Simple and complex synapses shown by freeze-etching of rat cortical synaptosomes

The shape of the synaptic sites (specialized contact areas) was examined on the synaptic membrane fracture faces of freeze-etched rat cortical synaptosomes. Simple and complex synapses were differentiated on the basis of the absence or presence of unspecialized areas in the synaptic sites. The particle-free nature of these areas is discussed.