GHoSToKeR you are partially right. Although I havn't read up on it I doubt that by raising blood preasure and dehydrating you will cause you to have the same effects as Datura.

I think the main ingreadient in Datura is tropanes as it says used in high doses it causes: disorientation, confusion, hallucinations, delusions,
panic, etc.

Some more info about it: "The interesting thing about this class of hallucinogens is
that the person taking the drug is often absolutely convinced that the
hallucinations/delusions are, in every sense, real; furthermore, he or she
may attempt to interact with them (and perceive normal response). This
can range from amusing to dangerous. There is often a severe distortion
of position/kinetic sense leading many to say they feel like they were
in free-fall or flying."

A reason why it is hard to judge doses: "The really dangerous thing about tropanes is that they have rather strong
peripheral effects in comparison to their psychoactive effects. The
lethal dose / effective dose ratio is dangerously low; furthermore, the
strength of tropanes in wild plants ranges considerably. The Datura
genus may contain alkaloids which have neurotoxic effects, in addition to
the tropane alkaloids."

I could post more but the post is long enough as it is..

Sounds to me it is the tropanes causing you to trip not the Body temperature + dehydration, although it is not something you want to put your body through.