Induction of food intake by a noradrenergic system using clonidine and fusaric acid in the neonatal chick

Possible interaction of central noradrenergic, serotoninergic and oxytocin systems with nesfatin-1 induced hypophagia and feeding behavior in newborn broiler

There are some differences between mammals and birds in terms of central food intake regulation. In avian species, the hypophagic role of nesfatin-1 has not been investigated with other neurotransmitters. Therefore, this study aimed to determine the alteration of feeding behavior following intracerebroventricular (ICV) injection of nesfatin-1 and its possible interaction with central noradrenergic, serotoninergic, and oxytocin systems in newborn broiler chicks. In experiment 1, birds received ICV injection of phosphate-buffered saline (PBS), prazosin (α₁ receptors antagonist, 10 nmol), nesfatin-1 (40 ng), and co-administration of prazosin and nesfatin-1. Experiments 2-10 were similar to experiment 1, except that yohimbine (α₂ receptors antagonist, 13 nmol), metoprolol (β₁ receptors antagonist, 24 nmol), IC1118,551 (β₂ receptors antagonist for, 5nmol), SR59230R (β₃ receptors antagonist, 20 nmol), fluoxetine (serotonin reuptake inhibitor, 10 µg), PCPA (serotonin synthesis inhibitor, 1.5 µg), 8-OH-DPAT (5-HT₁A receptors agonist, 15.25 nmol), SB242084 (5-HT₂C receptors antagonist,1.5 µg) and tocinoic acid (oxytocin receptors antagonist, 2 µg) were injected instead of prazosin. Immediately after the injection, food consumption and behavioral traits were recorded. Nesfatin-1 decreased food consumption (P < 0.05). Nesfatin-1 along with ICI118551 decreased food consumption (P < 0.05). The nesfatin-1- induced hypophagia were reduced by the simultaneous injection of PCPA and nesfatin-1 (P < 0.05). Nesfatin-1induced hypophagia were decreased by the simultaneous injection of SB242084 (P < 0.05). The nesfatin-1 -induced hypophagia were abolished by the simultaneous injection of the tocinoic acid and nesfatin-1 (P < 0.05). ICV injection of the nesfatin-1 decreased the number of steps, jumps, exploratory food, and pecks (P < 0.05) with no effect on drink pecks (P > 0.05). Nesfatin-1 significantly decreased standing time and increased both sitting time and rest time (P < 0.05). Nesfatin-1 could play an important role in feeding behavior, and its hypophagic effects were mediated by β₂ adrenergic, 5-HT₂C serotoninergic, and oxytocin receptors in neonatal chickens.

Possible effects of the central adrenergic and dopaminergic receptors on hypophagia induced by neuromedin S in neonatal layer-type chicks

The current study was aimed to determine the possible effects of the central adrenergic and dopaminergic receptors in neuromedin S (NMS)-induced hypophagia in neonatal layer-type chickens. In the first experiment, control solution, and NMS (0.25, 0.5, and 1 nmol), were injected (intracerebroventricular (ICV)) in chickens. In the second experiment, birds were injected with a control solution,SCH23390 (D₁receptor antagonist, 5 nmol), NMS (1 nmol), and a combination of the SCH23390 + NMS. Experiments 3-11 were similar to experiment 2, except that chickens were injected withAMI-193 (D₂receptor antagonist, 5 nmol), NGB2904(D₃receptor antagonist, 6.4 nmol), L-741,742(D₄receptor antagonist, 6 nmol), 6-OHDA(6-hydroxydopamine, 2.5 nmol),Prazosin(α₁receptor antagonist, 10 nmol),Yohimbine(α₂receptor antagonist, 13 nmol),Metoprolol(β₁receptor antagonist receptor, 24 nmol),ICI 118,551 (β₂receptor antagonist, 5 nmol),SR 59230R (β₃ receptor antagonist, 20 nmol) instead ofSCH23390. Then, cumulative food intake was recorded at 30, 60, and 120 min following the injection. According to the results, food intake was significantly decreased after ICV injection of NMS in a dose -dependent manner (P < 0.05). Also, the co-injection of the SCH23390 + NMS significantly attenuated NMS-induced hypophagia (P < 0.05). The co-administration of AMI-193 + NMS significantly reduced NMS- induced hypophagia (P < 0.05). In addition, the co-injection of ICI 118,551 + NMS and 6-OHDA + NMS considerably decreased NMS-induced food consumption (P < 0.05). However, NGB2904, L-741742, Prazosin, Yohimbine, Metoprolol and SR 59230R had no effect on hypophagia induced by NMS (P > 0.05). These results demonstrated thatNMS- induced hypophagia might be mediated by D₁/D₂ dopaminergic andβ₂adrenergic receptors in neonatal layer-type chickens.

Defence response in plants and animals against a common fungal pathogen, Fusarium oxysporum

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Fusarium oxysporum species complex (FOSC) is considered one of the most devastating plant pathogen.

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FOSC is an emerging pathogen of immunocompromised individuals.

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Mycotoxins produced by FOSC predisposes the host to other pathogens.

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Comparative immune reactions in plant and invertebrate show that several antimicrobial peptides (AMPs) and secondary metabolites maybe used as control against Fusarium infection.

Plant pathogens emerging as threat to human and animal health has been a matter of concern within the scientific community. Fusarium oxysporum, predominantly a phytopathogen, can infect both plants and animals. As a plant pathogen, F. oxysporum is one of the most economically damaging pathogen. In humans, F. oxysporum can infect immunocompromised individuals and is increasingly being considered as a problematic pathogen. Mycotoxins produced by F. oxysporum supress the innate immune pathways in both plants and animals. Hence, F. oxysporum is the perfect example for studying similarities and differences between defence strategies adopted by plants and animals. In this review we will discuss the innate immune response of plant and animal hosts for protecting against F. oxysporum infection. Such studies will be helpful for identifying genes, protein and metabolites with antifungal properties suitable for protecting humans.

Neuropeptide Y modifies a part of diencephalic catecholamine but not indolamine metabolism in chicks depending on feeding status

The role of the monoaminergic system in the feeding behavior of neonatal chicks has been reported, but the functional relationship between the metabolism of monoamines and appetite-related neuropeptides is still unclear. This study aimed to investigate the changes in catecholamine and indolamine metabolism in response to the central action of neuropeptide Y (NPY) in different feeding statuses and the underlying mechanisms. In Experiment 1, the diencephalic concentrations of amino acids and monoamines following the intracerebroventricular (ICV) injection of NPY (375 pmol/10 μl/chick), saline solution under ad libitum, and fasting conditions for 30 min were determined. Central NPY significantly decreased L-tyrosine concentration, the precursor of catecholamines under feeding condition, but not under fasting condition. Central NPY significantly increased dopamine metabolites, including 3,4-dihydroxyphenylacetic acid and homovanillic acid (HVA). The concentration of 3-methoxy-4-hydroxyphenylglycol was significantly reduced under feeding condition, but did not change under fasting condition by NPY. However, no effects of NPY on indolamine metabolism were found in either feeding status. Therefore, the mechanism of action of catecholamines with central NPY under feeding condition was elucidated in Experiment 2. Central NPY significantly attenuated diencephalic gene expression of catecholaminergic synthetic enzymes, such as tyrosine hydroxylase, L-aromatic amino acid decarboxylase, and GTP cyclohydrolase I after 30 min of feeding. In Experiment 3, co-injection of α-methyl-L-tyrosine, an inhibitor of tyrosine hydroxylase with NPY, moderately attenuated the orexigenic effect of NPY, accompanied by a significant positive correlation between food intake and HVA levels. In Experiment 4, there was a significant interaction between NPY and clorgyline, an inhibitor of monoamine oxidase A with ICV co-injection which implies that co-existence of NPY and clorgyline enhances the orexigenic effect of NPY. In conclusion, central NPY modifies a part of catecholamine metabolism, which is illustrated by the involvement of dopamine transmission and metabolism under feeding but not fasting conditions.

Noradrenergic alpha-2A receptor activation suppresses courtship vocalization in male Japanese quail

Male Japanese quail produce high-frequency crow vocalizations to attract females during the breeding season. The nucleus of intercollicularis (ICo) is the midbrain vocal center in birds and electrical stimulation of the ICo produces calls that include crowing. Noradrenaline plays a significant role in sexual behavior but the contribution of noradrenaline in the control of courtship vocalizations in quail has not been well established. Using dose-dependent intracerebroventricular injection of clonidine, an α2-adrenergic receptor-specific agonist, crowing vocalization was immediately suppressed. At the same time as crow suppression by clonidine there was a reduction of immediate early gene, zenk mRNA, in the ICo; no zenk mRNA expression was detected in the dorsomedial division of the nucleus. Using histochemistry, we determined that the ICo receives noradrenergic innervation and expresses α2A-adrenergic receptor mRNA. Taken together, these data suggest that noradrenaline regulates courtship vocalization in quail, possibly via the α2A-adrenergic receptor expressed on ICo neurons.

Fusaric acid decreases p53 expression by altering promoter methylation and m6A RNA methylation in human hepatocellular carcinoma (HepG2) cells

Fusaric acid (FA) is a food-borne mycotoxin that mediates toxicity with limited information on its epigenetic properties. p53 is a tumour suppressor protein that regulates cell cycle arrest and apoptotic cell death. The expression of p53 is regulated transcriptionally by promoter methylation and post-transcriptionally by N-6-methyladenosine (m6A) RNA methylation. We investigated the effect of FA on p53 expression and its epigenetic regulation via promoter methylation and m6A RNA methylation in human hepatocellular carcinoma (HepG2) cells. HepG2 cells were treated with FA [0, 25, 50, 104, and 150 µg/ml; 24 h] and thereafter, DNA, RNA, and protein was isolated. Promoter methylation and expression of p53 was measured using qPCR and Western blot. RNA immuno-precipitation was used to determine m6A-p53 levels. The expression of m6A methyltransferases (METTL3 and METTL14), demethylases (FTO and ALKBH5), and readers (YTHDF1-3 and YTHDC2) were measured using qPCR. FA induced p53 promoter hypermethylation (p < 0.0001) and decreased p53 expression (p < 0.0001). FA decreased m6A-p53 levels (p < 0.0001) by decreasing METTL3 (p < 0.0001) and METTL14 (p < 0.0001); and suppressed expression of YTHDF1 (p < 0.0001), YTHDF3 (p < 0.0001), and YTHDC2 (p < 0.0001) that ultimately reduced p53 translation (p < 0.0001). Taken together, the data shows that FA epigenetically decreased p53 expression by altering its promoter methylation and m6A RNA methylation in HepG2 cells. This study reveals a mechanism for p53 regulation by FA and provides insight into future therapeutic interventions.

Interaction between central GABAA receptor and dopaminergic system on food intake in neonatal chicks: role of D1 and GABAA receptors

OBJECTIVE

The present study was designed to examine the role of central γ-Aminobutyric acid_A receptors and dopaminergic system on feeding behaviour in neonatal layer-type chicken.

METHODS

In this study, six experiments were designed, each with four treatment groups (n = 44 in each experiment). In experiment 1, four groups of 3-h food-deprived chicks received a dose of either the intracerebroventricular injection of (1) control solution, (2) Levo-dihydroxyphenylalanine as precursor of dopamine; 125 nmol, (3) Gaboxadol (γ-Aminobutyric acid_A receptor agonist, 0.2 µg) and (4) Levo-dihydroxyphenylalanine (125 nmol) plus Gaboxadol (0.2 µg). Experiments 2-6 were similar to experiment 1, except that the chickens were intracerebroventricular-injected with 6-hydroxydopamine (is a neurotoxin; 2.5 nmol), SCH23390 (D₁ receptor antagonist, 5 nmol), AMI-193 (D2 receptor antagonist, 5 nmol), NGB2904 (D₃ receptor antagonist, 6.4 nmol) and L-741,742 (D₄ receptor antagonist, 6 nmol) instead of levo-dihydroxyphenylalanine. Then, the cumulative food intake was measured until 120 min post-injection.

RESULTS

According to the results, intracerebroventricular injection of Gaboxadol (0.2 µg) significantly increased the food intake (P < 0.05). Co-injection of the 6-hydroxydopamine + Gaboxadol significantly amplified the food intake (P < 0.05). Intracerebroventricular injection of SCH23390 (5 nmol) + Gaboxadol (0.2 µg) significantly amplified the Gaboxadol-induced hyperphagia (P < 0.05). No significant effect was observed by co-injection of the D₂-D₄ receptor antagonists + Gaboxadol (P > 0.05).

CONCLUSION

These results suggested the interconnection between central Dopaminergic and γ-Aminobutyric acid_A on the feeding behaviour mediates via D₁ and γ-Aminobutyric acid_A receptors in 3-h food-deprived neonatal layer-type chicken.

Neuropeptide Control of Feeding Behavior in Birds and Its Difference with Mammals

Feeding is an essential behavior for animals to sustain their lives. Over the past several decades, many neuropeptides that regulate feeding behavior have been identified in vertebrates. These neuropeptides are called “feeding regulatory neuropeptides.” There have been numerous studies on the role of feeding regulatory neuropeptides in vertebrates including birds. Some feeding regulatory neuropeptides show different effects on feeding behavior between birds and other vertebrates, particularly mammals. The difference is marked with orexigenic neuropeptides. For example, melanin-concentrating hormone, orexin, and motilin, which are regarded as orexigenic neuropeptides in mammals, have no effect on feeding behavior in birds. Furthermore, ghrelin and growth hormone-releasing hormone, which are also known as orexigenic neuropeptides in mammals, suppress feeding behavior in birds. Thus, it is likely that the feeding regulatory mechanism has changed during the evolution of vertebrates. This review summarizes the recent knowledge of peptidergic feeding regulatory factors in birds and discusses the difference in their action between birds and other vertebrates.

Adrenergic and noradrenergic regulation of poultry behavior and production

Norepinephrine and epinephrine (noradrenaline and adrenaline) are integral in maintaining behavioral and physiological homeostasis during both aversive and rewarding events. They regulate the response to stressful stimuli through direct activation of adrenergic receptors in the central and sympathetic nervous systems, hormonal activity and through the interaction of the brain, gut, and microbiome. The multiple functions of these catecholamines work synergistically to prepare an individual for a "fight or flight" response. However, hyper-reactivity of this system can lead to increased fearfulness and aggression, decreased health and productivity, and a reduction in overall well-being. Behaviors, such as aggression and certain fear-related behaviors, are a serious problem in the poultry industry that can lead to injury and cannibalism. For decades, catecholamines have been used as a measure of stress in animals. However, few studies have specifically targeted the adrenergic systems as means to reduce behaviors that are damaging or maladapted to their rearing environments and improve animal well-being. This article attempts to address our current understanding of specific, adrenergic-regulated behaviors that impact chicken well-being and production.

Ghrelin-induced hypophagia is mediated by the β2 adrenergic receptor in chicken

The purpose of this study was to examine the effects of intracerebroventricular injection of metoprolol (a β1 adrenergic receptor antagonist), ICI 118,551 (a β2 adrenergic receptor antagonist), and SR 59230R (a β3 adrenergic receptor antagonist) on ghrelin-induced food and water intake by 3-h food-deprived (FD3) cockerels. The chickens were randomly allocated to 4 treatment groups with 8 replicates in each group. A cannula was surgically implanted into the lateral ventricle of the brain. In experiment 1, chickens received the β1 adrenergic receptor antagonist (24 nmol) before injection of the ghrelin (0.6 nmol). In experiment 2, chickens received the β2 adrenergic receptor antagonist (5 nmol) before injection of the ghrelin (0.6 nmol). In experiment 3, birds were injected with ghrelin (0.6 nmol) after the β3 adrenergic receptor antagonist (20 nmol). Cumulative food and water intake were recorded 3-h post injection and analyzed by two-way analysis of variance. According to the results, ghrelin injection reduced food and water intake by broiler cockerels (p≤0.05). The effect of ghrelin on food intake was significantly attenuated by pretreatment with the β2 receptor antagonist (p≤0.05). Furthermore, the β2 receptor antagonist had no effect on water intake induced by ghrelin. Also, pretreatment with the β1 and β3 receptors antagonists had no effect on ghrelin-induced food and water intake. These results suggest that the effect of ghrelin on cumulative food intake by cockerels is mediated via β2 adrenergic receptors.

Central nervous system regulation of food intake and energy expenditure: role of galanin-mediated feeding behavior

Galanin is a neuropeptide widely expressed in the brain. It is implicated in energy expenditure, feeding, and the regulation of body weight. Numerous studies have revealed that galanin regulates food intake via galanin receptors, 5-HT(1A) receptor and adrenergic α-2 receptor. In this review, we summarize recent findings that reveal the essential role of galanin in increasing food intake as well as body weight and that identify the individual galanin receptor subtypes involved in the brain's modulation of food intake and energy expenditure, to provide a theoretical basis for further studies of different aspects of galanin action.

Role of adrenergic alpha-2-receptors on feeding behavior in layer-type chicks

The present study was designed to investigate the role of brain adrenergic alpha-2-receptors on feeding regulation of layer-type chicks. Intracerebroventricular injection of the adrenergic alpha-2-receptor agonist, clonidine, stimulated food intake. This effect was blocked by co-injection of the alpha-2-receptor antagonist, yohimbine, demonstrating that the alpha-2-receptor is related to stimulation of feeding in layer-type chicks. Stimulation of food intake caused by neuropeptide Y and beta-endorphin was attenuated by co-injection with yohimbine. However, yohimbine did not block prolactin-releasing peptide stimulation of food intake. It is therefore likely that brain adrenergic alpha-2-receptors mediate the orexigenic effects of neuropeptide Y and beta-endorphin in layer-type chicks.

Central administration of somatostatin stimulates feeding behavior in chicks

The purpose of the present study was to determine if central administration of somatostatin influences feeding behavior in layer chicks. Five- to 7-day-old chicks that received intracerebroventricular (ICV) injections of 0.5 or 2 nmol somatostatin increased their food intake at 30 and 60 min after the injection, suggesting that central somatostatin serves as an orexigenic neuropeptide in chicks. This hypothesis was further supported since chicks ICV injected with 0.5 or 2 nmol cortistatin, which binds to somatostatin receptors, also had increased food intake at the same time. Somatostatin-associated feeding behavior was attenuated by co-administration of 20 nmol beta-funaltrexamine (an opioidergic mu-receptor antagonist) (to 31% of the orexigenic effect of somatostatin at 60 min after the injection) but not ICI-174,864 or nor-binaltorphimine (antagonists of opioidergic delta- and kappa-receptors, respectively). Co-administration of 13 nmol yohimbine, an adrenergic alpha-2 receptor antagonist, also attenuated the orexigenic effect of somatostatin (to 31% of the orexigenic effect of somatostatin at 60 min after the injection). These results suggest that somatostatin-associated feeding behavior is mediated by opioidergic mu- and adrenergic alpha-2-receptors in chicks.

Inhibitory effect of ghrelin on food intake is mediated by the corticotropin-releasing factor system in neonatal chicks

It is known that, in rats, central and peripheral ghrelin increases food intake mainly through activation of neuropeptide Y (NPY) neurons. In contrast, intracerebroventricular (ICV) injection of ghrelin inhibits food intake in neonatal chicks. We examined the mechanism governing this inhibitory effect in chicks. The ICV injection of ghrelin or corticotropin-releasing factor (CRF), which also inhibits feeding and causes hyperactivity in chicks. Thus, we examined the interaction of ghrelin with CRF and the hypothalamo-pituitary-adrenal (HPA) axis. The ICV injection of ghrelin increased plasma corticosterone levels in a dose-dependent or a time-dependent manner. Co-injection of a CRF receptor antagonist, astressin, attenuated ghrelin-induced plasma corticosterone increase and anorexia. In addition, we also investigated the effect of ghrelin on NPY-induced food intake and on expression of hypothalamic NPY mRNA. Co-injection of ghrelin with NPY inhibited NPY-induced increase in food intake, and the ICV injection of ghrelin did not change NPY mRNA expression. These results indicate that central ghrelin does not interact with NPY as seen in rodents, but instead inhibits food intake by interacting with the endogenous CRF and its receptor.

Central pipecolic acid increases food intake under ad libitum feeding conditions in the neonatal chick

It has been demonstrated that L-pipecolic acid (L-PA) is a major metabolic intermediate of L-lysine in the mammalian and chicken brain. A previous study showed that intracerebroventricular (i.c.v.) injection of L-PA suppressed feeding in neonatal chicks, and the actions were associated with gamma-aminobutyric acid (GABA)-B receptor activation. It has been reported that endogenous L-PA in the brain fluctuated under different feeding conditions. In the present study, we investigated the effect of i.c.v. injection of L-PA on food intake in the neonatal chick under ad libitum feeding conditions. The food intake was increased by 0.5 or 1.0 mg L-PA under ad libitum feeding conditions contrary to previous studies using fasted birds. A hyperphagic effect of L-PA (0.5 mg) was attenuated by both GABA-A receptor antagonist (picrotoxin, 0.5 microg) and GABA-B receptor antagonist (CGP54626, 21.0 ng). These results indicate that a hyperphagic effect of L-PA is mediated by both GABA-A and GABA-B receptors and L-PA differentially affects food intake under different feeding conditions in the neonatal chick.

Beta 3-adrenergic receptor is involved in feeding regulation in chicks

We examined whether the brain beta 3-adrenergic receptor (B3-AR) is involved in the feeding regulation of chicks. Intracerebroventricular (ICV) injection of BRL37344, a B3-AR agonist, reduced food intake of chicks under ad libitum, but not fasting, feeding conditions. The ICV injection of BRL37344 did not affect chick posture or locomotion activity suggesting that BRL37344 inhibited feeding without induction of sleep-like behavior as caused by norepinephrine. Furthermore, the rectal temperature increased following the ICV injection of BRL37344. Intraperitoneal administration of BRL37344 did not reduce food intake under ad libitum feeding condition. The present study demonstrated that the brain B3-AR is involved in the inhibition of feeding in chicks. We also suggested that activation of the brain affects the energy metabolism in chicks.

Central administration of cocaine- and amphetamine-regulated transcript inhibits food intake in chicks

The present study was done to clarify whether intracerebroventricular (ICV) injection of cocaine- and amphetamine-regulated transcript (CART) affects feeding in chicks. ICV injection of CART significantly inhibited fasting-induced feeding of broiler chicks. In layer chicks, on the other hand, CART inhibited food intake in birds with ad libitum access to feed but only weakly affected intake of fasted birds. In addition, the ICV injection of CART attenuated neuropeptide Y (NPY)-induced feeding in both broiler and layer chicks. These results indicate that CART is one of the important regulators of feeding in chicks, but the suppressive effect on feeding is somewhat different between strains. Furthermore, the present study also demonstrates that CART interacts with NPY in the central nervous system to regulate feeding in chicks.

Intracerebroventricular administration of octopamine stimulates food intake of chicks through alpha(2)-adrenoceptor

Octopamine, known to be an important neurotransmitter in invertebrates, has been noted to have several similarities to noradrenaline (NA) in mammals. The present study was done to elucidate whether central injection of octopamine enhances the feeding behavior of chicks and to investigate the interaction of octopamine with both alpha(1)- and alpha(2)-adrenoceptors. We found that the intracerebroventricular injection of octopamine significantly stimulated food intake of neonatal chicks during 30 min postinjection, but not thereafter. Moreover, this octopamine-induced eating response was attenuated by the alpha(2)-antagonist yohimbine, but not by the alpha(1)-antagonist prazosin. These results suggest that the action of octopamine on the feeding behavior of the neonatal chick is similar to that of NA, since octopamine regulates food intake through the alpha(2)-adrenoceptor.

Intracerebroventricular injection of glucagon-like peptide-1 decreases monoamine concentrations in the hypothalamus of chicks

1. We measured the concentrations of dopamine (DA), norepinephrine (NE), epinephrine (E) and 5-hydroxytryptamine (5-HT) in the hypothalamus of 21-d-old male brown-egg layer-type chicks after intracerebroventricular injection of glucagon-like peptide-1 (GLP-1). 2. The monoamine concentrations of the whole hypothalamus, paraventricular nucleus and lateral hypothalamic area were not significantly affected by GLP-1. 3. However, concentrations of DA, NE and E, but not 5-HT, in the ventromedial hypothalamic nucleus (VMH) were significantly decreased by GLP-1. 4. These observations suggest that the anorexigenic effect of GLP-1 involves catecholaminergic systems in the VMH in the chick.

Feeding increases 5-hydroxytryptamine and norepinephrine within the hypothalamus of chicks

It is thought that hypothalamic 5-hydroxytryptamine (5HT) and norepinephrine (NE) are involved in the regulation of feeding in chicks. The present study was conducted to elucidate changes in the levels of extracellular 5HT and NE in the hypothalamus during feeding of chicks. In order to measure 5HT, NE and 4-hydroxy-3-methoxyphenylglycol (MHPG), which is a major metabolite of NE, we used brain microdialysis and high-pressure liquid chromatography with an electrochemical detector. After collecting samples to determine the basal levels of 5HT, NE and MHPG, food-deprived birds were given access to food. 5HT levels in the medial hypothalamus (MH) and lateral hypothalamus (LH) increased during the first 30 min of feeding, and then returned to basal levels. NE and MHPG in the LH increased during feeding, and remained elevated throughout the experiment. This study supports an idea that hypothalamic monoamines in the chick brain are involved in the regulation of feeding.

Interaction of corticotropin-releasing factor and glucagon-like peptide-1 on behaviors in chicks

Both corticortropin-releasing factor (CRF) and glucagon-like peptide-1 (GLP-1) inhibit food intake of chicks, but they also produce other behaviors. The present experiments were undertaken to clarify the interaction of CRF and GLP-1 regarding their anorectic actions as well as other behaviors. In Experiment 1, birds were injected intracerebroventricularly (i.c.v.), following a 3-h fast, with either saline, 0.1 microg of CRF, 0.1 microg of CRF+0.1 microg of GLP-1 or 0.1 microg of CRF+1 microg of GLP-1, and food intake was measured for 2 h. The injection of CRF decreased food intake, and CRF injected with GLP-1 suppressed food intake for up to 2 h. Birds were treated similarly in Experiment 2 in which the doses of CRF and GLP-1 were reversed. GLP-1 strongly suppressed food intake, and this effect was augmented by coadministration of CRF. In Experiment 3, the behaviors of chicks injected with saline, CRF (0.1 microg), GLP-1 (0.1 microg) or CRF (0.1 microg)+GLP-1 (0.1 microg) were monitored for the numbers of steps, vocalization and locomotion. Chicks were excited, moved more and vocalized loudly following injection of CRF, whereas an opposite response was seen with GLP-1. The behaviors were intermediate following the coinjection of the two peptides. In conclusion, CRF and GLP-1 interact in the chick brain, but the response depends on the behavior being measured.

Intracerebroventricular injection of fusaric acid attenuates the anorexia by glucagon-like peptide-1 in the neonatal chick

It is known that central injection of glucagon-like peptide-1 (GLP-1) suppresses feeding in rats and chicks, but the systems for GLP-1 are still open with special reference to the chick. The present study was done to determine whether a noradrenergic mechanism contributes to the anorexigenic effect of GLP-1 on the neonatal chick. Central administration of norepinephrine (NE) suppressed food intake with narcolepsy as GLP-1 in chicks. However, in spite of that dopamine (DA) did not affect food intake, coadministration of inhibitor of dopamine-beta-hydroxylase (DBH), fusaric acid (FA), attenuated the suppressive effect of GLP-1 on feeding behavior. It is suggested that there may be the interactive relationships between GLP-1 and noradrenergic system in the neonatal chick.