Data from: Peripherally injected ghrelin and leptin reduce food hoarding and mass gain in the coal tit (Periparus ater)

In birds little is known about the hormonal signals that communicate nutritional state to the brain and regulate appetitive behaviours. In mammals, the peptide hormones ghrelin and leptin elevate and inhibit consumption and food hoarding, respectively. In birds, administration of both ghrelin and leptin inhibit food consumption. The role of these hormones in the regulation of food hoarding in avian species has not been examined. To investigate this, we injected wild caught coal tits (Periparus ater) with leptin, high-dose ghrelin, low-dose ghrelin and a saline control in the laboratory. We then measured food hoarding and mass gain, as a proxy of food consumption, every 20 mins for two hours post-injection. Both high-dose ghrelin and leptin injections significantly reduced hoarding and mass gain compared with controls. Our results provide the first evidence that hoarding behaviour can be reduced by both leptin and ghrelin in a wild bird. These findings add to evidence that the hormonal control of food consumption and hoarding in avian species differs from that in mammals. Food hoarding and consumptive behaviours consistently show the same response to peripheral signals of nutritional state, suggesting that the hormonal regulation of food hoarding has evolved from the consumption regulatory system.目前学界对鸟类中将营养状态信号传递至大脑并调控食欲相关行为的激素信号知之甚少。在哺乳动物中，肽类激素胃饥饿素（ghrelin）与瘦素（leptin）分别促进与抑制摄食及食物贮藏行为。而在鸟类中，同时施用胃饥饿素与瘦素均会抑制动物的摄食行为。目前尚未有研究探讨这两类激素在鸟类食物贮藏行为调控中发挥的作用。为探究这一问题，本研究在实验室环境下对野生捕获的煤山雀（Periparus ater）分别注射瘦素、高剂量胃饥饿素、低剂量胃饥饿素与生理盐水对照剂。随后于注射后两小时内，每20分钟记录一次动物的食物贮藏量与体重增重，以此作为摄食水平的替代指标。与对照组相比，高剂量胃饥饿素与瘦素注射均显著降低了煤山雀的食物贮藏量与体重增重水平。本研究结果首次证实，在野生鸟类中，瘦素与胃饥饿素均可抑制其食物贮藏行为。上述发现进一步佐证了鸟类与哺乳动物在摄食及食物贮藏行为的激素调控机制上存在差异这一结论。食物贮藏与摄食行为对外周营养状态信号的响应模式始终一致，这表明食物贮藏行为的激素调控系统是由摄食调控系统演化而来。