Proctor W, Frenk S, Taylor B, Roper S
Proc Natl Acad Sci U S A. 1979 Sep;76(9):4695-9. doi: 10.1073/pnas.76.9.4695.
Selectivity of synapse formation after nerve regeneration was tested in the parasympathetic cardiac ganglion of frogs (Rana pipiens). First, we tested the ability of somatic motor axons to establish synaptic connections with denervated ganglion cells by implanting the hypoglossus nerve into the vagotomized heart. After several weeks, stimulation of the implanted hypoglossus mediated a parasympathetic-like inhibition of the heart rate, and synaptic responses produced by hypoglossal stimulation were recorded intracellularly in ganglion cells. Light and electron microscopy indicated that implanted hypoglossal nerve terminals contacted parasympathetic ganglion cells only on their axons and not on the cell body (where most vagal synapses are found in control animals). Second, we tested whether regenerating vagal preganglionic axons would complete with foreign (hypoglossal) terminals for innervation of cardiac ganglion cells. We allowed the vagus nerve to regenerate in animals in which the implanted hypoglossus had established functional contacts with the cardiac ganglion. Vagal axons were able to reinnervate the heart and reestablish synaptic connections on the cell bodies of ganglion cells. Furthermore, functional transmission at the foriegn (hypoglossal) terminals disappeared concomitant with vagal reinnervation.
在青蛙（豹蛙）的副交感心脏神经节中测试了神经再生后突触形成的选择性。首先，我们通过将舌下神经植入迷走神经切断的心脏来测试躯体运动轴突与去神经节细胞建立突触连接的能力。几周后，刺激植入的舌下神经介导了类似副交感神经的心率抑制，并且在神经节细胞内记录了舌下神经刺激产生的突触反应。光学显微镜和电子显微镜检查表明，植入的舌下神经末梢仅在其轴突上而非细胞体上（在对照动物中大多数迷走神经突触位于此处）与副交感神经节细胞接触。其次，我们测试了再生的迷走神经节前轴突是否会与外来（舌下）末梢竞争以支配心脏神经节细胞。我们让迷走神经在植入的舌下神经已与心脏神经节建立功能联系的动物中再生。迷走神经轴突能够重新支配心脏并在神经节细胞的细胞体上重新建立突触连接。此外，随着迷走神经的重新支配，外来（舌下）末梢的功能传递消失。
