老年大鼠学习行为与海马长时程突触增强和神经元核仁组织者的关系

RELATIONSHIP BETWEEN LONG-TERM POTENTIATION AND NUCLEOLAR ORGANIZER REGIONS OF HIPPOCAMPAL DENTATE GYRUS AND BEHAVIORAL LEARNING IN AGED RAT

主动回避条件反应率>80％的老年大鼠为学习好组,<30％的为学习差组。学习好组在高频短串刺激后颗粒细胞层出现海马长时程突触增强(LTP)效应:颗粒细胞核内Ag-NOR面积/胞核面积比值平均为0.154±0.0043;单个胞核内Ag-NOR平均为3.051±0.2212个,学习差组高频短串刺激引起颗粒细胞层群峰电位长时程抑制;颗粒细胞核内Ag-NOR面积/胞核面积比值平均为0.077±0.0023;单个胞核内Ag-NOR平均为1.839±0.1421个,2组间3指标均有显著差异,表明年老大鼠学习能力与LTP效应有关,学习差的老年大鼠海马齿状回颗粒细胞rDNA的转录活性较学习好的明显降低。

Six aged rats (36 Months old) were divided into good learning group (n=3). and poor learning group (n=3). The rates of passitive avoidance conditioned reflex of both groups were higher than 80% and lower than 30%, respectively. Following a brief train of high-frequency stimulation in the perforant path, the long-term potentiation (LTP) and the long-term depression (LTD) of synaptic transmission of the granule cell layer in both groups were observed. The results showed that the ability of behavioral learning in aged rats related to LTP. Silver staining NOR (Ag-NOR) method was used to demonstrate the NOR with transcriptional activity. The average of the ratio of the area of Ag-NOR over the area of nucleus and the average of the number of Ag-NOR in a the granule cell were 0. 154+0. 0043 and 3. 051+0. 2212, respectively, in the good learning group; but these were 0. 077+0. 0023 and 1. 839+0. 1421, respectively, in the poor learning group. The results showed the size and number of Ag-NOR in the granule cell of hippocampal dentate gyrus in the poor learning group were statistically significantly decreased in comparision with that in the good learning group. Because there is a linear relationship between the size and number of Ag-NOR and the level of rDNA transcription, these measurment results verified that the transcription activity of rDNA of the granule cells in the poor learning rats was markedly lower than that in the good learning ones.