Zhang Zizhen, Kindrat Alexandra N, Sharif-Naeini Reza, Bourque Charles W
Centre for Research in Neuroscience, Montreal General Hospital and McGill University, Montreal, Quebec, Canada H3G 1A4.
J Neurosci. 2007 Apr 11;27(15):4008-13. doi: 10.1523/JNEUROSCI.3278-06.2007.
Osmosensory transduction is a bidirectional process displayed by neurons involved in the control of thirst and antidiuretic hormone release, and is therefore crucial for body fluid homeostasis. Although this mechanism is known to involve the activation of nonselective cation channels during hypertonicity-evoked shrinking, and the inhibition of these channels during hypotonicity-evoked swelling, the basis for this regulation is unknown. Here, we investigated this process using whole-cell patch-clamp recordings from neurons acutely isolated from the supraoptic nucleus of adult rats. The mechanosensitivity index, defined as the ratio of conductance change to normalized volume change, was quantitatively equivalent whether cell volume was increased or decreased by changes in extracellular fluid osmolality, or by changes in pipette pressure. Moreover, responses induced by hyperosmotic or hypo-osmotic media could be reversed by increasing or decreasing pipette pressure, respectively. The mechanosensitivity index was significantly reduced in neurons treated with cytochalasin-D, a compound that promotes the depolymerization of actin filaments. Conversely, cells treated with jasplakinolide, a compound that promotes actin polymerization, showed a significant increase in mechanosensitivity index. Finally, the depolarizing and excitatory effects of hypertonic stimuli were significantly enhanced by jasplakinolide and reduced by cytochalasin-D. We conclude that osmosensory transduction in these neurons is a reversible mechanical process that depends on an intact actin cytoskeleton, and the sensitivity of the transducer appears to vary in proportion with the density of actin filaments.
渗透压感受转导是一个双向过程，由参与口渴控制和抗利尿激素释放的神经元表现出来，因此对体液稳态至关重要。尽管已知该机制在高渗诱发的细胞收缩过程中涉及非选择性阳离子通道的激活，而在低渗诱发的细胞肿胀过程中涉及这些通道的抑制，但这种调节的基础尚不清楚。在此，我们使用从成年大鼠视上核急性分离的神经元进行全细胞膜片钳记录来研究这一过程。机械敏感性指数定义为电导变化与归一化体积变化的比值，无论细胞体积是通过细胞外液渗透压的变化还是通过移液管压力的变化而增加或减少，该指数在数量上都是等效的。此外，高渗或低渗介质诱导的反应可分别通过增加或降低移液管压力来逆转。在用细胞松弛素-D（一种促进肌动蛋白丝解聚的化合物）处理的神经元中，机械敏感性指数显著降低。相反，用jasplakinolide（一种促进肌动蛋白聚合的化合物）处理的细胞显示机械敏感性指数显著增加。最后，jasplakinolide显著增强了高渗刺激的去极化和兴奋作用，而细胞松弛素-D则降低了这种作用。我们得出结论，这些神经元中的渗透压感受转导是一个可逆的机械过程，依赖于完整的肌动蛋白细胞骨架，并且转导器的敏感性似乎与肌动蛋白丝的密度成比例变化。
