Shin-Ichi Kawakami

Intracerebroventricular injection of agouti-related protein attenuates the anorexigenic effect of alpha-melanocyte stimulating hormone in neonatal chicks

It is well known that alpha-melanocyte stimulating hormone (alpha-MSH) inhibits feeding via melanocortin receptor-4 (MC4R) in the mammalian brain. The anorexigenic effect of alpha-MSH is attenuated by agouti-related protein (AGRP), an antagonist for MC4R. Present studies were carried out to clarify whether human AGRP (86-132) antagonizes the anorexigenic effect of alpha-MSH in broiler chicks. Intracerebroventricular injection of AGRP attenuated the anorexigenic effect of alpha-MSH. Furthermore, AGRP stimulated food intake of layer-type chicks under an ad libitum feeding condition but not broiler chicks, suggesting that the orexigenic effect of AGRP is different between two breeds. These also imply that the extent of the anorexigenic effect of endogenous alpha-MSH is different among two breeds. This may be a part of the difference in food intake between two breeds.

Feeding responses to several neuropeptide Y receptor agonists in the neonatal chick

Neuropeptide Y is one of the most potent neuropeptides known to induce feeding in animals, and has been suggested to be a physiological signal for food intake. It has been also reported that intracerebroventricular injection of neuropeptide Y stimulates feeding behavior of the neonatal chick. There are many neuropeptide Y receptor agonists that have not been investigated in feeding response of the neonatal chick. The aim of this study is to elucidate whether central injection of several neuropeptide Y receptor agonists stimulates feeding of the neonatal chick over 2 h. We found that central injections of [Leu(31), Pro(34)]neuropeptide Y, peptide YY, human pancreatic polypeptide and rat pancreatic polypeptide significantly stimulated food intake of neonatal chicks throughout the 2-h post-injection period. Neuropeptide Y-(13-36) significantly stimulated feeding at 30 min, but not thereafter. [D-Trp(32)]neuropeptide Y stimulated feeding at 60 and 120 min, but not 30 min, post-injection. Central administration of rat pancreatic polypeptide, which does not increase food intake in rats, stimulated feeding in chicks. This result reflects structural differences of the neuropeptide Y receptor subtypes and/or differences in mechanisms stimulating feeding behavior between mammals and chickens. In conclusion, neuropeptide Y receptor agonists, except for neuropeptide Y-(13-36), are potent stimulators of food intake in the neonatal chick.

Intracerebroventricular injection of mammalian motilin, melanin-concentrating hormone or galanin does not stimulate food intake in neonatal chicks.

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

Comparisons of insulin related parameters in commercial-type chicks: Evidence for insulin resistance in broiler chicks

The aim of this study is to elucidate whether insulin acts differentially within the central nervous system (CNS) of two types of commercial chicks to control ingestive behavior. Male layer and broiler chicks (4-day-old) were intracerebroventricularly (ICV) injected with saline or insulin under satiated and starved conditions. Feed intake was measured at 30, 60 and 120 min after treatment. Secondly, blood and hypothalamus were collected from both chick types under ad libitum feeding and fasting for 24 h. Plasma insulin concentration was measured by time-resolved fluoro-immunoassay. Hypothalamic insulin receptor mRNA expression levels were measured by quantitative RT-PCR. The ICV injection of insulin significantly inhibited feed consumption in layer chicks when compared with saline (P<0.05), but not broiler chicks (P>0.1). Plasma insulin concentration of both chick types significantly decreased following 24 h of fasting, while insulin concentrations in the broiler chicks were significantly higher compared to the layers fed under ad libitum conditions. Hypothalamic insulin receptor mRNA expression levels were significantly lower (P<0.05) in broiler chicks than in layer ones under ad libitum feeding. Feed deprivation significantly decreased insulin receptor mRNA levels in layer chicks (P<0.01), but not in broiler chicks (P>0.1). Moreover, plasma insulin concentrations correlated negatively with hypothalamic insulin receptor protein expression in the two types of chicks fed ad libitum (P<0.05). These results suggest that insulin resistance exists in the CNS of broiler chicks, possibly due to persistent hyperinsulinemia, which results in a down-regulation of CNS insulin receptor expression compared to that in layer chicks.

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.

Localization of hypothalamic insulin receptor in neonatal chicks: Evidence for insulinergic system control of feeding behavior

Feeding behavior is managed by various neuropeptides and/or neurotransmitters within the central nervous system in vertebrates. It is proposed that central insulin acts as the negative-feedback regulator of appetite via the central melanocortin system in neonatal chicks. The present study investigated the localization of insulin receptors in the chick hypothalamus using immunohistochemistry. Immunostaining revealed hypothalamic neuron expressing insulin receptors in the paraventricular nucleus, ventromedial hypothalamus, lateral hypothalamus and infundibular nucleus, the avian equivalent of the mammalian arcuate nucleus. Additionally, double-staining immunohistochemistry in the infundibular nucleus revealed the presence of insulin receptors in both α-melanocyto stimulating hormone and neuropeptide Y neurons. Immunohistological analysis indicates that the insulinergic system in the chick hypothalamus contributes to feeding behavior and this system regulates both anorexigenic and orexigenic neuropeptides. Furthermore, the mechanisms of central insulin induced-feeding behavior contributes to the regulation of the melanocortin system in the chick infundibular nucleus.

Central bombesin inhibits food intake and the orexigenic effect of neuropeptide Y in the neonatal chick

It is well known that central injection of bombesin (BN) suppresses feeding in mammalian and avian species, but the anorexigenic effect of central BN are still open with special reference to the chick. The dose response (0, 0.1 and 0.5 microg) of intracerebroventricular (ICV) injection of BN was examined in Experiment 1. ICV injection of BN inhibited food intake in a dose-dependent manner. Experiment 2 was done to determine whether BN interacts with the orexigenic effect of neuropeptide Y (NPY) in the neonatal chick. Central administration of NPY (2.5 microg) greatly enhanced food intake, but co-injection of BN (0.5 microg) suppressed food intake. The dose response of NPY (2.5 microg) co-injected with three levels of BN (0, 0.1 and 0.5 microg) was examined in Experiment 3. ICV injection of BN attenuated the hyperphagia by NPY in a dose-related fashion. It is suggested that central BN may interact with NPY for the regulation of feeding in the neonatal chick.

Screening of the Behavioral Tests for Monitoring Agonistic Behavior of Layer Chicks

Chicken agonistic behavior, a type of social behavior related to threatening and fighting, is among the most serious problems in the poultry industry. However, due to luck of effective models for investigating the brain mechanisms of the behavior, no effective measures have been taken. This study, therefore, aimed to select the behavioral tests available for monitoring chicken agonistic behavior. Two behavioral tests, resident-intruder (R-I) test and social interaction (SI) test, were performed for 10 minutes in 10 pairs of male layer chicks at 8, 12, 16, 20, and 24 days of age, and total agonistic frequencies (TAF: Sum of the frequencies of agonistic displays like pecking, biting, kicking, threatening, and leaping) and latency (the period of time from the beginning of the behavioral test to the occurrence of the first agonistic behavior) were measured as indices of agonistic behavior. Two-way repeated measures ANOVA revealed significant differences in TAF and latency between aggressors and opponents in both the behavioral tests. In the R-I test, the TAF of aggressors significantly increased from 8 to 20 days of age, and the latency significantly decreased from 8 to 24 days of age. In the SI test, however, the TAF of aggressors significantly increased and the latency significantly decreased only from 16 to 20 days of age. When the criterion of high agonistic behavior was defined as the TAF, where aggressors showed more than 30 times of TAF and the opponents did less than one-third TAF of aggressors, the aggression establishment rate (AER), which is equal to the number of aggressors showing high agonistic behavior per total behavioral trials, was significantly higher in the R-I test than in the SI test. These results suggest that the R-I test, rather than the SI test, is an effective tool for monitoring agonistic behavior of layer chicks.

Feeding and Drinking Responses and Hypothalamic Monoamine Concentrations of Neonatal Chicks Following Intracerebroventricular Injection of 6-OHDA

Abstract Bungo, T., Tachibana, T., Sashihara, K., Kawakami, S.-I., Ohgushi A., Furuse, M. and Ueda, H. 2002. Feeding and drinking responses and hypothalamic monoamine concentrations of neonatal chicks following intracerebroventricular injection of 6-OHDA. J. Appl. Anim. Res., 22: 183–192. To clarify the involvement of catecholaminergic systems in the regulation of food and water intake in the neonatal chick, 6-hydroxydopamine (6-OHDA) or fusaric acid (FA) was administered intracerebroventricularly ICV) and the concentrations of monoamine in the hypothalamus were determined. We found that food intake was significantly increased by ICV injection of 6-OHDA (25, 50 and 100 μg) until 60 min after injection, but the effect disappeared at 120 min. Although both 6-OHDA and FA had no significant effect on water intake, the water consumption in chicks treated with FA tended to be higher than that with saline (control). Norepinephrine (NE) in the hypothalamus was reduced in chicks treated with 6-OHDA (P<0.05). These results indicate that changes in NE concentration of the hypothalamus mainly influence food intake in chicks.