EVIDENCE FOR REMODELLING OF SYNAPTIC CONTACTS IN MUSCLES OF ADULT FROG

Abstract

This chapter describes an experiment to provide evidence for the remodeling of synaptic contacts in the muscles of adult frog. In microscopical investigations on frog neuromuscular junction, marked deviations from the usual appearance of synapses in curarized and untreated animals were found; similarly, unusual features were found in the sections that were randomly taken from such muscles and prepared for electron microscopy. These observations indicated nerve regression and nerve sprouting with synapse new formation to occur in these muscles. To verify this, serial sections were performed from selected parts of synapses, which showed typical deviations in their light microscopical appearance. Experiments were performed on freshly caught animals. In nerve muscle synapses from untreated frogs, the signs of nerve sprouting and nerve regression were observed after applying a combined axon and cholinesterase (ChE) staining technique. In frog, the average total synapse length increased with the body size of the animal. A concomitant increase in the number of branches per synapse was found, while ChE remnants were equally frequent in muscles taken from differently sized animals.