Neurotoxin refers to types of chemicals that damage, destroy or the functioning of central or peripheral nervous system.

These chemicals actions in various different ways as listed below :

• damage neurons, axons, and/or glia resulting in loss of specific nuclei and/or axonal tracts or demyelination.
• Blocking various Ion channels involved in neuron activity (e.g, inhibitors for Na, K, Cl, Ca)
• Inhibiting the release of neurotransmitter vesicles
• Inhibiting the recepters of neurotransmitters
• interfering with mitochondrial function
• increasing oxidative stress
• deregulating protein turnover
• and other mechanisms

I am personally interested in neurotoxins mainly for the personal reasons.

• I am interested in all kinds of venous animals(e.g, snakes, scorpions, puffer fish etc) and in how those venome works
• From my experience with working in various engineering field, I noticed that I learn more from problems and troubleshooting process than well-functioning cases.  Neurotoxin is chemicals that is creating problems. By studying on how those chemical works, I think I can learn and understand more clearly about various normal functions happening in our nervous system.

List of Neuro toxins

Naturally existing Atoms/Molecues

Arsenic

Arsenic (As)  occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Due to its toxicity, it often contains in various insecticides and pesticides

It functions as a neurotoxing as follows :

• brain inflammation, brain dysfunction
• increased risk for Alzheimers disease
• altere blood-glucose and HPA pathway functioning

Chromium

Chromium (Cr) can be both benificial and toxic depending on its chemical status. Cr(III) is necessary for body but Cr(VI) is toxic in following way

• DNA damage
• affect lung and brain function
• raise levels of oxidative stress and inflammation

Lead

Lead used to be quite widely used decades ago, but highly restricted recently. It would lead to followings :

• lowered IQ
• lowered attention span
• impared cognitive functioning
• various other neurodegenerative diseases

Cadmium

Cadmium can reaches in various different ways through soil, water and air. It can cause toxicity in almost all organs. It would cause neurotoxicity as in following ways :

• lead to neurodegenerative disorders such as Parkinsons, Alzheimers, and Huntingtons diseases
• cause general behavioral changes and memory loss

Mercury

Mercury can impare brain functions in many different ways as follows :

• impairing vision, hearing, olfactory senses, motor movement, and cognition
• leading to many different types of neurodegenerative diseases

Animal/Bacterium Toxins

Botulinum

It is produced by the bacterium Clostridium botulinum and is one of the most poisonous substances known. It is a potent neurotoxin that can cause botulism which is a serious and potentially life-threatening illness.

It blocks the release of acetylcholine

Fasciculins

This attacks cholinergic neurson (the nuerons using Acetylcholine as a transmitter) by destroying acetylcholinesterase (AChE). As a result, Achetylecholine is not broken down and stay attached to the receptor and remain in synatic cleft causing sever and long-lasting muscle contraction.

dendrotoxins

This inhibits neurotransmission of the signal by blocking various ion channels on cell membrane. As a result, it cause paralysis.

alpha-neurotoxins

This also attacks cholinergic neuron by mimicking Achetylcholine and sticking to Acetylcholine recetor preveting the Acetylecholine from attaching to its receptor and performing as neurotransmitter. As a result, it would lead to a feeling of numbness and paralysis.

Tetrodotoxin

It blocks the generation of action potention by blocking voltage-gated sodium channel in nerve cells.

Tetraethylammonium

It's molecular size is comparable to the size of hydrated potassium. It appears to inhibit K flow through channel by competing again K when it present in high concenturation.

Chlorotoxin

It is a peptide consisting of 36 amino acids, with 8 cysteines forming 4 disulfide bonds. It act as a ligand closing Cloride channels on cell membrane

It is found in the venom of some species of scorpions and is a neurotoxin that can cause symptoms such as muscle weakness and paralysis.

It has ability to selectively target and enter glioma cells which makes it a potential therapeutic agent for the treatment of brain tumors

Conotoxin

These are peptides consisting of 10 to 30 amino acid residues. There several different types and how it affects the nerve cell are different depending on the types as listed below (from wikipedia).

• α-conotoxin inhibits nicotinic acetylcholine receptors at nerves and muscles.
• δ-conotoxin inhibits fast inactivation of voltage-dependent sodium channels.
• κ-conotoxin inhibits potassium channels.
• μ-conotoxin inhibits voltage-dependent sodium channels in muscles.
• ω-conotoxin inhibits N-type voltage-dependent calcium channels.

Latrotoxins

These are a group of toxins produced by various species of spiders, including the black widow spider. These toxins work by causing the release of large amounts of the neurotransmitter acetylcholine from nerve cells, leading to overstimulation of the muscles and other organs.

They bind to receptors on  presynaptic membranes and  cause the neurons to release acetylcholine, which in turn activates receptors on muscle cells called postsynaptic membranes. This leads to overstimulation of the muscles and can cause symptoms such as muscle spasms, cramping, and rigidity

Veratridine

It is found in the venom of some species of snakes and is a neurotoxin that can cause convulsions and death.

Saxitoxin

It is found in some species of algae and shellfish and is a potent neurotoxin that can cause paralysis and death.

Tetanus toxin

It is produced by the bacterium Clostridium tetani and is a neurotoxin that can cause symptoms such as muscle spasms and death

Melittin

It is found in bee venom and is a neurotoxin that can cause symptoms such as pain, swelling, and difficulty breathing.

Apamin

It is found in bee venom and is a neurotoxin that can cause symptoms such as muscle spasms and respiratory failure.

Ciguatoxin

It is found in some species of fish such as barracuda, grouper, red snapper, and sea bass. It is a neurotoxin that can cause symptoms such as muscle weakness, numbness, and difficulty breathing. It is produced by certain species of algae and is accumulated by these fish through their diet.

It affects the function of sodium channels and cause changes in the electrical activity of nerve cells, leading to abnormal signaling and further disruption of nerve function

Palytoxin

It is found in some species of coral and shellfish, is a neurotoxin that can cause symptoms such as nausea, vomiting, and muscle weakness.

Plant Toxins

Aconitine

It is found in the plant Aconitum and is a potent neurotoxin that can cause symptoms such as tremors, seizures, and death.

Strychnine

It is found in the plant Strychnos nux-vomica and is a neurotoxin that can cause symptoms such as convulsions, respiratory failure, and death.

Coniine

If it's a toxic alkaloid found in the poison hemlock plant (Conium maculatum) and is a neurotoxin that can cause symptoms such as tremors, paralysis, and death.

It blocks the action of an enzyme called acetylcholinesterase, which is responsible for breaking down acetylcholine, a neurotransmitter that plays a vital role in muscle contraction and various other functions in the body. When acetylcholine levels build up in the body due to coniine's interference, it can lead to symptoms such as muscle weakness, tremors, and eventually paralysis.

Reference

• Neurotoxin - Wikipedia
• Snake Venome - Wikipedia
• Neurotoxins: Cause, Effect, and Prevention - Temecula Center
• The Chemistry of Spider Venom - Ci (2015)
• Spider Venom: Components, Modes of Action, and Novel Strategies in Transcriptomic and Proteomic Analyses - NIH/National Library of Medicine
• 10 Snakes with Neurotoxic Venom - AZ Animals (2022)

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