Kazon nerve toxin ring
A neurotoxin, neural toxin, or nerve toxin was a toxin which specifically affected the nervous system.
Adam Soong killing Tallinn with a neurotoxin applied to a patch on his hand
In 2024, Adam Soong used a neurotoxin applied to a silicon patch on his hand to kill Tallinn, who was impersonating the intended target: Renée Picard. (PIC: "Farewell")
In 2151, a Klingon ship raided a Xarantine outpost and stole, among other things, Xarantine ale. The Xarantines, however, had bonded a carbon dioxide-based neurotoxin to a unique molecule of the ale. After the Klingons had consumed the ale, they became unconscious and would have died within one or two days, but Phlox developed an antidote. (ENT: "Sleeping Dogs")
In 2153, Doctor Phlox gave Captain Jonathan Archer a hypospray filled with a neural toxin and asked him to use it against Phlox when he turned into a cybernetic creature. This toxin would terminate his synaptic functions within seconds. (ENT: "Regeneration")
Trellium-D was a potent neurotoxin to the Vulcan nervous system. (ENT: "Impulse")
A substance produced by Xindi-Insectoid eggs was a mild neurotoxin to the Human nervous system. Jonathan Archer was contaminated with this neurotoxin in January 2154; in addition, this substance also subconsciously forced him to care for the eggs like a Xindi-Insectoid. (ENT: "Hatchery")
In 2371, the Kazon used a nerve toxin to kill one of their own who was gravely injured while attempting to integrate a Federation replicator into a Kazon vessel. It was injected through the use of a needle projecting from a ring. (VOY: "State of Flux")
In a hallucination caused by a non-corporeal lifeform in 2373, Kathryn Janeway saw The Doctor use a neural toxic gas to euthanize her after diagnosing her with the Phage. (VOY: "Coda")