This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Which of the following inhibits appetite by counteracting the effects of neuropeptide Y? \nSelect and explain. \nA. Orexins, B. Neuropeptide Y, C. Ghrelin, D. Leptin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Leptin acts on receptors in the hypothalamus of the brain where it inhibits appetite by (1) counteracting the effects of neuropeptide Y (a potent feeding stimulant secreted by cells in the gut and in the hypothalamus); (2) counteracting the effects of anandamide (another potent feeding stimulant that binds to the same receptors as THC), and (3) promoting the synthesis of a-MSH, an appetite suppressant. Ghrelin is a hormone produced mainly by P/D1 cells lining the fundus of the human stomach and epsilon cells of the pancreas that stimulates hunger. Neuropeptide Y is a natural substance that acts on the brain to stimulate eating.Leptin reduces the output of NPY from the hypothalamus, a major production center. Orexins (hypocretins) are neuropeptides primarily localized in the hypothalamus and are implicated in the regulation of a variety of activities, including feeding behavior and energy balance.', 'role': 'assistant'}]