Evolutionary Aspects of the Neurophysiological Role of Tyramine and Octopamine

Currently, such biologically active substances of endogenous nature as tyramine and octopamine are classified as trace amines, which is associated with their relatively low concentration in tissues. However, this is true to a greater extent with respect to higher vertebrates, in which these amines play a wide range of physiological functions, including modulatory effects in the nervous system by activating their own receptors for trace amines. In invertebrates, the level of these amines is higher, and they act in the nervous system not so much as modulators, but as neurotransmitters activating receptors of a different nature. This review analyzes experimental data on the neurophysiological role of tyramine and octopamine in the body of invertebrates and vertebrates, demonstrating similarities and differences in both the functions and the receptors mediating these functions. A certain emphasis is placed on data indicating a close relationship between signaling mediated by trace amines and the sympathetic division of the nervous system in higher vertebrates. Based on this, the idea is formed that in the process of evolution the noradrenergic signaling system could take over the role of tyramine and octopamine signaling. However, this idea is still debated, and the signaling role of tyramine and octopamine in the nervous system of higher vertebrates remains significant and continues to be actively studied. Interest in this is due to the fact that it is in vertebrates that the amines in question "acquired" both a new spectrum of physiological functions and a new set of receptor proteins for their implementation in the process of evolution. These proteins, as it turned out, can act as potential targets for the treatment of a number of neuropsychiatric disorders.