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Dopaminergic means "related to dopamine" (literally, "working on dopamine"), dopamine being a common neurotransmitter. Dopaminergic substances or actions increase dopamine-related activity in the brain. Dopaminergic brain pathways facilitate dopamine-related activity. For example, certain proteins such as the dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2), and dopamine receptors can be classified as dopaminergic, and neurons that synthesize or contain dopamine and synapses with dopamine receptors in them may also be labeled as dopaminergic. Enzymes that regulate the biosynthesis or metabolism of dopamine such as aromatic L-amino acid decarboxylase or DOPA decarboxylase, monoamine oxidase (MAO), and catechol O-methyl transferase (COMT) may be referred to as dopaminergic as well. Also, any endogenous or exogenous chemical substance that acts to affect dopamine receptors or dopamine release through indirect actions (for example, on neurons that synapse onto neurons that release dopamine or express dopamine receptors) can also be said to have dopaminergic effects, two prominent examples being opioids, which enhance dopamine release indirectly in the reward pathways, and some substituted amphetamines, which enhance dopamine release directly by binding to and inhibiting VMAT2.
(–)-2-β-Carbomethoxy-3-β-(4-fluorophenyl)tropane is a stimulant drug used in scientific research. CFT is a phenyltropane based dopamine reuptake inhibitor and is structurally derived from cocaine. It is around 3-10x more potent than cocaine and lasts around 7 times longer based on animal studies. While the naphthalenedisulfonate salt is the most commonly used form in scientific research due to its high solubility in water, the free base and hydrochloride salts are known compounds and can also be produced. The tartrate is another salt form that is reported.
Vanoxerine is a piperazine derivative which is a potent and selective dopamine reuptake inhibitor (DRI). Vanoxerine binds to the target site on the dopamine transporter (DAT) ~ 50 times more strongly than cocaine, but simultaneously inhibits the release of dopamine. This combined effect only slightly elevates dopamine levels, giving vanoxerine only mild stimulant effects. Vanoxerine has also been observed to be a potent blocker of the IKr (hERG) channel. Vanoxerine also binds with nanomolar affinity to the serotonin transporter.
Troparil is a stimulant drug used in scientific research. Troparil is a phenyltropane-based dopamine reuptake inhibitor (DRI) that is derived from methylecgonidine. Troparil is a few times more potent than cocaine as a dopamine reuptake inhibitor, but is less potent as a serotonin reuptake inhibitor, and has a duration spanning a few times longer, since the phenyl ring is directly connected to the tropane ring through a non-hydrolyzable carbon-carbon bond. The lack of an ester linkage removes the local anesthetic action from the drug, so troparil is a pure stimulant. This change in activity also makes troparil slightly less cardiotoxic than cocaine. The most commonly used form of troparil is the tartrate salt, but the hydrochloride and naphthalenedisulfonate salts are also available, as well as the free base.
(–)-2β-Carboisopropoxy-3β-(4-iodophenyl)tropane is a stimulant drug used in scientific research, which was developed in the early 1990s. RTI-121 is a phenyltropane based, highly selective dopamine reuptake inhibitor and is derived from methylecgonidine. RTI-121 is a potent and long-lasting stimulant, producing stimulant effects for more than 10 hours after a single dose in mice which would limit its potential uses in humans, as it might have significant abuse potential if used outside a medical setting. However RTI-121 occupies the dopamine transporter more slowly than cocaine, and so might have lower abuse potential than cocaine itself.
2β-Propanoyl-3β-(2-naphthyl)-tropane or WF-23 is a cocaine analogue. It is several hundred times more potent than cocaine at being a serotonin-norepinephrine-dopamine reuptake inhibitor.
Dimethocaine, also known as DMC or larocaine, is a compound with a stimulatory effect. This effect resembles that of cocaine, although dimethocaine appears to be less potent. Just like cocaine, dimethocaine is addictive due to its stimulation of the reward pathway in the brain. However, dimethocaine is a legal cocaine replacement in some countries and is even listed by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) under the category “synthetic cocaine derivatives”. The structure of dimethocaine, being a 4-aminobenzoic acid ester, resembles that of procaine. It is found as a white powder at room temperature.
Difluoropine (O-620) is a stimulant drug synthesised from tropinone, which acts as a potent and selective dopamine reuptake inhibitor. Difluoropine is unique among the tropane-derived dopamine reuptake inhibitors in that the active stereoisomer is the (S) enantiomer rather than the (R) enantiomer, the opposite way round compared to natural cocaine. It is structurally related to benztropine and has similar anticholinergic and antihistamine effects in addition to its dopamine reuptake inhibitory action.
RTI(-4229)-336, is a phenyltropane derivative which acts as a potent and selective dopamine reuptake inhibitor and stimulant drug. It binds to the dopamine transporter with around 20x the affinity of cocaine, however it produces relatively mild stimulant effects, with a slow onset and long duration of action. These characteristics make it a potential candidate for treatment of cocaine addiction, as a possible substitute drug analogous to how methadone is used for treating heroin abuse. RTI-336 fully substitutes for cocaine in addicted monkeys and supports self-administration, and significantly reduces rates of cocaine use, especially when combined with SSRIs, and research is ongoing to determine whether it could be a viable substitute drug in human cocaine addicts.
Meprylcaine is a local anesthetic with stimulant properties that is structurally related to dimethocaine.
RTI(-4229)-112 is a synthetic stimulant drug from the phenyltropane family. In contrast to RTI-113, which is DAT selective, RTI-112 is a nonselective triple reuptake inhibitor.
(–)-2β-Carbomethoxy-3β-(4'-chlorophenyl)tropane (RTI-4229-31) is a synthetic analog of cocaine that acts as a stimulant. Semi-synthesis of this compound is dependent upon the availability of cocaine starting material. According to the article, RTI-31 is 64 x the strength of cocaine in terms of its potency to elicit self-administration in monkeys. WIN 35428 was 6 x weaker than RTI-31, whereas RTI-51 was 2.6 x weaker than RTI-31.
(–)-2β-Carbomethoxy-3β-(4-bromophenyl)tropane is a semi-synthetic alkaloid in the phenyltropane group of psychostimulant compounds. First publicized in the 1990s, it has not been used enough to have gained a fully established profile. RTI-51 can be expected to have properties lying somewhere in between RTI-31 and RTI-55. Importantly it has a ratio of monoamine reuptake inhibition of D > S > N which is an unusual balance of effects not produced by other commonly used compounds. It has been used in its 76Br radiolabelled form to map the distribution of dopamine transporters in the brain.
Salicylmethylecgonine, (2′-Hydroxycocaine) is a tropane derivative drug which is both a synthetic analogue and a possible active metabolite of cocaine. Its potency in vitro is around 10x that of cocaine, although it is only around three times more potent than cocaine when administered to mice Note however that the compound 2′-Acetoxycocaine would act as a prodrug to Salicylmethylecgonine in humans, and has a more efficient partition coefficient which would act as a delivery system and would circumvent this reason for a drop in potency. Salicylmethylecgonine also shows increased behavioral stimulation compared to cocaine similar to the phenyltropanes. The hydroxy branch renders the molecule a QSAR of a 10-fold increase over cocaine in its binding potency for the dopamine transporter & a 52-fold enhanced affinity for the norepinephrine transporter. It also has a reduced selectivity for the serotonin transporter though only due to its greater increase at NET binding; its SERT affinity being 4-fold increased compared to cocaine. However, in overall binding affinity it displaces ligands better across the board than cocaine in all monoamine categories.
RTI-229, also known as (–)-3β-(4-iodophenyl)tropane-2β-pyrrolidine carboxamide and RTI-4229-229, is a potent and long-lasting stimulant drug which was developed in the 1990s as part of a large group of related analogues from the phenyltropane family. With the combination of two potent dopamine transporter (DAT) binding motifs attached to the tropane ring, the p-iodophenyl group at the 3β-position and a pyrrolidine carboxamide at 2β, RTI-229 has extremely high selectivity for the dopamine transporter and is one of the most DAT-selective compounds in the RTI series.
Metaphit is a research chemical that acts as an acylator of NMDARAn, sigma and DAT binding sites in the CNS. It is the m-isothiocyanate derivative of phencyclidine (PCP) and binds irreversibly to the PCP binding site on the NMDA receptor complex. However, later studies suggest the functionality of metaphit is mediated by sites not involved in PCP-induced passive avoidance deficit, and not related to the NMDA receptor complex. Metaphit was also shown to prevent d-amphetamine induced hyperactivity, while significantly depleting dopamine content in the nucleus accumbens. Metaphit was the first acylating ligand used to study the cocaine receptor. It is a structural isomer of the similar research compound fourphit, as it and metaphit both are isothiocyanate substituted derivatives of an analogous scaffold shared with PCP.
SoRI-20041 is an "antagonist-like" allosteric modulator of amphetamine-induced dopamine release. SoRI-20041 is believed to be the first example of a drug that separately modulates uptake versus release in the dopamine transporter ; it produces the same effects as SoRI-20040 and SoRI-9804 in uptake assays and binding assays, inhibiting the re-uptake of dopamine, but does not modulate d-amphetamine-induced DA release by inhibiting that as well, like 'agonists' of the series do.
1-(3-Chlorophenyl)-4-(2-phenylethyl)piperazine (3C-PEP) is a designer drug of the piperazine class of chemical substances. 3C-PEP is related to meta-cholorophenylpiperazine (mCPP) and phenethylamine that can be thought of as mCPP having a phenylethyl group attached to the nitrogen atom at its 4-position. It was first described in 1994 in a patent disclosing a series of piperazine compounds as sigma receptor ligands. Later, it was discovered to be a highly potent dopamine reuptake inhibitor.
4-Hydroxy-1-methyl-4-(4-methylphenyl)-3-piperidyl 4-methylphenyl ketone is a dopamine transporter reuptake inhibitor used as a lead compound to find a DRI transporter site antagonist.
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