College of Life Sciences, Anhui Normal University, Wuhu, Anhui, 241000, China.
Department of Materials Science and Engineering, University of California, Los Angeles, CA, 90095, USA.
Sci Rep. 2017 Nov 2;7(1):14897. doi: 10.1038/s41598-017-15006-3.
Numerous studies have reported age-dependent degradation of neuronal function in the visual cortex and have attributed this functional decline to weakened intracortical inhibition, especially GABAergic inhibition. However, whether this type of functional decline is linked to compromised GABAergic inhibition has not been fully confirmed. Here, we compared the neuronal response properties and markers of GABAergic inhibition in the primary visual cortex (V1) of young adult and senescent rats. Compared with those of young adult rats, old rats' V1 neurons exhibited significantly increased visually evoked responses and spontaneous activity, a decreased signal-to-noise ratio and reduced response selectivity for the stimulus orientation and motion direction. Additionally, the ratio of GABA-positive neurons to total cortical neurons in old rats was significantly decreased compared with that in young rats. Expression of the key GABA-synthesizing enzyme GAD67 was significantly lower in old rats than in young rats, although GAD65 expression showed a marginal difference between the two age groups. Further, expression of an important GABA receptor subunit, GABAR α, was significantly attenuated in old rats relative to young ones. These results demonstrate that ageing may result in decreased GABAergic inhibition in the visual cortex and that this decrease in GABAergic inhibition accompanies neuronal function degradation.
大量研究报告称，视觉皮层中的神经元功能会随年龄增长而退化，并将这种功能下降归因于皮质内抑制作用减弱，尤其是 GABA 能抑制作用减弱。然而，这种功能下降是否与 GABA 能抑制作用受损有关尚未得到充分证实。在这里，我们比较了年轻成年大鼠和衰老大鼠初级视觉皮层（V1）的神经元反应特性和 GABA 能抑制的标志物。与年轻成年大鼠相比，老年大鼠 V1 神经元的视觉诱发反应和自发活性显著增加，信号噪声比降低，对刺激方向和运动方向的反应选择性降低。此外，与年轻大鼠相比，老年大鼠中 GABA 阳性神经元与皮质总神经元的比例显著降低。尽管 GAD65 在两个年龄组之间的表达略有差异，但老年大鼠中关键 GABA 合成酶 GAD67 的表达明显低于年轻大鼠。此外，重要的 GABA 受体亚基 GABARα的表达在老年大鼠中相对于年轻大鼠显著减弱。这些结果表明，衰老可能导致视觉皮层 GABA 能抑制作用减弱，而这种 GABA 能抑制作用的减弱伴随着神经元功能的退化。
