Department of Biomedicine, Aarhus University, Aarhus, Denmark.
Acta Physiol (Oxf). 2021 Oct;233(2):e13690. doi: 10.1111/apha.13690. Epub 2021 Jun 2.
The skeletal muscle Cl channels, the ClC-1 channels, stabilize the resting membrane potential and dampen muscle fibre excitability. This study explored whether ClC-1 inhibition can recover nerve-stimulated force in isolated muscle under conditions of compromised neuromuscular transmission akin to disorders of myasthenia gravis and Lambert-Eaton syndrome.
Nerve-muscle preparations were isolated from rats. Preparations were exposed to pre-or post-synaptic inhibitors (ω-agatoxin, elevated extracellular Mg , α-bungarotoxin or tubocurarine). The potential of ClC-1 inhibition (9-AC or reduced extracellular Cl ) to recover nerve-stimulated force under these conditions was assessed.
ClC-1 inhibition recovered force in both slow-twitch soleus and fast-twitch EDL muscles exposed to 0.2 µmol/L tubocurarine or 3.5 mmol/L Mg . Similarly, ClC-1 inhibition recovered force in soleus muscles exposed to α-bungarotoxin or ω-agatoxin. Moreover, the concentrations of tubocurarine and Mg required for reducing force to 50% rose from 0.14 ± 0.02 µmol/L and 4.2 ± 0.2 mmol/L in control muscles to 0.45 ± 0.03 µmol/L and 4.7 ± 0.3 mmol/L in muscles with 9-AC respectively (P < .05, paired T test). Inhibition of acetylcholinesterase (neostigmine) and inhibition of voltage-gated K channels (4-AP) relieve symptoms in myasthenia gravis and Lambert-Eaton syndrome, respectively. Neostigmine and 9-AC additively increased the tubocurarine concentration required to reduce nerve-stimulated force to 50% (0.56 ± 0.05 µmol/L with 9-AC and neostigmine) and, similarly, 4-AP and 9-AC additively increased the Mg concentration required to reduce nerve-stimulated force to 50% (6.5 ± 0.2 mmol/L with 9-AC and 4-AP).
This study shows that ClC-1 inhibition can improve neuromuscular function in pharmacological models of compromised neuromuscular transmission.
骨骼肌 Cl 通道，即 ClC-1 通道，稳定静息膜电位并抑制肌纤维兴奋性。本研究探讨 ClC-1 抑制是否能在类似于重症肌无力和 Lambert-Eaton 综合征的神经肌肉传递受损的情况下，恢复神经刺激引起的分离肌肉的力。
从大鼠中分离出神经肌肉标本。标本暴露于突触前或突触后抑制剂（ω-银环蛇毒素、升高的细胞外镁、α-银环蛇毒素或筒箭毒碱）下。评估 ClC-1 抑制（9-AC 或降低细胞外 Cl-）在这些条件下恢复神经刺激力的潜力。
ClC-1 抑制恢复了暴露于 0.2 μmol/L 筒箭毒碱或 3.5 mmol/L Mg2+的慢收缩比目鱼肌和快收缩 EDL 肌肉的力。同样，ClC-1 抑制恢复了暴露于 α-银环蛇毒素或 ω-银环蛇毒素的比目鱼肌的力。此外，使力降低到 50%所需的筒箭毒碱和 Mg2+浓度分别从对照肌肉中的 0.14±0.02 μmol/L 和 4.2±0.2 mmol/L 升高到 9-AC 肌肉中的 0.45±0.03 μmol/L 和 4.7±0.3 mmol/L（P<.05，配对 T 检验）。乙酰胆碱酯酶抑制剂（新斯的明）和电压门控 K 通道抑制剂（4-AP）分别缓解重症肌无力和 Lambert-Eaton 综合征的症状。新斯的明和 9-AC 可使筒箭毒碱浓度相加，使神经刺激力降低到 50%所需的浓度（9-AC 和新斯的明时为 0.56±0.05 μmol/L），同样，4-AP 和 9-AC 使神经刺激力降低到 50%所需的 Mg2+浓度相加（9-AC 和 4-AP 时为 6.5±0.2 mmol/L）。
本研究表明，ClC-1 抑制可改善神经肌肉传递受损的药理学模型中的神经肌肉功能。
