Brain Molecule Could Help Control Cocaine Addiction
Scientists have identified a particular genetic fragment that may help control the brain’s vulnerability to cocaine addiction. Researcher Jonathan A. Hollander and his team at the Scripps Research Institute in Jupiter, Florida, have discovered that the genetic material known as microRNA-212--a type of small, regulatory ribonucleic acid molecule that is involved with the translation of DNA into proteins--may help pave the way for new, more effective methods of therapeutic treatment for the highly addictive disorder of cocaine abuse.
Other studies have already found that naturally occurring microRNAs may have the potential to manipulate certain multifaceted psychiatric disorders. Now, the Scripps Research Institute scientists have discovered that these tiny non-protein coding RNAs may also play a huge role in regulating addiction disorders as well due to their ability to match similar genes involved in the brain.
In their study, researchers mapped the level of microRNA-212 in the brains of rats that were either exposed to extended access to cocaine or limited access to cocaine. Rats that received extended access to cocaine were exposed to the drug for a period of six hours each day, whereas the control group had either no access or access for only one hour to cocaine each day. According to Scripps study models, rats that are exposed to drugs for extended periods are most likely to develop drug-seeking compulsions, similar to how humans develop drug dependencies.
Following their exposures, scientists injected all the rats with a virus that encourages the over-production of microRNA-212 in the brain. The rats that had received extended access to cocaine developed nearly two times the amount of microRNA-212 in the dorsal striatum region of the brain--the area involved with developing habit formation--than the control rats that had received limited access. The study found that cocaine consumption had increased the levels of microRNA-212 sequence in the rats’ brains; as a result of this overexposure, these rats began developing a growing dislike for cocaine. The presence of increased microRNA-212 in these rats’ brains actually helped control how much cocaine they consumed. The rats even showed an apparent avoidance of the cocaine when exposed to it. On the other hand, when scientists blocked the actions of microRNA-212 in the rats’ brains, the rats began consuming more cocaine and developed compulsive drug-seeking habits.
The researchers conclude that increased levels of microRNA-212 actually protect the brain from developing addictive habits by controlling the desire to consume the drug. In contrast, lower levels of microRNA-212 increased the brain’s vulnerability to creating compulsive behavior. This suggests that humans with severe addiction disorders might have insufficient amounts of this exact microRNA, or that the molecule is functioning improperly. This new research has opened the door to revolutionary new molecule therapies that can simulate or mimic the production and presence of microRNA-212 in the brain.
The presence of cocaine in the body’s system manipulates the brain’s natural reward circuitry, or neurotransmission. When consumed, cocaine averts dopamine in the brain from reaching the receiving neurons, causing excess amounts of dopamine to build up and therefore disrupts normal transmission. This excess buildup amplifies the feelings of pleasure, known as a state of euphoria or ‘high.’ After repeated cocaine use, this neurological interference can create long-term damages in the brain’s reward system, such as building tolerance to cocaine’s toxic effects. This requires the user to take more frequent or larger amounts of cocaine to achieve the same high. These changes caused by habitual use can lead to addiction.
The damage caused to the brain by cocaine use is considered as a neuroplasticity disorder since the brain gradually becomes less able to repair or create new neural connections after suffering injury. Now, medical professionals may be able to survey the amount of microRNA-212 in the brains of cocaine addicts to measure their susceptibility to addiction, and increase the molecule’s presence to help control the addict’s compulsive drug-taking habits and more effectively treat the addiction disorder. The increased level of microRNA-212 can significantly attenuate cravings and prevent the addict from consuming. This promising new type of treatment would be the first of its kind in anti-addiction therapies.
The study, called “Striatal MicroRNA Controls Cocaine Intake through Regulation of CREB Signaling,” was sponsored by the National Institute on Drug Abuse (NIDA) and was published in the latest issue of the scientific journal Nature.
