MECHANISMS OF ADAPTATION AND EXCITATION

该提案的总体目标是阐明该机制 光在光感受器中产生感受器电位。 这个过程可以分为早期阶段，涉及光- 敏感分子视紫红质，中间阶段， 化学放大，以及化学放大的最后阶段， 信息影响离子通道，从而产生受体 潜力 早期步骤的一个方面，G的平均数量- 由单一异构化视紫红质激活的蛋白质，将被 在实验中研究了涉及阻断或 刺激G蛋白。 此外，使用肽的可能性 以抑制涉及视紫红质的特定反应 通过将这些肽透析到虎蝾螈棒或鲎中， 光感受器 涉及中间事件的主要问题 这与新的假设有关，即cGMP的增加介导了 无脊椎动物光感受器的兴奋。 这将是 在光对鸟苷酸的影响的生物化学测定中研究 环化酶活性，磷酸二酯酶活性， cGMP浓度在活鱿鱼的眼睛。 生理 方法将被用来研究推定的激活剂的影响 和环核苷酸酶的抑制剂 新陈代谢. 总的目标是确定哪种酶是 负责cGMP的光依赖性变化，以及这是如何 酶可以控制。 最后，解剖学方法将 用于确定非常不均匀的结构基础 对注射cGMP的敏感性。 正在进行的关于光- 使用膜片钳方法激活鲎中的通道， 持续期间内的 初步结果表明，这些通道事件 有两种尺寸。 我们将试图确定这些是否是由于 同一信道的两个不同状态或两个不同状态 频道类型 这些渠道也将在切除研究 可以测试感兴趣的物质是否 会对频道产生直接影响。

The general goal of this proposal is elucidation of the mechanism by which light generates the receptor potential in photoreceptors. This process can be divided into early stages involving the light- sensitive molecule rhodopsin, intermediate stages involving chemical amplification, and the final stage in which the chemical message affects ion channels, thereby generating the receptor potential. An aspect of the early steps, the average number of G- proteins activated by a single isomerized rhodopsin, will be investigated in experiments involving agents which block or stimulate G-protein. In addition the possibility of using peptides to inhibit specific reactions involving rhodopsin will be explored by dialyzing such peptides into tiger salamander rods or Limulus photoreceptors. The main questions involving intermediate events have to do with the new hypothesis that a rise in cGMP mediates the excitation of invertebrate photoreceptors. This will be studied in biochemical assays of the effect of light on guanylate cyclase activity, phosphodiesterase activity, and the concentration of cGMP in the living squid eye. Physiological methods will be used to study the effect of putative activators and inhibitors of enzymes involved in cyclic nucleotide metabolism. The general goal is to determine which enzyme is responsible for light-dependent changes in cGMP and how this enzyme might be controlled. Finally, anatomical methods will be used to identify the structural basis for the very inhomogeneous sensitivity to injected cGMP. Ongoing work on the light- activated channels in Limulus using the patch clam method will be continued. Preliminary results indicate that these channel events have two sizes. We will attempt to determine if these are due to two different states of the same channel or to two different channel types. These channels will also be studied in excised patches where it is possible to test whether substances of interest can have direct effects on the channel.