The balance between neural excitation and inhibition has been shown to be crucial for normal brain function. However, it is unclear whether this balance is maintained through healthy aging. This study investigated the effect of aging on the temporal dynamics of the somatosensory evoked local field potential (LFP) in rats and tested the hypothesis that excitatory and inhibitory post-synaptic activities remain balanced during the aging process. The LFP signal was obtained from the barrel cortex of three different age groups of anesthetized rats (pre-adolescence: 4–6 weeks, young adult: 2–3 months, middle-aged adult: 10–20 months) under whisker pad stimulation. To confirm our previous finding that the initial segment of the evoked LFP was solely associated with excitatory post-synaptic activity, we micro-injected gabazine into the barrel cortex to block inhibition while LFP was collected continuously under the same stimulus condition. As expected, the initial slope of the evoked LFP in the granular layer was unaffected by gabazine injection. We subsequently estimated the excitatory and inhibitory post-synaptic activities through a balanced model of the LFP with delayed inhibition as an explicit constraint, and calculated the amplitude ratio of inhibition to excitation. We found an age-dependent slowing of the temporal dynamics in the somatosensory-evoked post-synaptic activity, as well as a significant age-related decrease in the amplitude of the excitatory component and a decreasing trend in the amplitude of the inhibitory component. Furthermore, the delay of inhibition with respect to excitation was significantly increased with age, but the amplitude ratio was maintained. Our findings suggest that aging reduces the amplitude of neural responses, but the balance between sensory evoked excitatory and inhibitory post-synaptic activities is maintained to support normal brain function during healthy aging. Further whole cell patch clamp experiments will be needed to confirm or refute these findings by measuring sensory evoked synaptic excitatory and inhibitory activities in vivo during the normal aging process.

中文翻译：

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尽管大鼠桶状皮层的感觉诱发局部场电位随年龄相关性下降，但模型预测的神经兴奋和抑制之间的平衡得到维持

神经兴奋和抑制之间的平衡已被证明对正常的大脑功能至关重要。然而，尚不清楚这种平衡是否通过健康老龄化得以维持。本研究调查了衰老对大鼠体感诱发局部场电位 (LFP) 时间动态的影响，并检验了兴奋性和抑制性突触后活动在衰老过程中保持平衡的假设。在晶须垫刺激下，从三个不同年龄组的麻醉大鼠（青春期前：4-6 周，青年：2-3 个月，中年：10-20 个月）的桶状皮层获得 LFP 信号。为了证实我们之前的发现，即诱发 LFP 的初始部分仅与兴奋性突触后活动相关，我们将gabazine微注射到桶状皮质中以阻断抑制，同时在相同刺激条件下连续收集LFP。正如预期的那样，颗粒层中诱发的 LFP 的初始斜率不受加巴嗪注射液的影响。我们随后通过 LFP 的平衡模型估计兴奋性和抑制性突触后活动，延迟抑制作为显式约束，并计算抑制与兴奋的幅度比。我们发现体感诱发的突触后活动的时间动态随年龄而变慢，兴奋性成分的振幅与年龄相关的显着下降和抑制性成分的振幅呈下降趋势。此外，随着年龄的增长，兴奋抑制的延迟显着增加，但幅度比保持不变。我们的研究结果表明，衰老会降低神经反应的幅度，但维持感觉诱发的兴奋性和抑制性突触后活动之间的平衡，以支持健康衰老期间的正常大脑功能。需要进一步的全细胞膜片钳实验，通过在正常衰老过程中测量体内感觉诱发的突触兴奋和抑制活动来证实或反驳这些发现。