Venoms, Poisons, et. al Flashcards
Conotoxins
Peptide neurotoxins from the marine fish-hunting snails of the genus CONUS. They contain 13 to 29 amino acids which are strongly basic and are highly cross-linked by disulfide bonds. There are three types of conotoxins, omega-, alpha-, and mu-. OMEGA-CONOTOXINS inhibit voltage-activated entry of calcium into the presynaptic membrane and therefore the release of ACETYLCHOLINE. Alpha-conotoxins inhibit the postsynaptic acetylcholine receptor. Mu-conotoxins prevent the generation of muscle action potentials. (From Concise Encyclopedia Biochemistry and Molecular Biology, 3rd ed)
Year introduced: 2000
(Ziconotide is used as an intrathecal analgesic)
Strychnine
- Convulsant
- Glycine antagonist
An alkaloid found in the seeds of STRYCHNOS NUX-VOMICA. It is a competitive antagonist at glycine receptors and thus a convulsant. It has been used as an analeptic, in the treatment of nonketotic hyperglycinemia and sleep apnea, and as a rat poison.
The strychnine tree also known as nux vomica, poison nut, semen strychnos and quaker buttons, is a deciduous tree native to India, and southeast Asia. It is a medium-sized tree in the family Loganiaceae that grows in open habitats.
Picrotoxin
A noncompetitive antagonist at GABA-A receptors and thus a convulsant. Picrotoxin blocks the GAMMA-AMINOBUTYRIC ACID-activated chloride ionophore. Although it is most often used as a research tool, it has been used as a CNS stimulant and an antidote in poisoning by CNS depressants, especially the barbiturates.
- Picrotoxin is obtained from Anamirta cocculus, a climbing shrub indigenous to Malabar and the East Indies. The drug is present in the seeds of the plant, commonly known as fishberries …
Tetrodotoxin
- sodium channel blocker
- found in puffer fish
An aminoperhydroquinazoline poison found mainly in the liver and ovaries of fishes in the order TETRAODONTIFORMES, which are eaten. The toxin causes paresthesia and paralysis through interference with neuromuscular conduction.
Year introduced: 1968(1964)
Muscarine
- muscarinic agonist
A toxic alkaloid found in Amanita muscaria (fly fungus) and other fungi of the Inocybe species. It is the first parasympathomimetic substance ever studied and causes profound parasympathetic activation that may end in convulsions and death. The specific antidote is atropine.
Year introduced: 1977
- Muscarine poisoning is characterized by miosis, blurred vision, increased salivation, excessive sweating, lacrimation, bronchial secretions, bronchoconstriction, bradycardia, abdominal cramping, increased gastic acid secretion, diarrhea and polyuria.
Curari
Curare /kjuːˈrɑːriː/ is a common name for various arrow poisons originating from Central and South America. These poisons function by competitively and reversibly inhibiting the nicotinic acetylcholine receptor (nAChR), which is a subtype of acetylcholine receptor found at the neuromuscular junction. This causes weakness of the skeletal muscles and, when administered in a sufficient dose, eventual death by asphyxiation due to paralysis of the diaphragm.
Chlorotoxin
Chlorotoxin is a 36-amino acid peptide found in the venom of the deathstalker scorpion (Leiurus quinquestriatus) which blocks small-conductance chloride channels.[1] The fact that chlorotoxin binds preferentially to glioma cells has allowed the development of new methods, that still are under investigation, for the treatment and diagnosis of several types of cancer. Chlorotoxin immobilizes the envenomated prey.
Chlorotoxin is the first reported high-affinity peptide ligand for Cl- channels and it blocks small conductance chloride channels. Each chloride channel can be closed by only one ligand molecule.[1][3]
Using a recombinant chlorotoxin it was demonstrated that chlorotoxin specifically and selectively interacts with MMP-2 isoforms which are specifically upregulated in gliomas and related cancers, but are not normally expressed in brain.[2]
Tetanospasmin (Tetanus toxin)
A neurotoxin produced by the Gram-positive, rod-shaped, obligate anaerobic bacterium Clostridium tetani. The tetanus toxin initially binds to peripheral nerve terminals. It is transported within the axon and across synaptic junctions until it reaches the central nervous system. There it becomes rapidly fixed to gangliosides at the presynaptic inhibitory motor nerve endings, and is taken up into the axon by endocytosis.
The effect of the toxin is to block the release of inhibitory neurotransmitters glycine and (GABA) across the synaptic cleft, which is required to check the nervous impulse. If nervous impulses cannot be checked by normal inhibitory mechanisms, the generalized muscular spasms characteristic of tetanus are produced. The toxin appears to act by selective cleavage of a protein component of synaptic vesicles, synaptobrevin II, and this prevents the release of neurotransmitters by the cells.
The action of the A-chain stops the affected neurons from releasing the inhibitory neurotransmitters GABA and glycine, but also excitatory transmitters, by degrading the protein synaptobrevin 2. The consequence of this is dangerous overactivity in the muscles from the smallest stimulus—the failure of inhibition of motor reflexes by sensory stimulation. This causes generalized contractions of the agonist and antagonist musculature, termed a tetanic spasm.
Mambalgins
Mambalgins are peptides found in the venom of the deadly African snake known as Black Mamba (Dendroaspis polylepsis), from the Elapidae family. This peptide toxin was discovered, after a number of experiments carried out with venoms of a wide range of snakes, by a group of researchers of Niza (France), directed by Dr. Silvie Diochot (publ. 2012).
Mambalgins have been found to take away pain by inhibiting acid-sensing ion channels (ASIC) in the peripheral and central nervous system.[1] To make it simpler, when an external pain stimulus is received by the body, our damaged cells release an ‘inflammatory soup’ containing ions and other chemicals that provoke the feeling of pain.[5] The ions released by the damaged cells are detected by the ASIC channels, which open up due to a change in the pH levels that the ions cause. As the protein ion channels open, they trigger the electric impulse sent to the brain telling him that the body is suffering. What mambalgins do in order to lessen pain is that they bind to these ASIC channels and prevent them from opening, thus causing the body not to send pain messages to the brain and acting as a powerful analgesic.[5] Nevertheless, it is important to bear in mind that mambalgins do not block all ion channels, because these kinds of toxins are normally highly specific. Researchers have found that mambalgins have a potent, rapid and reversible effect in homomeric ASIC1 and heteromeric ASIC1a+ASIC2a or ASIC1a+ASIC2b channels, which are the entire ASIC channel subtypes found in the central nervous system. On the other hand, they have no effect on ASIC2a, ASIC3, ASIC1a+ASIC3 and ASIC1b+ASIC3 channels.
These polypeptide toxins found in black mamba’s venom have been proved to have a strong analgesic effect in both central and peripheral nerves, being able to be as potent as morphine but better because they cause less tolerance and no respiratory distress. While morphine acts on the opioid pathway of the brain causing addiction, headaches, difficulty thinking and vomiting, mambalgins ameliorate pain using a completely different route, which is potentially capable of causing fewer side effects.[4]
