College of Life Sciences, Anhui Normal University, Wuhu, Anhui, China.
J Physiol. 2020 Sep;598(17):3727-3745. doi: 10.1113/JP279340. Epub 2020 Jun 22.
The present study showed that anodal and cathodal transcranial direct current stimulation (tDCS) can respectively increase and decrease the amplitude of visually evoked field potentials in the stimulated visual cortex of cats, with the effect lasting for ∼60-70 min. We directly measured tDCS-induced changes in the concentration of inhibitory and excitatory neurotransmitters in the visual cortex using the enzyme-linked immunosorbent assay method and showed that anodal and cathodal tDCS can selectively decrease the concentration of GABA and glutamate in the stimulated cortical area. Anodal and cathodal tDCS can selectively inhibit the synthesis of GABA and glutamate by suppressing the expression of GABA- and glutamate-synthesizing enzymes, respectively.
Transcranial direct current stimulation (tDCS) evokes long-lasting neuronal excitability in the target brain region. The underlying neural mechanisms remain poorly understood. The present study examined tDCS-induced alterations in neuronal activities, as well as the concentration and synthesis of GABA and glutamate (GLU), in area 21a (A21a) of cat visual cortex. Our analysis showed that anodal and cathodal tDCS respectively enhanced and suppressed neuronal activities in A21a, as indicated by a significantly increased and decreased amplitude of visually evoked field potentials (VEPs). The tDCS-induced effect lasted for ∼60-70 min. By contrast, sham tDCS had no significant impact on the VEPs in A21a. On the other hand, the concentration of GABA, but not that of GLU, in A21a significantly decreased after anodal tDCS relative to sham tDCS, whereas the concentration of GLU, but not that of GABA, in A21a significantly decreased after cathodal tDCS relative to sham tDCS. Furthermore, the expression of GABA-synthesizing enzymes GAD65 and GAD67 in A21a significantly decreased in terms of both mRNA and protein concentrations after anodal tDCS relative to sham tDCS, whereas that of GLU-synthesizing enzyme glutaminase (GLS) did not change significantly after anodal tDCS. By contrast, both mRNA and protein concentrations of GLS in A21a significantly decreased after cathodal tDCS relative to sham tDCS, whereas those of GAD65/GAD67 showed no significant change after cathodal tDCS. Taken together, these results indicate that anodal and cathodal tDCS may selectively reduce GABA and GLU syntheses and thus respectively enhance and suppress neuronal excitability in the stimulated brain area.
本研究表明，阳极和阴极经颅直流电刺激（tDCS）分别可增加和减少猫受激视觉皮层中视觉诱发电场的幅度，其效果持续约 60-70 分钟。我们使用酶联免疫吸附测定法直接测量 tDCS 诱导的视觉皮层中抑制性和兴奋性神经递质浓度的变化，并表明阳极和阴极 tDCS 可选择性地降低刺激皮质区域中 GABA 和谷氨酸的浓度。阳极和阴极 tDCS 可通过抑制 GABA 和谷氨酸合成酶的表达，分别选择性地抑制 GABA 和谷氨酸的合成。
经颅直流电刺激（tDCS）可在目标脑区引发持久的神经元兴奋性。其潜在的神经机制仍知之甚少。本研究检查了 tDCS 诱导的猫视觉皮层 21a 区（A21a）神经元活动以及 GABA 和谷氨酸（GLU）浓度和合成的变化。我们的分析表明，阳极和阴极 tDCS 分别增强和抑制了 A21a 中的神经元活动，这表现为视觉诱发电位（VEP）的幅度显著增加和降低。tDCS 诱导的效应持续约 60-70 分钟。相比之下，假刺激 tDCS 对 A21a 中的 VEP 没有显著影响。另一方面，与假刺激 tDCS 相比，阳极 tDCS 后 A21a 中的 GABA 浓度显著降低，而 GLU 浓度没有显著变化。相反，与假刺激 tDCS 相比，阴极 tDCS 后 A21a 中的 GLU 浓度显著降低，而 GABA 浓度没有显著变化。此外，与假刺激 tDCS 相比，阳极 tDCS 后 A21a 中 GABA 合成酶 GAD65 和 GAD67 的 mRNA 和蛋白浓度均显著降低，而 GLU 合成酶谷氨酰胺酶（GLS）的 mRNA 和蛋白浓度没有显著变化。相比之下，与假刺激 tDCS 相比，阴极 tDCS 后 A21a 中 GLS 的 mRNA 和蛋白浓度均显著降低，而 GAD65/GAD67 则无明显变化。综上所述，这些结果表明，阳极和阴极 tDCS 可能选择性地减少 GABA 和 GLU 的合成，从而分别增强和抑制刺激脑区的神经元兴奋性。
