MECHANICAL, THERMAL, AND OPTICAL SIGNS OF EXCITATION IN THE NERVOUS SYSTEM

在本财政年度初期，我们集中精力 检测和分析两栖动物的热变化和机械变化 由交感神经刺激产生的真皮腺。我们捏造了 热传感器设计成与研究中的皮肤区域相匹配 成功地记录了与去甲肾上腺素释放相关的热量 神经末梢。我们的发现是，这股热浪的开始先于 交感神经的机械和电学反应的开始 刺激在研究神经递质的作用中具有特殊的意义 真皮腺上的去甲肾上腺素。 在一次物理化学家和化学工程师的会议上 1989年12月10日在校园里，一条有趣的信息是 据报道。具有负电荷的聚合物凝胶被证明经历了 相变伴随着可逆的、不连续的体积变化。 因为我们正在寻找一个坚实的物理化学基础来解释 神经组织的快速机械变化的本质，我们开始了一个 合成聚合物凝胶中溶胀现象的研究。我们 发现聚丙烯酸凝胶浸泡在含盐溶液中 一价阳离子(如钠或钾)和二价阳离子 (例如，钙)以两种稳定状态之一存在，要么是肿胀，要么是 紧凑(缩小)。我们还测量了与这些相关的热量产生 不连续的卷转换。我们现在认为，类似的 不连续的转换发生在神经的浅层。 细胞和纤维，这些转变对应于开始和 动作电势的结束。

During the early part of this fiscal year, we concentrated our effort in detecting and analyzing thermal and mechanical changes in the amphibian dermal glands produced by sympathetic nerve stimulation. We fabricated heat sensors designed to match the area of the skin under study and succeeded in recording the heat associated with noradrenaline release from the nerve terminals. Our finding that the onset of this heat precedes the beginning of the mechanical and electrical responses to sympathetic nerve stimulation is of special significance in the study of the action of noradrenaline on the dermal glands. In a meeting of physical chemists and chemical engineers held at this campus on December 10, 1989, an interesting piece of information was reported. Polymer gels with negative fixed charges were shown to undergo phase transitions accompanying reversible, discontinuous volume changes. Since we were in search of a solid physicochemical basis for explaining the nature of the rapid mechanical changes in nervous tissues, we began an investigation of the phenomenon of swelling in synthetic polymer gels. We found that poly (acrylic acid) gels immersed in salt solutions containing both univalent cations (e.g., sodium or potassium) and divalent cations (e.g., calcium) exist in one of the two stable states, either swollen or compact (shrunk). We also measured heat production associated with these discontinuous volume transitions. We now believe that similar discontinuous transitions take place in the superficial layer of nerve cells and fibers and that these transitions correspond to the beginning and end of an action potential.