Ultrastructural correlates of naturally occurring differences in transmitter release efficacy in frog motor nerve terminals.

摘要: Motor nerve terminals in cutaneous pectoris muscles of the frogRana pipiens release more transmitter and form synapses with higher levels effectiveness than do those sartorius muscles. Neuromuscular junctions from these two were compared electron microscope to search for ultrastructural correlates differences synaptic effectiveness. The following measurements made cross-sections known effectiveness: (a) presence active zones, presumed sites release, (b) zone size, (c) perimeter, cross-sectional area, height width terminals, (d) number mitochondria, (e) vesicle density, (f) extent which Schwann cells wrap terminals. Nerve did not differ shape or density. strongly releasing did, however, have significantly larger zones due deeper invagination terminal into postsynaptic gutter lesser interposition cell processes between presynaptic membranes. Cutaneous also contained presumably supply greater energy demand imposed by high levels.