Nature:为什么冷饮特别解渴?
Nature自然科研 · 2016/08/08
本周发表于《自然》杂志的研表明,口渴的反应可能是穹窿下器(室周器之一)通过整合多种不同信息而预判的。这一发现有助于解释口渴反应的形成机制,为什么吃得太快会让我们感觉口渴,以及冷饮为何特别解渴。


以前,口渴一向被视为对血容量或血液浓度变化的稳定反应。血液成分失衡会被大脑室周器的特殊神经元感受到,由它们产生口渴的感觉,从而驱使动物饮水以维持体液平衡。

然而,大多数饮水行为的调节速度太快,喝水之后很快就解渴了,但水分真正补充到体液还需要十分钟左右。这表示口渴感觉不可能是完全由血液成分控制的,而是通过某种机制,在体液不平衡发生之前就预测到会缺水然后进行调节。具体怎么预测到的尚不清楚。

本周发表于《自然》杂志的研究 Thirst neurons anticipate the homeostatic consequences of eating and drinking 表示,口渴的反应可能是穹窿下器(室周器之一)通过整合多种不同信息而预判的。这一发现有助于解释口渴反应的形成机制,为什么吃得太快会让我们感觉口渴,以及冷饮为何特别解渴。

加州大学旧金山分校的Zachary Knight及同事在小鼠的脑内穹窿下器中,发现了一套预测口渴并且提前调节体液不平衡的神经元群。他们报告了脑内穹窿下器在口渴的预期调控中发挥作用,这一作用超出了人们先前的预期,或许能说明这一问题的答案。

他们显示,在监控血液的同时,穹窿下器中的神经元也会在进食和饮水时,通过来自口腔、包含食物与饮水摄取及温度信息的信号发生调整。这一反馈与血液成分信息结合,使得实时“预测”正在进行的食物和饮水摄取将会如何影响体液平衡成为可能,并带来了饮水行为的调节。之前被认为是被动感受血液的室周器,其实是接受到另一类神经信号之后启动调节行为的。

研究者发现,即使没有喝水,单纯降低舌头的温度都可以抑制口渴的感觉,而当进食时,又会增强口渴的感觉。

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  • Thirst neurons anticipate the homeostatic consequences of eating and drinking

    Thirst motivates animals to drink in order to maintain fluid balance. Thirst has conventionally been viewed as a homeostatic response to changes in blood volume or tonicity1, 2, 3. However, most drinking behaviour is regulated too rapidly to be controlled by blood composition directly, and instead seems to anticipate homeostatic imbalances before they arise4, 5, 6, 7, 8, 9, 10, 11. How this is achieved remains unknown. Here we reveal an unexpected role for the subfornical organ (SFO) in the anticipatory regulation of thirst in mice. By monitoring deep-brain calcium dynamics, we show that thirst-promoting SFO neurons respond to inputs from the oral cavity during eating and drinking and then integrate these inputs with information about the composition of the blood. This integration allows SFO neurons to predict how ongoing food and water consumption will alter fluid balance in the future and then to adjust behaviour pre-emptively. Complementary optogenetic manipulations show that this anticipatory modulation is necessary for drinking in several contexts. These findings provide a neural mechanism to explain longstanding behavioural observations, including the prevalence of drinking during meals10, 11, the rapid satiation of thirst7, 8, 9, and the fact that oral cooling is thirst-quenching12, 13, 14.

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