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.\"
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).
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.
The research was funded by the NIAAA and by the Minnie & Bernard Lane Foundation and Edward Lane Foundation.
Contact: Steven Schultz
sschultz@princeton.edu
609-258-5729
Princeton University