Long-term potentiation of synaptic transmission in hyperstriatum of neonatal chicks : Mechanisms of "Imprinting"

(1)摄食行为的习惯化和强化学习行为学研究。新生的小鸡啄小而显眼的物体。这种行为是天生的，不需要后天的经历，然而，后天的经历会极大地改变啄食行为的偏好。本研究考察了中性刺激的习惯化和强化一次性学习。无论时间间隔是短（5min）还是长（1小时），对重复呈现的刺激对象，啄动作都表现出强烈的习惯化。当呈现大小、形状相同但颜色不同的物体时，没有观察到习惯反应，说明记忆内容主要是物体的颜色。而被厌恶味道强化的被动回避学习则是在一次啄苦味物体的经历后形成的，伴随的记忆内容不仅包括物体呈现的颜色，还包括物体呈现的形状和过程。因此，同样的物体可以在中枢神经系统中以不同的方式存储，这两种形式的记忆背后的神经机制应该被分析。(2)直接早期基因（c-fos）与LTP因果关系的神经学研究。高纹状体区（IMHV）的即时早期基因（c-fos）的表达已被证明与印迹范式中完成的学习强度显著相关（McCabe和Horn 1994）。另一方面，突触传递的长期增强（LTP）被认为是构成记忆形成的细胞基础（Matsushima和Aoki 1995）。本研究分析了c-fos表达与LTP之间的因果关系。足以诱导局部突触传递LTP的实验条件（5hzx300脉冲）未能增强c-fos的表达。相反，内源性c-fos表达高的切片，条件反射电刺激未能诱导LTP。此外，GABA-A受体拮抗剂（biuculline）锁定LTP，而c-fos表达有所增强。c-fos的表达和突触LTP都是依赖于之前的神经活动的可塑性过程，但其潜在的细胞机制被证明是不同的。相反，c-fos表达与LTP呈负相关。这些过程的分子级联仍有待揭示，特别是在孝道学习的敏感时期。少

(1) Behavioral studies on habituation and reinforced learning in the feeding behavior.Neonatal chicks peck at small and conspicuous objects. This action is innate and not requiring postnatal experiences, which however drastically change the preferences of the pecking action. In this study, habituation to neutral stimuli and reinforced one-trial learning were examined in this study.The pecking action showed a strong habituation for stimulus object that was repeatedly presented, irrespectively of where the interval was short (5min) or long (1 hour). The habituated response was not observed when an object of the same size, shape but of sifferenent color was presented, indicating that the memory content was mainly its color. The passive avoidance learning reinforced by aversive taste, on the other hand, was formed after a single experience of pecking a bitter object, and the accompanying memory content covered not only the color, but also its shape and procedure of the object presentation. … More The same object could thus be stored in different manners in the central nervous system, and the neural mechanisms underlying these two forms of memory should be analyzed.(2) Neurological studies on causal relationships between immediate early gene (c-fos) and LTP.Expression of immediate early gene (c-fos) in a hyperstriatal region (IMHV) has been shown to correlate significantly with the strength of learming accomplished in the imprinting paradigm (McCabe and Horn 1994). Long-term potentiation (LTP) of synaptic transmission, on the other hand, has been assumed to constitute the cellular basis of memory formation (Matsushima and Aoki 1995). In this study, the causal relationships between the c-fos expression and LTP has been analyzed.Experimental condition sufficient for inducing LTP in the local synaptic transmission (5Hzx300pulses) failed to enhance the c-fos expression. Conversely, those slices where endogenous expression of c-fos was high, the conditioning electrical stimulation failed to induce LTP.Furthermore, an antagonist of GABA-A receptors (biuculline) locked the LTP,while the c-fos expression was somewhat enhanced.Both of the c-fos expression and the synaptic LTP are plastic process which depend on the preceding neural activities, however, the underlying cellular mechanisms proved to be distinct. Rather, the c-fos expression tended to negatively correlated with the LTP.The molecular cascades for these processes remains to be unraveled, particularly in relation to the sensitive period of the filial learning. Less