Mutation stops worms from getting drunk

Neuroscientists at The University of Texas at Austin have generated mutant worms that do not get intoxicated by alcohol, a result that could lead to new drugs to treat the symptoms of people going through alcohol withdrawal.

The scientists accomplished this feat by inserting a modified human alcohol target into the worms, as reported this week in The Journal of Neuroscience.

"This is the first example of altering a human alcohol target to prevent intoxication in an animal," says corresponding author, Jon Pierce-Shimomura, assistant professor in the university’s College of Natural Sciences and Waggoner Center for Alcohol and Addiction Research.

An alcohol target is any neuronal molecule that binds alcohol, of which there are many.

One important aspect of this modified alcohol target, a neuronal channel called the BK channel, is that the mutation only affects its response to alcohol. The BK channel typically regulates many important functions including activity of neurons, blood vessels, the respiratory tract and bladder. The alcohol-insensitive mutation does not disrupt these functions at all.

"We got pretty lucky and found a way to make the channel insensitive to alcohol without affecting its normal function," says Pierce-Shimomura.

The scientists believe the research has potential application for treating people addicted to alcohol.

"Our findings provide exciting evidence that future pharmaceuticals might aim at this portion of the alcohol target to prevent problems in alcohol abuse disorders," says Pierce-Shimomura. "However, it remains to be seen which aspects of these disorders would benefit."

Unlike drugs such as cocaine, which have a specific target in the nervous system, the effects of alcohol on the body are complex and have many targets across the brain. The various other aspects of alcohol addiction, such as tolerance, craving and the symptoms of withdrawal, may be influenced by different alcohol targets.

The worms used in the study, Caenorhabditis elegans, model intoxication well. Alcohol causes the worms to slow their crawling with less wriggling from side to side. The intoxicated worms also stop laying eggs, which build up in their bodies and can be easily counted.

Unfortunately, C. elegans are not as ideal for studying the other areas of alcohol addiction, but mice make an excellent model. The modified human BK channel used in the study, which is based on a mutation discovered by lead author and graduate student Scott Davis, could be inserted into mice. These modified mice would allow scientists to investigate whether this particular alcohol target also affects tolerance, craving and other symptoms relevant to humans.

Pierce-Shimomura speculated that their research could even be used to develop a ‘James Bond’ drug someday, which would enable a spy to drink his opponent under the table, without getting drunk himself. Such a drug could potentially be used to treat alcoholics, since it would counteract the intoxicating and potentially addicting effects of the alcohol.

A Brain Region for Resisting Alcohol’s Allure

As recovering spring breakers are regretting binge drinking escapades, it may be hard for them to appreciate that there is a positive side to the nausea, sleepiness, and stumbling. University of Utah neuroscientists report that when a region of the brain called the lateral habenula is chronically inactivated in rats, they repeatedly drink to excess and are less able to learn from the experience. The study, published online in PLOS ONE on April 2, has implications for understanding behaviors that drive alcohol addiction.

While complex societal pressures contribute to alcoholism, physiological factors are also to blame. Alcohol is a drug of abuse, earning its status because it tickles the reward system in the brain, triggering the release of feel-good neurotransmitters. The dreaded outcomes of overindulging serve the beneficial purpose of countering the pull of temptation, but little is understood about how those mechanisms are controlled.

U of U professor of neurobiology and anatomy Sharif Taha, Ph.D., and colleagues, tipped the balance that reigns in addictive behaviors by inactivating in rats a brain region called the lateral habenula. When the rats were given intermittent access to a solution of 20% alcohol over several weeks, they escalated their alcohol drinking more rapidly, and drank more heavily than control rats.

“In people, escalation of intake is what eventually separates a social drinker from someone who becomes an alcoholic,” said Taha. “These rats drink amounts that are quite substantial. Legally they would be drunk if they were driving.”

The lateral habenula is activated by bad experiences, suggesting that without this region the rats may drink more because they fail to learn from the negative outcomes of overindulging. The investigators tested the idea by giving the rats a desirable, sweet juice then injecting them with a dose of alcohol large enough to cause negative effects.

“It’s the same kind of learning that mediates your response in food poisoning. You taste something and then you get sick, and then of course you avoid that food in future meals,” explained Taha.

Yet rats with an inactivated lateral habenula sought out the juice more than control animals, even though it meant a repeat of the bad experience.

“The way I look at it is the rewarding effects of drinking alcohol compete with the aversive effects,” explained Andrew Haack, who is co-first author on the study with Chandni Sheth, both neuroscience graduate students. “When you take the aversive effects away, which is what we did when we inactivated the lateral habenula, the rewarding effects gain more purchase, and so it drives up drinking behavior.”

The group’s findings may help explain results from previous clinical investigations demonstrating that men who were less sensitive to the negative effects of alcohol drank more heavily, and were more likely to become problem drinkers later in life.

The researches think the lateral habenula likely works in one of two ways. The region may regulate how badly an individual feels after over-drinking. Alternatively, it may control how well an individual learns from their bad experience. Future work will resolve between the two.

“If we can understand the brain circuits that control sensitivity to alcohol’s aversive effects, then we can start to get a handle on who may become a problem drinker,” said Taha.

Researchers Study Alcohol Addiction Using Optogenetics

Wake Forest Baptist Medical Center researchers are gaining a better understanding of the neurochemical basis of addiction with a new technology called optogenetics.

In neuroscience research, optogenetics is a newly developed technology that allows researchers to control the activity of specific populations of brain cells, or neurons, using light. And it’s all thanks to understanding how tiny green algae, that give pond scum its distinctive color, detect and use light to grow.

The technology enables researchers like Evgeny A. Budygin, Ph.D., assistant professor of neurobiology and anatomy at Wake Forest Baptist, to address critical questions regarding the role of dopamine in alcohol drinking-related behaviors, using a rodent model.

"With this technique, we’ve basically taken control of specific populations of dopamine cells, using light to make them respond - almost like flipping a light switch," said Budygin. "These data provide us with concrete direction about what kind of patterns of dopamine cell activation might be most effective to target alcohol drinking."

The latest study from Budygin and his team published online in last month’s journal Frontiers in Behavioral Neuroscience. Co-author Jeffrey L. Weiner, Ph.D., professor of physiology and pharmacology at Wake Forest Baptist, said one of the biggest challenges in neuroscience has been to control the activity of brain cells in the same way that the brain actually controls them. With optogenetics, neuroscientists can turn specific neurons on or off at will, proving that those neurons actually govern specific behaviors.

"We have known for many years what areas of the brain are involved in the development of addiction and which neurotransmitters are essential for this process," Weiner said. "We need to know the causal relationship between neurochemical changes in the brain and addictive behaviors, and optogenetics is making that possible now."

The researchers used cutting-edge molecular techniques to express the light-responsive channelrhodopsin protein in a specific population of dopamine cells in the brain-reward system of rodents. They then implanted tiny optical fibers into this brain region and were able to control the activity of these dopamine cells by flashing a blue laser on them.

"You can place an electrode in the brain and apply an electrical current to mimic the way brain cells get excited, but when you do that you’re activating all the cells in that area," Weiner said. "With optogenetics, we were able to selectively control a specific population of dopamine cells in a part of the brain-reward system. Using this technique, we discovered distinct patterns of dopamine cell activation that seemed to be able to disrupt the alcohol-drinking behavior of the rats."

Weiner said there is translational value from the study because “it gives us better insight into how we might want to use something like deep-brain stimulation to treat alcoholism. Doctors are starting to use deep-brain stimulation to treat everything from anxiety to depression, and while it works, there is little scientific understanding behind it, he said.

Budygin agreed and said this kind of project wouldn’t be possible without cross campus collaboration between neurobiology and anatomy, physiology and pharmacology and physics. “Now we are taking the first steps in this direction,” he said. “It was impossible before the optogenetic era.”

Research Provides Clues to Alcohol Addiction Vulnerability

A Wake Forest Baptist Medical Center team studying alcohol addiction has new research that might shed light on why some drinkers are more susceptible to addiction than others.

Jeff Weiner, Ph.D., professor of physiology and pharmacology at Wake Forest Baptist, and colleagues used an animal model to look at the early stages of the addiction process and focused on how individual animals responded to alcohol. Their findings may lead not only to a better understanding of addiction, but to the development of better drugs to treat the disease as well, Weiner said.

"We know that some people are much more vulnerable to alcoholism than others, just like some people have a vulnerability to cancer or heart disease," Weiner said. "We don’t have a good understanding of what causes this vulnerability, and that’s a big question. But if we can figure it out, we may be able to better identify people at risk, as well as gain important clues to help develop better drugs to treat the disease."

The findings are published in the March 13 issue of the Journal of Neuroscience. Weiner, who directs the Translational Studies on Early-Life Stress and Vulnerability to Alcohol Addiction project at Wake Forest Baptist, said the study protocol was developed by the first author of the paper, Karina Abrahao, a graduate student visiting from the collaborative lab of Sougza-Formigoni, Ph.D, of the Department of Psychobiology at the Federal University of Sao Paulo, Brazil.

Weiner said the study model focused on how individual animals responded to alcohol. Typically, when a drug like alcohol is given to a mouse every day, the way the animals respond increases - they become more stimulated and run around more. “In high doses, alcohol is a depressant, but in low doses, it can have a mellowing effect that results in greater activity,” he said. “Those low dose effects tend to increase over time and this increase in activity in response to repeated alcohol exposure is called locomotor sensitization.”

Prior studies with other drugs, such as cocaine and amphetamine, have suggested that animals that show the greatest increases in locomotor sensitization are also the animals most likely to seek out or consume these drugs. However, the relationship between locomotor sensitization and vulnerability to high levels of alcohol drinking is not as well established, Weiner said.

Usually when researchers are studying a drug, they give it to one test group while the other group gets a control solution, and then they look for behavioral differences between the two, Weiner said. But in this study, the researchers focused on individual differences in how each animal responded to the alcohol. A control group received a saline injection while another was injected with the same amount of alcohol every day for three weeks. Weiner said they used mice bred to be genetically variable like humans to make the research more relevant.

"We found large variations in the development of locomotor sensitization to alcohol in these mice, with some showing robust sensitization and others showing no more of a change in locomotor activity than control mice given daily saline injections," Weiner said. "Surprisingly, when all of the alcohol-exposed mice were given an opportunity to voluntarily drink alcohol, those that had developed sensitization drank more than those that did not. In fact, the alcohol-treated mice that failed to develop sensitization drank no more alcohol than the saline-treated control group."

The authors also conducted a series of neurobiological studies and discovered that mice that showed robust locomotor sensitization had deficits in a form of brain neuroplasticity - how experiences reorganize neural pathways in the brain - that has been linked with cocaine addiction in other animal models.

"We found that this loss of the ability of brain cells to change the way that they communicate with each other only occurred in the animals that showed the behavioral response to alcohol," he said. "What this suggests for the first time in the alcohol addiction field is that this particular deficit may represent an important brain correlate of vulnerability to alcoholism. It’s a testable hypothesis. That’s why I think it’s an important finding."