<unk>  is an alkaloid found in tobacco and is also the predominant metabolite of nicotine. An anagram of the word "nicotine", it is used as a biomarker for exposure to tobacco smoke.<unk>  is currently being studied as a treatment for depression, PTSD, schizophrenia, Alzheimer's disease and Parkinson's disease.<unk>  was developed as an antidepressant as a fumaric acid salt,<unk>  fumarate, to be sold under the brand name Scotine but it was never marketed. Similarly to nicotine,<unk>  binds to, activates, and desensitizes neuronal nicotinic acetylcholine receptors, though at much lower potency in comparison. It has demonstrated nootropic and antipsychotic-like effects in animal models.<unk>  treatment has also been shown to reduce depression, anxiety, and fear-related behavior as well as memory impairment in animal models of depression, PTSD, and Alzheimer's disease. Nonetheless, treatment with<unk>  in humans was reported to have no significant physiologic, subjective, or performance effects in one study, though others suggest that this may not be the case. Because<unk>  is the main metabolite to nicotine and has been shown to be pharmacologically active, it has been suggested that some of nicotine's effects in the nervous system may be mediated by<unk>  and/or complex interactions with nicotine itself.
Cotinine
Haloalkane
Carbon monoxide
Mustard gas
3-Indolepropionic acid
Benzene
Hydrogen water
Vinyl chloride