strychnine
n. an alkaloid derived from nux vomica. It is a stimulant of the central nervous system (see CNS stimulant)—through its ability to antagonize the inhibitory neurotransmitter glycine—and a powerful convulsant, with death usually resulting from paralysis of muscles of respiration. Strychnine has long been used as a rodenticide, and this use continues to the present; there are, however, no clinical applications for it. No marked tolerance develops for it, and increased susceptibility to poisoning is likely from repeated exposure.