RESUMO
Growth hormone-releasing hormone (GHRH) is well known as a stimulator of growth hormone (GH) secretion. GHRH not only stimulates GH release but also modifies feeding behavior and energy homeostasis in rodents. In chickens (Gallus gallus domesticus), on the other hand, two types of GHRH, namely, chicken GHRH (cGHRH) and cGHRH-like peptide (cGHRH-LP), have been identified. The purpose of the present study was to investigate the effect of central injection of cGHRH and cGHRH-LP on feeding behavior in chicks. Intracerebroventricular (ICV) injection of both cGHRH and cGHRH-LP (0.04 to 1 nmol) significantly decreased food intake without any abnormal behavior in chicks. Furthermore, the feeding-inhibitory effect was not abolished by co-injection of the antagonist for pituitary adenylate cyclase-activating polypeptide (PACAP) or corticotropin-releasing hormone (CRH) receptors, suggesting that the anorexigenic effect of cGHRH and cGHRH-LP might not be related to the PACAP and CRH systems in the brain of chicks. Finally, 24-h food deprivation increased mRNA expression of cGHRH but not cGHRH-LP in the diencephalon. These results suggest that central cGHRH is related to inhibiting feeding behavior and energy homeostasis in chicks.
Assuntos
Proteínas Aviárias/metabolismo , Encéfalo/fisiologia , Galinhas/fisiologia , Ingestão de Alimentos/fisiologia , Hormônio Liberador de Hormônio do Crescimento/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Corticosterona/sangue , Hormônio Liberador da Corticotropina/metabolismo , Ingestão de Alimentos/efeitos dos fármacos , Privação de Alimentos/fisiologia , Hormônio Liberador de Hormônio do Crescimento/administração & dosagem , Hormônios/farmacologia , Injeções Intraventriculares , Masculino , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Polipeptídeo Hipofisário Ativador de Adenilato Ciclase/metabolismo , RNA Mensageiro/metabolismo , Receptores de Hormônio Liberador da Corticotropina/antagonistas & inibidores , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Receptores de Polipeptídeo Hipofisário Ativador de Adenilato Ciclase/antagonistas & inibidores , Receptores de Polipeptídeo Hipofisário Ativador de Adenilato Ciclase/metabolismoRESUMO
Corticotrophin-releasing hormone (CRH) plays an important role in response to stress, and exerts a physiological effect via its receptor, CRH receptor type-1 (CRH-R1) and CRH receptor type-2 (CRH-R2) with high affinity to CRH-R1 in mammals. Urocortin-3 (UCN-3), a CRH family peptide, is an endogenous ligand for CRH-R2 in mammals. The physiological roles of UCN-3 and CRH-R2 have been investigated in mammals, although their roles still need to be clarified in chicks (Gallus gallus). Few studies have been performed comparing the physiological responses of CRH and UCN-3 in chicks. Therefore the present study was conducted to investigate the effect of intracerebroventricular (ICV) injection of UCN-3 on food intake, rectal temperature, crop-emptying rate and behaviors in chicks, and to compare these physiological responses with the effects resulting from CRH injection. The ICV injection of 20 and 80 pmol UCN-3 decreased food intake, increased rectal temperature and decreased crop-emptying rate and the results were similar to those achieved with CRH. The injection of both UCN-3 and CRH increased spontaneous activity but the behavioral patterns were different: CRH increased the number of vocalizations while UCN-3 increased the number of jumps, wing-flaps and scratching behaviors. These results suggest that UCN-3 regulates food intake, body temperature, and gastric emptying via the CRH-R2 in the brain of chicks, and these effects were similar to those induced by CRH.