CRF1/CRF2 and MC3/MC4 Receptors Affect Glutamate- Induced Food Intake in Neonatal Meat-Type Chicken

ABSTRACT Central glutamate, melanocortin and corticotropin systems have mediatory role on several physiologic functions in the brain, but their interactions on appetite regulation are not fully elicited. So, the aim of the current study was to determine interaction of the glutamate with melanocortin and corticotropin systems on food intake in 3-h food-deprived (FD3) neonatal meat-type chicken. In experiment 1, chicken intracerebroventricular (ICV) injected (A) phosphate-buffered saline (PBS), (B) glutamate (75 nmol), (C) glutamate (150 nmol) and (D) glutamate (300 nmol). In experiment 2, (A) PBS, (B) astressin-B (CRF1/CRF2 receptors antagonist, 30 µg), (C) glutamate (300 nmol) and (D) astressin-B+glutamate were ICV injected. Experiments 3-5 were similar to experiment 2, except birds were injected with astressin2-B (CRF2 receptor antagonist, 30 µg), SHU9119 (MC3/MC4 receptor antagonist, 0.5 nmol) and MCL0020 (MC4 receptor antagonist, 0.5 nmol) instead of the astressin-B. In experiment 6, the injections were (A) PBS, (B) MTII (MC3/MC4 receptor agonist, 2.5ng), (C) glutamate (75nmol) and (D) MTII+glutamate. Then, cumulative feed intake was recorded at 30, 60 and 120 minutes after injection. According to the results, dose dependent hypophagia observed by ICV injection of the glutamate (75, 150 and 300nmol) compared to control group in neonatal broiler chicken (p<0.05). Co-injection of the astressin-B+glutamate and astressin2-B+glutamate decreased glutamate-induced hypophagia in neonatal broiler chicken (p<0.05). Co-injection of the glutamate+MC3/MC4 receptors antagonist decreased hypophagic effect of the glutamate (p<0.05). These results suggested hypophagic effect of the glutamate mediates via CRF1/CRF2 and MC3/MC4 receptors in chickens.

摘要 中枢谷氨酸、黑皮质素（melanocortin）与促肾上腺皮质激素（corticotropin）系统在大脑多项生理功能中发挥介导作用，但其在食欲调控中的相互作用尚未完全阐明。为此，本研究旨在探究3小时禁食（FD3）的新生肉鸡体内，谷氨酸与黑皮质素、促肾上腺皮质激素系统在摄食调控中的相互作用。实验1中，对雏鸡进行脑室内（intracerebroventricular, ICV）注射：（A）磷酸盐缓冲液（phosphate-buffered saline, PBS）、（B）谷氨酸（75 nmol）、（C）谷氨酸（150 nmol）以及（D）谷氨酸（300 nmol）。实验2中，采用脑室内注射方式给予以下试剂：（A）PBS、（B）astressin-B（CRF1/CRF2受体拮抗剂，30 μg）、（C）谷氨酸（300 nmol）以及（D）astressin-B与谷氨酸联合注射。实验3至5与实验2操作基本一致，仅将astressin-B分别替换为astressin2-B（CRF2受体拮抗剂，30 μg）、SHU9119（MC3/MC4受体拮抗剂，0.5 nmol）及MCL0020（MC4受体拮抗剂，0.5 nmol）进行注射。实验6的注射分组为：（A）PBS、（B）MTII（MC3/MC4受体激动剂，2.5 ng）、（C）谷氨酸（75 nmol）以及（D）MTII与谷氨酸联合注射。随后，分别记录注射后30、60及120分钟的累积摄食量。结果显示，与对照组相比，脑室内注射75、150及300 nmol剂量的谷氨酸可使新生肉鸡产生剂量依赖性的摄食抑制（p<0.05）。联合注射astressin-B与谷氨酸、astressin2-B与谷氨酸，均可显著削弱谷氨酸诱导的摄食抑制效应（p<0.05）；联合注射谷氨酸与MC3/MC4受体拮抗剂，同样可降低谷氨酸的摄食抑制作用（p<0.05）。上述结果表明，谷氨酸的摄食抑制效应是通过鸡体内的CRF1/CRF2及MC3/MC4受体介导的。