Harada Keita, Inoue Masumi
Department of Cell and Systems Physiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu 807-8555, Japan.
Acta Histochem Cytochem. 2023 Aug 30;56(4):67-75. doi: 10.1267/ahc.23-00042. Epub 2023 Aug 23.
Adrenal medullary chromaffin (AMC) and sympathetic ganglion cells are derived from the neural crest and show a similar developmental path. Thus, these two cell types have many common properties in membrane excitability and signaling. However, AMC cells function as endocrine cells while sympathetic ganglion cells are neurons. In rat sympathetic ganglion cells, muscarinic M and M receptors mediate excitation and inhibition via suppression of M-type K channels and suppression of voltage-dependent Ca channels, respectively. On the other hand, M receptor stimulation in rat AMC cells also produces excitation by suppressing TWIK-related acid sensitive K (TASK) channels. However, whether M receptors are coupled with voltage-dependent Ca channel suppression is unclear. We explore this issue electrophysiologically and biochemically. Electrical stimulation of nerve fibers in rat adrenal glands trans-synaptically increased the Ca signal in AMC cells. This electrically evoked increased Ca signal was not altered during muscarine-induced increase in Ca signal, whereas it decreased significantly during a GABA-induced increase, due to a shunt effect of increased Cl conductance. The whole-cell current recordings revealed that voltage-dependent Ca currents in AMC cells were suppressed by adenosine triphosphate, but not by muscarinic agonists. The fractionation analysis and immunocytochemistry indicated that Ca1.2 Ca channels and M receptors are located in the raft and non-raft membrane domains, respectively. We concluded that muscarinic stimulation in rat AMC cells does not produce voltage-dependent Ca channel inhibition. This lack of muscarinic inhibition is at least partly due to physical separation of voltage-dependent Ca channels and M receptors in the plasma membrane.
肾上腺髓质嗜铬细胞（AMC）和交感神经节细胞起源于神经嵴，且发育路径相似。因此，这两种细胞类型在膜兴奋性和信号传导方面具有许多共同特性。然而，AMC细胞作为内分泌细胞发挥作用，而交感神经节细胞是神经元。在大鼠交感神经节细胞中，毒蕈碱型M和M受体分别通过抑制M型钾通道和电压依赖性钙通道来介导兴奋和抑制。另一方面，大鼠AMC细胞中的M受体刺激也通过抑制TWIK相关酸敏感钾（TASK）通道产生兴奋。然而，M受体是否与电压依赖性钙通道抑制偶联尚不清楚。我们通过电生理学和生物化学方法探讨了这个问题。对大鼠肾上腺神经纤维的电刺激通过突触传递增加了AMC细胞中的钙信号。这种电诱发的钙信号增加在毒蕈碱诱导的钙信号增加期间没有改变，而在GABA诱导的增加期间由于氯离子电导增加的分流效应而显著降低。全细胞电流记录显示，AMC细胞中的电压依赖性钙电流被三磷酸腺苷抑制，但不被毒蕈碱激动剂抑制。分级分离分析和免疫细胞化学表明，Ca1.2钙通道和M受体分别位于筏状和非筏状膜结构域。我们得出结论，大鼠AMC细胞中的毒蕈碱刺激不会产生电压依赖性钙通道抑制。这种毒蕈碱抑制的缺乏至少部分是由于质膜中电压依赖性钙通道和M受体的物理分离。
