In a recent study, binge-drinking rats lost their taste for alcohol when scientists prompted the animals’ brains to release a chemical called dopamine. This got UB researcher Caroline Bass thinking: What would happen if binge-drinkers got a low dose of the neurotransmitter, without consuming alcohol?
To find out, she and colleagues at Wake Forest University used light to activate brain cells to release dopamine on command. Such light-based stimulation is called optogenetics.
Dopamine, a neurotransmitter, plays a role in how we make decisions and form habits. It’s also central to addiction; indulging in drugs like cocaine or alcohol causes levels of dopamine in the nucleus accumbens, a region of the brain associated with pleasure and rewards, to spike.
1. One of the main ingredients for optogenetics is an algae protein called channelrhodopsin. Channelrhodopsin is a tiny gateway or channel that opens in response to light.
2. To get neurons to start making the gateways, researchers used a specially engineered virus to feed the gene for channelrhodopsin into rodent brains. The virus targeted only dopamine-producing neurons, which started making the gateways.
3. Next, the team used a fiber-optic cable to shine light on neurons that had made the gateways. The gateways opened in response, allowing molecules called ions to enter the cells.
4. The flood of ions caused the neurons to “fire” and release dopamine. After this initial success, the scientists continued stimulating the brain in a pattern that resulted in low but prolonged levels of dopamine release.
5. The rats stopped drinking. This held true even after the lights went off. “The treatment was effective,” says Bass, “most likely because it broke a conditioned response, suppressing the initial cravings the rats had formerly experienced every time they entered their ‘drinking cage,’ where they were used to receiving alcohol.”
A treatment for addiction?
This study is the first to show that tweaking the levels of dopamine can lead to changes in drinking, says Bass, an assistant professor of pharmacology and toxicology. Optogenetics is a new technique, but she believes it may one day be used in humans to treat substance abuse.
Infographic by 12 Grain Studio