Abstract
Nerve terminals of unknown origin at the chronically denervated neuromuscular junctions of the cat intrinsic laryngeal muscles were studied. Light-microscopically, TH (tyrosine hydroxylase) fibers approached the acetylcholinestelase-stained sites 5 weeks after denervation. Electron-microscopically, nerve varicosities labeled by 5-OHDA (5-hydroxydopamine) were observed in the Schwann tubes (the Böngner's bands). Nine to 30 weeks after denervation nerve terminals were found at the original neuromuscular junctions in all nine experimental animals. A cat in which the recurrent laryngeal nerve was sectioned 20 weeks before and the ipsilateral vagus nerve was transected three weeks before demonstrated nerve terminals at the neuromuscular junction. This implied that the regenerated nerve terminals were not from the recurrent laryngeal nerve.
Electromyographically, fibrillation-like activities were recognized in seven of ten animals. The results indicated that autonomic nerve fibers around the blood vessels entered the Schwann tubes and ultimately made synaptic contact with the neuromuscular junctions.
