RTI(-''4229'')-112 (2β-carbomethoxy-3β-(3-methyl-4-chlorophenyl)tropane) is a synthetic stimulant drug from the

phenyltropane Phenyltropanes (PTs) were originally developed to reduce cocaine addiction and dependency. In general these compounds act as inhibitors of the plasmalemmal monoamine reuptake transporters. Although RTI holds a strong position in this field, ...

family. In contrast to

RTI-113 RTI(-''4229'')-113 (2β-carbophenoxy-3β-(4-chlorophenyl)tropane) is a stimulant drug which acts as a potent and fully selective dopamine reuptake inhibitor (DRI). It has been suggested as a possible substitute drug for the treatment of cocaine ...

, which is DAT selective, RTI-112 is a nonselective triple reuptake inhibitor. ''

In vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology ...

'' tests show a very similar

serotonin transporter The serotonin transporter (SERT or 5-HTT) also known as the sodium-dependent serotonin transporter and solute carrier family 6 member 4 is a protein that in humans is encoded by the SLC6A4 gene. SERT is a type of monoamine transporter protein tha ...

(SERT)/

dopamine transporter The dopamine transporter (also dopamine active transporter, DAT, SLC6A3) is a membrane-spanning protein that pumps the neurotransmitter dopamine out of the synaptic cleft back into cytosol. In the cytosol, other transporters sequester the dop ...

(DAT)/

norepinephrine transporter The norepinephrine transporter (NET), also known as noradrenaline transporter (NAT), is a protein that in humans is encoded by the solute carrier family 6 member 2 (SLC6A2) gene. NET is a monoamine transporter and is responsible for the sodium- ...

(NET) selectivity to

cocaine Cocaine (from , from , ultimately from Quechua: ''kúka'') is a central nervous system (CNS) stimulant mainly used recreationally for its euphoric effects. It is primarily obtained from the leaves of two Coca species native to South Ameri ...

, although in vivo behaviour is different: "The nonselective monoamine transporter inhibitor RTI-126 and the DAT-selective inhibitors RTI-150 and

RTI-336 RTI(-''4229'')-336, (LS-193,309, (−)-2β-(3-(4-methylphenyl)isoxazol-5-yl)-3β-(4-chlorophenyl)tropane) is a phenyltropane derivative which acts as a potent and selective dopamine reuptake inhibitor and stimulant drug. It binds to the dopamine ...

both had a faster rate of onset (30 min) and a short duration of action (4h). In contrast, the nonselective monoamine transporter inhibitor RTI-112 had a slower rate of onset (30–60 min) and a longer duration of action (10h). The DAT-selective inhibitors

RTI-171 (–)-2β-(3-Methylisoxazol-5-yl)-3β-(p-tolyl)tropane (RTI-''4229''-171) is a phenyltropane derivative which acts as a selective dopamine reuptake inhibitor, with a relatively slow onset of action and short duration of effects found in animal st ...

and RTI-177 also had slower rates of onset (30–120 min), but RTI-171 had a short duration of action (2.5 h) while RTI-177 had a very long duration of action (20 h)." The efficacy of cocaine analogs to elicit self-administration is related to the rate at which they are administered. Slower onset analogs are less likely to function as behavioral stimulants than analogs eliciting a faster rate of onset. Nonselective analogs are less likely to function as "reinforcers" than reuptake inhibitors that have DAT specificity. In order for a

dopamine reuptake inhibitor 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 dop ...

(DRI) such as cocaine to induce euphoria,

PET scan Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, ...

s on primates reveal that the DAT occupancy needs to be >60%. Howell, L.L. and Wilcox, K.M. "The dopamine transporter and cocaine medication development: Drug self-administration in nonhuman primates." ''Journal of Pharmacology and Experimental Therapeutics'', 298: 1-6, 2001. RTI-112 has equipotent in vitro affinity at the SERT, NET and DAT, respectively. RTI-112 was not reliably self-administered, in contrast to the DAT selective reuptake inhibitors that were used in this study. Lindsey, K.P., Wilcox, K.M., Votaw, J.R., Goodman, M.M., Plisson, C., Carroll, F.I., Rice, K.C., Howell, L.L. (2004) "Effects of dopamine transporter inhibitors on cocaine self-administration in rhesus monkeys: relationship to transporter occupancy determined by positron emission tomography neuroimaging." ''Journal of Pharmacology and Experimental Therapeutics'', 309: 959-969 In vivo at the ED50, RTI-112 had no DAT occupancy at all. At the ED50, almost all of the RTI-112 occupied the SERT at this dose. A significantly higher dose was required to get >70% DAT occupancy in the case of RTI-112; however, RTI-112 was still able to suppress cocaine administration at the ED50, suggesting a serotonergic mechanism was responsible for this.

References

{{Phenyltropanes Chlorobenzenes Tropanes RTI compounds Dopamine reuptake inhibitors Stimulants