ANSWER: DOPAMINE
EXPLANATION:
DOPAMINE works jointly as a hormone and neurotransmitter in the body. Dopamine’s role or effects in the body system ranges from high libido, anxiety, difficulty sleeping, increased energy, improved focus and learning ability etc.
However, Dopamine also makes us feel satisfied after food consumption, ensue happiness after stimulating drugs use (such as amphetamines).
It's also responsible for making high risk decisions which generates high risk activities (such as jumping out of a moving train).
Thus, Gregory have been using dopamine triggering addictive drugs, presumably with tradename of Intropin, Dopastat, or Revimine.
