The studies on the brain mechanisms relating to the spatial learning disorder in aged and dmentia model rats.

本研究采用Morris水迷宫技术，在开始Morris水迷宫空间学习任务前，用渗透泵皮下注射东莨菪碱（2.5μl/hr）28天，观察东莨菪碱对大鼠和老年大鼠空间学习能力的影响。另将30只大鼠分为12月龄（12 A）、18月龄（18 A）和24月龄（24 A）三组，训练大鼠学习隐藏逃生平台的位置（位置学习）每天进行四次试验，试验间隔约为10分钟，总共进行4天。在每次试验中，大鼠游泳90秒或直到它们找到平台。第五天是探针测试，其中平台缩回，并且大鼠游泳60秒。随后在4次试验的单个阶段中测试线索学习，其中大鼠游泳到突出于池表面的可见的逃生平台，每次试验持续90秒。在sc ...更多信息 注射了阿朴胺的大鼠，仅在位置学习的早期，对隐藏平台的逃避潜伏期显著增加。结果提示，慢性注射东莨菪碱可诱导齿状回颗粒细胞吻侧部的神经发生，并使海马苔藓纤维终末体积增加，以补充胆碱能神经元的耗竭。24 A组大鼠的逃避潜伏期与平均游泳时间呈显著负相关，在位置学习中，逃避潜伏期显著延长，而在线索学习中，逃避潜伏期无显著变化。在12 A和18 A组中，观察到这些结果，但与24 A组中的结果不显著。在本研究中，所有年龄组在位置学习任务中停留在逃离平台所在象限03的时间百分比显著减少，这些结果表明，空间学习缺陷开始于1.2月龄左右，并在以后阶段逐渐恶化。12 A组和18 A组的这些缺陷可能与24 A组或更高年龄组中观察到的内鼻-海马网络的形态学和功能退化的类似背景机制有关。少

The present studies examined the acquisition of spatial learning using Morris water maze in the chronically scoporamine injected rats and aged rats.Scoporamine was injected subcutaneously by means of osmotic pump(2.5μl/hr)for 28 days before starting the task of spatial learning of the Morris water maze. And also 30 rats were reared and divided into three group, that is, 12 month(12A) 18 month(18A), and 24 month(24A) old group.All rats were trained to learn the position of a hidden escape platform(place learning)for four trials per day, with an intertrial interval of approxiamately 10 minutes, for a total of 4 days.On each trial, rats swam for 90 seconds or until they found the platform.The fifth day was a probe test in which the platform was retracted, and rats swam for 60 seconds.Then cue learning was tested subsequently in a single session of 4 trials in which rats swam to the visible escape platform that protruded above the surface of the pool, for 90 seconds on each trial.In the sc … More oporamine injected rats, the escape latency to the hidden platform significantly increased only in the early stage of the place learning. Additionally, the volume of the hippocampal mossy fiber terminals at the rostral portion increased exclusively in these learning impaired rats.These results suggested that the chronic injection of scoporamine might induce the neurogenesis of the rostral part of the dentate granule cells and also augment the volume of the mossy fiber terminals to supplement the cholinergic depletion.In the 24A group, the escape latency to the platform was significantly prolonged in the place learning but not in the cue learning.And a significant negative correlation between the escape latency and the mean swimming time was observed in the 24A group. In the 12A and 18A group, these results were observed, but not significant, as those in the 24A group. Also in the preaent study, percent time staying in quadrant 03 in which the escape platform was located during the place learning task was significant decreased in all aging group.These results suggest that the spatial learning deficits begin to appear around 1.2 months old and gradually go from bad to worse in later stages, and these deficits in 12A and 18A groups are probably related to the similar background mechanisms to the 24A group or more elderly groups in which the morphologi-cal and functional deteriorations are observed in the entorhinal-hippocampal networks. Less