Neuron: 长时记忆形成的过程研究取得新进展
生物谷报道：Baylor医学院的研究人员发表在2006年12月的《神经学杂志》上的文章指出：对果蝇进行特殊的训练其中也包括休息时期后，发现钙离子流向覃型神经元细胞促使了长时记忆的形成。
“我们有证据表明长时记忆的形成确实是分子方面的改变”。Baylor医学院的分子和细胞生物学教授Ronald Davis博士说“这看起来长时记忆的形成中记忆痕迹是存在的。
Davis和他的同事们用间隔试验方法使果蝇能够把某种气味与轻微的电击联系起来。这种方法给果蝇一种训练，然后休息再进行另一种训练。这种休息是诱导产生数天以上的长时记忆的关键步骤。在这项研究中，五次间隔的试验能够产生持续超过一天的记忆。他们接着用一种称为成像功能的技术来看果蝇大脑何时形成记忆。
“在训练前，我们能看到当果蝇处在某种气味下覃型神经元就有钙离子流入”，Davis说。当他们在间隔训练后把果蝇暴露在某种气味下24小时，他们就会看到有大量的钙离子流向覃神经元细胞，钙离子的增加与果蝇长时记忆的形成是相平行的。使用特殊的实验室技术，他和实验室其他同事表示他们能够通过阻断蛋白质的功能而阻断钙离子的流向，这种蛋白质是形成新的神经突触进而产生长期记忆的关键。
Figure 1. The α/β Mushroom Body Neurons Respond with Calcium Influx into Their α and β Axon Branches when Odors or Electric Shock Stimuli Are Delivered to Drosophila
(A) Cartoon illustrating the Drosophila α/β Mushroom Body (MB) neurons in isolation along with their processes and the locations from which functional images were obtained. The cell bodies of the MB neurons are clustered in the posterior and dorsal part of the brain. Each α/β MB neuron extends a single axon in a common nerve that extends toward the anterior face of the brain, where each axon splits into a vertically oriented branch (α branch) and a horizontally oriented branch (β branch). The branches of the α/β MB neurons remain clustered in brain neuropil regions known as the α lobe and the β lobe, which contain the α branches and the β branches of the neurons, respectively. For functional imaging, a small portion of cuticle was removed from the dorsal head and the fly was stably mounted under a confocal microscope. Functional images from living flies were collected from a dorsal and slightly frontal perspective of the fly at two depths: one to visualize calcium influx into the α branches of the α/β neurons, and one to visualize calcium influx into the β branches. The pinhole of the confocal was open during imaging so that fluorescence was collected from a thick optical section encompassing the structures of interest.
(B) Representative time course for the fluorescence response to the odor 3-octanol (Oct) in the α and β branches of MB neurons. The response was calculated as the percent increase in fluorescence over baseline (%ΔF/Fo) as a function of time. For subsequent bar graphs, the %ΔF/Fo was calculated as the percent difference between the maximum average intensity over five successive imaging frames during the 3 s odor application and the average intensity over five successive frames just prior to odor application.
(C) Images of the basal fluorescence of Uas-G-CaMP expressed with c739-Gal
(D) The amplitude of the response to odor from group data for both the α and β branches (n = 6 to 8) is shown. The ratio ΔF/Fo was typically close to 4% and proved to be statistically significant (t test) compared with zero for both odors. Error bars are the standard error of the mean.
(E) Images of the basal fluorescence of Uas-G-CaMP expressed with c739-Gal
(F) Calcium influx into the α and β branches of the axons of α/β MB neurons that occurs with 90V, 1.25 s electric shock pulses every 5 s. The traces represent the average %ΔF/Fo across the region of interest in both α and β branches. An obvious calcium response was observed, with each shock pulse riding on top of a decaying background due to bleaching over a 60 s scanning period.
原文出处：
December 7, 2006: 52 (5) 845－856
Drosophila α/β Mushroom Body Neurons Form a Branch-Specific, Long-Term Cellular Memory Trace after Spaced Olfactory Conditioning
Dinghui Yu, David-Benjamin G. Akalal, and Ronald L. Davis
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