Acetylcholinesterase: An enzyme that catalyzes the hydrolysis of ACETYLCHOLINE to CHOLINE and acetate. In the CNS, this enzyme plays a role in the function of peripheral neuromuscular junctions. EC 3.1.1.7.Cholinesterase Inhibitors: Drugs that inhibit cholinesterases. The neurotransmitter ACETYLCHOLINE is rapidly hydrolyzed, and thereby inactivated, by cholinesterases. When cholinesterases are inhibited, the action of endogenously released acetylcholine at cholinergic synapses is potentiated. Cholinesterase inhibitors are widely used clinically for their potentiation of cholinergic inputs to the gastrointestinal tract and urinary bladder, the eye, and skeletal muscles; they are also used for their effects on the heart and the central nervous system.Butyrylcholinesterase: An aspect of cholinesterase (EC 3.1.1.8).Acetylthiocholine: An agent used as a substrate in assays for cholinesterases, especially to discriminate among enzyme types.CholinesterasesCholinesterase Reactivators: Drugs used to reverse the inactivation of cholinesterase caused by organophosphates or sulfonates. They are an important component of therapy in agricultural, industrial, and military poisonings by organophosphates and sulfonates.Electrophorus: A genus of fish, in the family GYMNOTIFORMES, capable of producing an electric shock that immobilizes fish and other prey. The species Electrophorus electricus is also known as the electric eel, though it is not a true eel.Tacrine: A cholinesterase inhibitor that crosses the blood-brain barrier. Tacrine has been used to counter the effects of muscle relaxants, as a respiratory stimulant, and in the treatment of Alzheimer's disease and other central nervous system disorders.Paraoxon: An organophosphate cholinesterase inhibitor that is used as a pesticide.Physostigmine: A cholinesterase inhibitor that is rapidly absorbed through membranes. It can be applied topically to the conjunctiva. It also can cross the blood-brain barrier and is used when central nervous system effects are desired, as in the treatment of severe anticholinergic toxicity.Torpedo: A genus of the Torpedinidae family consisting of several species. Members of this family have powerful electric organs and are commonly called electric rays.Galantamine: A benzazepine derived from norbelladine. It is found in GALANTHUS and other AMARYLLIDACEAE. It is a cholinesterase inhibitor that has been used to reverse the muscular effects of GALLAMINE TRIETHIODIDE and TUBOCURARINE and has been studied as a treatment for ALZHEIMER DISEASE and other central nervous system disorders.Pralidoxime Compounds: Various salts of a quaternary ammonium oxime that reconstitute inactivated acetylcholinesterase, especially at the neuromuscular junction, and may cause neuromuscular blockade. They are used as antidotes to organophosphorus poisoning as chlorides, iodides, methanesulfonates (mesylates), or other salts.Sarin: An organophosphorus ester compound that produces potent and irreversible inhibition of cholinesterase. It is toxic to the nervous system and is a chemical warfare agent.Isoflurophate: A di-isopropyl-fluorophosphate which is an irreversible cholinesterase inhibitor used to investigate the NERVOUS SYSTEM.Thiocholine: A mercaptocholine used as a reagent for the determination of CHOLINESTERASES. It also serves as a highly selective nerve stain.Indans: Aryl CYCLOPENTANES that are a reduced (protonated) form of INDENES.Pseudocholinesterase: An aspect of cholinesterases.Edrophonium: A rapid-onset, short-acting cholinesterase inhibitor used in cardiac arrhythmias and in the diagnosis of myasthenia gravis. It has also been used as an antidote to curare principles.Electric Organ: In about 250 species of electric fishes, modified muscle fibers forming disklike multinucleate plates arranged in stacks like batteries in series and embedded in a gelatinous matrix. A large torpedo ray may have half a million plates. Muscles in different parts of the body may be modified, i.e., the trunk and tail in the electric eel, the hyobranchial apparatus in the electric ray, and extrinsic eye muscles in the stargazers. Powerful electric organs emit pulses in brief bursts several times a second. They serve to stun prey and ward off predators. A large torpedo ray can produce of shock of more than 200 volts, capable of stunning a human. (Storer et al., General Zoology, 6th ed, p672)Organothiophosphorus Compounds: Compounds containing carbon-phosphorus bonds in which the phosphorus component is also bonded to one or more sulfur atoms. Many of these compounds function as CHOLINERGIC AGENTS and as INSECTICIDES.Chlorpyrifos: An organothiophosphate cholinesterase inhibitor that is used as an insecticide and as an acaricide.Insecticides: Pesticides designed to control insects that are harmful to man. The insects may be directly harmful, as those acting as disease vectors, or indirectly harmful, as destroyers of crops, food products, or textile fabrics.Pyridostigmine Bromide: A cholinesterase inhibitor with a slightly longer duration of action than NEOSTIGMINE. It is used in the treatment of myasthenia gravis and to reverse the actions of muscle relaxants.Soman: An organophosphorus compound that inhibits cholinesterase. It causes seizures and has been used as a chemical warfare agent.Bungarus: A genus of poisonous snakes of the subfamily Elapinae of the family ELAPIDAE. They comprise the kraits. Twelve species are recognized and all inhabit southeast Asia. They are considered extremely dangerous. (Moore: Poisonous Snakes of the World, 1980, p120)Neostigmine: A cholinesterase inhibitor used in the treatment of myasthenia gravis and to reverse the effects of muscle relaxants such as gallamine and tubocurarine. Neostigmine, unlike PHYSOSTIGMINE, does not cross the blood-brain barrier.Carbamates: Derivatives of carbamic acid, H2NC(=O)OH. Included under this heading are N-substituted and O-substituted carbamic acids. In general carbamate esters are referred to as urethanes, and polymers that include repeating units of carbamate are referred to as POLYURETHANES. Note however that polyurethanes are derived from the polymerization of ISOCYANATES and the singular term URETHANE refers to the ethyl ester of carbamic acid.Dichlorvos: An organophosphorus insecticide that inhibits ACETYLCHOLINESTERASE.Phenylcarbamates: Phenyl esters of carbamic acid or of N-substituted carbamic acids. Structures are similar to PHENYLUREA COMPOUNDS with a carbamate in place of the urea.Organophosphates: Carbon-containing phosphoric acid derivatives. Included under this heading are compounds that have CARBON atoms bound to one or more OXYGEN atoms of the P(=O)(O)3 structure. Note that several specific classes of endogenous phosphorus-containing compounds such as NUCLEOTIDES; PHOSPHOLIPIDS; and PHOSPHOPROTEINS are listed elsewhere.Echothiophate Iodide: A potent, long-acting cholinesterase inhibitor used as a miotic in the treatment of glaucoma.Tetraisopropylpyrophosphamide: N,N',N'',N'''-Tetraisopropylpyrophosphamide. A specific inhibitor of pseudocholinesterases. It is commonly used experimentally to determine whether pseudo- or acetylcholinesterases are involved in an enzymatic process.Elapid Venoms: Venoms from snakes of the family Elapidae, including cobras, kraits, mambas, coral, tiger, and Australian snakes. The venoms contain polypeptide toxins of various kinds, cytolytic, hemolytic, and neurotoxic factors, but fewer enzymes than viper or crotalid venoms. Many of the toxins have been characterized.Oximes: Compounds that contain the radical R2C=N.OH derived from condensation of ALDEHYDES or KETONES with HYDROXYLAMINE. Members of this group are CHOLINESTERASE REACTIVATORS.Eels: Common name for an order (Anguilliformes) of voracious, elongate, snakelike teleost fishes.Organophosphate Poisoning: Poisoning due to exposure to ORGANOPHOSPHORUS COMPOUNDS, such as ORGANOPHOSPHATES; ORGANOTHIOPHOSPHATES; and ORGANOTHIOPHOSPHONATES.Malathion: A wide spectrum aliphatic organophosphate insecticide widely used for both domestic and commercial agricultural purposes.Organophosphorus Compounds: Organic compounds that contain phosphorus as an integral part of the molecule. Included under this heading is broad array of synthetic compounds that are used as PESTICIDES and DRUGS.Chemical Warfare Agents: Chemicals that are used to cause the disturbance, disease, or death of humans during WARFARE.Obidoxime Chloride: Cholinesterase reactivator occurring in two interchangeable isomeric forms, syn and anti.Neuromuscular Junction: The synapse between a neuron and a muscle.Butyrylthiocholine: A sulfur-containing analog of butyrylcholine which is hydrolyzed by butyrylcholinesterase to butyrate and thiocholine. It is used as a reagent in the determination of butyrylcholinesterase activity.Choline O-Acetyltransferase: An enzyme that catalyzes the formation of acetylcholine from acetyl-CoA and choline. EC 2.3.1.6.Acetylcholine: A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.Trichlorfon: An organochlorophosphate cholinesterase inhibitor that is used as an insecticide for the control of flies and roaches. It is also used in anthelmintic compositions for animals. (From Merck, 11th ed)Trimedoxime: Cholinesterase reactivator used as an antidote in alkyl phosphate poisoning.Propoxur: A carbamate insecticide.Histocytochemistry: Study of intracellular distribution of chemicals, reaction sites, enzymes, etc., by means of staining reactions, radioactive isotope uptake, selective metal distribution in electron microscopy, or other methods.Insecticide Resistance: The development by insects of resistance to insecticides.Organothiophosphates: Carbon-containing thiophosphoric acid derivatives. Included under this heading are compounds that have carbon bound to either SULFUR atom, or the OXYGEN atom of the SPO3 core structure.Kinetics: The rate dynamics in chemical or physical systems.Parathion: A highly toxic cholinesterase inhibitor that is used as an acaricide and as an insecticide.Motor Endplate: The specialized postsynaptic region of a muscle cell. The motor endplate is immediately across the synaptic cleft from the presynaptic axon terminal. Among its anatomical specializations are junctional folds which harbor a high density of cholinergic receptors.Aldicarb: Carbamate derivative used as an insecticide, acaricide, and nematocide.Antidotes: Agents counteracting or neutralizing the action of POISONS.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Piperidines: A family of hexahydropyridines.Receptors, Cholinergic: Cell surface proteins that bind acetylcholine with high affinity and trigger intracellular changes influencing the behavior of cells. Cholinergic receptors are divided into two major classes, muscarinic and nicotinic, based originally on their affinity for nicotine and muscarine. Each group is further subdivided based on pharmacology, location, mode of action, and/or molecular biology.Cholinergic Fibers: Nerve fibers liberating acetylcholine at the synapse after an impulse.Benzyl CompoundsPyridinium CompoundsPesticides: Chemicals used to destroy pests of any sort. The concept includes fungicides (FUNGICIDES, INDUSTRIAL); INSECTICIDES; RODENTICIDES; etc.Muscles: Contractile tissue that produces movement in animals.Diazinon: A cholinesterase inhibitor that is used as an organothiophosphorus insecticide.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Erythrocytes: Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.Nootropic Agents: Drugs used to specifically facilitate learning or memory, particularly to prevent the cognitive deficits associated with dementias. These drugs act by a variety of mechanisms. While no potent nootropic drugs have yet been accepted for general use, several are being actively investigated.Dimethoate: An organothiophosphorus cholinesterase inhibitor that is used as a systemic and contact insecticide.Decamethonium Compounds: Compounds that contain the decamethylenebis(trimethyl)ammonium radical. These compounds frequently act as neuromuscular depolarizing agents.Alzheimer Disease: A degenerative disease of the BRAIN characterized by the insidious onset of DEMENTIA. Impairment of MEMORY, judgment, attention span, and problem solving skills are followed by severe APRAXIAS and a global loss of cognitive abilities. The condition primarily occurs after age 60, and is marked pathologically by severe cortical atrophy and the triad of SENILE PLAQUES; NEUROFIBRILLARY TANGLES; and NEUROPIL THREADS. (From Adams et al., Principles of Neurology, 6th ed, pp1049-57)Propidium: Quaternary ammonium analog of ethidium; an intercalating dye with a specific affinity to certain forms of DNA and, used as diiodide, to separate them in density gradients; also forms fluorescent complexes with cholinesterase which it inhibits.Diazonium Compounds