Suppression of foreign innervation in axolotl muscle may not be dependent on juxtaposition of native and foreign nerve terminals.

The posterior supracoracoideus nerve of the axolotl, Ambystoma mexicanum, was induced to make synapses outside its normal muscle territory. Muscle fibres with inputs from both native and foreign nerves were studied during the period of suppression of foreign transmission and in only 8% of fibres were foreign and native terminals found within 120 micrometer of each other. A combined cholinesterase/silver staining technique revealed non-innervated endplates in foreign-innervated fibres just prior to the return of the native nerve. These results suggest a mechanism enabling suppression of foreign synapses at some distance from native synapses probably beginning with the reinnervation of empty sites by the native nerve.