Neuronal functions and emerging pharmacology of TAAR1

Trace amine-associated receptor 1 (TAAR1) is a member of TAAR family of G protein-coupled receptors (GPCRs). The members of this class of receptors discovered in 2001 have been found in some tissues ranging from the central nervous system to the olfactory epithelium and in some peripheral organs. The best studied receptor, TAAR1, is activated by a class of compounds named trace amines (TAs) that include compounds such as β-phenylethylamine (PEA), p-tyramine, octopamine, and tryptamine normally present at low levels in the mammalian brain. Although TA levels have been associated with many neuropsychiatric disorders, only the discovery of TAAR1 validated their physiological role. TAAR1 can modulate monoamine neurotransmission and, in particular, dopamine systems. Several studies have demonstrated that TAAR1 knockout (TAAR1-KO) mice display a supersensitive dopaminergic system, while activation of TAAR1 can reduce dopaminergic hyperactivity obtained either with pharmacological tools or present in genetic mouse model. For these reasons, TAAR1 has been proposed as a novel therapeutic target for neuropsychiatric disorders such as schizophrenia, bipolar disorder, and addiction. Moreover, several peripheral functions of TAAR1 have been described recently indicating intriguing novel TAAR1 roles in system physiology. Here we will review brain and peripheral functions mediated by TAAR1 and other TAARs.