Toxicology: The Basic Science of Poisons
PESTAB. Toxic responses of the central nervous system are examined. Structural and functional toxicity are considered. Six types of nervous system toxicants are discussed. Anoxia is caused by barbiturates, carbon monoxide, cyanide, azide and nitrogen chloride. Agents causing damage to myelin include hexachlorophene, lead and thallium. Organophosphorus compounds cause peripheral axonopathies. Several episodes of serious poisoning have occurred from unintentional contamination of food by TOCP. Delayed neurotoxicity has been shown to occur in poisoning from DFP, leptofos, and mipafox. Related insecticides, such as parathion and malathion, and carbamate anticholinesterase insecticides, have not been shown to cause neuropathies. Agents causing primary damage to perikarya of peripheral neurons include organomercury compounds. Organomercury compounds more readily affect the sensory cell bodies in the dorsal root ganglion of the spinal cord because of the lack of a blood barrier such as exists over much of the brain capillaries. Neuromuscular junctions of motor nerves are affected by DDT, allethrin and lead. DDT and other similar insecticides caused repetitive firing of the motor end plate through repeated depolarizations of the presynaptic nerve terminal. Repetitive discharge occurs in sensory, central, and motor neurons in DDT poisoned insects. Pyrethrum induces various nervous system effects. Allethrin has effects resembling DDT, causing repetitive firing of the motor end plate. Neurotoxicants causing localized CNS lesions include DDT and mercury.