Morphological and Cytochemical Studies on the Synapses in the Autonomic Nervous System

Abstract

Publisher Summary This chapter presents morphological and cytochemical studies on the synapses in the autonomic nervous system. At the ultrastructural level, the interneuronal synapses exhibit morphological differentiations both in the nerve endings, such as synaptic vesicles, and in the effector, such as the thickening of the postsynaptic membrane in synaptic complexes or active zones. The motor endplate is characterized by a special differentiation of the muscular membrane, which is the subneural apparatus of Couteaux. In the tissues innervated by the autonomic nervous system, it is not possible to distinguish, with the techniques available, the limited areas morphologically differentiated both on the nerve side and on the effector side that might be clearly recognized as synaptic contacts. Because of the lack of morphological evidence and precise physiological data on a true synaptic transmission, it is inadequate to call synapses the neuroeffector connections of the autonomic nervous system, but because the peripheral part of the autonomic nerve fibers can release a transmitter, this can be called the “efficient part” of the sympathetic or parasympathetic fibers, and the study of its properties can take place with that of the presynaptic fibers sensu stricto.