Soman gas (GD) is a real nerve agent, it is related to the more commonly known (and far more deadly) nerve agent sarin (GB). Both soman and sarin are organophosphate neurotoxins, they are classified as both chemical weapons and weapons of mass destruction by the United Nations. Production of agents like soman and sarin are strictly regulated and controlled, and stockpiling of either agent was outlawed by the Chemical Weapons Convention of 1993; production of sarin for any reason was outlawed by an addition to the UN ban in 1997, only very limited quantities of other related nerve agents like soman can be produced and only for the purpose of medical research to find more effective antidotes and treatments. Organophosphate nerve agents like soman and sarin work by inhibiting the enzyme cholinesterase, which is used to produce an enzyme (acetylcholinesterase) that degrades the neurotransmitter acetylcholine. Acetylcholine is the neurotransmitter the nervous system uses to cause muscles to contract, acetylcholine activates motor neurons causing the muscle to contract and acetylcholinesterase then strips the acetylcholine away from the nerve receptor causing the muscle to relax. Without the ability to produce acetylcholinesterase all of the body's muscles cannot relax after being contracted, leading to death by asphyxiation due to the muscles in the diaphragm no longer functioning. Symptoms of soman and sarin exposure are very similar: constricted pupils, drooling, nausea, vomiting, muscle spasms, trouble concentrating, pain in the extremities, loss of control over bladder and bowels; as death nears the person starts twitching and jerking (sometimes violently), until they become comatose and suffocate while spasming. Sarin is one of the most toxic substances known, it is almost three times as toxic as soman and 26 times as cyanide. The main treatment for organophosphate exposure is atropine, prompt treatment is essential even if exposed to minute amounts, doses as small as 1% of the lethal dose can cause permanent nerve damage. People exposed to these agents that are successfully treated, even when exposed to small doses, can have permanent neurological damage as well, they have been known to suffer from depression, antisocial personality disorder, insomnia, night terrors and suicidal thoughts for years afterwards.