Brain’s response to addictive drugs, stress:

This is big. Stanford researchers have characterized a central mechanism underlying addiction, regardless of which substance a subject is addicted to. It appears to involve dopamine-induced sensitization of neurons in a brain region called the ventral Tegmental area to another neurotransmitter, glutamate. Interestingly, the same process occurs in response to stress. Neuronal sensitization to glutamate is at the core of the biochemical mechanism of learning and memory as well. The investigators appear at a loss to explain the similarities between stress-induced and drug-induced VTA changes, but the link may be the theory, of Bessel van der Kolk in Boston and others, that traumatic stress induces a cascade of endogenous opiate release. van der Kolk has long maintained that, in effect, the trauma victim becomes addicted to stress (explaining the risk-taking behaviors and the so-called compulsion to repeat the trauma often seen in this population), and we may be seeing the neurophysiological evidence for it here. Traumatic memory is different from ordinary memory — walled off, experienced inchoately and nonverbally, perhaps repressed; the elucidation of stress-induced changes in a system that regulates learning and memory may help us to understand why. EurekAlert!