<unk>  is a neurotransmitter involved in multiple complex biological processes including aggression, pain, sleep, appetite, anxiety, depression, migraine, and vomiting. In humans the effects of excess<unk>  were first noted in 1960 in patients receiving a monoamine oxidase inhibitor (MAOI) and tryptophan. The syndrome is caused by increased<unk>  in the central nervous system. It was originally suspected that agonism of 5-HT1A receptors in central grey nuclei and the medulla was responsible for the development of the syndrome. Further study has determined that overstimulation of primarily the 5-HT2A receptors appears to contribute substantially to the condition. The 5-HT1A receptor may still contribute through a pharmacodynamic interaction in which increased synaptic concentrations of a<unk>  agonist saturate all receptor subtypes. Additionally, noradrenergic CNS hyperactivity may play a role as CNS norepinephrine concentrations are increased in<unk>  and levels appear to correlate with the clinical outcome. Other neurotransmitters may also play a role; NMDA receptor antagonists and GABA have been suggested as affecting the development of the syndrome.<unk>  toxicity is more pronounced following supra-therapeutic doses and overdoses, and they merge in a continuum with the toxic effects of overdose. Spectrum concept A postulated "spectrum concept" of<unk>  toxicity emphasises the role that progressively increasing<unk>  levels play in mediating the clinical picture as side effects merge into toxicity. The dose-effect relationship is the effects of progressive elevation of<unk> , either by raising the dose of one drug, or combining it with another serotonergic drug which may produce large elevations in<unk>  levels. Some experts prefer the terms<unk>  toxicity or<unk>  toxidrome, to more accurately reflect that it is a form of poisoning.
Serotonin syndrome
Malignant hyperthermia
Cannabinoid hyperemesis syndrome
Neuroleptic malignant syndrome
Post-acute-withdrawal syndrome
Methanol toxicity
Glycine encephalopathy
Anticonvulsant hypersensitivity syndrome