A monoamine neurotoxin, or monoaminergic neurotoxin, is a drug that selectively damages or destroys monoaminergic neurons. [1] Monoaminergic neurons are neurons that signal via stimulation by monoamine neurotransmitters including serotonin, dopamine, and norepinephrine. [1]
Examples of monoamine neurotoxins include the serotonergic neurotoxins para-chloroamphetamine (PCA), methylenedioxymethamphetamine (MDMA), and 5,7-dihydroxytryptamine (5,7-DHT); [2] the dopaminergic neurotoxins oxidopamine (6-hydroxydopamine), MPTP, and methamphetamine; and the noradrenergic neurotoxins oxidopamine and DSP-4. [1]
In the case of serotonergic neurotoxins like MDMA, research suggests that simultaneous induction of serotonin and dopamine release, serotonin depletion, dopamine uptake and metabolism, hyperthermia, oxidative stress and antioxidant depletion, and/or drug metabolites may all be involved in the neurotoxicity. [3] [4] On the other hand, there is evidence that drug metabolites may not be involved. [3] [4]
Dopaminergic neurotoxins can induce a Parkinson's disease-like condition in animals and humans. [1] [5] Serotonergic neurotoxins have been associated with cognitive and memory deficits and psychiatric changes. [6] [7] [8] [9]
Empathogens or entactogens are a class of psychoactive drugs that induce the production of experiences of emotional communion, oneness, relatedness, emotional openness—that is, empathy or sympathy—as particularly observed and reported for experiences with 3,4-methylenedioxymethamphetamine (MDMA). This class of drug is distinguished from the classes of hallucinogen or psychedelic, and amphetamine or stimulants. Major members of this class include MDMA, MDA, MDEA, MDOH, MBDB, 5-APB, 5-MAPB, 6-APB, 6-MAPB, methylone, mephedrone, GHB, αMT, and αET, MDAI among others. Most entactogens are phenethylamines and amphetamines, although several, such as αMT and αET, are tryptamines. When referring to MDMA and its counterparts, the term MDxx is often used. Entactogens are sometimes incorrectly referred to as hallucinogens or stimulants, although many entactogens such as ecstasy exhibit psychedelic or stimulant properties as well.
MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is an organic compound. It is classified as a tetrahydropyridine. It is of interest as a precursor to the monoaminergic neurotoxin MPP+, which causes permanent symptoms of Parkinson's disease by destroying dopaminergic neurons in the substantia nigra of the brain. It has been used to study disease models in various animals.
Oxidopamine, also known as 6-hydroxydopamine (6-OHDA) or 2,4,5-trihydroxyphenethylamine, is a synthetic monoaminergic neurotoxin used by researchers to selectively destroy dopaminergic and noradrenergic neurons in the brain.
5,7-Dihydroxytryptamine (5,7-DHT) is a monoaminergic neurotoxin used in scientific research to decrease concentrations of serotonin in the brain. The mechanism behind this effect is not well understood, but it is speculated to selectively destroy serotonergic neurons, in a manner similar to the dopaminergic neurotoxicity of 6-hydroxydopamine (6-OHDA). What is known is that this compound is in fact not selective in depleting serotonin content, but also depletes norepinephrine. To selectively deplete serotonin stores, it is commonly administered in conjunction with desmethylimipramine (desipramine), which inhibits the norepinephrine transporter.
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.
MDAI, also known as 5,6-methylenedioxy-2-aminoindane, is an entactogen drug of the 2-aminoindane group which is related to MDMA and produces similar subjective effects.
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; monoamine releasing agents 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.
α-Methyldopamine (α-Me-DA), also known as 3,4-dihydroxyamphetamine or as catecholamphetamine, is a research chemical of the catecholamine and amphetamine families. It is a monoamine releasing agent and a metabolite of MDMA and MDA. The bis-glutathionyl metabolite of α-methyldopamine is slightly neurotoxic when directly injected into the brain's ventricles.
UWA-101 is a phenethylamine derivative researched as a potential treatment for Parkinson's disease. Its chemical structure is very similar to that of the illegal drug MDMA, the only difference being the replacement of the α-methyl group with an α-cyclopropyl group. MDMA has been found in animal studies and reported in unauthorised human self-experiments to be effective in the short-term relief of side-effects of Parkinson's disease therapy, most notably levodopa-induced dyskinesia. However the illegal status of MDMA and concerns about its potential for recreational use, neurotoxicity and potentially dangerous side effects mean that it is unlikely to be investigated for medical use in this application, and so alternative analogues were investigated.
5-MAPB, also known as 5-(N-methyl-2-aminopropyl)benzofuran, is an entactogen and designer drug of the amphetamine family that is similar to MDMA in its structure and effects.
2,4,5-Trihydroxymethamphetamine is a neurotoxin and a metabolite of MDMA. It has structural similarity to the dopamine neurotoxin 6-hydroxydopamine, and produces lasting serotonin deficits when administered centrally.
Animal models of Parkinson's disease are essential in the research field and widely used to study Parkinson's disease. Parkinson's disease is a neurodegenerative disorder, characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). The loss of the dopamine neurons in the brain, results in motor dysfunction, ultimately causing the four cardinal symptoms of PD: tremor, rigidity, postural instability, and bradykinesia. It is the second most prevalent neurodegenerative disease, following Alzheimer's disease. It is estimated that nearly one million people could be living with PD in the United States.
5,6-Dihydroxytryptamine (5,6-DHT) is a monoaminergic neurotoxin and tryptamine derivative related to serotonin (5-hydroxytryptamine) and 5,7-dihydroxytryptamine (5,7-DHT). It is a relatively selective serotonergic neurotoxin, but also acts as a dopaminergic and noradrenergic neurotoxin at higher doses. In addition, it produces widespread generalized toxicity at higher doses. Its selective serotonergic neurotoxicity is due to its high affinity for the serotonin transporter (SERT). Because of its SERT affinity, 5,6-DHT has activity as a serotonin reuptake inhibitor.
ODMA is a bioisosteric analogue of 3,4-methylenedioxy-N-methylamphetamine (MDMA) which was developed in an attempt to create an improved MDMA alternative for potential clinical use. It is the analogue of MDMA in which the 1,3-benzodioxole ring has been replaced with a 2,1,3-benzoxadiazole ring. TDMA and SeDMA are closely related analogues. ODMA, TDMA, and SeDMA are releasing agents of serotonin, norepinephrine, and dopamine similarly to MDMA. However, they are less potent and efficacious in activating the serotonin 5-HT2A, 5-HT2B, and 5-HT2C receptors than MDMA and show differing and potentially improved metabolic and pharmacokinetic properties in comparison. ODMA, TDMA, and SeDMA were first described in the scientific literature in June 2024.
TDMA is a bioisosteric analogue of 3,4-methylenedioxy-N-methylamphetamine (MDMA) which was developed in an attempt to create an improved MDMA alternative for potential clinical use. It is the analogue of MDMA in which the 1,3-benzodioxole ring has been replaced with a 2,1,3-benzothiadiazole ring. ODMA and SeDMA are closely related analogues. ODMA, TDMA, and SeDMA are releasing agents of serotonin, norepinephrine, and dopamine similarly to MDMA. However, they are less potent and efficacious in activating the serotonin 5-HT2A, 5-HT2B, and 5-HT2C receptors than MDMA and show differing and potentially improved metabolic and pharmacokinetic properties in comparison. ODMA, TDMA, and SeDMA were first described in the scientific literature in June 2024.
SeDMA is a bioisosteric analogue of 3,4-methylenedioxy-N-methylamphetamine (MDMA) which was developed in an attempt to create an improved MDMA alternative for potential clinical use. It is the analogue of MDMA in which the 1,3-benzodioxole ring has been replaced with a 2,1,3-benzoselenadiazole ring. ODMA and TDMA are closely related analogues. ODMA, TDMA, and SeDMA are releasing agents of serotonin, norepinephrine, and dopamine similarly to MDMA. However, they are less potent and efficacious in activating the serotonin 5-HT2A, 5-HT2B, and 5-HT2C receptors than MDMA and show differing and potentially improved metabolic and pharmacokinetic properties in comparison. ODMA, TDMA, and SeDMA were first described in the scientific literature in June 2024.
3,4-Dihydroxymethamphetamine, or 3,4-dihydroxy-N-methylamphetamine, also known as α-methylepinine or α,N-dimethyldopamine, is the major metabolite of 3,4-methylenedioxy-N-methylamphetamine (MDMA). It is formed from MDMA by O-demethylation via cytochrome P450 enzymes including CYP2D6 as well as CYP1A2 and CYP3A4. Like MDMA, HHMA is a monoamine releasing agent.
2′-NH2-MPTP, also known as 2′-amino-MPTP, is a monoaminergic neurotoxin that was derived from MPTP and is used in scientific research to lesion brain monoaminergic systems in animals. Whereas MPTP is a selective dopaminergic neurotoxin, 2′-NH2-MPTP is a specific serotonergic and noradrenergic neurotoxin that does not affect dopaminergic neurons. 2′-NH2-MPTP is transported by the serotonin transporter (SERT) into serotonergic neurons and by the norepinephrine transporter (NET) into noradrenergic neurons, and its serotonergic and noradrenergic neurotoxicity is dependent on this transport by the SERT and NET, respectively. 2′-NH2-MPTP was first described in the scientific literature by 1993.
The Borax combo, also known by the informal brand names Blue Bliss and Pink Star, is a combination recreational and designer drug described as an MDMA-like entactogen.
While a single injection of MDMA into the brain (intracerebroventricularly) had no effect on TPH activity, slow infusion of 1 mg/kg MDMA into the brain over 1 hr produced enough oxidative stress to acutely reduce TPH activity (Schmidt and Taylor 1988). The acute decrease in TPH activity is an early effect of MDMA and can be measured at post 15 min (Stone et al. 1989b). TPH inactivation can also be produced by non-neurotoxic MDMA doses (Schmidt and Taylor 1988; Stone et al. 1989a; Stone et al. 1989b). It therefore appears that MDMA rapidly induces oxidative stress but only produces neurotoxicity when endogenous free radical scavenging systems are overwhelmed.
5-MAPB has been marketed as a less neurotoxic analogue of MDMA, but no studies have addressed whether 5-MAPB can cause the long lasting serotonergic changes seen with high or repeated MDMA dosing. [...] Neurochemical analyses indicated a statistically significant reduction in 5‑HT and 5-HIAA in all brain regions assessed 24 hours and two weeks after 6 mg/kg 5‑MAPB, with no statistically significant differences in monoamine levels between 1.2 mg/kg and saline-treated rats. There were also non-significant trends for reductions in striatal dopamine at both time intervals after 6 mg/kg 5-MAPB. These results show that 5-MAPB can dose-dependently produce persistent changes in 5-HT and 5-HIAA that appear analogous to those produced by MDMA.
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ignored (help)Ironically, in the 1960s, MPP+ itself had been tested as an herbicide under the commercial name of cyperquat (Di Monte, 2001).
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