DMT, Bufotenine, and 5-MeO-DMT have all been shown to be present within the human body, including blood, cerebral spinal fluid, and urine.  The amounts vary significantly between tissue and individuals.  Other factors such as MAO isozymes amoung individuals and even time of day, certainly may influence plasma concentrations.  While no one doubts their prescense the exact role of these compounds in the body is unknown. Check out these articles for proposed roles of the endogenous hallucinogens.  Additionally these articles give references to known articles that show the prescense of these compounds in the human body.

Wallach JV.

“Endogenous hallucinogens as ligands of the trace amine receptors: A possible role in sensory perception”.

Med Hypotheses. 2008;.

[URL unfurl="true"]http://www.erowid.org/references/refs_view.php?ID=7404[/URL]

and

Jacob MS, Presti DE.

“Endogenous psychoactive tryptamines reconsidered: an anxiolytic role for dimethyltryptamine”.

Med Hypotheses. 2005;64(5):930-7.

[URL unfurl="true"]http://www.erowid.org/references/refs_view.php?ID=7064[/URL]

 

Trouts notes on simple tryptamines also has an incredible reference for articles on all of these compounds in plants and animals as well as tons of other useful information.  Anyone who is legitimately interested in DMT and other tryptamines for any reason, that does not own trouts notes is seriously missing out.