西亚试剂：Neurons for hunger and thirst transmit a negative-valence t

Homeostasis is a biological principle for regulation of essential physiological parameters within a set range. Behavioural responses due to deviation from homeostasis are critical for survival, but motivational processes engaged by physiological need states are incompletely understood. We examined motivational characteristics of two separate neuron populations that regulate energy and fluid homeostasis by using cell-type-specific activity manipulations in mice. We found that starvation-sensitive AGRP neurons exhibit properties consistent with a negative-valence teaching signal. Mice avoided activation of AGRP neurons, indicating that AGRP neuron activity has negative valence. AGRP neuron inhibition conditioned preference for flavours and places. Correspondingly, deep-brain calcium imaging revealed that AGRP neuron activity rapidly reduced in response to food-related cues. Complementary experiments activating thirst-promoting neurons also conditioned avoidance. Therefore, these need-sensing neurons condition preference for environmental cues associated with nutrient or water ingestion, which is learned through reduction of negative-valence signals during restoration of homeostasis.

动物通过设计用来重新平衡它们状态的特定行为来对生理平衡的变化做出反应。我们对为追求平衡所做出的这些调整背后的动机还不是很了解。在这篇论文中，Scott Sternson及同事对由身体自平衡神经元介导的饥渴的动机过程进行了研究。他们发现，除了促进寻找食物或水的行为外，对饥饿敏感的AGRP神经元和促进渴感的神经元还会传递被主动避开的“负价教育信号”(negative valence teaching signal)。这样所产生的净效应也许是，使动物对与食物摄取相关的提示有一个偏好，从而当动物通过食物和水的摄取达到生理平衡时抵消负价信号。

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