The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. Substantia nigra is Latin for "black substance", reflecting the fact that parts of the substantia nigra appear darker than neighboring areas due to high levels of neuromelanin in dopaminergic neurons. Parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta.
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.
Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specifically, a neurotoxin or neurotoxicant– alters the normal activity of the nervous system in such a way as to cause permanent or reversible damage to nervous tissue. This can eventually disrupt or even kill neurons, which are cells that transmit and process signals in the brain and other parts of the nervous system. Neurotoxicity can result from organ transplants, radiation treatment, certain drug therapies, recreational drug use, exposure to heavy metals, bites from certain species of venomous snakes, pesticides, certain industrial cleaning solvents, fuels and certain naturally occurring substances. Symptoms may appear immediately after exposure or be delayed. They may include limb weakness or numbness, loss of memory, vision, and/or intellect, uncontrollable obsessive and/or compulsive behaviors, delusions, headache, cognitive and behavioral problems and sexual dysfunction. Chronic mold exposure in homes can lead to neurotoxicity which may not appear for months to years of exposure. All symptoms listed above are consistent with mold mycotoxin accumulation.
3,4-Methylenedioxyamphetamine is an empathogen-entactogen, psychostimulant, and psychedelic drug of the amphetamine family that is encountered mainly as a recreational drug. In its pharmacology, MDA is a serotonin–norepinephrine–dopamine releasing agent (SNDRA). In most countries, the drug is a controlled substance and its possession and sale are illegal.
α-Ethyltryptamine, also known as etryptamine, is an entactogen and stimulant drug of the tryptamine family. It was originally developed and marketed as an antidepressant under the brand name Monase by Upjohn in the 1960s before being withdrawn due to toxicity.
Dopaminergic means "related to dopamine", a common neurotransmitter. Dopaminergic substances or actions increase dopamine-related activity in the brain.
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 substituted amphetamine and monoamine releaser similar to MDMA, but with substantially higher activity as a monoaminergic neurotoxin, thought to be due to the unrestrained release of both serotonin and dopamine by a metabolite. It is used as a neurotoxin by neurobiologists to selectively kill serotonergic neurons for research purposes, in the same way that 6-hydroxydopamine is used to kill dopaminergic neurons.
MDAI (5,6-methylenedioxy-2-aminoindane) is a drug developed in the 1990s by a team led by David E. Nichols at Purdue University. It acts as a non-neurotoxic and highly selective serotonin releasing agent (SSRA) in vitro and produces entactogen effects in humans.
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.
3,4-Dihydroxyphenylacetaldehyde (DOPAL), also known as dopamine aldehyde, is a metabolite of the monoamine neurotransmitter dopamine formed by monoamine oxidase (MAO).
Norsalsolinol is a chemical compound that is produced naturally in the body through the metabolism of dopamine. It has been shown to be a selective dopaminergic neurotoxin, and has been suggested as a possible cause of neurodegenerative conditions such as Parkinson's disease and the brain damage associated with alcoholism, although evidence for a causal relationship is unclear.
4-Chlorophenylisobutylamine, also known as 4-chloro-α-ethylphenethylamine, is an entactogen and stimulant drug of the phenethylamine class. It is an analogue of para-chloroamphetamine (PCA) where the alpha position methyl has been replaced with an ethyl group.
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-Chloro-α-methyltryptamine (5-Chloro-αMT), also known as PAL-542, is a tryptamine derivative related to α-methyltryptamine (αMT) and one of only a few known specific serotonin-dopamine releasing agents (SDRAs). It has been investigated in animals as a potential treatment for cocaine dependence. The EC50 values of 5-chloro-αMT in evoking the in vitro release of serotonin (5-HT), dopamine (DA), and norepinephrine (NE) in rat synaptosomes were reported as 16 nM, 54 nM, and 3434 nM, with an NE/DA ratio of 63.6 and a DA/5-HT ratio of 3.38, indicating that it is a highly specific and well-balanced SDRA. However, 5-chloro-αMT has also been found to act as a potent full agonist of the 5-HT2A receptor, with an EC50 value of 6.27 nM and an efficacy of 105%. It is likely to act as a potent agonist of other serotonin receptors as well.
2,4,5-Trihydroxymethamphetamine (THMA) 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.
The catecholaldehyde hypothesis is a scientific theory positing that neurotoxic aldehyde metabolites of the catecholamine neurotransmitters dopamine and norepinephrine are responsible for neurodegenerative diseases involving loss of catecholaminergic neurons, for instance Parkinson's disease. The specific metabolites thought to be involved include 3,4-dihydroxyphenylacetaldehyde (DOPAL) and 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL), which are formed from dopamine and norepinephrine by monoamine oxidase, respectively. These metabolites are subsequently inactivated and detoxified by aldehyde dehydrogenase (ALDH). DOPAL and DOPEGAL are monoaminergic neurotoxins in preclinical models and inhibition of and polymorphisms in ALDH are associated with Parkinson's disease. The catecholaldehyde hypothesis additionally posits that DOPAL oligomerizes with α-synuclein resulting in accumulation of oligomerized α-synuclein and that this contributes to cytotoxicity.
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.
HPP+, also known as haloperidol pyridinium, is a monoaminergic neurotoxin and a metabolite of haloperidol.
