Dopamine
Dopamine is a neurotransmitter and hormone naturally produced in the nervous system and adrenal glands of the Human body. It affects the heart rate, blood pressure, locomotion, pleasure, and motivation.

In 2374, as part of an unethical experiment, Alzen, a Srivani medical researcher, increased Captain Kathryn Janeway's dopamine levels to test her "behavioral restraints". ()

In 2375, The Doctor discovered heightened dopamine levels when he conducted "routine examinations" of the  crew while they were under the influence of the telepathic pitcher plant, apparently caused by the powerful neurogenic field that it generated. ()

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Biochemical compounds