While not trace amines themselves, the classical monoamines dopamine, norepinephrine, serotonin, and histamine are all partial TAAR1 agonists in humans.N,N-Dimethyltryptamine is an endogenous amine in humans and a known rat TAAR1 agonist, but its human TAAR1 binding has not yet been documented; some ligands at rat TAAR1 have no affinity at human TAAR1 (e.g., LSD).
^ abcdefgBerry MD (January 2007). "The potential of trace amines and their receptors for treating neurological and psychiatric diseases". Rev Recent Clin Trials2 (1): 3–19. doi:10.2174/157488707779318107. PMID18473983. "changes in trace amines, in particular PE, have been identified as a possible factor for the onset of attention deficit/hyperactivity disorder (ADHD) [5, 27, 43, 78]. PE has been shown to induce hyperactivity and aggression, two of the cardinal clinical features of ADHD, in experimental animals . Hyperactivity is also a symptom of phenylketonuria, which as discussed above is associated with a markedly elevated PE turnover . Further, amphetamines, which have clinical utility in ADHD, are good ligands at trace amine receptors . Of possible relevance in this aspect is modafanil, which has shown beneficial effects in ADHD patients  and has been reported to enhance the activity of PE at TAAR1 . Conversely, methylphenidate, which is also clinically useful in ADHD, showed poor efficacy at the TAAR1 receptor . In this respect it is worth noting that the enhancement of functioning at TAAR1 seen with modafanil was not a result of a direct interaction with TAAR1 .
More direct evidence has been obtained recently for a role of trace amines in ADHD. Urinary PE levels have been reported to be decreased in ADHD patients in comparison to both controls and patients with autism [103-105]. Evidence for a decrease in PE levels in the brain of ADHD patients has also recently been reported . In addition, decreases in the urine and plasma levels of the PE metabolite phenylacetic acid and the precursors phenylalanine and tyrosine have been reported along with decreases in plasma tyramine . Following treatment with methylphenidate, patients who responded positively showed a normalization of urinary PE, whilst non-responders showed no change from baseline values ."
^ abcdefghijklLindemann L, Hoener MC (May 2005). "A renaissance in trace amines inspired by a novel GPCR family". Trends Pharmacol. Sci.26 (5): 274–281. doi:10.1016/j.tips.2005.03.007. PMID15860375. "In addition to the main metabolic pathway, TAs can also be converted by nonspecific N-methyltransferase (NMT)  and phenylethanolamine N-methyltransferase (PNMT)  to the corresponding secondary amines (e.g. synephrine , N-methylphenylethylamine and N-methyltyramine ), which display similar activities on TAAR1 (TA1) as their primary amine precursors...Both dopamine and 3-methoxytyramine, which do not undergo further N-methylation, are partial agonists of TAAR1 (TA1). ...
The dysregulation of TA levels has been linked to several diseases, which highlights the corresponding members of the TAAR family as potential targets for drug development. In this article, we focus on the relevance of TAs and their receptors to nervous system-related disorders, namely schizophrenia and depression; however, TAs have also been linked to other diseases such as migraine, attention deficit hyperactivity disorder, substance abuse and eating disorders [7,8,36]. Clinical studies report increased β-PEA plasma levels in patients suffering from acute schizophrenia  and elevated urinary excretion of β-PEA in paranoid schizophrenics , which supports a role of TAs in schizophrenia. As a result of these studies, β-PEA has been referred to as the body’s ‘endogenous amphetamine’ "
^ abcdefghijBroadley KJ (March 2010). "The vascular effects of trace amines and amphetamines". Pharmacol. Ther.125 (3): 363–375. doi:10.1016/j.pharmthera.2009.11.005. PMID19948186. "Trace amines are metabolized in the mammalian body via monoamine oxidase (MAO; EC 184.108.40.206) (Berry, 2004) (Fig. 2) ... It deaminates primary and secondary amines that are free in the neuronal cytoplasm but not those bound in storage vesicles of the sympathetic neurone ... Similarly, β-PEA would not be deaminated in the gut as it is a selective substrate for MAO-B which is not found in the gut ...
Brain levels of endogenous trace amines are several hundred-fold below those for the classical neurotransmitters noradrenaline, dopamine and serotonin but their rates of synthesis are equivalent to those of noradrenaline and dopamine and they have a very rapid turnover rate (Berry, 2004). Endogenous extracellular tissue levels of trace amines measured in the brain are in the low nanomolar range. These low concentrations arise because of their very short half-life ..."
^ abEiden LE, Weihe E (January 2011). "VMAT2: a dynamic regulator of brain monoaminergic neuronal function interacting with drugs of abuse". Ann. N. Y. Acad. Sci.1216: 86–98. doi:10.1111/j.1749-6632.2010.05906.x. PMID21272013. "[Trace aminergic] neurons in mammalian CNS would be identiﬁable as neurons expressing VMAT2 for storage, and the biosynthetic enzyme aromatic amino acid decarboxylase (AADC)."
^Offermanns, S; Rosenthal, W, eds. (2008). Encyclopedia of Molecular Pharmacology (2nd ed.). Berlin: Springer. pp. 1219–1222. ISBN3540389164.
^Sotnikova TD, Caron MG, Gainetdinov RR (August 2009). "Trace amine-associated receptors as emerging therapeutic targets". Mol. Pharmacol.76 (2): 229–35. doi:10.1124/mol.109.055970. PMC2713119. PMID19389919. "Although the functional role of trace amines in mammals remains largely enigmatic, it has been noted that trace amine levels can be altered in various human disorders, including schizophrenia, Parkinson's disease, attention deficit hyperactivity disorder (ADHD), Tourette syndrome, and phenylketonuria (Boulton, 1980; Sandler et al., 1980). It was generally held that trace amines affect the monoamine system indirectly via interaction with plasma membrane transporters [such as plasma membrane dopamine transporter (DAT)] and vesicular storage (Premont et al., 2001; Branchek and Blackburn, 2003; Berry, 2004; Sotnikova et al., 2004). ...
Furthermore, DAT-deficient mice provide a model to investigate the inhibitory actions of amphetamines on hyperactivity, the feature of amphetamines believed to be important for their therapeutic action in ADHD (Gainetdinov et al., 1999; Gainetdinov and Caron, 2003). It should be noted also that the best-established agonist of TAAR1, β-PEA, shared the ability of amphetamine to induce inhibition of dopamine-dependent hyperactivity of DAT-KO mice (Gainetdinov et al., 1999; Sotnikova et al., 2004).
Furthermore, if TAAR1 could be proven as a mediator of some of amphetamine's actions in vivo, the development of novel TAAR1-selective agonists and antagonists could provide a new approach for the treatment of amphetamine-related conditions such as addiction and/or disorders in which amphetamine is used therapeutically. In particular, because amphetamine has remained the most effective pharmacological treatment in ADHD for many years, a potential role of TAAR1 in the mechanism of the “paradoxical” effectiveness of amphetamine in this disorder should be explored."
^ abWainscott DB, Little SP, Yin T, Tu Y, Rocco VP, He JX, Nelson DL (January 2007). "Pharmacologic characterization of the cloned human trace amine-associated receptor1 (TAAR1) and evidence for species differences with the rat TAAR1". The Journal of Pharmacology and Experimental Therapeutics320 (1): 475–85. doi:10.1124/jpet.106.112532. PMID17038507.