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

采用Morris水迷宫实验方法，观察了大鼠和老年大鼠在慢性注射东莨菪碱后，经皮下注射东参碱(2.5μ，L/小时)28d后，开始进行Morris水迷宫的空间学习任务。将30只大鼠分成12月龄(12A)、18月龄(18A)和24月龄(24A)三组。每天训练4次，每次训练间隔约10分钟，学习隐蔽逃生平台的位置(位置学习)。每次训练时，大鼠游泳90秒或直到找到平台。第5天是平台缩回的探查试验。然后在随后的4次试验中测试线索学习，在这4次试验中，大鼠游到露出池面的可见逃生平台，每次试验持续90秒。在sc…注射多孔胺后，大鼠对隐蔽平台的逃避潜伏期仅在位置学习的早期显著增加。此外，学习障碍大鼠海马吻部苔藓纤维终末体积明显增加，提示慢性注射东莨菪碱可诱导齿状颗粒细胞吻部神经元再生，增加苔藓纤维终末体积以补充胆碱能缺乏。在24A组，位置学习的逃避潜伏期显著延长，而线索学习的逃避潜伏期无明显延长。24A组的逃避潜伏期与平均游泳时间呈显著负相关。在12A和18A组中，观察到了这些结果，但不像24A组那样显著。在先前的研究中，所有老年组在位置学习任务中停留在逃生平台所在的03象限的时间百分比都显著减少。这些结果表明，空间学习障碍在1.2月龄左右开始出现，并在后期逐渐恶化，12A和18A组的这些缺陷可能与24A组或更多的老年组相似的背景机制有关，在24A组或更多的老年组中，内嗅觉-海马网出现了形态和功能的恶化。较少

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trial, rats swam for 90 seconds or until they found the platform.The fifth day was a probe test in which the platform was retracted, and rats swam for 60 seconds.Then cue learning was tested subsequently in a single session of 4 trials in which rats swam to the visible escape platform that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