[Comparison of motor endplate and central synapses. An ultrastructural study].

The fine structural characteristics of motor endplate (paradigm of a cholinergic synapse) and central synapses are briefly summarized giving major emphasis on recent observations in freeze fractured material. Special attention is paid to the concepts of "Active Zones" (presynaptic membrane complex) and "Specific Sites" (postsynaptic membrane complex). Comparison and functional interpretations are made specifically with respect to secretion and receptor mechanisms that are so characteristic of chemically transmitting junctions.