Contributions of New Impregnation Methods and Freeze Etching to the Problems of Synaptic Fine Structure

Abstract

Publisher Summary This chapter reviews information on a synaptic fine structure that is obtained by using iodide compounds of heavy metals for block staining and examining synaptic areas in specimens prepared with the freeze-etching technique. The chapter focuses on synaptic vesicles—internal and external coats of nerve membranes and their specializations at the synaptic junction. The complex interplay of molecular mechanisms at the synapse is discussed in the chapter. Impregnation of synaptic junctions with bismuth iodide and subsequent contrasting with uranyl acetate and lead hydroxide give significant details on the presynaptic membrane and its densities. The methods are useful in monitoring experimental approaches to the problems of excitation, memory, and individuality, which remain great mysteries of living matter and the nervous tissue. Freeze-etching preparations of synapses confirm the true existence and spheric shape of synaptic vesicles. The chapter describes the differences between the outer and inner surfaces of the plasmalemma of presynaptic terminals. The presence of micropinocytosis at the surface of boutons terminaux is demonstrated in a study discussed in the chapter.