From http://www.sciencedaily.com/releases...1216201414.htm

"ScienceDaily (Dec. 25, 2008) — Rewarding and stressful signals don't seem to have much in common. But researchers studying diseases ranging from drug addiction to anxiety disorders are finding that the brain's reward and stress signaling circuits are intertwined in complex ways....

Vanderbilt University Medical Center investigators have now discovered a functional link between reward and stress. They found that dopamine – the brain's chief reward signal – works through corticotrophin-releasing factor (CRF) – the brain's main stress signal – to increase the activity of a brain region involved in addiction relapse... <Release of CRF is the first thing that happens when the jerk behind you gets impatient..>

Thomas Kash, Ph.D., a research instructor in Winder's laboratory, decided to explore dopamine's actions in the extended amygdala. Using an in vitro brain slice system, he discovered that dopamine increased excitatory glutamate signaling in this brain region. Surprisingly, he found that dopamine required CRF signaling to increase glutamate signaling....
<This last sentence could have said "The sudden increase in CRF combined with dopamine to increase glutamate signaling and the stimulation of NMDA receptors thereby locking Rick up tight..."