Chronic cocaine use modifies gene expression

Chronic cocaine use changes gene expression in the hippocampus, according to research in mice recently published in JNeurosci.

Chronic drug users learn to associate the drug-taking environment with the drug itself, reinforcing memories that contribute to addiction. These memories are thought to be created by changes in gene expression in the hippocampus and potentially involve the gene FosB, but the exact mechanism is unknown.

A.J. Robinson and colleagues at Michigan State University examined how cocaine exposure affected expression of the FosB gene in the hippocampus. Mice that were administered cocaine daily showed increased expression of FosB compared to mice that received saline. Chronic cocaine use caused epigenetic modification of the gene, leading it to becoming more active. Additionally, when the scientists blocked the changes made to FosB, the mice were unable to form associations between cocaine and the environment where they received it, implicating epigenetic regulation of the gene in drug memory formation.

Full story at Science Daily

In rats that can’t control glutamate, cocaine is less rewarding, staving off relapse

Rats missing a neuroreceptor that controls the release of the neurotransmitter glutamate are less amenable to the rewarding effects of cocaine, increasing their chance of kicking the habit once addicted, researchers from the National Institute on Drug Abuse (NIDA) find. Their work, appearing July 11 in Cell Reports, suggests that the receptor, which protects nerve cells from fatal inundation by excess glutamate, is involved in modulating the reward-seeking behavior associated with drug addiction.

By silencing the gene responsible for expressing the receptor, called mGluR2, the researchers studied its effect across the stages of the cocaine addiction cycle. Rats without the receptor were more likely to consume cocaine when it was made freely available but less likely to seek out cocaine when they had to demonstrate more effort to obtain it. When cocaine was no longer available to them, the rats were quicker to cease the behaviors that had previously resulted in the drug’s delivery. Even when cocaine was subsequently re-introduced, they showed reduced interest for drug seeking, constituting a lower rate of relapse.

Full story of glutamate control from control use at Science Daily