CNS serotonin content mediating food deprivation-enhanced learning is regulated by hemolymph tryptophan concentration and autophagic flux in the pond snail
CNS serotonin content mediating food deprivation-enhanced learning is regulated by hemolymph tryptophan concentration and autophagic flux in the pond snail
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DOI：
10.1080/1028415x.2022.2033045
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发表时间：
2022-02
影响因子：
3.6
通讯作者：
Y. Totani;Junko Nakai;D. Hatakeyama;V. Dyakonova;K. Lukowiak;E. Ito
中科院分区：
文献类型：
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作者：
Y. Totani;Junko Nakai;D. Hatakeyama;V. Dyakonova;K. Lukowiak;E. Ito
摘要 营养状况影响多种生物体的认知功能。在池塘蜗牛 Lymnaea stagnalis 中，禁食 1 天可以通过降低中枢神经系统 (CNS) 中的血清素（5-羟色胺；5-HT）含量来增强味觉厌恶学习能力。另一方面，禁食5天后，学习能力和CNS 5-HT浓度恢复到基础水平。然而，食物匮乏如何导致中枢神经系统 5-HT 水平发生变化尚不清楚。在这里，我们测量了血淋巴和中枢神经系统中 5-HT 前体色氨酸的浓度，并证明禁食 5 天的蜗牛的中枢神经系统色氨酸浓度高于非禁食或禁食 1 天的蜗牛，而血淋巴色氨酸浓度不受禁食时间的影响。这一发现表明，中枢神经系统色氨酸浓度的介质的存在与食物剥夺无关。为了确定介质，我们研究了不同食物剥夺条件下中枢神经系统的自噬通量。我们发现，在 5 天禁食的蜗牛中枢神经系统中，通过抑制原肌球蛋白受体激酶 (Trk)-Akt-雷帕霉素复合物 1 (MTORC1) 机制，自噬通量显着上调。此外，当自噬受到抑制时，5天禁食的蜗牛中CNS 5-HT含量显着下调。我们的结果表明，中枢神经系统中的血淋巴色氨酸浓度和自噬通量协同调节受不同食物剥夺持续时间影响的学习能力。这种机制可能是根据营养程度选择适合动物生存的行为的基础。图解摘要
ABSTRACT Nutritional status affects cognitive function in many types of organisms. In the pond snail Lymnaea stagnalis, 1 day of food deprivation enhances taste aversion learning ability by decreasing the serotonin (5-hydroxytryptamin; 5-HT) content in the central nervous system (CNS). On the other hand, after 5 days of food deprivation, learning ability and the CNS 5-HT concentration return to basal levels. How food deprivation leads to alterations of 5-HT levels in the CNS, however, is unknown. Here, we measured the concentration of the 5-HT precursor tryptophan in the hemolymph and CNS, and demonstrated that the CNS tryptophan concentration was higher in 5-day food-deprived snails than in non-food-deprived or 1-day food-deprived snails, whereas the hemolymph tryptophan concentration was not affected by the duration of food deprivation. This finding suggests the existence of a mediator of the CNS tryptophan concentration independent of food deprivation. To identify the mediator, we investigated autophagic flux in the CNS under different food deprivation conditions. We found that autophagic flux was significantly upregulated by inhibition of the tropomyosin receptor kinase (Trk)-Akt-mechanistic target of rapamycin complex 1 (MTORC1) pathway in the CNS of 5-day food-deprived snails. Moreover, when autophagy was inhibited, the CNS 5-HT content was significantly downregulated in 5-day food-deprived snails. Our results suggest that the hemolymph tryptophan concentration and autophagic flux in the CNS cooperatively regulate learning ability affected by different durations of food deprivation. This mechanism may underlie the selection of behaviors appropriate for animal survival depending on the degree of nutrition. GRAPHICAL ABSTRACT