Interaction of neuropeptide Y receptors (NPY1, NPY2 and NPY5) with somatostatin on somatostatin-induced feeding behaviour in neonatal chicken

The effect of intraperitoneal injection of Glycyrrhizin on central regulation of food intake in broilers injected with LPS

1. Poultry farming faces challenges regarding correct hygiene and nutrition. One of the challenges is gram-negative bacteria that stimulate pro-inflammatory reactions through lipopolysaccharide (LPS) and cause disease and anorexia. Liquorice, a medicinal plant containing glycyrrhizin (Glz; a saponin and emulsifier compound) as its main active ingredient, was injected into broilers to investigate any beneficial effects on feed intake in LPS-injected broilers.2. The study involved three experiments using 72 male broiler chickens in each, to examine the impact of Glz on feed intake, especially when challenged with lipopolysaccharide (LPS) by intra-peritoneal (IP) injection to cause inflammation (n = 24). Experiment 1 was conducted to examine the effects of intraperitoneal injection of Glz (12.5, 25 and 50 mg) on feed intake in chickens. In experiment 2, the effects of intracerebroventricular injections of LPS (6.25, 12.5 and 25 ng) were examined. The third experiment investigated the impact of IP injection of Glz on inflammation induced by LPS.3. Injection of Glz significantly increased feed intake in a dose-dependent manner. Whereas LPS significantly reduced the feed intake in feed-deprived chickens (p < 0.05).4. In conclusion, Glz can neutralise the feed intake reduction caused by inflammation in broilers, highlighting its potential role in modulating feed intake in broilers.

Role of the intracerebroventricular injection α- klotho on food intake in broiler chicken: a novel study

This novel study investigated the effects of intracerebroventricular (ICV) injection α- klotho and its interaction with neuropeptide Y (NPY) receptors on food intake in broiler chicken. This study included 4 experiments with 4 groups in each with 11 replicates per group. Birds were feed deprived 3 h prior injection, following injection returned to their cage and food provided. In experiment 1, group 1 received ICV injection of the saline and groups 2 to 4 received ICV injection of the α-klotho (1, 2, and 4 µg), respectively. In experiment 2, chicken received ICV injection of the saline, B5063 (NPY1 receptor antagonist, 1.25 µg), α-klotho (4 µg) and co-injection of the B5063 + α-klotho. In experiments 3 and 4, SF22 (NPY2 receptor antagonist, 1.25 µg), and SML0891 (NPY5 receptor antagonist, 1.25 µg) were injected instead of the B5063. Then consumed food was measured at 30, 60, and 120 min post the injection. Based on results, ICV injection of the α-klotho (2 and 4 µg) significantly decreased food intake (P < 0.05). Co-injection of the B5063 + α-klotho significantly amplified hypophagic effect of the α-klotho (P < 0.05). α-klotho-induced hypophagia was not influenced by SF22 or SML0891. These results suggest that α-klotho-induced hypophagia is mediated via NPY1 receptors in broiler chicken.

Neural mechanisms of mutualistic fish cleaning behaviour: a study in the wild

One crucial interaction for the health of fish communities in coral reefs is performed by cleaner fish by removing ectoparasites from the body of other fish, so-called clients. Studying the underlying mechanisms of this behaviour is essential to understanding how species react to social stimuli and defining the drivers of mutualistic social behaviour. Here, we pinpoint the neural molecular mechanisms in the cleaning behaviour of Labroides dimidiatus in the wild through an in situ interaction experiment at a coral reef in New Caledonia. Five cleaners and clients (Abudefduf saxatilis) were placed into underwater aquaria to interact, while five were not presented with a client. The brain transcriptomes revealed 233 differentially expressed genes in cleaners that were interacting with a client. Among these genes, grin2d, npy, slc6a3 and immediate early genes (IEGs; fosb and fosl1) were related to learning and memory, glutamate and dopamine pathways, which confirm molecular pathways observed in laboratory studies. However, a new potential mechanism was found with npy (neuropeptide Y) as a driver of feeding behaviour. These results show the role of neurotransmitters and IEGs in mutualistic social behaviour, unveiling the mechanism behind the feeding stimulus that leads the cleaner fish to establish mutualistic interactions in coral reefs.

Effect of intracerebroventricular (ICV) injection of adrenomedullin and its interaction with NPY and CCK pathways on food intake regulation in neonatal layer-type chicks

Adrenomedullin has various physiological roles including appetite regulation. The objective of present study was to determine the effects of ICV injection of adrenomedullin and its interaction with NPY and CCK receptors on food intake regulation. In experiment 1, chickens received ICV injection of saline and adrenomedullin (1, 2, and 3 nmol). In experiment 2, birds injected with saline, B5063 (NPY1 receptor antagonist, 1.25 µg), adrenomedullin (3 nmol) and co-injection of B5063+adrenomedullin. Experiments 3 to 5 were similar to experiment 2 and only SF22 (NPY2 receptor antagonist, 1.25 µg), SML0891 (NPY5 receptor antagonist, 1.25 µg) and CCK4 (1 nmol) were injected instead of B5063. In experiment 6, ICV injection of saline and CCK8s (0.125, 0.25, and 0.5 nmol) were done. In experiment 7, chickens injected with saline, CCK8s (0.125 nmol), adrenomedullin (3 nmol) and co-injection of CCK8s+adrenomedullin. After ICV injection, birds were returned to their individual cages immediately and cumulative food intake was measured at 30, 60, and 120 min after injection. Adrenomedullin (2 and 3 nmol) decreased food intake compared to control group (P < 0.05). Coinjection of B5063+adrenomedullin amplified hypophagic effect of adrenomedullin (P < 0.05). The ICV injection of the CCK8s (0.25 and 0.5 nmol) reduced food intake (P < 0.05). Co-injection of the CCK8s+adrenomedullin significantly potentiated adrenomedullin-induced hypophagia (P < 0.05). Administration of the SF22, SML0891 and CCK4 had no effect on the anorexigenic response evoked by adrenomedullin (P > 0.05). These results suggested that the hypophagic effect of the adrenomedullin is mediated by NPY1 and CCK8s receptors. However, our novel results should form the basis for future experiments.

The effects of neuropeptide W on food consumption and feeding behavior in neonatal meat-type chicks: Role of CRF1/CRF2 and NPY1 receptors

In several studies, the regulatory role of the neuropeptide W (NPW) system in food intake has been demonstrated. Considering the lack of avian studies in this field, the current research was conducted to evaluate the effects of intracerebroventricular (ICV) infusion of NPW and its interferences with corticotropin, melanocortin, and neuropeptide Y (NPY) receptors on meal consumption and feeding behaviors of broilers. In the first experiment, birds were injected with NPW (0.75, 1.5, and 3 nmol) in addition to saline. In the second experiment, saline, CRF1 receptor antagonist (NBI35965, 30 μg), NPW (3 nmol), and simultaneous injections of NBI35965 and NPW were performed. Experiments 3-8 were identical to experiment 2, except that CRF2 receptor antagonist (K41498, 30 μg), MC3/MC4 receptor antagonist (SHU9119, 0.5 nmol), MC4 receptor antagonist (HS024, 0.5 nmol), NPY1 receptor antagonist (BMS193885, 1.25 nmol), NPY2 receptor antagonist (CYM9484, 1.25 nmol), and NPY5 receptor (antagonist L-152,804, 1.25 nmol) were administrated instead of NBI35965. After that, cumulative feed intake and feeding behavior were monitored for 2 h and 30 min after injections, respectively. Following the infusion of NPW (1.5 and 3 nmol), there was a significant stimulation of meal consumption in chickens (P < 0.05). Concomitant injection of NBI35965 and K41498 with NPW enhanced the appetite-increasing effect of NPW (P < 0.05); while BMS193885 suppressed this effect of NPW (P < 0.05). Injection of SHU9119, HS024, CYM9484, and L-152804 with NPW at the same time, had no significant effect on NPW-induced hyperphagia (P > 0.05). NPW also significantly decreased the standing period and the number of jumps, steps, and exploratory pecks, and led to an increase in sitting period and feeding pecks (P < 0.05). Based on the observations, it seems that NPW-induced hyperphagia could be mediated through CRF1, CRF2, and NPY1 receptors in neonatal broilers.

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.

Regulation of the central melanocortin system on energy balance in mammals and birds

Agouti-related protein/neuropeptide Y (AgRP/NPY) neurons promote feeding, while proopiomelanocortin/cocaine- and amphetamine-regulated transcript (POMC/CART) neurons and melanocortin receptor neurons inhibit feeding; these three types of neurons play vital roles in regulating feeding. The central melanocortin system composed of these neurons is critical for the regulation of food intake and energy metabolism. It regulates energy intake and consumption by activating or inhibiting the activities of AgRP/NPY neurons and POMC/CART neurons and then affects the feeding behaviour of animals to maintain the energy balance. Meanwhile, organisms can also positively or negatively regulate energy homeostasis through the negative feedback of the neuron system. With further studies, understanding of the process and factors involved in the energy balance regulation of mammals and birds can be improved, which will provide a favourable scientific basis to reduce costs and improve meat production in production and breeding.

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.

Recent advances in neuropeptide-related omics and gene editing: Spotlight on NPY and somatostatin and their roles in growth and food intake of fish

Feeding and growth are two closely related and important physiological processes in living organisms. Studies in mammals have provided us with a series of characterizations of neuropeptides and their receptors as well as their roles in appetite control and growth. The central nervous system, especially the hypothalamus, plays an important role in the regulation of appetite. Based on their role in the regulation of feeding, neuropeptides can be classified as orexigenic peptide and anorexigenic peptide. To date, the regulation mechanism of neuropeptide on feeding and growth has been explored mainly from mammalian models, however, as a lower and diverse vertebrate, little is known in fish regarding the knowledge of regulatory roles of neuropeptides and their receptors. In recent years, the development of omics and gene editing technology has accelerated the speed and depth of research on neuropeptides and their receptors. These powerful techniques and tools allow a more precise and comprehensive perspective to explore the functional mechanisms of neuropeptides. This paper reviews the recent advance of omics and gene editing technologies in neuropeptides and receptors and their progresses in the regulation of feeding and growth of fish. The purpose of this review is to contribute to a comparative understanding of the functional mechanisms of neuropeptides in non-mammalians, especially fish.