New Study On Cocaine Craving
By Will Dunham
WASHINGTON (Reuters) - The brain stores the craving for cocaine in a
different place than it registers the high caused by the drug,
researchers said on Thursday in a finding that points to a promising new
approach for treating addicts.
Scientists at the Albert Einstein College of Medicine in New York
used rats to study a vexing problem -- how to prevent cocaine addicts
who seem to have kicked the habit from relapsing. The findings suggest
that a solution may be blocking a brain chemical that largely has been
overlooked in addiction research.
"If you listen to patients' stories, one thing that you hear
over and over again are the intense cravings that are very, very hard to
suppress and that eventually lead to the relapse," Dr. Stanislav
Vorel, who led the research, said in an interview.
"So a major question is -- what are these cravings, how are they
triggered, how can we prevent them or how can patients learn to cope
with them?" he added.
The researchers hooked the rats on cocaine by delivering intravenous
doses when the rodents pushed a lever in their cages. The researchers
then made the rats quit cold turkey by replacing the cocaine with a
saline solution. After a week, the animals stopped pressing the lever
seeking a cocaine fix.
The researchers then sought to trigger a relapse by electrically
stimulating two parts of the brain.
One was the "reward" or "liking" center that
registers the high from using the drug -- a brain pathway that involves
a chemical called dopamine.
The other was in the hippocampus region of the brain, which is
associated with memory and involves glutamate, an entirely different
brain chemical. This region appears to register the memory of a drug's
effects and the craving for it, Vorel said.
Stimulating the hippocampus caused an intense craving for cocaine,
the study found. The rats repeatedly pressed the lever that previously
had delivered cocaine.
The researchers then demonstrated that a chemical that blocks
glutamate prevented the relapse even in rats whose hippocampus region
had been electrically stimulated.
The study was published in the journal Science.
In separate research that has not yet been published, Vorel said his
laboratory found that electrical stimulation of the almond-shaped brain
structure related to memory, the amygdala, also caused relapse.
NEW ADDICTION TREATMENT APPROACH
Glutamate is a neurotransmitter involved in essential brain functions
such as learning and memory. Vorel said developing a drug targeting
glutamate may be able to help a cocaine addict quit the drug for good.
The development of drugs to treat cocaine addiction has consistently
focused on dopamine, which is connected to the brain's
"liking" region rather than the "wanting" produced
by stimulating the memory area, said Vorel.
But Vorel's new research shows that glutamate could be a better
target for anti-craving medication, he added.
Vorel said relapse is the single biggest obstacle to successful
cocaine addiction treatment.
"I believe that an addicted brain is different than a normal
brain, and it becomes for a very, very long time -- if not forever --
sensitive to triggers of relapse," Vorel said.
"Patients will do well for long or short periods of time. But
even years after their last cocaine use, they're still vulnerable to