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Involvement of central opioid and melanocortin receptors in spexin-induced hypophagia following intracerebroventricular injection in neonatal broiler chicks

BMC Veterinary Research volume 21, Article number: 110 (2025) Cite this article

Abstract

Background

Numerous physiological properties have been documented in the literature pertaining to spexin, such as its role in appetite regulation. Therefore, the present research aimed to assess the impacts of centrally administering spexin and its interaction with opioid and melanocortin receptors on feeding behavior in neonatal broiler chicks. In experiment 1, the chickens were administered intracerebroventricular (ICV) injection of saline and spexin at varying doses of 5, 7.5 and 10 nmol. During the experiment 2, the broilers were subjected to an ICV injection containing saline, β-FNA (µ-opioid receptor antagonist, 5 µg), spexin (10 nmol), and a mixture of β-FNA plus spexin. Experiments 3 to 6 bore resemblance to experiment 2, with the exception that NTI (δ-opioid receptor antagonist, 5 µg), nor-BNI (κ-opioid receptor antagonist, 5 µg), SHU9119 (MC3/MC4 receptor antagonist, 0.5 nmol) and MCL0020 (MC4 receptor antagonist, 0.5 nmol) were administered instead of β-FNA. Then, the birds were promptly placed back into their individual cages and cumulative food intake was assessed at intervals of 30, 60, and 120 min postinjection.

Results

Spexin demonstrated a significant and dose-dependent decrease in food intake when compared to the control group (P < 0.05). Co-injection of β-FNA + spexin diminished spexin-induced hypophagia (P < 0.05) whereas concurrent administration of NTI and nor-BNI with spexin led to an amplification of the decrease in food consumption induced by spexin (P < 0.05). Additionally, anorexigenic impact of spexin was reversed by combined injection of SHU9119 and MCL0020 with spexin (P < 0.05).

Conclusion

These observations suggest that both opioid and melanocortin receptors play crucial role in spexin-induced hypophagia.

Peer Review reports

Background

The regulation of food intake in avian species is vital for their proper growth and development and involves a complicated physiological mechanism that relies on the integration of both internal and external signals processed by hypothalamic neural networks in the central nervous system (CNS). Therefore, the study on neurotransmitters, peptides and regulatory mechanisms controlling appetite in chickens has garnered significant attention from researchers over the past few decades [1, 2].

Spexin, also known as neuropeptide Q or NPQ, is a novel neuropeptide which consists of 14 amino acids and is encoded by the C12ORF39 gene [3, 4]. Spexin was initially discovered in the human genome using a bioinformatic approach that relied on a hidden Markov model screening [5]. The evolutionary relationship among bioactive peptides spexin, galanin, and kisspeptin was validated through gene structure analysis [6]. Expression of the spexin gene and protein has been found widely in various CNS areas (such as cerebral cortex, hypothalamus, and hippocampus) as well as in peripheral tissues in human, rat, mouse and goldfish [7,8,9,10]. Meng and colleagues have recently demonstrated that spexin exhibits extensive expression throughout various chicken tissues, particularly in the CNS [11]. The various biological processes carried out by spexin are mediated via its interaction with different subtypes of galanin receptor (GALR1, GALR2 and GALR3) which belong to the family of G protein-coupled receptors (GPCRs) [12, 13]. Spexin has been proven to be implicated in mood and behavioural disorders such as anxiety and depression [14, 15], pain management [16], cardiovascular disease and endothelial function [17], renal modulation [18], regulation of reproductive axis [19], endocrine regulation [20] and obesity and diabetes [21]. Furthermore, a variety of studies have indicated the significant impact of spexin in relation to food intake and appetite regulation. For instance, in the case of meat-type chickens, when spexin is injected intracerebroventricular (ICV), it leads to a reduction in food intake by acting through galanin receptor subtypes (GALR2 and GALR3) [22]. Likewise, feeding response was noticeably inhibited after peripheral injection with spexin in chicks (Gallus gallus) [23]. Moreover, anorectic effect of spexin was observed in mice following its peripheral injection [24]. In this regard, administration of spexin resulted in a decrease in food consumption and subsequently facilitated weight reduction in rodents (mice and rats) with diet-induced obesity [25]. Additionally, ICV injection of spexin in goldfish led to the suppression of both feeding activity and food consumption [10].

Opioid peptides act as inhibitory neurotransmitters and are extensively distributed throughout functional neural pathways in the CNS. These peptides interact with 3 distinct subtypes of receptors known as µ-opioid receptor (MOR), δ-opioid receptor (DOR), and κ-opioid receptor (KOR), which are linked to G protein-coupled receptors (GPCRs) [26]. The opioidergic system is considered a crucial component in the regulation of food intake in birds, and it is intricately connected to other systems that play a role in controlling appetite [27]. For example, ICV injection of DAMGO (selective µ-opioid receptor agonist) was found to reduce food intake while the use of DPDPE (selective δ-opioid receptor agonist) and U-50,488 H (selective κ-opioid receptor agonist) were observed to stimulate food consumption in neonatal layer-type and meat-type chicks [28, 29]. The melanocortin peptides such as adrenocorticotropic hormone (ACTH) and various types of melanocyte-stimulating hormones (α-MSH, β-MSH, γ-MSH and δ-MSH) are derived from the precursor molecule known as proopiomelanocortin (POMC) [30]. The primary locations within the CNS where POMC is expressed predominantly are the arcuate nucleus of the hypothalamus (ARC), the anterior pituitary, and the nucleus tractus solitarius (NTS) in the brainstem [31, 32]. The melanocortin system comprises five receptor subtypes (MC1R-MC5R), classified as GPCRs, and has been demonstrated to participate in various biological pathways [33]. Several pieces of evidence suggest that the central melanocortin system plays a crucial role in regulating food intake and energy expenditure in avian species and rodents especially via MC3R/MC4R. For example, there are reports indicating that the ICV infusion of α-MSH and β-MSH resulted in an anorexigenic response in neonatal chicks [34, 35]. Furthermore, the ability of melanotan-II (MTII), a nonselective MC3R/MC4R agonist, to reduce food intake in mice following ICV administration has been documented [36].

It seems evident that there exists a functional interplay among spexin, opioid, and melanocortin receptors, which implies a complex network of communication and regulation within physiological systems. In this regard, it has been shown that spexin-induced analgesia can be reversed by naloxone and nor-BNI in formalin model of nociception in mice. Moreover, spexin through GALR3 (but not GALR2) demonstrated an up-regulation of gene and protein expression of dynorphin and κ-opioid receptor [37]. In addition, the hypophagic effect of central administration of spexin in goldfish was triggered by up-regulation of anorexigenic neuropeptides such as POMC and cocaine- and amphetamine-regulated transcript (CART) [10]. Moreover, the suppressive impact of spexin on food consumption was observed alongside a rise in the levels of MC4R expression in the hypothalamus of mice [38].

Based on findings in the previous literature and considering that spexin, opioidergic and melanocortinergic pathways and their interaction have regulatory role in food intake and other physiological processes in animal models, the current research was conducted to explore the interaction of centrally administered spexin with opioidergic and melanocortinergic pathways on food intake regulation in neonatal broiler chicks.

Table 1 Ingredient and nutrient analysis of experimental diet
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Materials and methods

Animals

In the current investigation, 264 Ross-308 broiler one-day-old male chicks were included in the research sample. Experimental chicks were acquired from a local hatchery known as Morghak Company, located in Tehran, Iran. Firstly, the chickens were housed in flocks for a period of 2 days, following which they were randomly moved to separate cages and maintained based on the specified parameters of controlled temperature (30 ± 1 ºC), relative humidity (50 ± 2%) and 23:1 lighting/dark schedule. Throughout the research, birds were supplied with ad libitum access to fresh water and a commercial starter diet comprising 21% crude protein and 2850 kcal/kg metabolizeable energy (Chineh Company, Tehran, Iran, Table 1). 3 h before ICV injections were administered, the chickens underwent a period of food deprivation (FD3), although they were still permitted to have unrestricted access to water. The commencement of the experiments occurred once the chickens had reached the specific age of 5 days [1, 29]. Approval for all experimental procedures and animal handling in this study were granted by the Animal Ethics Committee of Razi University, with the approval number IR.RAZI.REC.1402.027. Additionally, the aforementioned protocols were executed in compliance with the Guidelines for the Care and Utilization of Laboratory Animals in Scientific Studies [39].

Experimental drugs

Spexin, β-funaltrexamine (β-FNA) (µ-opioid receptor antagonist), Naltrindole (NTI) (δ-opioid receptor antagonist), nor-binaltorphimine (nor-BNI) (κ-opioid receptor antagonist), SHU9119 (nonselective MC3/MC4 receptor antagonist), MCL0020 (selective MC4 receptor antagonist), and Evans Blue, along with all the other substances, were acquired from Sigma Co. (Sigma, Saint Louis, MO). In order to ready the drugs for administration, they were dissolved in a solution of 0.1% Evans Blue, which was itself formulated in a 0.85% saline solution at a proportion of 1/250. In the control group, a solution of saline mixed with Evans Blue dye was employed.

Intracerebroventricular (ICV) injection procedures

Before each treatment, the weight of the chicks was measured, and subsequently, they were classified into different experimental groups based on their body weight (BW). The allocation was performed to ensure that the average weight within the treatment groups was evenly distributed. The administration of ICV injections was conducted by employing a microsyringe (Hamilton, Switzerland) without anesthesia in accordance with the methods outlined in prior research [40, 41]. In this procedure, an acrylic apparatus was used to secure the chick’s head, with the bill holder set at a 45° angle and the calvarium aligned parallel to the table surface, following the previous guideline [42]. An orifice was created in a plate positioned directly above the right lateral ventricle of the skull. The microsyringe was inserted into the ventricle through this orifice, with the needle’s tip penetrating 4 mm beneath the surface of the skull and the test solution was administered [43]. Saline solution or a drug solution was injected into each chick in a volume of 10 µL [44]. Neonatal chicks do not experience any physiological stress from this injection technique [45]. At the end of the experiments, in order to assess the precision of the ICV injection, the chicks were humanely euthanized via an intraperitoneal administration of sodium thiopental overdose (50 mg/kg) (Rotexmedica, Germany; according to AVMA Guidelines for the Euthanasia of Animals ‘No: S5.2.1.1’, Acceptable Methods; non-inhaled agents) [46, 47]. Subsequently, the brains were excised. The confirmation of the direct injection into the lateral ventricle was fully validated by the detection of Evans Blue dye upon examination of the sliced brain tissue. It is crucial to note that data analysis only included information from individual chicks in cases where the lateral ventricle exhibited the presence of Evans Blue color. All experimental protocols were carried out between 8:00 am and 3:30 pm [1].

Table 2 Treatments procedure in experiments 1–6
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Feeding experiments

In this study, a total of 6 experiments were conducted on each of the 4 treatment groups. Each group comprised of at least 11 neonatal chicks, leading to a combined total of 44 chicks for every trial. The procedures outlining the treatments utilized in the experiments are detailed in Table 2. Experiment 1 was performed to evaluate the impact of ICV injection of spexin at doses of 5, 7.5 and 10 nmol on the food intake of FD3 chickens. In experiment 2, FD3 chicks ICV injected with saline, β-FNA (5 µg), spexin (10 nmol), and a combination of β-FNA and spexin. In experiment 3, ICV injections to FD3 chicks were saline, NTI (5 µg), spexin (10 nmol), and the co-administration of NTI and spexin. In experiment 4, ICV injections of the saline, nor-BNI (5 µg), spexin (10 nmol) and nor-BNI plus spexin were done in the chicks. In experiment 5, the chicks were given ICV the saline, SHU9119 (0.5 nmol), spexin (10 nmol) and a combination of SHU9119 and spexin. Lastly, in experiment 6, the chicks were ICV injected with saline, MCL0020 (0.5 nmol), spexin (10 nmol), and a combination of MCL0020 and spexin. After receiving the ICV injections, the chicks were promptly placed back into their individual cages. Fresh water and food were supplied, and the cumulative food intake (measured in grams) was recorded at 30, 60, and 120 min postinjection. The food intake was normalized by expressing it as percentage of body weight in order to reduce the impact of differences in weight among chicks on their food intake. Every chick was utilized only once within each experimental group. The doses of the substances administered via ICV injection were determined based on previous reports [22, 48, 49] and pilot studies that have not yet been published. It is noteworthy to mention that all doses that were used for experiments in this study had no behavioral changings such as sedation or hyperactivity by drugs in chicks.

Statistical analysis

Data were presented as mean ± SEM and subjected to analysis through a 2-way analysis of variance (ANOVA) with repeated measures. This analysis was conducted using the SPSS software version 21 for Windows (SPSS, Inc., Chicago, IL). For treatments that exhibited a notable primary impact in the ANOVA analysis, comparisons between their means were conducted utilizing the Tukey-Kramer test. The presence of significant differences between the various treatments tested in the experimental design was demonstrated using a significance level of less than 0.05 (P < 0.05).

Fig. 1
figure 1

Schematic image showing involvement of central opioid and melanocortin receptors in spexin-induced hypophagia in neonatal broiler chicks

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Fig. 2
figure 2

Chickens’ brains at the end of the experiments to assess the accuracy of the ICV injection

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Fig. 3
figure 3

Effect of ICV injection of control solution (normal saline + 0.1% Evans Blue) and different levels of the spexin (5, 7.5 and 10 nmol) on cumulative food intake (g/100 g BW) in neonatal broiler chicks (n = 11 per group). Data are expressed as mean ± SEM. Different letters (a-d) indicate significant differences between treatments at each time (P < 0.05). [Treatment effect: F(3,40) = 1723.13, P < 0.05; time effect: F(2,80) = 4281.06, P < 0.05; treatment × time interaction: F(6,80) = 38.53; P < 0.05]

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Fig. 4
figure 4

Effect of ICV injection of control solution (normal saline + 0.1% Evans Blue), β-FNA (β-Funaltrexamine; µ-opioid receptor antagonist, 5 µg), spexin (10 nmol) and a combination of β-FNA plus spexin on cumulative food intake (g/100 g BW) in neonatal broiler chicks (n = 11 per group). Data are expressed as mean ± SEM. Different letters (a, b and c) indicate significant differences between treatments at each time (P < 0.05). [Treatment effect: F(3,40) = 2521.36, P < 0.05; time effect: F(2,80) = 3481.58, P < 0.05; treatment × time interaction: F(6,80) = 29.81; P < 0.05]

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Fig. 5
figure 5

Effect of ICV injection of control solution (normal saline + 0.1% Evans Blue), NTI (Naltrindole; δ-opioid receptor antagonist, 5 µg), spexin (10 nmol) and a combination of NTI plus spexin on cumulative food intake (g/100 g BW) in neonatal broiler chicks (n = 11 per group). Data are expressed as mean ± SEM. Different letters (a, b and c) indicate significant differences between treatments at each time (P < 0.05). [Treatment effect: F(3,40) = 3281.52, P < 0.05; time effect: F(2,80) = 4128.16, P < 0.05; treatment × time interaction: F(6,80) = 28.37; P < 0.05]

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Fig. 6
figure 6

Effect of ICV injection of control solution (normal saline + 0.1% Evans Blue), nor-BNI (Norbinaltorphimine; κ-opioid receptor antagonist, 5 µg), spexin (10 nmol) and a combination of nor-BNI plus spexin on cumulative food intake (g/100 g BW) in neonatal broiler chicks (n = 11 per group). Data are expressed as mean ± SEM. Different letters (a, b and c) indicate significant differences between treatments at each time (P < 0.05). [Treatment effect: F(3,40) = 2894.27, P < 0.05; time effect: F(2,80) = 3841.73, P < 0.05; treatment × time interaction: F(6,80) = 26.48; P < 0.05]

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Fig. 7
figure 7

Effect of ICV injection of control solution (normal saline + 0.1% Evans Blue), SHU9119 (nonselective MC3/MC4 receptor antagonist, 0.5 nmol), spexin (10 nmol) and a combination of SHU9119 plus spexin on cumulative food intake (g/100 g BW) in neonatal broiler chicks (n = 11 per group). Data are expressed as mean ± SEM. Different letters (a, b and c) indicate significant differences between treatments at each time (P < 0.05). [Treatment effect: F(3,40) = 3641.92, P < 0.05; time effect: F(2,80) = 2951.45, P < 0.05; treatment × time interaction: F(6,80) = 28.63; P < 0.05]

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Fig. 8
figure 8

Effect of ICV injection of control solution (normal saline + 0.1% Evans Blue), MCL0020 (selective MC4 receptor antagonist, 0.5 nmol), spexin (10 nmol) and a combination of MCL0020 plus spexin on cumulative food intake (g/100 g BW) in neonatal broiler chicks (n = 11 per group). Data are expressed as mean ± SEM. Different letters (a, b and c) indicate significant differences between treatments at each time (P < 0.05). [Treatment effect: F(3,40) = 2847.59, P < 0.05; time effect: F(2,80) = 3475.38, P < 0.05; treatment × time interaction: F(6,80) = 24.73; P < 0.05]

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Results

Figure 1 shows a simplified schematic image of the participation of central opioid and melanocortin receptors in spexin-mediated hypophagia in neonatal broiler chicks. Figure 2 demonstrates the brains of the chicks upon the conclusion of the experimental procedures to evaluate the accuracy of the ICV administration. In experiment 1, a significant and dose dependent hypophagia was noted following the ICV injection of the different doses of the spexin (5, 7.5 and 10 nmol) in comparison to the control group over the entire 120-min observation period (P < 0.05) (Fig. 3). In experiment 2, ICV administration of β-FNA (5 µg) had no significant effect on food intake compared to the control group (P > 0.05) while food intake was markedly reduced by spexin (10 nmol) at 30, 60, and 120 min postinjection when compared to the control group (P < 0.05). Considerable hypophagic effect of spexin was significantly attenuated by coinjection of β-FNA + spexin (P < 0.05) (Fig. 4). In experiment 3, ICV injection of NTI (5 µg) did not result in any notable impact on food consumption compared to the control group (P > 0.05) while 10 nmol of the spexin caused a significant reduction in food intake at 30, 60, and 120 min postinjection compared to the control group (P < 0.05). However, coinjection of the NTI + spexin amplified spexin-induced hypophagia (P < 0.05) (Fig. 5). In experiment 4, ICV administration of nor-BNI (5 µg) had no significant effect on food intake compared to the control group (P > 0.05). Spexin (10 nmol) was associated with decreased food intake at 30, 60, and 120 min following injection in comparison to the control group (P < 0.05). Nevertheless, the concurrent administration of nor-BNI + spexin enhanced the hypophagic effect caused by spexin (P < 0.05) (Fig. 6). In experiment 5, ICV injection of SHU9119 (0.5 nmol) alone did not elicit any significant change in the food consumption compared to the control group (P > 0.05). The administration of spexin (10 nmol) effectively suppressed food intake up to 120 min compared to the control group (P < 0.05). Coinjection of the SHU9119 + spexin weakened hypophagia induced by spexin (P < 0.05) (Fig. 7). In experiment 6, injection of MCL0020 (0.5 nmol) via the ICV route did not result in any notable alteration in food intake when compared to the control group (P > 0.05). The inhibitory action of spexin (10 nmol) on food intake was observed after ICV injection up to 120 min when compared with control group (P < 0.05). The hypophagic effect of spexin was remarkably reversed by concurrent injection of MCL0020 + spexin (P < 0.05) (Fig. 8).

Discussion

Understanding the regulatory mechanisms of food intake, energy expenditure, and body weight in broiler birds is crucial for the development and improvement of management practices [50]. To the best of the authors’ knowledge, this research provides the first report on the participation of central opioid and melanocortin receptors in spexin-induced hypophagia following ICV injection in neonatal broiler chicks. The findings from the current study in Fig. 3 clearly illustrated that the ICV injection of the spexin caused a considerable decline in cumulative food intake in a dose-dependent fashion in FD3 neonatal broiler chicks, indicating that spexin might act as a potential anorexigenic factor in the brain of broiler chicks, which was in line with prior studies that have been carried out on chickens [22, 23], rodents [24, 25], goldfish [10], zebrafish [51] and Siberian sturgeon [52]. Regarding the suppressive impact of spexin on food intake, it is possible to identify the following mechanisms. The anorexigenic effect of spexin is primarily associated with the activation of GALR2, GALR2L, and GALR3 (members of the GPCR family) within the brain, leading to the subsequent initiation of intracellular MAPK/ERK signaling cascades. Then, spexin functions as a satiety agent by reducing the levels of agouti gene-related protein (AgRP) and melanin-concentrating hormone (MCH) expressions, while simultaneously increasing the mRNA levels of cocaine- and amphetamine-regulated transcript I (CART1) in the hypothalamus [11]. Moreover, through its interaction with GALRs, spexin has the potential to induce c-Fos expression in the anterior hypothalamic area (AHA) and suprachiasmatic nucleus (SCN) via phosphorylated calmodulin kinase 2 (p-CaMK2), leading to the down-regulation of hypothalamic NPY mRNA expression, thereby resulting in the anorectic impact [24]. It is also important to mention that spexin via ICV route has the ability to decrease food intake by diminishing food-seeking behaviors, decreasing feeding traits, and enhancing food rejection activity [10, 22].

As indicated in the present study, the concurrent injection of β-FNA (β-Funaltrexamine; µ-opioid receptor antagonist) and spexin markedly reduced the hypophagic effect of spexin whereas the inhibition of food intake by spexin was amplified by coinjection of spexin with NTI (Naltrindole; δ-opioid receptor antagonist) and nor-BNI (Norbinaltorphimine; κ-opioid receptor antagonist) (Figs. 4, 5 and 6). These findings indicate the presence of a possible correlation between spexin and the opioidergic system in regulating feeding behavior in neonatal broiler chicks. The significant role of different classes of opioid receptors relevant to control of food intake has been elucidated. For example, ICV injection of DAMGO (selective µ-opioid receptor agonist) decreased cumulative food intake while DPDPE (selective δ-opioid receptor agonist) and U-50,488 H (selective κ-opioid receptor agonist) induced hyperphagia in neonatal broiler chicks [28] and neonatal layer-type chicks [29, 53]. There are functional interactions between the opioidergic system with neurotransmitters and neuropeptides in order to control feeding behavior mechanisms. For instance, it has been documented that ICV injection of β-FNA completely blocked the hypophagic effect of DAMGO in neonatal broiler chicks [54]. The hypophagic effect of serotonin was reversed by the ICV injection of the β-FNA but not by NTI and nor-BNI in neonatal broilers [55]. Furthermore, the hypophagia caused by the ICV administration of oxytocin in neonatal layer-type chicks was entirely prevented by β-FNA, whereas nor-BNI potentiated anorexigenic effect of oxytocin [48]. On the other hand, a correlation was identified between spexin and opioidergic system where ICV injection of naloxone and nor-BNI reversed the analgesic response of spexin in the mouse formalin test [37]. The connection between the opioid receptors and various other elements has been confirmed; however, the specific relationship between spexin and the opioidergic system in terms of spexin’s role in reducing food intake has not been documented thus far.

Another finding uncovered during our investigation demonstrated that the coinjection of SHU9119 (MC3/MC4 receptor antagonist) and spexin resulted in the mitigation of spexin-induced hypophagia in neonatal broiler chicks (Fig. 7). Moreover, the anorexigenic impact of spexin was reduced when MCL0020 (MC4 receptor antagonist) was administered concurrently with spexin (Fig. 8). The melanocortinergic system is recognized as another regulatory pathway that plays a role in feeding behavior and body weight in poultry, mammalian, and rodents. Nevertheless, the MC3/MC4 receptor subtypes play a crucial role in the alterations caused by melanocortin signaling [56]. In this regard, prior research has indicated that ICV administration of both agonists (MTII) and antagonists (SHU9119 and HS014 at higher doses) targeting the MC3/MC4 receptor can lead to reduced and elevated food consumption in birds, respectively [57, 58]. Furthermore, suppressive impact on food intake has been observed after ICV infusion of MC3/MC4 receptor agonists in animal models, including rodents and nonhuman primates [59]. There is a possibility of neuroendocrine interrelationships between the central melanocortin system and the hormones involved in regulating food intake and energy utilization. For example, leptin functions as a peptide with anorexigenic properties, leading to a decrease in food intake at the level of the arcuate nucleus of the hypothalamus (ARC) through the activation of melanocortin receptors [60]. Neurons in the ARC that express POMC serve as crucial components of the melanocortin system. These neurons exhibit sensitivity to circulating molecules and integrate numerous excitatory and inhibitory signals originating from diverse brain regions. Subsequently, they regulate multiple facets of feeding behavior [61]. According to functional electrophysiological investigations, kisspeptin, another member of the spexin/galanin/kisspeptin family, has been documented to excite hypothalamic anorexigenic POMC neurons through direct means involving the augmentation of Na+/Ca2+ exchange and activation of nonselective cation channels [62]. Additionally, another functional link between anorexigenic neuropeptide spexin and POMC/CART neurons has been established in the brain of goldfish [10]. Likewise, the inhibitory effect of ICV injection of spexin on the food intake was noted to coincide with an increase in the levels of MC4R expression in the hypothalamus of mice [38]. Since there is a lack of available data on chicks, our ability to analyze our results in relation to previous research findings is limited.

Conclusion

In summary, these observations suggest that both opioid (via µ-, δ-, κ) and melanocortin (via MC3-, MC4) receptors play crucial role in spexin-induced hypophagia in neonatal broiler chicks. Nonetheless, it is crucial that these novel findings be utilized as the basis for upcoming research endeavors, as additional inquiries are required to elucidate the fundamental cellular and molecular signaling mechanisms that link spexin to the regulation of food intake in poultry through the opioidergic and melanocortinergic systems.

Data availability

No datasets were generated or analysed during the current study.

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Acknowledgements

This research was supported by a grant from the Research Council of the Faculty of Veterinary Medicine, Razi University, Kermanshah, Iran. The authors would like to thank the central laboratory of the Faculty of Veterinary Medicine, Tehran University, Tehran, Iran.

Funding

This research was supported by a grant from the Research Council of the Faculty of Veterinary Medicine, Razi University, Iran.

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Authors and Affiliations

  1. Section of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Razi University, Kermanshah, Iran

    Mohanna Badri & Samad Alimohammadi

  2. Section of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

    Morteza Zendehdel

  3. Section of Physiology, Department of Basic Sciences, Faculty of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran

    Shahin Hassanpour

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  1. Mohanna Badri
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Contributions

M.B. and S.H. operated the experimental procedure and animal handling. S.A. and M.Z. participated in acquisition and analysis of behavioral studies data, statistical analysis, project supervision and preparation of the manuscript. The final manuscript was read and approved by all authors.

Corresponding author

Correspondence to Samad Alimohammadi.

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Ethics approval and consent to participate

Animal experiments in this study were approved by the Animal Ethics Committee of Razi University and followed with the Guidelines for the Care and Use of Laboratory Animals in Research (Animal Ethical Approval Number: IR.RAZI.REC.1402.027). Informed consent was obtained from the Faculty of Veterinary Medicine, Razi University and Central Laboratory of the Faculty of Veterinary Medicine, Tehran University to use the chicks in this study.

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The authors declare no competing interests.

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Badri, M., Alimohammadi, S., Zendehdel, M. et al. Involvement of central opioid and melanocortin receptors in spexin-induced hypophagia following intracerebroventricular injection in neonatal broiler chicks. BMC Vet Res 21, 110 (2025). https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s12917-025-04564-8

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BMC Veterinary Research

ISSN: 1746-6148

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