据日本《朝日新闻》8月15日报道，日本北海道大学的科学家研究发现，咖啡和茶含有的咖啡因可以刺激人脑中的记忆细胞发生变化，从而于增强人类的记忆力。研究成果已经在美国《国家科学院院刊》网站发表。
人为什么能记忆？科学家们对这个问题的争论从未停止。一般的看法是，神经细胞产生变化，使得外界信号能够在神经系统中发生传递，人才能产生记忆。神经细胞的变化速度和细胞的钙浓度有关，而调节细胞钙浓度的是一种特殊的蛋白质——肌质网如兰尼碱受体。
日本北海道大学的神经生物学研究实验室经过对老鼠反复试验发现，饮用含有咖啡因的茶或者咖啡后，肌质网如兰尼碱受体受到刺激，神经细胞的钙浓度就会上升，从而使得外界信号更容易在神经细胞中得到传递，老鼠因此变得越来越”聪明”。
研究小组的组长、北海道大学教授神谷温之称，这种新的刺激反应和以往人们认为的刺激系统完全不同。据悉，新发现将应用到医学领域，开发治疗、改善痴呆症和记忆障碍症的药物。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS Published online before print August 7, 2008, doi: 10.1073/pnas.0802175105
Use-dependent amplification of presynaptic Ca2+ signaling by axonal ryanodine receptors at the hippocampal mossy fiber synapse
Hidemi Shimizu*, Masahiro Fukaya*, Miwako Yamasaki*, Masahiko Watanabe*, Toshiya Manabe?,?,§, and Haruyuki Kamiya§,?,‖
Abstract
Presynaptic Ca2+ stores have been suggested to regulate Ca2+ dynamics within the nerve terminals at certain types of the synapse. However, little is known about their mode of activation, molecular identity, and detailed subcellular localization. Here, we show that the ryanodine-sensitive stores exist in axons and amplify presynaptic Ca2+ accumulation at the hippocampal mossy fiber synapses, which display robust presynaptic forms of plasticity. Caffeine, a potent drug inducing Ca2+ release from ryanodine-sensitive stores, causes elevation of presynaptic Ca2+ levels and enhancement of transmitter release from the mossy fiber terminals. The blockers of ryanodine receptors, TMB-8 or ryanodine, reduce presynaptic Ca2+ transients elicited by repetitive stimuli of mossy fibers but do not affect those evoked by single shocks, suggesting that ryanodine receptors amplify presynaptic Ca2+ dynamics in an activity dependent manner. Furthermore, we generated the specific antibody against the type 2 ryanodine receptor (RyR2; originally referred to as the cardiac type) and examined the cellular and subcellular localization using immunohistochemistry. RyR2 is highly expressed in the stratum lucidum of the CA3 region and mostly colocalizes with axonal marker NF160 but not with terminal marker VGLUT1. Immunoelectron microscopy revealed that RyR2 is distributed around smooth ER within the mossy fibers but is almost excluded from their terminal portions. These results suggest that axonal localization of RyR2 at sites distant from the active zones enables use dependent Ca2+ release from intracellular stores within the mossy fibers and thereby facilitates robust presynaptic forms of plasticity at the mossy fiber-CA3 synapse.
