Geusz M E, Block G D
Department of Biology, University of Virginia, Charlottesville 22903.
Neurosci Biobehav Rev. 1994 Winter;18(4):555-61. doi: 10.1016/0149-7634(94)90011-6.
Circadian clock systems contain three components--an entrainment pathway, a pacemaker mechanism, and an output or expressed rhythm. The entrainment pathway for light stimuli can be studied by separating steps involved in light transduction and subsequent events acting on the pacemaker mechanism from the steps critical for continued motion of the pacemaker. Studies indicate that calcium entry across the plasma membrane is a required step in the light entrainment pathway of the ocular circadian pacemaker of the marine snail Bulla gouldiana. A calcium influx due to phase-shifting stimuli has recently been measured using the calcium-sensitive dye Fura-2 in dissociated pacemaker neurons from Bulla. Studies preceding these calcium imaging experiments are presented together with a simple model of the role of Ca2+ influx in entrainment and a discussion of problems in demonstrating that calcium influx alone is a sufficient step in the entrainment pathway.
昼夜节律时钟系统包含三个组成部分——一个输入途径、一个起搏器机制以及一个输出或表达的节律。光刺激的输入途径可以通过将光转导过程中涉及的步骤以及作用于起搏器机制的后续事件与起搏器持续运行所必需的关键步骤区分开来进行研究。研究表明，钙离子跨质膜进入是海蜗牛Bulla gouldiana眼昼夜节律起搏器光输入途径中的一个必要步骤。最近，利用钙敏染料Fura-2在分离的Bulla起搏器神经元中测量了由相移刺激引起的钙内流。在这些钙成像实验之前的研究与钙离子内流在输入过程中的作用的简单模型以及关于证明仅钙内流是输入途径中一个充分步骤时所存在问题的讨论一同呈现。
