Effects of redirecting the vagosympathetic trunk into the hypothalamus

The cat vagosympathetic trunk was redirected into the hypothalamus to study peripheral and central nervous system interrelationships and their possible effects on the regenerative responses. Electron microscopy permitted detailed scrutiny of the morphologic characteristics of degeneration, growth, and other cytological changes. Three months after insertion into the hypothalamus, the vasgosympathetic fibers appeared healthy and many axonal growth cones and incompletely ensheathed neurites were present—features characteristic of regenerating axons. Signs of active growth were relatively sparse in the surrounding central nervous system tissue but central axonal and presumed dendritic growth cones were observed. These were more numerous after the peripheral nerve had been cut and allowed to undergo degeneration prior to insertion into the central nervous system. Although there was considerable intermingling of peripheral and central elemets in the boundary zone between them, evidence of synaptic union between the peripheral and central neurons was not observed.