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Other names | o-PIT; o-Phenyl-iodotyramine; o-Phenyliodotyramine |
Drug class | Trace amine-associated receptor 1 (TAAR1) agonist |
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Chemical and physical data | |
Formula | C14H14INO |
Molar mass | 339.176 g·mol−1 |
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o-Phenyl-3-iodotyramine (o-PIT) is a drug which acts as a selective agonist for the trace amine-associated receptor 1 (TAAR1). [1] It has reasonable selectivity for TAAR1 but relatively low potency, and is rapidly metabolised in vivo , making it less useful for research than newer ligands such as RO5166017. [2] [3] [4] [5] Its EC50 values have been reported to be 35 nM for the mouse TAAR1, [4] [6] 2.4 nM at the rat TAAR1, [6] and 9.5 nM at the human TAAR1. [5]
o-PIT has been found to produce effects in animals including hypothermia, hypolocomotion, antidepressant-like effects, anxiolytic-like effects, anti-obsessional-like effects, and antipsychotic-like effects, and inhibition of prepulse inhibition (PPI). [1] [5] [7] These actions may be partially to fully dependent on TAAR1 agonism depending on the effect in question. [5]
TAAR1 agonism has been implicated in modulating the effects of monoamine releasing agents (MRAs) like amphetamines. [8] The MRA 3,4-methylenedioxymethamphetamine (MDMA) is a potent agonist of the mouse TAAR1, whereas the MRA para-chloroamphetamine (PCA) is not a significant agonist of the human TAAR1 or presumably of the mouse TAAR1. [5] [9] MDMA-induced in-vivo brain serotonin and dopamine release and hyperlocomotion are augmented in TAAR1 knockout mice relative to normal mice, whereas the in-vivo brain serotonin and dopamine release of PCA are not different between normal mice and TAAR1 knockout mice. [5] [10] In the same study, o-PIT blunted the dopamine and serotonin release of PCA in mouse synaptosomes in vitro , an effect that was absent in synaptosomes from TAAR1 knockout mice. [5] [10] These findings led to conclusions that TAAR1 agonism by MDMA auto-inhibits and constrains its own effects in rodents. [10] [5] Although MDMA is a potent TAAR1 agonist in rodents, it is a very weak and non-significant TAAR1 agonist in humans. [9] [11] [12] [13]
3,4-Methyl
Tryptamine is an indolamine metabolite of the essential amino acid tryptophan. The chemical structure is defined by an indole—a fused benzene and pyrrole ring, and a 2-aminoethyl group at the second carbon. The structure of tryptamine is a shared feature of certain aminergic neuromodulators including melatonin, serotonin, bufotenin and psychedelic derivatives such as dimethyltryptamine (DMT), psilocybin, psilocin and others.
3,4-Methylenedioxyamphetamine (MDA), sometimes referred to as sass, is an empathogen-entactogen, stimulant, and psychedelic drug of the amphetamine family that is encountered mainly as a recreational drug. In its pharmacology, MDA is a serotonin–norepinephrine–dopamine releasing agent (SNDRA). In most countries, the drug is a controlled substance and its possession and sale are illegal.
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3-Iodothyronamine (T1AM) is an endogenous thyronamine. It is a high-affinity ligand of the trace amine-associated receptor 1 (TAAR1). T1AM is the most potent endogenous TAAR1 agonist yet discovered. It is also an agonist of the TAAR2 and TAAR5 with similar potency as for the TAAR1 (all in the case of the human proteins). T1AM is not a ligand of the thyroid hormone receptors. However, it is additionally a ligand of various monoamine and other receptors. For instance, it is a muscarinic acetylcholine receptor antagonist.
Trace amine-associated receptor 1 (TAAR1) is a trace amine-associated receptor (TAAR) protein that in humans is encoded by the TAAR1 gene.
para-Chloroamphetamine (PCA), also known as 4-chloroamphetamine (4-CA), is a serotonin–norepinephrine–dopamine releasing agent (SNDRA) and serotonergic neurotoxin of the amphetamine family. It is used in scientific research in the study of the serotonin system, as a serotonin releasing agent (SRA) at lower doses to produce serotonergic effects, and as a serotonergic neurotoxin at higher doses to produce long-lasting depletions of serotonin.
A monoamine releasing agent (MRA), or simply monoamine releaser, is a drug that induces the release of one or more monoamine neurotransmitters from the presynaptic neuron into the synapse, leading to an increase in the extracellular concentrations of the neurotransmitters and hence enhanced signaling by those neurotransmitters. The monoamine neurotransmitters include serotonin, norepinephrine, and dopamine; MRAs can induce the release of one or more of these neurotransmitters.
A serotonin releasing agent (SRA) is a type of drug that induces the release of serotonin into the neuronal synaptic cleft. A selective serotonin releasing agent (SSRA) is an SRA with less significant or no efficacy in producing neurotransmitter efflux at other types of monoamine neurons, including dopamine and norepinephrine neurons.
RO5166017, or RO-5166017, is a drug developed by Hoffmann-La Roche which acts as a potent and selective agonist for the trace amine-associated receptor 1 (TAAR1), with no significant activity at other targets. It is a partial agonist or near-full agonist depending on the species.
EPPTB, also known as RO5212773 or RO-5212773, is a drug developed by Hoffmann-La Roche which acts as a potent and selective antagonist or inverse agonist of the trace amine-associated receptor 1 (TAAR1). The drug was the first selective antagonist developed for the TAAR1. It is a potent agonist of the mouse and rat TAAR1, but is dramatically less potent as an agonist of the human TAAR1. EPPTB has been used in scientific research to demonstrate an important role for TAAR1 in regulation of dopaminergic signaling in the limbic system.
Locomotor activity is a measure of animal behavior which is employed in scientific research.
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RO5256390 or RO-5256390 is a drug developed by Hoffmann-La Roche which acts as an agonist for the trace amine associated receptor 1 (TAAR1). It is a full agonist of the rat, cynomolgus monkey, and human TAAR1, but a partial agonist of the mouse TAAR1.
RTI-7470-44 is a potent and selective antagonist of the human trace amine-associated receptor 1 (TAAR1) which is used in scientific research. It was discovered in 2022 and is the first potent antagonist of the human TAAR1 to be identified, following the potent mouse TAAR1 inverse agonist EPPTB in 2009.
RO5263397, or RO-5263397, is a trace amine-associated receptor 1 (TAAR1) partial or full agonist which is used in scientific research. It is the most well-studied of all of the synthetic TAAR1 ligands. In addition to its use in research, RO5263397 is or was under development for potential clinical use as a medication.
RO5203648 is a trace amine-associated receptor 1 (TAAR1) partial agonist. It is a potent and highly selective partial agonist of both rodent and primate TAAR1. The drug suppresses the effects of psychostimulants like cocaine and methamphetamine. It also produces a variety of other behavioral effects, such as antidepressant-like, antipsychotic-like, and antiaddictive effects. Research with RO5203648 has led to interest in TAAR1 agonists for potential treatment of drug addiction. RO5203648 itself was not developed for potential medical use due to poor expected human pharmacokinetics.
RO5073012 is a selective low-efficacy partial agonist of the trace amine-associated receptor 1 (TAAR1) which has been used in scientific research. TAAR1 partial agonists like RO5073012 can have agonist- or antagonist-like effects at the TAAR1 depending on the context and level of TAAR1 signaling.
RO5166017 exhibits high binding affinity for TAAR1 and high potency to stimulate cAMP production, particularly at rodent TAAR1. Compared with pTyr, RO5166017 exhibited 200- fold higher affinity (Ki = 1.9 vs. 404 nM) and potency to activate cAMP production (EC50 = 3.3 vs. 545 nM) at mouse TAAR1 (17), whereas T1AM and its derivative o-phenyl-3-iodotyramine show EC50 values of 112 and 35 nM, respectively (30).
Di Cara et al. (2011) showed that TAAR1 decreases the amplitude of Methylenedioxymethamphetamine (MDMA) induced dopamine release both in ventral and dorsal striatum. In the same study it was observed that the TAAR1 agonist, o-phenyl-3-iodotyramine (o-PIT) blunted the para-chloroamphetamine (PCA) induced dopamine release in both structures (Di Cara et al., 2011).
[...] it is unclear if TAAR1 plays any role in the effects of MDMA in humans, as MDMA does not activate human TAAR1 in cellular assays like it does mouse and rat TAAR1.84