the production of large amounts of NO. However, there is a lack of knowledge regarding neuronal NOS (nNOS) and endothelial NOS (eNOS) in birds during pathogenic challenge. Therefore, the present study was conducted to determine the influence of intraperitoneal (IP) injection of zymosan (cell wall component of yeast) and lipopolysaccharide (LPS, a cell wall component of gram-negative bacteria) on NOS expression in chicks (Gallus gallus). Furthermore, the effect of NOS inhibitors on the corresponding behavioral and physiological parameters was investigated. Zymosan and LPS injections induced iNOS mRNA expression in several organs. Zymosan had no effect on eNOS mRNA expression in the organs investigated, whereas LPS increased its expression in the pancreas. Zymosan and LPS decreased nNOS mRNA expression in the lung, heart, kidney, and pancreas. The decreased nNOS mRNA expression in pancreas was probably associated with the NO from iNOS provided that such effect was reproduced by IP injection of sodium nitroprusside, which is a NO donor. Furthermore, pancreatic nNOS mRNA expression decreased following subcutaneous injection of corticosterone. Furthermore, IP injections of a nonspecific NOS inhibitor, NG-nitro-L-arginine methyl ester, and an nNOS-specific inhibitor, 7-nitroindazole, resulted in the significant decreases in food intake, cloacal temperature, and feed passage via the digestive tract in chicks. Collectively, the current findings imply the decreased nNOS expression because of fungal and bacterial infections, which affects food intake, body temperature, and the digestive function in birds.

Pituitary transcriptome profile from laying period to incubation period of Changshun green-shell laying hens

BACKGROUND

Incubation behaviour, an instinct for natural breeding in poultry, is strictly controlled by the central nervous system and multiple neuroendocrine hormones and neurotransmitters, and is closely associated with the cessation of egg laying. Therefore, it is essential for the commercial poultry industry to clarify the molecular regulation mechanism of incubation behaviour. Here, we used high-throughput sequencing technology to examine the pituitary transcriptome of Changshun green-shell laying hen, a local breed from Guizhou province, China, with strong broodiness, in two reproductive stages, including egg-laying phase (LP) and incubation phase (BP). We also analyze the differences in gene expression during the transition from egg-laying to incubation, and identify critical pathways and candidate genes involved in controlling the incubation behaviour in the pituitary.

RESULTS

In this study, we demonstrated that a total of 2089 differently expressed genes (DEGs) were identified in the pituitary, including 842 up-regulated and 1247 down-regulated genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that steroid biosynthesis pathway and neuroactive ligand-receptor interaction were significantly enriched based on DEGs commonly identified in pituitary. Further analysis revealed that SRC, ITGB4, ITGB3, PIK3R3 and DRD2 may play crucial roles in the regulation of incubation behaviour.

CONCLUSIONS

We identified 2089 DEGs and the key signaling pathways which may be closely correlated with incubation in Changshun green-shell laying hens, and clarified the molecular regulation mechanism of incubation behaviour. Our results indicate the complexity and variety of differences in reproductive behaviour of different chicken breeds.

Possible role of neuropeptide Y on zymosan- and lipopolysaccharide-induced change in gastrointestinal feed passage via the medulla oblongata in chicks

Zymosan is a fungi-derived pathogen-associated molecular pattern. It activates the immune system and induces the reduction of feed passage rate in the gastrointestinal tract of vertebrates including birds. However, the mechanism mediating the zymosan-induced inhibition of feed passage in the gastrointestinal tract remains unknown. Since the medulla oblongata regulates the digestive function, it is plausible that the medulla oblongata is involved in the zymosan-induced inhibition of feed passage. The present study was performed to identify the genes that were affected by zymosan within the medulla oblongata of chicks (Gallus gallus) using an RNA sequencing approach. We found that mRNAs of several bioactive molecules including neuropeptide Y (NPY) were increased with an intraperitoneal (IP) injection of zymosan. The increase of mRNA expression of NPY in the medulla oblongata was also observed after the IP injection of lipopolysaccharide, derived from gram-negative bacteria. These results suggest that medullary NPY is associated with physiological changes during fungal and bacterial infection. Furthermore, we found that intracerebroventricular injection of NPY and its receptor agonists reduced the feed passage from the crop. Additionally, the injection of NPY reduced the feed passage from the proventriculus to lower digestive tract. NPY also suppressed the activity of duodenal activities of amylase and trypsin. The present study suggests that fungi- and bacteria-induced activation of the immune system may activate the NPY neurons in the medulla oblongata and thereby reduce the digestive function in chicks.

Poultry nutrition

Nutrition is the most important environmental factor affecting development, health status, growth performance and profitability of poultry production. Feeds for poultry constitute up to 70–75% of total production costs. Poultry nutrition differs considerably from that of other livestock, which is determined by the specific anatomy of the gastrointestinal tract. Protein, energy, fat, fiber, minerals, vitamins, and water are of basic importance for poultry nutrition and their content in feeds must cover the requirement that differ depending on the bird’s age and species. In general, feed protein must be of good value including the content of essential amino acids. Among them lysine, methionine, cysteine, threonine and tryptophan are the limiting ones. The main ingredient of poultry feeds are cereal grains, i.e. wheat and maize, which predominantly constitute an energy source because their protein content is insufficient for birds. Because of that cereals cannot be the only feed for poultry and must be combined with protein sources such as soybean or rapeseed meal, legume seeds or protein concentrates. Despite birds’ requirement for nutrients and chemical composition of feeds are well known, nutrition must face many problems. One of the most important issues is to find alternatives to antibiotic growth promoters.

Effect of ornithokinin on feeding behavior, cloacal temperature, voluntary activity and crop emptying rate in chicks

Bradykinin is a well-studied bioactive peptide associated with several physiological functions, including vasodilation and inflammation, in mammals. However, its avian homolog, ornithokinin, has received less research attention in birds. Therefore this study aimed to investigate the effect of intraperitoneal (IP) and intracerebroventricular (ICV) injections of ornithokinin on feeding behavior, cloacal temperature, voluntary activity, crop emptying rate, and blood constituents in chicks (Gallus gallus). We also investigated the effect of lipopolysaccharide (LPS), a cell wall component of gram-negative bacteria, on ornithokinin-associated gene expression was also investigated to determine whether activation of the ornithokinin system is induced by bacterial infection. Both IP and ICV injections of ornithokinin significantly decreased feed intake, cloacal temperature, voluntary activity, and crop emptying rate in chicks, but they did not affect the plasma concentration of corticosterone. Additionally, LPS significantly increased the expression of ornithokinin B2 receptor mRNA in several organs. Hence, ornithokinin is associated with a range of physiological responses in chicks and may be related to their response to bacterial infection.

Effect of lithium chloride on food intake, cloacal temperature, voluntary activity, and crop-emptying rate in chicks

Infections frequently accompany with non-specific symptoms such as anorexia and hyperthermia. In addition, there may be unpleasant sensations such as visceral discomfort during infection. Lipopolysaccharide (LPS), a Gram-negative bacteria cell wall component, is known to induce the unpleasant sensation of conditioned taste aversion in mammals. However, the relationship between unpleasant sensations and changes in behavior and physiological conditions has not been investigated extensively in birds. Lithium chloride (LiCl) is a compound that induces unpleasant sensations, including visceral discomfort, although its effects on behavior and physiological conditions have also not been investigated extensively in birds. Thus, the present study was aimed to investigate the effect of an intraperitoneal (IP) injection of LiCl on conditioned visual aversion, food intake, cloacal temperature, voluntary activity, crop-emptying rate, and blood constituents in chicks (Gallus gallus). We also examined the effect of IP injections of LPS and zymosan, a cell wall component of fungus, on conditioned visual aversion formation. First, IP injection of LiCl was confirmed to induce conditioned visual aversion in chicks. An IP injection of LiCl significantly decreased food intake, voluntary activity, and crop-emptying rate but did not affect the temperature. In addition, the injection of LiCl significantly increased plasma corticosterone concentration, indicating that LiCl serves as a stressor in chicks. Finally, IP injections of LPS and zymosan were found to induce conditioned visual aversion in chicks. Collectively, these results suggest that LiCl induces conditioned aversion, anorexia, hypoactivity, and inhibition of crop-emptying in chicks. In addition, LPS and zymosan would induce unpleasant sensations in chicks.

Effect of sodium nitroprusside on feeding behavior, voluntary activity, and cloacal temperature in chicks

Nitric oxide (NO) is a well-known gaseous signaling molecule that is involved in a variety of physiological and pathological processes in vertebrates. The role of NO in physiological responses of birds has been investigated primarily using NOS inhibitors. Therefore, the effect of the absence of NO is well characterized. However, there is little knowledge on the effects of abundant NO in birds, which is the case in birds that have infections. Therefore, the purpose of the present study was to determine if intraperitoneal (IP) and intracerebroventricular (ICV) injections of sodium nitroprusside (SNP), a NO donor, affected feed intake, voluntary activity, cloacal temperature, crop emptying rate, and blood constituents in domesticated chicks (Gallus gallus) as model birds. We found that both IP and ICV injections of SNP significantly decreased feed intake while there was little effect on voluntary activity. Cloacal temperature was temporarily, but significantly, decreased by both types of injection of SNP. Additionally, both IP and ICV injections of SNP significantly decreased the crop emptying rate. The IP injection of SNP significantly increased the plasma concentrations of NO₂/NO₃, which are metabolites of NO, and corticosterone, and decreased the plasma glucose concentrations, while the ICV injection had no effect. The IP injection of SNP also showed the tendency to increase the nitrotyrosine level, to increase superoxide dismutase activity, and to decrease catalase activity in the plasma. These results suggest that under specific situations which produce abundant NO such as infection, NO would induce anorexia, hypothermia, inhibition of feed passage, and activation of the hypothalamus-pituitary-adrenal axis in chicks.

Role of nitric oxide on zymosan-induced inhibition of crop emptying in chicks

Zymosan, a component of yeast cell walls, reduces feed passage through the digestive tract in chicks (Gallus gallus), although the mechanism mediating this effect is poorly understood. Nitric oxide (NO) is associated with a variety of biological actions including effects on the immune system. In addition, it has been suggested that NO is involved in relaxation of the digestive tract and affects feed passage in mammals. It is therefore possible that NO might be related to zymosan-induced reduction of feed passage in chicks. However, the role of NO on the effect of zymosan feed passage has not been clarified yet. Thus, the purpose of the present study was to investigate whether NO is associated with zymosan-induced alteration of feed passage in chicks. Intraperitoneal (IP) injection of zymosan significantly increased plasma nitrate and nitrite (NOx) concentrations at 6 h after injection. Zymosan-induced elevation of plasma NOx concentration was abolished by co-injection of S-methylisothiourea (SMT), a selective inhibitor for inducible NO synthase (iNOS), indicating that zymosan facilitated the induction of iNOS. Furthermore, because zymosan increased iNOS mRNA expression in the digestive tract, NO is likely associated with the effect of zymosan on the digestive tract. IP injection of NO donors significantly decreased crop emptying rate, suggesting that NO functions as an inhibitor of crop emptying. This result implied that zymosan stimulates NO production by the induction of iNOS in the digestive tract and thereby inhibits crop emptying rate. However, the co-injection of SMT did not attenuate the inhibitory effect of zymosan on crop emptying. The present study provides evidence that some changes in the digestive tract caused by zymosan are mediated by iNOS-induced NO in chicks, but NO does not mediate the effect of zymosan on feed passage through the crop.

Behavioral and physiological responses to peripheral injection of flagellin in chicks

Flagellin (Flg) is a globular protein, found in bacterial flagella, that serves as a pathogen-associated molecular pattern and also serves as a toll-like receptor-5 (TLR5) ligand in vertebrates. Most ligands for TLRs are involved in non-specific effects such as anorexia and hypoactivity in an animal infected by bacteria. However, there is little knowledge on the effects of Flg in birds. Therefore, the purpose of the present study was to determine if intraperitoneal (IP) injection of Flg affects food intake, voluntary activity, cloacal temperature, crop emptying rate, blood constituents, and splenic gene expression of cytokines in chicks (Gallus gallus). The effect of Flg22, an N-terminus fragment of Flg, was also investigated. IP injection of 10 µg Flg significantly increased the splenic gene expression of interleukin-8, interferon-γ (IFN-γ), and tumor necrosis factor-like cytokine-1A, suggesting that Flg activated the innate immune system in chicks. The injection of Flg significantly decreased food intake, voluntary activity, blood glucose concentration, and crop emptying rate, and increased cloacal temperature and plasma concentrations of nitrite, nitrate, and corticosterone. However, the injection of Flg22 only affected the splenic gene expression of IFN-γ, indicating that the full-length of Flg is required for its action. These results suggest that Flg, a ligand for TLR5, is related to non-specific symptoms including anorexia, hypoactivity, increase in body temperature, disturbance of food passage in the digestive tract, and the activation of hypothalamic-pituitary-adrenal axis during bacterial infection in chicks.

Effect of zymosan on feed passage in the digestive tract in chicks

1. The purpose of the present study was to examine whether zymosan, which is a component of fungi, affects feed passage through the digestive tract in chicks (Gallus gallus).2. Intraperitoneal (IP) injection of 2.5 mg zymosan significantly reduced the crop-emptying rate and this effect was similar to that of 100 µg lipopolysaccharide (LPS). Zymosan affected phenol red transit from the proventriculus.3. Zymosan significantly affected the gene expression of interleukin-1β (IL-1β), IL-6, IL-8 and histidine decarboxylase in various regions of the digestive tract.4. The present study suggested that zymosan retarded feed passage through the digestive tract in chick and interleukins and histamine may be participating in this process.

Effects of toll-like receptor-7 agonists on feeding behaviour, voluntary activity, cloacal temperature and crop emptying in chicks

1. The purpose of the present study was to determine if an intraperitoneal injection of two toll-like receptor-7 (TLR7) agonists, imiquimod and resiquimod, affect feed intake, voluntary activity, cloacal temperature, crop-emptying rate, plasma corticosterone (CORT) and glucose concentrations, and splenic gene expression of cytokines in chicks (Gallus gallus). 2. Although intraperitoneal injection of 100 µg imiquimod significantly increased splenic gene expression of interleukin-1β (IL-1β), IL-6, IL-8, and interferon-γ (IFN-γ), it did not affect feed intake, voluntary activity, cloacal temperature, crop-emptying rate or plasma constituents. 3. Intraperitoneal injection of 100 µg resiquimod significantly decreased feed intake, voluntary activity, cloacal temperature, crop-emptying rate and increased plasma corticosterone concentrations. 4. Intraperitoneal injection of resiquimod significantly increased splenic gene expression of IL-1β, IL-6, IL-8, IFN-γ, and tumour necrosis factor-like cytokine 1A. 5. The results showed that activation of TLR7 is associated with anorexia, hypoactivity, hypothermia, disturbance of feed passage in the digestive tract and the response to stress in chicks.

Compound 48/80 reduces the crop-emptying rate, likely through a histamine-associated pathway in chicks

Infectious conditions are associated with reduced food passage through the digestive tract in both mammals and chicks; however, the precise mechanism mediating this response in chicks remains unclear. The purpose of the present study was to determine if mast cells, a blood cell type which plays an important role in the immune system, might affect food passage through the digestive tract in chicks. Specifically, we performed intraperitoneal (IP) injections of compound 48/80, an inducer of mast cell degranulation, and measured crop emptying. The IP injection of compound 48/80 significantly reduced the crop-emptying rate, but it did not affect the proventriculus to small intestine transit rate or the number of defecations. We also found that IP-injected histamine, which is secreted by mast cells, also reduced the crop-emptying rate. In addition, IP injection of 2-pyridylethylamine (histamine H1 receptor agonist), but not dimaprit, (R)-(-)-α-methylhistamine, and VUF8430 (histamine H2, H3, and H4 receptor agonists, respectively), reduced the crop-emptying rate, implying that histamine reduces the crop emptying rate via the histamine H1 receptor. Finally, we found that IP injection of compound 48/80 reduced mRNA expression of histidine decarboxylase, a rate-limiting enzyme for histamine synthesis, in the esophagus and proventriculus at 1 h and the proventriculus and duodenum at 3 h after the injection. In sum, the present study suggests that the degranulation of mast cells causes a reduction in the crop-emptying rate, possibly via the histamine pathway in chicks.

Physiological responses to central and peripheral injection of polyinosinic-polycytidylic acid in chicks

1. The purpose of the present study was to determine if intracerebroventricular (ICV) and intraperitoneal (IP) injection of polyinosinic-polycytidylic acid (poly I:C), a viral mimetic that binds to toll-like receptor-3 (TLR3), affects food intake, voluntary activity, cloacal temperature, plasma corticosterone (CORT) and glucose concentrations, and crop emptying rate in chicks (Gallus gallus). 2. Both ICV and IP injection of poly I:C significantly decreased food intake. 3. IP but not ICV injection of poly I:C significantly suppressed voluntary activity, whereas ICV injection decreased time spent sitting. Both ICV and IP injection of poly I:C significantly increased plasma CORT and glucose concentration. Neither ICV nor IP injection of poly I:C significantly affected cloacal temperature. 4. In addition, ICV injection of poly I:C significantly reduced crop emptying rate, whereas IP injection had no effect. 5. These results suggested that central TLR3 is related to anorexia, stress response and retardation of crop emptying while peripheral TLR3 is related to anorexia, change in behaviour and stress responses during viral infection in chicks.

Effect of l-tryptophan and its metabolites on food passage from the crop in chicks

l-tryptophan (l-Trp), an essential amino acid, is well known as a precursor of 5-hydroxytryptamine (5-HT) and melatonin. In mammals, l-Trp itself has been reported to suppress gastric emptying in mammals. In addition, 5-HT and melatonin are found in the gastrointestinal tract and affect food passage from the digestive tract in mammals. While the function of these factors in mammals is documented, there is little knowledge on their function in the digestive tract of birds. Therefore, the purpose of the present study was to determine if l-Trp and its metabolites affect the crop emptying rate in chicks (Gallus gallus). We also investigated the effects of kynurenic acid (KYNA) and quinolinic acid (QA), which are metabolites of the kynurenine pathway for l-Trp. Oral administration of l-Trp significantly reduced the crop emptying rate in chicks. Among the metabolites, intraperitoneal injection of 5-HT and melatonin significantly reduced the crop emptying rate, whereas KYNA and QA had no effect. The present study suggests that l-Trp, 5-HT, and melatonin inhibit the movement of food in the digestive tract and thereby affect the utilization of nutrients in the diet of chicks.

Characterization of NMB, GRP and their receptors (BRS3, NMBR and GRPR) in chickens

The two structurally and functionally related peptides, gastrin-releasing peptide (GRP) and neuromedin B (NMB) play critical roles in many physiological/pathological processes in mammals. However, the information regarding the expression and functionality of avian NMB, GRP and their receptors is limited. Here, we characterized cNMB, cGRP and their receptors (cNMBR, cGRPR and cBRS3) in chickens. Our results showed that: (1) cNMBR and cGRPR expressed in CHO cells could be potently activated by cNMB and cGRP, respectively, as monitored by cell-based luciferase reporter assays, indicating that cNMBR and cGRPR are cNMB- and cGRP-specific receptors; strikingly, BRS3 of chickens (/spotted gars), which is orthologous to mouse bombesin receptor subtype-3 (BRS3), could be potently activated by GRP and NMB, demonstrating that both peptides are the endogenous ligands for chicken (/spotted gar) BRS3; (2) quantitative real-time PCR (qPCR) revealed that cGRPR is widely expressed in chicken tissues with abundant expression in the ovary, pancreas, proventriculus, spinal cord and brain, whereas cNMB, cNMBR and cBRS3 are mainly expressed in the brain and testes; (3) interestingly, qPCR, Western blot and immunostaining revealed that cGRP is predominantly expressed in the anterior pituitary and mainly localized to LH-cells, suggesting that cGRP is likely a novel pituitary hormone in chickens. In summary, our data help to uncover the roles of GRP, NMB and their receptors in birds, and provide the first persuasive evidence from an evolutionary prospective that in vertebrates, GRP and NMB are the endogenous ligands for BRS3, an orphan receptor that has puzzled endocrinologists for more than two decades.

Effect of central and peripheral injection of prostaglandin E2 and F2α on feeding and the crop-emptying rate in chicks

Prostaglandins (PGs) have been shown to cause several physiological changes in mammals including anorexia, awakening and sleeping, change in digestive function, and activation of the hypothalamus-pituitary-adrenal gland (HPA) axis. However, there is a paucity of information about the effect of PGs on physiological parameters in birds. The purpose of the present study was to clarify whether intracerebroventricular (ICV) and intraperitoneal (IP) injections of prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) affect feeding, voluntary movement, crop-emptying rate, and corticosterone release in chicks (Gallus gallus). ICV injection of either PGE2 or PGF2α (2 and 4μg) significantly decreased food intake in chicks. The anorexigenic effect was also observed after IP injection of the PGs. Voluntary movement was significantly suppressed by ICV injection of PGE2 or PGF2α, although the time-course change was different between the two. In contrast, IP injection of the PGs had no or less effect on voluntary movement. Both ICV and IP injection of PGE2 significantly retarded the crop-emptying rate, whereas PGF2α significantly lowered the crop-emptying rate only after IP injection. The plasma corticosterone concentration significantly increased after ICV and IP injection of PGE2, whereas PGF2α had no effect. These results suggest that central and peripheral PGs are involved in the regulation of appetite, voluntary movement, food passage in the digestive tract, and activation of the HPA axis in chicks, although the effects depend on the site of action and type of PGs.

Lipopolysaccharide reduces food passage rate from the crop by a prostaglandin-independent mechanism in chickens

1. We examined the effect of lipopolysaccharide (LPS), a component of Gram-negative bacteria, on food passage in the digestive tract of chickens (Gallus gallus) in order to clarify whether bacterial infection affects food passage in birds.

2. Food passage in the crop was significantly reduced by intraperitoneal (IP) injection of LPS while it did not affect the number of defecations, suggesting that LPS may affect food passage only in the upper digestive tract.

3. Similar to LPS, prostaglandin E2 (PGE2), one of the mediators of LPS, also reduced crop-emptying rate in chickens while it had no effect on the number of defecations.

4. Pretreatment with indomethacin, which is an inhibitor of cyclooxygenase (COX), a prostaglandin synthase, had no effect on LPS-induced inhibition of crop emptying.

5. IP injection of LPS did not affect the mRNA expression of COX2 in the upper digestive tract of chickens.

6. It is therefore likely that LPS and PGE2 reduced food passage rate in the crop by a prostaglandin-independent pathway in chickens.

Acute injections of corticosterone, norepinephrine and epinephrine retards food passage in the crop of chicks

The purpose of the present study was to clarify whether acute injection of stress-related hormones, corticosterone (CORT), norepinephrine (NE) and epinephrine (E) affect food passage in the crop of chicks (Gallus gallus). Subcutaneous (SQ) injection of CORT significantly retarded the food passage in the crop of chicks. Intraperitoneal (IP) injection of NE and E also significantly decreased the crop emptying rate. Additional experiments by using agonists of adrenergic receptors found that IP injection of phenylephrine and clonidine but not isoproterenol retarded the food passage in the crop of chicks. These results demonstrated that the effect of NE and E would be mediated by alpha-1-, alpha-2- rather than beta-adrenergic receptor. Finally, we found that injection of CORT, NE and E had no effect on the number of defecations while intracerebroventricular injection of corticotropin-releasing hormone and urocortin-3 significantly increased it. These results suggest that CORT, NE and E might affect the food passage in the upper digestive tract in chicks.

Conformational ensembles of neuromedin C reveal a progressive coil-helix transition within a binding-induced folding mechanism

NMR has been used to elucidate the folding pathway of neuromedin C and to characterize the architecture of the NMC–SDS micelle complex. Its C-terminal region is more prone to acquire an α-helical fold than the N-terminus, and it also binds to micelles.

When do we eat? Ingestive behavior, survival, and reproductive success

The neuroendocrinology of ingestive behavior is a topic central to human health, particularly in light of the prevalence of obesity, eating disorders, and diabetes. The study of food intake in laboratory rats and mice has yielded some useful hypotheses, but there are still many gaps in our knowledge. Ingestive behavior is more complex than the consummatory act of eating, and decisions about when and how much to eat usually take place in the context of potential mating partners, competitors, predators, and environmental fluctuations that are not present in the laboratory. We emphasize appetitive behaviors, actions that bring animals in contact with a goal object, precede consummatory behaviors, and provide a window into motivation. Appetitive ingestive behaviors are under the control of neural circuits and neuropeptide systems that control appetitive sex behaviors and differ from those that control consummatory ingestive behaviors. Decreases in the availability of oxidizable metabolic fuels enhance the stimulatory effects of peripheral hormones on appetitive ingestive behavior and the inhibitory effects on appetitive sex behavior, putting a new twist on the notion of leptin, insulin, and ghrelin "resistance." The ratio of hormone concentrations to the availability of oxidizable metabolic fuels may generate a critical signal that schedules conflicting behaviors, e.g., mate searching vs. foraging, food hoarding vs. courtship, and fat accumulation vs. parental care. In species representing every vertebrate taxa and even in some invertebrates, many putative "satiety" or "hunger" hormones function to schedule ingestive behavior in order to optimize reproductive success in environments where energy availability fluctuates.