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] Some research suggests that serotonergic neurotoxicity might represent neuroadaptive mechanisms rather than neuronal damage per se. [5] [6]
Dopaminergic neurotoxins can induce a Parkinson's disease-like condition in animals and humans. [1] [7] Serotonergic neurotoxins have been associated with cognitive and memory deficits and psychiatric changes. [8] [9] [10] [11]
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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