[Neuromediators and neuromodulators. Evolution of compounds and the evolution of hypotheses]

Probable peculiarities of evolution of neurotransmitters (NM) and neuromodulators (NR) of various types are discussed. The hypothesis of higher evolutionary rate of peptide NM and NR, and of more diverse possibilities of the formation of this type of NM and NR is suggested. Monomolecular MN and NR are presumably more conservative, although they exhibit some advantage with respect to strict differentiation of the systems of synthesis and degradation. Probably, the most ancient NM and NR are presented by such compounds as peptides, some amino acids, and ATP.