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

The role of central neurotransmitters in appetite regulation of broilers and layers: similarities and differences

The importance of feeding as a vital physiological function, on the one hand, and the spread of complications induced by its disorder in humans and animals, on the other hand, have led to extensive research on its regulatory factors. Unfortunately, despite many studies focused on appetite, only limited experiments have been conducted on avian, and our knowledge of this species is scant. Considering this, the purpose of this review article is to examine the role of central neurotransmitters in regulating food consumption in broilers and layers and highlight the similarities and differences between these two strains. The methodology of this review study includes a comprehensive search of relevant literature on the topic using appropriate keywords in reliable electronic databases. Based on the findings, the central effect of most neurotransmitters on the feeding of broilers and laying chickens was similar, but in some cases, such as dopamine, ghrelin, nitric oxide, and agouti-related peptide, differences were observed. Also, the lack of conducting a study on the role of some neurotransmitters in one of the bird strains made it impossible to make an exact comparison. Finally, it seems that although there are general similarities in appetite regulatory mechanisms in meat and egg-type chickens, the long-term genetic selection appropriate to breeding goals (meat or egg production) has caused differences in the effect of some neurotransmitters. Undoubtedly, conducting future studies while completing the missing links can lead to a comprehensive understanding of this process and its manipulation according to the breeding purposes of chickens.

The role of lateral hypothalamic nucleus in mediating locomotive behaviors in pigeons (Columba livia)

The lateral hypothalamic nucleus (LHy) is located in the dorsolateral hypothalamus of birds, and it is essential to many life processes. However, limited information is available about the role of LHy in mediating locomotive behaviors. In this work, we investigated the structure and function of LHy in pigeons (Columba livia) by Nissl staining, immunohistochemical (IHC) staining, insituhybridization (ISH) staining and constant current stimulation methods. The results showed that LHy appears crescent in shape, and three-dimensional coordinate value range of LHy is: A: 5.0-8.0 mm, L: 0.7-1.2 mm, D: 9.5-10.3 mm. The dopaminergic neurons in LHy were distributed in small amount and concentrated manner, while the glutamatergic neurons were distributed in a large number and uniform manner. The distribution of the above two neurons at each coronal level showed a significant positive correlation (R2 = 0.7516, P < 0.001). Our work demonstrated that LHy mainly mediates forward movement (P < 0.01) and ipsilateral lateral movement (P < 0.001), and these movements were significantly effected by electrical stimulation intensity. Our results showed that LHy can mediate the generation of directional behavior and this will provide technical support for the study of locomotor behavior regulation in birds.

Hypophagia induced by intracerebroventricular injection of apelin-13 is mediated via CRF1/CRF2 and MC3/MC4 receptors in neonatal broiler chicken

Previous studies have shown the role of apelin and its receptors in the regulation of food intake. In the present study, we investigate the mediating role of melanocortin, corticotropin, and neuropeptide Y systems in apelin-13- induced food intake in broilers. Eight trials were run in the current investigation to ascertain the relationships between the aforementioned systems and apelin-13 on food intake and behavioral changes after apelin-13 administration. In experiment 1, hens were given an intracerebroventricular administration of a solution for control in addition to apelin-13 (0.25, 0.5, and 1 µg). Astressin-B (a CRF1/CRF2 receptor antagonist, 30 µg), apelin-13 (1 µg), and administration of astressin-B and apelin-13 concurrently, were all injected into the birds in experiment 2. Experiments 3 through 8 were quite similar to experiment 2, with the exception of astressin2-B (CRF2 receptor antagonist, 30 µg), SHU9119 (MC3/MC4 receptor antagonist, 0.5 nmol), MCL0020 (MC4 receptor antagonist, 0.5 nmol), BIBP-3226 (NPY1 receptor antagonist, 1.25 nmol), BIIE 0246 (NPY2 receptor antagonist, 1.25 nmol), and CGP71683A (NPY5 receptor antagonist, 1.25 nmol) were injected instead of astressin-B. After then, total food consumption was monitored for 6 h. Apelin-13 injections of 0.5 and 1 µg decreased feeding (P < 0.05). The hypophagic effects of apelin were attenuated following the simultaneous administration of Astressin-B and Astressin2-B with apelin-13 (P > 0.05). Co-infusion of SHU9119 and apelin-13 reduced the appetite-decreasing effects of apelin-13 (P > 0.05). When MCL0020 and apelin-13 were injected at the same time, the hypophagia that apelin-13 induced was eliminated (P > 0.05). BIBP-3226, BIIE 0246, and CGP71683A had no effect on the hypophagia brought on by apelin-13 (P > 0.05). Also, apelin-13 significantly increased number of steps, jumps, exploratory food, pecks and standing time while decreased siting time (P < 0.05). These findings suggest that apelin-13-induced hypophagia in hens may involve the CRF1/CRF2 and MC3/MC4 receptors.

Effects of mesotocin manipulation on the behavior of male and female common waxbills

The oxytocin family of neuropeptides is implicated in the regulation of sociality across vertebrates. Non-mammalian homologs of oxytocin, such as isotocin in fish and mesotocin in amphibians, reptiles and birds, all play crucial roles modulating social and reproductive behavior. In this study, we exogenously manipulated the mesotocinergic system in a highly social bird, the common waxbill Estrild astrild, and tested the effects on affiliative and aggressive behavior by performing tests of competition over food. Birds treated with mesotocin showed a sedative state, decreasing almost all the behaviors we studied (movement, feeding, allopreening), while birds treated with an oxytocin antagonist showed a decrease only in social behaviors (aggressions and allopreening). We also found two sex-specific effects: mesotocin reduced allopreening more in males than females, and the oxytocin antagonist reduced aggressiveness only in females. Our results suggest sex-specific effects in the modulation of affiliative and aggressive behaviors via mesotocinergic pathways.

Mediatory role of the central NPY, melanocortine and corticotrophin systems on phoenixin-14 induced hyperphagia in neonatal chicken

Animal research indicates the neuropeptide Y (NPY), corticotrophin and melanocortin systems have a mediatory role in reward, however, how these substances interact with phenytoin-14 (PNX-14) induced food intake in birds remains to be identified. Accordingly, in this research eight tests were carried out to investigate the potential interactions of the NPY, melanocortin, as well as corticotrophin systems with PNX-14 on food consumption in neonatal chickens. In the first experiment, chickens were intracerebroventricular (ICV) injected with phosphate-buffered saline (PBS) and PNX-14 (0.8, 0.16, and 3.2 nmol). In second experiment, PBS, the antagonist of CRF₁/CRF₂ receptors (astressin-B, 30 μg) and PNX-14 + astressin-B were injected. In the rest of the experiments chicken received astressin2-B (CRF₂ receptor antagonist; 30 µg), SHU9119 (MCR₃/MCR₄ receptor antagonist, 0.5nomol), MCL0020 (MCR₄ receptor agonist, 0.5 nmol), B5063 (NPY₁ receptor antagonist, 1.25 μg), SF22 (NPY₂ receptor antagonist, 1.25 μg) and SML0891 (NPY₅ receptor antagonist, 1.25 μg) rather than astressin-B. Then, cumulative intake of food was recorded for 2 h. Based on the findings, PNX-14 (0.16 and 3.2 nmol) led to increment in food consumption compared with the control (P < 0.05). Co-administration of the PNX-14 and astressin-B promoted PNX-14-induced hyperphagia (P < 0.05). Co-injection of the PNX-14 + astressin2-B potentiated hyperphagia PNX-14 (P < 0.05). Co-injection of PNX-14 + B5063 inhibited the effects of the PNX-14 (P < 0.05). The co-administration of the PNX-14 and SML0891 potentiated hypophagic effects of the PNX-14 (P < 0.05). The results showed that PNX-14-induced hyperphagia mediates via NPY₁, NPY_5, and CRF₁/CRF₂ receptors in neonatal chickens.

Neural Functions of Hypothalamic Oxytocin and its Regulation

Oxytocin (OT), a nonapeptide, has a variety of functions. Despite extensive studies on OT over past decades, our understanding of its neural functions and their regulation remains incomplete. OT is mainly produced in OT neurons in the supraoptic nucleus (SON), paraventricular nucleus (PVN) and accessory nuclei between the SON and PVN. OT exerts neuromodulatory effects in the brain and spinal cord. While magnocellular OT neurons in the SON and PVN mainly innervate the pituitary and forebrain regions, and parvocellular OT neurons in the PVN innervate brainstem and spinal cord, the two sets of OT neurons have close interactions histologically and functionally. OT expression occurs at early life to promote mental and physical development, while its subsequent decrease in expression in later life stage accompanies aging and diseases. Adaptive changes in this OT system, however, take place under different conditions and upon the maturation of OT release machinery. OT can modulate social recognition and behaviors, learning and memory, emotion, reward, and other higher brain functions. OT also regulates eating and drinking, sleep and wakefulness, nociception and analgesia, sexual behavior, parturition, lactation and other instinctive behaviors. OT regulates the autonomic nervous system, and somatic and specialized senses. Notably, OT can have different modulatory effects on the same function under different conditions. Such divergence may derive from different neural connections, OT receptor gene dimorphism and methylation, and complex interactions with other hormones. In this review, brain functions of OT and their underlying neural mechanisms as well as the perspectives of their clinical usage are presented.

Fluid intake, what's dopamine got to do with it?

Maintaining fluid balance is critical for life. The central components that control fluid intake are only partly understood. This contribution to the collection of papers highlighting work by members of the Society for the Study of Ingestive Behavior focuses on the role that dopamine has on fluid intake and describes the roles that various bioregulators can have on thirst and sodium appetite by influencing dopamine systems in the brain. The goal of the review is to highlight areas in need of more research and to propose a framework to guide that research. We hope that this framework will inspire researchers in the field to investigate these interesting questions in order to form a more complete understanding of how fluid intake is controlled.

Evaluation of the Relationship between Adipose Metabolism Patterns and Secretion of Appetite-Related Endocrines on Chicken

Simple Summary

The weight of an animal conforms to a certain growth pattern. Among others, feed, environment, and body composition, in addition to genetics, affect the animal’s feed consumption and body weight. Under normal circumstances, the body weight of an animal is mainly affected by feed intake, and body composition may significantly influence feed intake. Therefore, this report sets out the effects of fat accumulation on lipid metabolism and appetite, and finally introduces the effects of feeding patterns on animal feed intake.

Abstract

In addition to the influence of genes, the quality of poultry products is mainly controlled by the rearing environment or feed composition during rearing, and has to meet human use and economical needs. As the only source of energy for poultry, feed considerably affects the metabolic pattern of poultry and further affects the regulation of appetite-related endocrine secretion in poultry. Under normal circumstances, the accumulation of lipid in adipose reduces feed intake in poultry and increases the rate of adipose metabolism. When the adipose content in cells decreases, endocrines that promote food intake are secreted and increase nutrient concentrations in serum and cells. By regulating the balance between appetite and adipose metabolism, the poultry’s growth and posture can maintain a balanced state. In addition, increasing fiber composition in feed can effectively increase poultry welfare, body weight, lean composition and antioxidant levels in poultry. According to this, the concept that proper fiber content should be added to feed should be considered for better economic benefits, poultry welfare and meat productivity.