These Brain Cells could Influence How Fast You Eat - and When You Stop
Brain cells that control how quickly mice eat, and when they stop, have been identified. The findings, published in Nature, could lead to a better understanding of human appetite, the researchers say. Nerves in the gut, called vagal nerves, had already been shown to sense how much mice have eaten and what nutrients they have consumed. The vagal nerves use electrical signals to pass this information to a small region in the brainstem that is thought to influence when mice, and humans, stop eating. This region, called the caudal nucleus of the solitary tract (cNTS), contains prolactin-releasing hormone neurons (PRLH) and GCG neurons. But, until now, studies have involved filling the guts of anaesthetized mice with liquid food, making it unclear how these neurons regulate appetite when mice are awake. To answer this question, physiologist Zachary Knight at the University of California, San Francisco, and his colleagues implanted a light sensor in the brains of mice that had been genetically modified so that the PRLH neurons released a fluorescent signal when activated by electrical signals transmitted along neurons from elsewhere in the body. Knight and his team infused a liquid food called Ensure — which contains a mixture of fat, protein, sugar, vitamins and minerals — into the guts of these mice. Over a ten-minute period, the neurons became increasingly activated as more of the food was infused. This activity peaked a few minutes after the infusion ended. By contrast, the PRLH neurons did not activate when the team infused saline solution into the mice’s guts.
控制小鼠進食速度和停止時間的腦細胞已經被發現。 研究人員表示，這項發表在《自然》雜誌上的研究結果可能有助於更了解人類的食慾。 腸道中的神經（稱為迷走神經）已經被證明可以感知小鼠吃了多少食物以及它們吸收了哪些營養物質。 迷走神經利用電訊號將訊息傳遞到腦幹中的一個小區域，該區域被認為會影響小鼠和人類停止進食的時間。 此區域稱為孤束尾核 (cNTS)，包含催乳素釋放激素神經元 (PRLH) 和 GCG 神經元。目前研究多使用麻醉小鼠和液體食物填充的腸道，這將使得人們不清楚這些神經元在老鼠清醒時如何調節食慾。 為了回答這個問題，加州大學舊金山分校的生理學家Zachary Knight 和他的同事在老鼠的大腦中植入了一個經過基因改造的光感測器，當受到來自身體其他部位的神經元傳輸的電信號，PRLH 神經元被激活時會釋放出螢光訊號。Knight和他的團隊將一種名為 Ensure，含脂肪、蛋白質、糖、維生素和礦物質的混合物，液體食物注入這些小鼠的腸道中。 在十分鐘的時間裡，隨著更多的食物被注入，神經元變得越來越活躍。 這種活動在輸注結束後幾分鐘達到高峰。 相較之下，當研究小組將鹽水溶液注入小鼠腸道時，PRLH 神經元並沒有活化。