Key Laboratory of Biomedical Engineering of Education Ministry, College of Biomedical Engineering and Instrumentation Science, Zhejiang University, Hangzhou, 310027, Zhejiang, China.
Biomed Eng Online. 2019 Jul 23;18(1):79. doi: 10.1186/s12938-019-0700-z.
Deep brain stimulation (DBS) has a good prospect for treating many brain diseases. Recent studies have shown that axonal activation induced by pulse stimulations may play an important role in DBS therapies through wide projections of axonal fibers. However, it is undetermined whether the downstream neurons are inhibited or excited by axonal stimulation. The present study addressed the question in rat hippocampus by in vivo experiments.
Pulse stimulations with different frequencies (10-400 Hz) were applied to the Schaffer collateral, the afferent fiber of hippocampal CA1 region in anaesthetized rats. Single-unit spikes of interneurons and pyramidal cells in the downstream region of stimulation were recorded and evaluated.
Stimulations with a lower frequency (10 or 20 Hz) did not change the firing rates of interneurons but decreased the firing rates of pyramidal cells (the principal neurons) significantly. The phase-locked firing of interneurons during these stimulations might increase the efficacy of GABAergic inhibitions on the principal neurons. However, stimulations with a higher frequency (100-400 Hz) increased the firing rates of both types of the neurons significantly. In addition, the increases of interneurons' firing were greater than the increases of pyramidal cells. Presumably, increase of direct excitation from afferent impulses together with failure of GABAergic inhibition might result in the increase of pyramidal cells' firing by a higher stimulation frequency. Furthermore, silent periods appeared immediately following the cessation of stimulations, indicating a full control of the neuronal firing by the stimulation pulses during axonal stimulation. Furthermore longer silent periods were associated with higher stimulation frequencies.
Low-frequency (10-20 Hz) and high-frequency (100-400 Hz) stimulations of afferent axonal fibers exerted opposite effects on principal neurons in rat hippocampus CA1. These results provide new information for advancing deep brain stimulation to treat different brain disorders.
脑深部电刺激（DBS）在治疗许多脑部疾病方面具有良好的前景。最近的研究表明，脉冲刺激诱导的轴突激活可能通过轴突纤维的广泛投射在 DBS 治疗中发挥重要作用。然而，轴突刺激是否会抑制或兴奋下游神经元仍未确定。本研究通过在体实验在大鼠海马体中解决了这个问题。
在麻醉大鼠的海马体 CA1 区传入纤维 Schaffer 侧支上施加不同频率（10-400 Hz）的脉冲刺激。记录和评估刺激下游区域的中间神经元和锥体神经元的单个单位尖峰。
较低频率（10 或 20 Hz）的刺激不会改变中间神经元的放电率，但会显著降低锥体神经元（主要神经元）的放电率。这些刺激期间中间神经元的锁相放电可能会增加 GABA 能抑制对主要神经元的抑制效果。然而，较高频率（100-400 Hz）的刺激会显著增加两种神经元的放电率。此外，中间神经元放电的增加大于锥体神经元放电的增加。推测，由于传入冲动的直接兴奋增加以及 GABA 能抑制的失败，较高的刺激频率可能导致锥体神经元放电增加。此外，刺激停止后立即出现沉默期，表明在轴突刺激期间刺激脉冲可以完全控制神经元的放电。此外，更长的沉默期与更高的刺激频率相关。
传入轴突纤维的低频（10-20 Hz）和高频（100-400 Hz）刺激对大鼠海马体 CA1 中的主要神经元产生相反的影响。这些结果为推进深部脑刺激治疗不同脑疾病提供了新的信息。
