Barnes C A, Rao G, Orr G
Arizona Research Laboratories, Division of Neural Systems, Memory and Aging and Department of Psychology, University of Arizona, Tucson, AZ 85274, USA.
Neural Plast. 2000;7(3):167-78. doi: 10.1155/NP.2000.167.
Synaptic response size in the CA1 region of the hippocampus in aged rats is reduced for a given stimulus intensity, compared with that elicited in young rats. Consistent with the in vitro findings of reduced Schaffer collateral-evoked CA1 EPSPs in old rats, the population currents evoked to iontophoretically applied AMPA are also smaller relative to the presynaptic fiber potential amplitude. On the other hand, the size of the presynaptic fiber potential and amplitude of unitary intra-cellularly recorded EPSP responses do not change across age in the CA1 region. These electrophysiological findings are consistent with the hypothesis that old rats have fewer functional synaptic contacts per Schaffer collateral axon than do young rats. The possibility that this age change arises as a result of a differential tissue recovery response to in vitro preparation was examined in the present study. CA1 presynaptic fiber potential and EPSP amplitudes evoked by the stimulation of Schaffer collateral afferents were studied in intact, freely behaving young and old rats. We confirmed in vivo the pattern of electrophysiophysiological results previously reported in vitro and found significant correlations between the synaptic response amplitudes and the accuracy of spatial behavior in the Morris swim task. The data suggest that changes in functional connectivity of old rats may be a significant contributor to cognitive changes during aging.
与年轻大鼠相比，在给定刺激强度下，老年大鼠海马体CA1区的突触反应大小会降低。与老年大鼠体外实验中观察到的Schaffer侧支诱发的CA1区兴奋性突触后电位（EPSP）降低的结果一致，相对于突触前纤维电位幅度，离子导入AMPA诱发的群体电流也较小。另一方面，CA1区突触前纤维电位的大小和单细胞内记录的EPSP反应的幅度在不同年龄之间没有变化。这些电生理结果与以下假设一致：与年轻大鼠相比，老年大鼠每条Schaffer侧支轴突的功能性突触联系更少。本研究检验了这种年龄变化是否是由于对体外制备的不同组织恢复反应所致。在完整、自由活动的年轻和老年大鼠中研究了刺激Schaffer侧支传入神经诱发的CA1区突触前纤维电位和EPSP幅度。我们在体内证实了先前体外实验报道的电生理结果模式，并发现突触反应幅度与Morris游泳任务中空间行为的准确性之间存在显著相关性。数据表明老年大鼠功能连接性的变化可能是衰老过程中认知变化의一个重要因素。
