Preservation of Synaptic Structure by Rapid Freezing

Abstract

It is becoming apparent that aldehyde fixatives cannot arrest many synaptic activities fast enough to reveal their structural basis in the electron microscope (Heuser et al. 1974). What is needed is a reliable technique to freeze synapses while they are active so that they can be examined directly in freeze-fracture replicas or can be fixed while still frozen and then examined in thin sections. Here we describe a machine that is potentially capable of freezing nerve and muscle tissues fast enough to capture the fleeting morphological changes that occur during synaptic transmission. Tissues frozen in this machine can be put directly into a Balzers freeze-fracture apparatus.