Sigurdson W J, Morris C E
Department of Biology, University of Ottawa, Ontario, Canada.
J Neurosci. 1989 Aug;9(8):2801-8. doi: 10.1523/JNEUROSCI.09-08-02801.1989.
Using single-channel recording, we show that neurons contain ion channels sensitive to membrane tension. Neurons isolated from the snail, Lymnaea stagnalis, actively rearborized in culture yielding cell bodies and growth cones suitable for patch clamping. All neurons contained, in both their soma and growth cones (at a density of approximately 1-2 micron-2), stretch-activated channels highly selective for K+. The presence of this mechanosensitive channel in the motile region of the neuron, a region characterized by insertion of new membrane--the growth cone--is of particular interest. Under physiological conditions, the channel was permeable to K+, but not to Na+ or Cl-. Its conductance to K+ under these conditions was approximately 44 pS. Channel activation was steeply dependent on membrane tension, showing thresholds at between -50 to -100 mm Hg (suction was applied through the recording pipette). Kinetic analysis indicated that the stretch-dependent increase in the channel's open probability was related to a long closed state rather than to one of the open states. Given the importance of Ca2+ in the regulation of growth cone motility, we speculate that this stretch-activated K+ channel could play a role in neurite elongation by a tension-dependent modulation of membrane voltage which in turn would act on voltage-gated Ca2+ channels.
通过单通道记录，我们发现神经元含有对膜张力敏感的离子通道。从椎实螺（Lymnaea stagnalis）分离出的神经元在培养中能积极地重新形成树突，产生适合膜片钳记录的细胞体和生长锥。所有神经元的胞体和生长锥（密度约为1 - 2个/微米²）均含有对K⁺具有高度选择性的牵张激活通道。该机械敏感通道存在于神经元的运动区域，即一个以新膜插入为特征的区域——生长锥，这一点尤其令人感兴趣。在生理条件下，该通道对K⁺通透，但对Na⁺或Cl⁻不通透。在此条件下其对K⁺的电导约为44 pS。通道激活强烈依赖于膜张力，在 - 50至 - 100 mmHg之间显示出阈值（通过记录微电极施加吸力）。动力学分析表明，通道开放概率的牵张依赖性增加与一个长的关闭状态有关，而非与开放状态之一有关。鉴于Ca²⁺在调节生长锥运动性方面的重要性，我们推测这种牵张激活的K⁺通道可能通过对膜电压的张力依赖性调节在神经突伸长中发挥作用，而膜电压调节又会作用于电压门控Ca²⁺通道。
