Published in Journal of Neuroscience, the study's findings are the first to directly link addiction with the process, called neurogenesis, in the region of the brain called the hippocampus.
While the research specifically focused on what happens when neurogenesis is blocked, the scientists said the results suggest that increasing adult neurogenesis might be a potential way to combat drug addiction and relapse.
Increasingly, addiction researchers have recognized that some aspects of the condition – such as forming drug-context associations – might involve the hippocampus, which is a region of the brain associated with learning and memory. Only with recent technological advances have scientists been able to test their theories in animals by manipulating the birth of new nerve cells in the hippocampus of the adult brain.
Physical activity and novel and enriched environments have been shown in animal studies to be good for the brain in general, but more research is needed to see if they can increase human adult neurogenesis.
Researchers used advanced radiation delivery techniques to prevent hippocampal neurogenesis. Rats were allowed to self-administer cocaine by pressing a lever. Rats with radiated brains took more cocaine and seemed to find it more rewarding than rats that did not receive radiation.
In a second experiment, rats first self-administered cocaine and then received radiation to decrease neurogenesis during a period of time that they were without drugs. Rats with reduced neurogenesis took more time to realize that a drug lever was no longer connected to the drug dispenser.
"The nonirradiated rats didn't like the cocaine as much and learned faster to not press the formerly drug-associated lever," said Dr. Amelia Eisch, associate professor of psychiatry at UT Southwestern and senior author of the study. "In the context of this experiment, decreased neurogenesis fueled the process of addiction, instead of the cocaine changing the brain."
"If we can create and implement therapies that prevent addiction from happening in the first place, we can improve the length and quality of life for millions of drug abusers, and all those affected by an abuser's behavior," she said.
Citation: Noonan et al., 'Reduction of Adult Hippocampal Neurogenesis Confers Vulnerability in an Animal Model of Cocaine Addiction', J. Neurosci., Jan 2010, 30: 304 - 315; doi:10.1523/JNEUROSCI.4256-09.2010