Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1.
J Exp Biol. 2012 Oct 15;215(Pt 20):3566-76. doi: 10.1242/jeb.070300.
Dietary consumption of flavonoids (plant phytochemicals) may improve memory and neuro-cognitive performance, though the mechanism is poorly understood. Previous work has assessed cognitive effects in vertebrates; here we assess the suitability of Lymnaea stagnalis as an invertebrate model to elucidate the effects of flavonoids on cognition. (-)Epicatechin (epi) is a flavonoid present in cocoa, green tea and red wine. We studied its effects on basic snail behaviours (aerial respiration and locomotion), long-term memory (LTM) formation and memory extinction of operantly conditioned aerial respiratory behaviour. We found no significant effect of epi exposure (15 mg l(-1)) on either locomotion or aerial respiration. However, when snails were operantly conditioned in epi for a single 0.5 h training session, which typically results in memory lasting ~3 h, they formed LTM lasting at least 24 h. Snails exposed to epi also showed significantly increased resistance to extinction, consistent with the hypothesis that epi induces a more persistent LTM. Thus training in epi facilitates LTM formation and results in a more persistent and stronger memory. Previous work has indicated that memory-enhancing stressors (predator kairomones and KCl) act via sensory input from the osphradium and are dependent on a serotonergic (5-HT) signalling pathway. Here we found that the effects of epi on LTM were independent of osphradial input and 5-HT, demonstrating that an alternative mechanism of memory enhancement exists in L. stagnalis. Our data are consistent with the notion that dietary sources of epi can improve cognitive abilities, and that L. stagnalis is a suitable model with which to elucidate neuronal mechanisms.
黄酮类化合物（植物化学物质）的饮食摄入可能会改善记忆和神经认知表现，尽管其机制尚不清楚。以前的工作已经评估了脊椎动物的认知影响；在这里，我们评估了静水蜗牛作为阐明黄酮类化合物对认知影响的无脊椎动物模型的适用性。(-)表儿茶素（epi）是可可、绿茶和红酒中存在的一种类黄酮。我们研究了它对基本蜗牛行为（空气呼吸和运动）、长期记忆（LTM）形成和操作性条件反射空气呼吸行为的记忆消退的影响。我们发现 epi 暴露（15mg l(-1)）对运动或空气呼吸没有显著影响。然而，当蜗牛在 epi 中进行单次 0.5 小时的训练时，通常会形成持续约 3 小时的记忆，它们形成了至少持续 24 小时的 LTM。暴露在 epi 中的蜗牛也表现出明显增强的抗消退能力，这与 epi 诱导更持久的 LTM 的假设一致。因此，在 epi 中进行训练有助于形成 LTM，并导致更持久和更强的记忆。以前的工作表明，增强记忆的应激源（捕食者信息素和 KCl）通过来自 osphradium 的感觉输入起作用，并且依赖于 5-羟色胺（5-HT）信号通路。在这里，我们发现 epi 对 LTM 的影响与 osphradial 输入和 5-HT 无关，这表明在 L. stagnalis 中存在另一种增强记忆的机制。我们的数据与以下观点一致，即 epi 的饮食来源可以改善认知能力，并且 L. stagnalis 是阐明神经元机制的合适模型。
