Central administration of ghrelin induces conditioned avoidance in rodents.
Central administration of ghrelin induces conditioned avoidance in rodents.
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DOI：
10.1016/j.euroneuro.2017.05.001
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发表时间：
2017-08
期刊：
影响因子：
--
通讯作者：
Dickson SL
中科院分区：
文献类型：
--
作者：
Schéle E;Cook C;Le May M;Bake T;Luckman SM;Dickson SL
饥饿感携带一种负价（情绪）信号，该信号似乎是通过下丘脑弓状核中的刺相关肽（AgRP）神经元传递的。循环中的饥饿激素，胃饥饿素，激活了这些神经元，尽管尚不清楚它是否也携带负价信号。鉴于胃饥饿素也激活了中脑中对奖励很重要的通路，它仍然有可能作为一种正强化物，因此携带了正效价信号。本研究采用条件偏好/回避试验探讨脑室内（ICV）注射胃饥饿素（2µg/注射1次，每天1次，连续4天）的增强/厌恶特性。我们发现ICV胃饥饿素在条件位置偏好/回避测试（CPP/CPA，动物避开先前与胃饥饿素注射配对的房间）和条件风味偏好/回避测试（CFP/CFA，动物消耗/避免先前与胃饥饿素注射配对的味道）中产生条件回避。当饥饿素在没有或有食物的情况下发生调节时，可以观察到饥饿素诱导CPA的这些作用。然而，我们没有发现证据表明脑生长素给大鼠会引起不适（在异食癖试验中）。我们的数据表明，ICV ghrelin携带负价信号，与其作为循环饥饿激素的作用和激活AgRP神经元的作用一致。
Feelings of hunger carry a negative-valence (emotion) signal that appears to be conveyed through agouti-related peptide (AgRP) neurons in the hypothalamic arcuate nucleus. The circulating hunger hormone, ghrelin, activates these neurons although it remains unclear whether it also carries a negative-valence signal. Given that ghrelin also activates pathways in the midbrain that are important for reward, it remains possible that ghrelin could act as a positive reinforcer and hence, carry a positive-valence signal. Here we used condition preference/avoidance tests to explore the reinforcing/aversive properties of ghrelin, delivered by intracerebroventricular (ICV) injection (2 µg/injection once a day for 4 days). We found that ICV ghrelin produces conditioned avoidance, both in a conditioned place preference/avoidance test (CPP/CPA, in which the animals avoid a chamber previously paired to ghrelin injection) and in a conditioned flavor preference/avoidance test (CFP/CFA, in which the animals consume/avoid a taste previously paired to ghrelin injection). These effects of ghrelin to induce a CPA were observed when conditioning to ghrelin occurred in the absence or presence of food. We did not find evidence, however, that brain ghrelin delivery to rats induces malaise (in the pica test). Our data indicate that ICV ghrelin carries a negative-valence signal consistent with its role as a circulating hunger hormone and with its effects to activate AgRP neurones.
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