PCP site 2 is a binding site that was identified as a high-affinity target for phencyclidine (PCP), an anesthetic and dissociative hallucinogen that acts primarily as an NMDA receptor antagonist. [1] The site is distinct from the PCP binding site on the NMDA receptor (otherwise known as PCP site 1) and the common/main sites on the monoamine transporters (SERT , DAT , NET ). [1] It is associated with monoamine reuptake inhibition, and it has been suggested that the site may be an allosteric/regulatory site of the monoamine transporters. [1]
RTI-4793-14 (HBMP), a ligand with high affinity for the PCP site 2 and high selectivity for this site over the PCP site 1, has been developed. [2] [3] Similarly to PCP, RTI-4793-1 inhibits monoamine reuptake with moderate potency, but unlike PCP, has very low potency as an NMDA receptor antagonist. [2] It shows a profile of a serotonin–norepinephrine–dopamine reuptake inhibitor (SNDRI). [2] Although this was inferred to be related to binding to the PCP site 2, subsequent research found that RTI-4793-14 also has considerable affinity for the DAT; it does not appear to have been characterized at the SERT or NET, but may bind to them similarly, and these interactions could potentially explain its monoamine reuptake inhibition as an alternative to the PCP site 2. [3]
Compound | RTI-4793-14 | Phencyclidine | (+)-MK801 | Indatraline |
---|---|---|---|---|
PCP site 2 | 37.9 | 92.4 | >10000 | 2529 |
PCP site 1 (NMDAR) | >36000 | 117 | 4.58 | >20000 |
[3H]5-HT uptake | 1024 | 1424 | >4700 | 4.49 |
[3H]DA uptake | 547 | 347 | >10000 | 3.23 |
[3H]CFT binding | 850 | 1547 | >15000 | 4.32 |
[3H]Nisoxetine binding | 609 | 16628 | 6576 | 2.27 |
NMDA-induced current | 768 | 2 | 0.020 | 95 |
All values are IC50 (nM), except NMDA-induced current, which is IC50 (μM). |
Compound | PCP site 1 (Ki, nM) | PCP site 2 (Ki, nM) | Site 1 / Site 2 |
---|---|---|---|
(+)-MK-801 | 8.9 | 11367 | 0.00078 |
Tenocyclidine | 19.8 | 197 | 0.10 |
Phencyclidine | 43.8 | 154 | 0.28 |
Dexoxadrol | 92 | 1234 | 0.075 |
Tiletamine | 93 | 17050 | 0.0055 |
Ketamine | 831 | 59388 | 0.014 |
Vanoxerine | 30925 | 6841 | 4.5 |
BTCP | 46436 | 2102 | 22.1 |
Benztropine | 78179 | 2338 | 33.4 |
Bupropion | 101239 | 37519 | 2.7 |
Fluoxetine | 106402 | 1677 | 63.4 |
(–)-Cocaine | 26739 | 423055 | 0.063 |
Compound | PCP site 1 (Ki, nM) | PCP site 2 (Ki, nM) | Site 1 / Site 2 |
---|---|---|---|
Pargyline | >1000000 | 3643 | >274 |
D-Amphetamine | 80501 | 959 | 41.1 |
Clomipramine | 63437 | 4684 | 13.5 |
(–)-Cocaine | 282362 | 6014 | 46.9 |
(+)-Cocaine | >1000000 | 6383 | >157 |
Fluoxetine | 264590 | 929 | 285 |
Mazindol | 218993 | 919 | 238 |
Vanoxerine | 102118 | 3167 | 32 |
Benztropine | 156890 | 183 | 857 |
Xylamine | >1000000 | 679 | >1473 |
Desipramine | 11954 | 2137 | 5.6 |
Nomifensine | 139456 | 2604 | 54 |
Bupropion | >1000000 | 704 | >1420 |
BTCP | >1000000 | 1083 | >923 |
Ketamine | 813 | 4702 | 0.17 |
Tiletamine | 79.3 | 1394 | 0.057 |
JMIII41C | 70 | 9298 | 0.0075 |
JMII79B | 12.7 | 18557 | 0.00068 |
PCA | 1262 | 1327 | 1.05 |
PPA | 6463 | 3200 | 2.0 |
Phencyclidine or phenylcyclohexyl piperidine (PCP), also known in its use as a street drug as angel dust among other names, is a dissociative anesthetic mainly used recreationally for its significant mind-altering effects. PCP may cause hallucinations, distorted perceptions of sounds, and violent behavior. As a recreational drug, it is typically smoked, but may be taken by mouth, snorted, or injected. It may also be mixed with cannabis or tobacco.
Monoamine transporters (MATs) are proteins that function as integral plasma-membrane transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are serotonin transporters (SERTs), dopamine transporters (DATs), and norepinephrine transporters (NETs) and are responsible for the reuptake of their associated amine neurotransmitters. MATs are located just outside the synaptic cleft (peri-synaptically), transporting monoamine transmitter overflow from the synaptic cleft back to the cytoplasm of the pre-synaptic neuron. MAT regulation generally occurs through protein phosphorylation and post-translational modification. Due to their significance in neuronal signaling, MATs are commonly associated with drugs used to treat mental disorders as well as recreational drugs. Compounds targeting MATs range from medications such as the wide variety of tricyclic antidepressants, selective serotonin reuptake inhibitors such as fluoxetine (Prozac) to stimulant medications such as methylphenidate (Ritalin) and amphetamine in its many forms and derivatives methamphetamine (Desoxyn) and lisdexamfetamine (Vyvanse). Furthermore, drugs such as MDMA and natural alkaloids such as cocaine exert their effects in part by their interaction with MATs, by blocking the transporters from mopping up dopamine, serotonin, and other neurotransmitters from the synapse.
A dopamine reuptake inhibitor (DRI) is a class of drug which acts as a reuptake inhibitor of the monoamine neurotransmitter dopamine by blocking the action of the dopamine transporter (DAT). Reuptake inhibition is achieved when extracellular dopamine not absorbed by the postsynaptic neuron is blocked from re-entering the presynaptic neuron. This results in increased extracellular concentrations of dopamine and increase in dopaminergic neurotransmission.
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Nisoxetine, originally synthesized in the Lilly research laboratories during the early 1970s, is a potent and selective inhibitor for the reuptake of norepinephrine (noradrenaline) into synapses. It currently has no clinical applications in humans, although it was originally researched as an antidepressant. Nisoxetine is now widely used in scientific research as a standard selective norepinephrine reuptake inhibitor. It has been used to research obesity and energy balance, and exerts some local analgesia effects.
Reuptake inhibitors (RIs) are a type of reuptake modulators. It is a drug that inhibits the plasmalemmal transporter-mediated reuptake of a neurotransmitter from the synapse into the pre-synaptic neuron. This leads to an increase in extracellular concentrations of the neurotransmitter and an increase in neurotransmission. Various drugs exert their psychological and physiological effects through reuptake inhibition, including many antidepressants and psychostimulants.
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A monoamine releasing agent (MRA), or simply monoamine releaser, is a drug that induces the release of a monoamine neurotransmitter from the presynaptic neuron into the synapse, leading to an increase in the extracellular concentrations of the neurotransmitter. Many drugs induce their effects in the body and/or brain via the release of monoamine neurotransmitters, e.g., trace amines, many substituted amphetamines, and related compounds.
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