Trace amines are an endogenous group of amines structurally and metabolically related to classical monoamine neurotransmitters, such as dopamine, norepinephrine, and serotonin. Compared to the classical monoamines, they are present in trace concentrations. They are distributed heterogeneously throughout the mammalian brain and peripheral nervous tissues and exhibit high rates of metabolism. Although, they can be synthesized within parent monoamine neurotransmitter systems, there is evidence that suggests that some of them may comprise their own independent neurotransmitter systems.
Trace amines may play very significant roles in the coordination of biogenic monoamine-based synaptic physiology. At high concentrations, they have well-characterized presynaptic ‘‘amphetamine-like’’ effects on monoamine release, reuptake and biosynthesis; at lower concentrations, they possess postsynaptic modulatory effects that potentiate the activity of other neurotransmitters, particularly dopamine and serotonin. A family of G protein coupled receptors known as TAARs (trace amine associated receptors) has been characterized to be responsive to trace amines and structurally related psychoactive drugs, such as amphetamine, MDMA, LSD, and DMT. Like dopamine, noradrenaline, and serotonin, the trace amines have been implicated in a vast array of human disorders of affect and cognition, such as depression and schizophrenia.
A thorough review of trace amines and trace amine receptors that discusses the historical evolution of this research particularly well is that of Grandy.