Neurotoxin in the context of "Excitotoxicity"

Cleopatra VII, the last ruler of the Ptolemaic Kingdom of Egypt, died on either 10 or 12 August, 30 BC, in Alexandria, when she was 39 years old. According to popular belief, Cleopatra killed herself by allowing an asp (Egyptian cobra) to bite her, but according to the Roman-era writers Strabo, Plutarch, and Cassius Dio, Cleopatra poisoned herself using either a toxic ointment or by introducing the poison with a sharp implement such as a hairpin. Modern scholars debate the validity of ancient reports involving snakebites as the cause of death and whether she was murdered. Some academics hypothesize that her Roman political rival Augustus (Octavian) forced her to kill herself in a manner of her choosing. The location of Cleopatra's tomb is unknown. It was recorded that Octavian allowed for her and her husband, the Roman politician and general Mark Antony, who stabbed himself with a sword, to be buried together properly.

Cleopatra's death effectively ended the final war of the Roman Republic between the remaining triumvirs Octavian and Antony, in which Cleopatra aligned herself with Antony, father to three of her children. Antony and Cleopatra fled to Egypt following their loss at the 31 BC Battle of Actium in Roman Greece, after which Octavian invaded Egypt and defeated their forces. Committing suicide allowed her to avoid the humiliation of being paraded as a prisoner in a Roman triumph celebrating the military victories of Octavian, who would become Rome's first emperor in 27 BC and be known as Augustus. Octavian, rival heir of Julius Caesar had Cleopatra's son Caesarion (also known as Ptolemy XV) killed in Egypt but spared her children with Antony and brought them to Rome. Cleopatra's death marked the end of the Hellenistic period and Ptolemaic rule of Egypt, as well as the beginning of Roman Egypt, which became a province of the Roman Empire.

Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved venom apparatus, such as fangs or a stinger, in a process called envenomation. Venom is often distinguished from poison, which is a toxin that is passively delivered by being ingested, inhaled, or absorbed through the skin, and toxungen, which is actively transferred to the external surface of another animal via a physical delivery mechanism.

Venom has evolved in terrestrial and marine environments and in a wide variety of animals: both predators and prey, and both vertebrates and invertebrates. Venoms kill through the action of at least four major classes of toxin, namely necrotoxins and cytotoxins, which kill cells; neurotoxins, which affect nervous systems; myotoxins, which damage muscles; and haemotoxins, which disrupt blood clotting. Venomous animals cause tens of thousands of human deaths per year.

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.

The term neurotoxicity implies the involvement of a neurotoxin; however, the term neurotoxic may be used more loosely to describe states that are known to cause physical brain damage, but where no specific neurotoxin has been identified.

Botulinum toxin, botulinum neurotoxin, or botox is a neurotoxic protein produced by the bacterium Clostridium botulinum and related species, and it is the deadliest known substance ever recorded in the chemical literature. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromuscular junction, thus causing flaccid paralysis. The toxin causes the disease botulism. The toxin is also used commercially for medical and cosmetic purposes. Botulinum toxin is an acetylcholine release inhibitor and a neuromuscular blocking agent.

The seven main types of botulinum toxin are named types A to G (A, B, C1, C2, D, E, F and G). New types are occasionally found. Types A and B are capable of causing disease in humans, and are also used commercially and medically. Types C–G are less common; types E and F can cause disease in humans, while the other types cause disease in other animals.

Tetanus toxin (TeNT) is an extremely potent neurotoxin produced by the vegetative cell of Clostridium tetani in anaerobic conditions, causing tetanus. It has no known function for clostridia in the soil environment where they are normally encountered. It is also called spasmogenic toxin, tentoxilysin, tetanospasmin, or tetanus neurotoxin. The LD₅₀ of this toxin has been measured to be approximately 2.5–3 ng/kg, making it second only to the related botulinum toxin (LD₅₀ 2 ng/kg) as the deadliest toxin in the world. However, these tests are conducted solely on mice, which may react to the toxin differently from humans and other animals.

C. tetani also produces the exotoxin tetanolysin, a hemolysin, that causes destruction of tissues.

Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered in these fish, it is found in several other animals (e.g., in blue-ringed octopuses, rough-skinned newts, and moon snails). It is also produced by certain infectious or symbiotic bacteria like Pseudoalteromonas, Pseudomonas, and Vibrio as well as other species found in symbiotic relationships with animals and plants.

Although it produces thousands of intoxications annually and several deaths, it has shown efficacy for the treatment of cancer-related pain in phase II and III clinical trials.

Clostridium botulinum is a gram-positive, rod-shaped, anaerobic, spore-forming, motile bacterium that has the ability to produce botulinum toxin, which is a neurotoxin known to be the deadliest substance ever recorded in the chemical literature.

C. botulinum is a diverse group of pathogenic bacteria. Initially, they were grouped together by their ability to produce botulinum toxin and are now known as four distinct groups, C. botulinum groups I–IV. Along with some strains of Clostridium butyricum and Clostridium baratii, these bacteria all produce the toxin.