Trace Amine-Associated Receptor (TAAR) neurons express a family of G protein-coupled receptors that detect trace amines—endogenous compounds structurally related to classical monoamine neurotransmitters but present at much lower concentrations. TAAR1, the most extensively studied member, modulates dopaminergic, serotonergic, and glutamatergic neurotransmission and has emerged as a therapeutic target for psychiatric and neurodegenerative disorders.[1]
The TAAR family comprises 9 functional receptors in humans (TAAR1-9), with TAAR1 being the only non-olfactory member expressed in the brain:[2]
| Receptor | Primary Ligands | Expression | Function |
|---|---|---|---|
| TAAR1 | β-phenylethylamine, dopamine, amphetamine | VTA, SNpc, DRN, raphé | Monoamine modulation |
| TAAR2 | Unknown | Olfactory epithelium | Olfaction |
| TAAR5 | Trimethylamine | Olfactory epithelium | Olfaction |
| TAAR6-9 | Various amines | Olfactory epithelium | Olfaction |
TAAR1 is a class A GPCR with characteristic features:[3]
| Compound | Source | Relative Potency | Notes |
|---|---|---|---|
| β-Phenylethylamine (β-PEA) | Decarboxylation of phenylalanine | High | "Love molecule," trace amine |
| Tryptamine | Tryptophan metabolism | High | Serotonin precursor |
| Tyramine | Tyrosine metabolism | Moderate | In foods, MAOI concern |
| Dopamine | Catecholamine synthesis | Low (agonist) | Also at DA receptors |
| Thyronamine | Thyroid hormone metabolite | High | Metabolic effects |
TAAR1 expression in the brain is strategically positioned to modulate monoamine systems:[4]
TAAR1 activation produces complex effects on monoamine transporters:[5]
DAT (Dopamine Transporter):
SERT (Serotonin Transporter):
NET (Norepinephrine Transporter):
TAAR1 functions as an inhibitory autoreceptor:[6]
TAAR1 in Parkinson's disease has complex implications:[7]
Neuroprotective Potential:
Motor Symptom Modulation:
Non-Motor Symptoms:
Emerging evidence suggests TAAR1 involvement in Alzheimer's disease:[8]
TAAR1 agonists show promise as antipsychotics:[9]
| Compound | Status | Indication | Selectivity |
|---|---|---|---|
| Ulotaront (SEP-363856) | Phase III | Schizophrenia | TAAR1 agonist |
| Ralmitaront (RO6889450) | Phase II | Schizophrenia | TAAR1 partial agonist |
| RO5166017 | Preclinical | Depression/PD | Full agonist |
| Marker | Type | Function |
|---|---|---|
| TAAR1 | GPCR | Primary receptor |
| TH | Enzyme | Dopamine synthesis (co-expression) |
| DAT | Transporter | Dopamine reuptake (modulated) |
| VMAT2 | Transporter | Vesicular monoamine storage |
| c-Fos | Transcription factor | Activity marker |
TAAR1 mediates effects of several drugs:[10]
Gainetdinov RR, Hoener MC, Berry MD. Trace amines and their receptors. Pharmacol Rev. 2018. ↩︎
Grandy DK. Trace amine-associated receptor family: a world of possibilities. J Pharmacol Exp Ther. 2007. ↩︎
Bunzow JR, Sonders MS, Arttamangkul S, et al. Amphetamine, 3,4-methylenedioxymethamphetamine, lysergic acid diethylamide, and metabolites of the catecholamine neurotransmitters are agonists of a rat trace amine receptor. Mol Pharmacol. 2001. ↩︎
Lindemann L, Ebeling M, Kratochwil NA, et al. Trace amine-associated receptors form structurally and functionally distinct subfamilies of novel G protein-coupled receptors. Genomics. 2005. ↩︎
Xie Z, Miller GM. β-Phenylethylamine alters monoamine transporter function via trace amine-associated receptor 1. J Pharmacol Exp Ther. 2009. ↩︎
Wolinsky TD, Swanson CJ, Smith KE, et al. The trace amine 1 receptor is an inhibitory modulator of dopaminergic transmission. J Pharmacol Exp Ther. 2007. ↩︎
Schwartz MD, Canales JJ, Zucchi R, et al. Trace amine-associated receptor 1: a multimodal therapeutic target for Parkinson's disease. Pharmacol Res. 2018. ↩︎
Cisneros IE, Ghorai PK, Bhattacharya D, et al. Trace amines and the trace amine-associated receptor 1: pharmacology and perspectives in Alzheimer's disease. Neuropharmacology. 2024. ↩︎
Koblan KS, Kent J, Hopkins SC, et al. A non-D2-receptor-binding drug for the treatment of schizophrenia. N Engl J Med. 2020. ↩︎
Krasnova IN, Cadet JL. Amphetamine-type stimulants and TAAR1 signaling: implications for neurotoxicity and therapeutic potential. J Neurochem. 2023. ↩︎