Morphological characteristics of neuromuscular junctions of the opossum (Didelphis albiventris) extraocular muscles: A scanning-electron-microscopic study

Three types of neuromuscular junctions were described in the extraocular mu scles of the opossum, The present study demonstrates the three-dimensional characteristics of these neuromuscular junctions after HCl connective tissu e digestion. Adult opossum of both sexes were used and the neuromuscular ju nctions of the extraocular muscles were examined after removal of the intra muscular connective tissue and basal layer. This material was examined with a scanning electron microscope, Two types of 'en plaque' neuromuscular jun ction were described: the continuous type revealed elongated and branched p rimary synaptic grooves separated from each other by sarcolemma protuberanc es with different sizes, and the discontinuous or punctiform type which pre sents very shallow and discontinuous grooves when compared with the former. The multiple neuromuscular junctions were observed as two or three junctio ns associated with the same muscular fiber. The multiple junctions were pre sent in thin fibers (around 11 mu m caliber); the en plaque junctions were associated with large diameter fibers (around 21 mu m), This study confirms and reveals the detailed morphological characteristics of the three neurom uscular junction types previously described by transmission electron micros cope in the extraocular muscles of opossum, Copyright (C) 2000 S. Karger AG, Basel.