**4. Toxic substances that cause seizures**

Exposure to toxins can trigger seizures due to their damaging effect on the nervous system through different mechanisms (**Table 1**). The ability of organophosphate insecticides to induce epileptic seizures is known through the inhibition of acetylcholinesterase due to its chemical structure that contain the groups carbamoyl and thiocarbamoyl, due to its capacity to phosphorylate and inactivate acetylcholinesterase and in addition to stimulating cholinergic receptors, these pesticides include parathion, chlorpyrifos, aldicarb, and carbaryl. Certain toxins present a dual mechanism for epileptic seizures production through the facilitation of the activation and the inhibition of voltage-gated Na+ channels, how is the case for chemical and biological warfare agents like sarin and soman, as well as toxins such as scorpion venom and ciguatoxin that can lead to seizures by modulating ion flow through Na+ channels. In other instance, anatoxin is a potent agent that causes seizures by the nicotinic receptor activation. The imbalance in inhibitory and excitatory neurotransmission is one of the mechanisms by which seizures occur. Par excellence GABA is the inhibitory neurotransmitter and glutamate is the excitatory neurotransmitter in the CNS, seizures are triggered by the activation of glutamate receptors by kainic acid and domoic acid, cyanide and azide both display the same process after cellular damage. Interference with the inhibition produced by GABA can trigger epileptic events, GABA receptor inhibition is caused by lindane, picrotoxin, strychnine, and tetramethylenedisulfotetramine [27–29].


#### **Table 1.**

*Toxic substances that can trigger seizures and their exerting mechanism.*
