Historical evolution of the neurotransmission concept.

In this review we analyse the evolution of the neurotransmission phenomenon, whose nature have had three basic historical interpretations; a first, of an humoral nature, formulated by the classical Greeks (Alexandrian School), and which lasted, thanks to the work of Galen, until the sixteenth century (the theory of spiritus animalis); a second, purely mechanical one, developed on the basis of Cartesian conceptions, and which dominated in the seventeenth and eighteenth centuries; and finally, the electrochemical interpretation, which emerged in the nineteenth century, coinciding with the coming of age of numerous scientific disciplines, such as microscopic anatomy (Cajal), physiology (Sherrington), pharmacology (Bernard, Schmiedeberg) or experimental chemistry (Hensing). This latest interpretation can be broken down into an electrical hypothesis, dominant in the nineteenth century (Galvani, Du Bois-Reymond), and the current chemical hypothesis, which can be dated back to 1904, thanks to the research and the research by Elliott (chemical mediators) and Langley (receptive substances) on sympathetic stimulation. Finally, we describe the process of the discovery of the different neurotransmitters and neuroreceptors, and analyse the new interpretations postulated in relation to the neurotransmission concept at the dawn of the twenty-first century.