The human nervous system consists of approximately 10¹² nerve cells, or neurons. A neuron can be considered a secretory cell that functions by releasing chemical substances. Once released, this substance binds to a specific receptor on one of the body’s cells, either activating or inhibiting its activity.

To date, more than fifty chemical substances functioning as neurotransmitters or neuromediators have been identified, among which acetylcholine is one of the most important.

To regulate the action of this neurotransmitter, the body contains an enzyme called acetylcholinesterase, which hydrolyzes acetylcholine into two inactive substances, thereby preventing excessive activity. If the body is exposed to agents that inhibit this enzyme, acetylcholine levels rise abnormally, leading to serious side effects. For example, soman is an acetylcholinesterase inhibitor and belongs to the category of organophosphorus compounds. Nerve agents are among the chemical weapons that were used by Iraq against Iran during the Iran–Iraq War.

These agents are highly potent nerve gases, present in both liquid and vapor forms. They are typically brownish in color and have an odor resembling that of fruit. Nerve agents affect the nervous system, cause severe breathing difficulties, and are readily absorbed through the skin, lungs, gastrointestinal tract, and the conjunctiva of the eyes, making them highly dangerous to humans.

The possibility of using such compounds as chemical warfare agents makes it essential to have adequate knowledge of how to treat poisoning caused by these substances.

Common early symptoms of poisoning include constricted pupils, excessive salivation, excessive sweating, diarrhea, vomiting, weakness and fatigue, limpness of the limbs, confusion, and a sensation of pressure on the chest. In such cases, the central nervous system is usually affected very rapidly.

There are also drugs that bind to acetylcholine receptors, thereby blocking the effects of this neurotransmitter. One instance is atropine, which is used in cases of poisoning by nerve agents. Atropine is naturally derived from plants such as Atropa belladonna, and can also be produced in synthetic and semi-synthetic forms. After administration and absorption, it is widely distributed throughout the body and reaches a significant level in the central nervous system within 30 to 60 minutes.

To counteract the effects of extremely potent compounds such as nerve gases, large doses of atropine may be required. For this purpose, one to two milligrams of atropine sulfate are administered intravenously every five to fifteen minutes, until signs of atropine’s effect—such as dryness of the mouth—appear. In wartime conditions, where repeated intravenous injections are difficult, automatic injector devices were developed. When inserted into the inner thigh muscle, each injection delivers two milligrams of atropine into the victim’s body. This injector is a green-and-yellow cylindrical device, usually carried in the pocket of soldiers’ gas mask bags for first aid. To use it, the yellow cap (safety catch) is removed, and the green end is pressed firmly against the injection site. If symptoms persist after ten minutes, a second injector is used, followed by a third if necessary. However, administering more than three injections without a physician’s authorization is not permitted. During the Iran-Iraq War, this injector saved the lives of many combatants. Hesitation or delay in its administration could mean the difference between life and death.

During the Iran–Iraq War, military commanders repeatedly emphasized to operational units the importance of preparedness against chemical attacks, including the use of protective gas masks equipped with anti-gas filters and atropine injectors. For example, in a directive issued by the Joint Staff of the Islamic Republic of Iran Army to all subordinate forces, the Ministry of National Defense, and the Islamic Revolutionary Guard Corps, it was stated: “According to received reports, the enemy has repeatedly used nausea-inducing chemical shells in recent weeks. Please instruct the units and forces to take the following measures to protect themselves against chemical agents: (1) When observing shells without shrapnel accompanied by gas release and the perception of unusual odors, they must immediately use protective gas masks equipped with anti-gas filters; (2) If a person does not have a mask, he should cover his mouth and nose with a damp cloth and move from low-lying areas to higher ground; (3) If the nausea-inducing agent progresses to the point that the combatant experiences dizziness and severe nausea accompanied by abdominal pain, he may use the automatic atropine injector”.⁠[1]