A brain chemical that stokes hunger for food and fat also triggers thirst for alcohol and may play a role in chronic drinking, according to a study led by Princeton University scientists.
The study showed that rats injected with galanin, a natural signaling agent in the brain, chose to drink increasing quantities of alcohol even while consuming normal amounts of food and water. The finding helps explain one of the mechanisms involved in alcohol dependence and strengthens scientists' understanding of the neurological link between the desires for alcohol and food.
"There seems to be a cycle of positive feedback," said Bartley Hoebel, co-author of a paper appearing in the December issue of Alcoholism: Clinical and Experimental Research. "Consumption of alcohol produces galanin, and galanin promotes the consumption of alcohol. That would perpetuate the behavior."
This suggests the obvious possibility that a compound that blocked the synthesis or binding of galanin to some target would help alcoholics stop drinking.
The research was conducted by Michael Lewis, a visiting research fellow in Hoebel's lab, in collaboration with Hoebel, a professor of psychology; Deanne Johnson, a research staff member; Daniel Waldman, a senior undergraduate; and Sarah Leibowitz, a neurobiologist at Rockefeller University.
Galanin, a kind of small protein fragment called a neuropeptide, had previously been shown to play a role in appetite, particularly for fatty foods. Consumption of fat causes a part of the brain called the hypothalamus to produce more galanin, which, in turn, increases the appetite for fat. In a healthy person, however, there are counteracting signals that break this loop, said Hoebel.
In animals given galanin and access to alcohol, the role of the chemical appeared to be subverted: it boosted alcohol intake instead of eating. The effect was especially noticeable during daylight hours, when the nocturnal animals normally do not eat and drink much. Those given galanin drank alcohol during the day, but did not consume any more food or water than normal.
"Alcohol is the only drug of abuse that is also a calorie-rich food, and it undoubtedly has important interactions with systems that control food intake and nutrition," said Lewis, who is also a senior fellow of the National Institute on Alcohol Abuse and Alcoholism (NIAAA).
A drug that blocks the efect of galanin reduced alcohol consumption. However, it would be difficult ot make a drug that would do the same in humans.
When the animals were given a drug that blocked the effects of galanin, they maintained normal eating and drinking habits. This observation helps confirm the conclusion that galanin affects alcohol consumption and also suggests the possibility of someday creating a drug that blocks galanin in order to fight alcoholism. However, Hoebel noted that such an achievement would be a long way off, because it is hard to make drugs that cross from the blood into the brain and interact with neuropeptide receptors. In addition, galanin plays many roles in other parts of the brain, which could be adversely affected by trying to block its effects related to food or alcohol.
The researchers plan to explore further the role of galanin and other neuropeptides in alcohol use, as well as the role of fat intake and metabolism on alcohol intake.
An effective drug to stop alcohol cravings would prevent enormous economic losses from brain damage in alcoholics, brain damage to fetuses of alcohol abusing pregnant women, work time lost, crimes committed while drunk, accidental deaths and injuries, and still other losses. Addictions cost the US economy hundreds of billions per year. In 1992 a US government study tallied up total alcohol abuse costs as about $150 billion yearly. The health care costs alone were $18 billion in 1992. A separate category for motor vehicle crash costs was $24.7 billion. My guess is these costs are higher today.
My guess is that there are some major categories of cost which are not captured by that analysis. For example, there are children who have a genetic variation in Mono Amine Oxidase A (MAOA) which causes them to react to child abuse by becoming permanently more impulsive and violent and to lack remorse for their assaults upon others. Well, how many of those children were sent down the path of a life of crime by fathers abusing them while on alcoholic benders? WHat is the cost to the rest of us from the assaults, murders, rapes, and other acts that come as a result of that abuse?
|Share |||Randall Parker, 2005 January 05 06:40 PM Brain Addiction|