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Chapter 1 Coexistence of Neuromessenger Molecules – A Perspective

Chemical transmission is a fundamental process in nervous system function. The chemicals involved were originally termed neurotransmitters, but other names have subsequently also been used: messenger molecule, signaling/transmitter substance, modulator and more – in Sweden we say ‘‘a loved child has many names’’. Early on, with only few substances around, the term ‘‘neurotransmitter’’ appeared distinct and sufficient. However, as more and more categories of molecules appeared to have a signaling function in the nervous system, and sometimes with additional, even not well-defined functions, the name not rarely became on issue of controversy. For example, in the 1960s some eminent neurophysiologists would not accept the monoamines as neurotransmitters. This discussion is today less intense, perhaps because of the insight that the name really is not the critical issue, but rather to understand under what circumstances this spectrum of molecules is produced and released and what their functional significance is.