When someone becomes dependent on drugs or alcohol, the brain's pleasure center gets hijacked, disrupting the normal functioning of its reward circuitry.
Researchers investigating this addiction "switch" have now implicated
the naturally occurring protein — called BDNF (brain-derived
neurotrophic factor) — a dose of which allowed them to get rats
"hooked" (assuming drug-dependent behavior) with no drugs at all. The
research appears in the journal Science.
"This work may reveal a mechanism that underlies drug addiction," said Hector Vargas Perez, a post-doctoral fellow with the University of Toronto's Department of Molecular Genetics. "Our work suggests that BDNF is crucial for inducing a drug dependent state, one important aspect of drug addiction."
This new understanding of BDNF's role in addiction could yield new strategies for combating addiction.
Earlier research has noted that chronic drug users
can experience an increase in BDNF in the brain's reward circuitry, a
region scientists call the ventral tegmental area. In this study, the
researchers took the drugs out of the equation and directly infused
extra BDNF onto this part of the brain in rats.
The Toronto team noted
that a single injection of BDNF made rats behave as though they were dependent on opiates (which they had never received).
In collaboration with a team from Brigham Young University, the researchers determined that after the BDNF injection, specific chemicals that normally inhibit neurons in this part of the brain instead excited them, a "switch" known to occur when people become dependent on drugs.
"If we can understand how the brain's circuitry changes in association with drug abuse, it could potentially suggest ways to medically counteract the effects of dependency," said Scott Steffensen, a neuroscientist at Brigham Young University and collaborator on the research.