Transport of Messenger Substances to Targets

Abstract

A typical neurotransmitter is released from a neuron and transported to its target across a synaptic cleft of 10- to 40-nm width. We call this mode of messenger secretion “synaptocrinia” (the term proposed by Fujita 1983b). A typical hormone,on the other hand, is released from an endocrine cell—or endocrine paraneuron, if we restrict the subject to the peptide/amine producing system) to be conveyed to its remote target via the general circulation. This type of messenger secretion can be called “telecrinia” (the term proposed by Leibson 1979), “hemocrinia” (proposed by Feyrter 1962), or, more precisely “macrohemocrinia” (Fujita 1983b). Between these two extreme cases of the typical neurotransmitter and hormone, every gradation can be found. In other words, a large variety of intermediate routes and ranges of messenger transport may occur, and these will now be classified.