Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA.
Tulane Brain Institute, Tulane University, New Orleans, LA, USA.
Neurobiol Aging. 2021 Feb;98:88-98. doi: 10.1016/j.neurobiolaging.2020.10.007. Epub 2020 Nov 1.
Sensorimotor performance declines during advanced age, partially due to deficits in somatosensory acuity. Cortical receptive field expansion contributes to somatosensory deficits, suggesting increased excitability or decreased inhibition in primary somatosensory cortex (S1) pyramidal neurons. To ascertain changes in excitability and inhibition, we measured both properties in neurons from vibrissal S1 in brain slices from young and aged mice. Because adapting and non-adapting neurons-the principal pyramidal types in layer 5 (L5)-differ in intrinsic properties and inhibitory inputs, we determined age-dependent changes according to neuron type. We found an age-dependent increase in intrinsic excitability in adapting neurons, caused by a decrease in action potential threshold. Surprisingly, in non-adapting neurons we found both an increase in excitability caused by increased input resistance, and a decrease in synaptic inhibition. Spike frequency adaptation, already small in non-adapting neurons, was further reduced by aging, whereas sag, a manifestation of I, was increased. Therefore, aging caused both decreased inhibition and increased intrinsic excitability, but these effects were specific to pyramidal neuron type.
感觉运动性能在老年时下降，部分原因是感觉灵敏度下降。皮层感受野扩展导致感觉缺陷，表明初级体感皮层 (S1) 锥体神经元的兴奋性增加或抑制性降低。为了确定兴奋性和抑制性的变化，我们测量了来自年轻和老年小鼠脑片的触须 S1 中的神经元的这两种特性。因为适应和不适应神经元——第 5 层 (L5) 中的主要锥体类型——在内在特性和抑制性输入方面存在差异，所以我们根据神经元类型确定了年龄依赖性变化。我们发现适应神经元的内在兴奋性随年龄增长而增加，这是由于动作电位阈值降低所致。令人惊讶的是，在不适应神经元中，我们发现兴奋性增加是由于输入电阻增加所致，而抑制性降低。不适应神经元中的尖峰频率适应本来就很小，随着年龄的增长进一步降低，而 sag，即 I 的表现，增加了。因此，衰老导致抑制性降低和内在兴奋性增加，但这些影响是特定于锥体神经元类型的。
