Study Says Impulsive Rats More Vulnerable to Addiction
March 5, 2007
Rats that are genetically
predisposed to being impulsive also are more likely to
become addicted to cocaine, leading researchers to
conclude that addiction may have a biological basis in
reported March 2 that the researchers said that the
findings point to a "hidden vulnerability" that the
impulsive rats had for addiction. The study involved a
test where rats were given a food reward when a light
was shined; most rats waited for the light, but a few
could not resist the urge to run to the food place
before the light came on. Further studies showed that
these impulsive rats were more likely to become addicted
than the other rats, and had fewer dopamine receptors in
the nuclear accubens region of their brains.
"Being impulsive to begin
with seems to be an important vulnerability trait marker
that predisposes to excessive cocaine taking," said
researcher Jeffrey Dalley of Cambridge University.
"There are several studies now showing [dopamine]
receptors to be a natural 'brake' in the brain that
regulates the amount of drug intake; too few and intake
seems to increase ... this is the first study to link
such changes with impulsivity."
"We have known for a long
time that some behaviors are associated with drug
addiction -- such as impulsivity and risk taking in
general," added Gerome Breen, an addiction researcher at
the Institute of Psychiatry at King's College London.
"What this study does is identify a biological basis for
the behavior and the mechanism by which it leads to
addiction." Breen was not involved in the study.
The research was
published in the March 2007 issue of the journal
Dalley, J.W., et al. (2007) Nucleus Accumbens D2/3
Receptors Predict Trait Impulsivity and Cocaine
Reinforcement. Science, 315(5816): 1267-1270; doi: