Quantal currents at single-site central synapses

The mode of operation of synaptic transmission has been primarily worked ou t at the vertebrate neuromuscular junction, thus providing a framework for the interpretation of studies at central synapses. However, differences hav e been found between the two systems, and a coherent model is still lacking for central synapses. Research in this area revolves around several questi ons. (1) Is the variability of quantal amplitudes determined pre- or postsy naptically? (2) What is the occupancy of postsynaptic receptors following t he release of a synaptic vesicle? And (3) does multivesicular release occur at single release sites following one presynaptic action potential? To ans wer these questions, it is essential to investigate synaptic processes at t he level of single release sites. This is technically difficult because of the complex morphology and small dimensions of central synapses. Neverthele ss significant advances have been made in the past few years.