BRECKENRIDGE, CO, Jan 27 (Reuters Health) -- Food, sex, and illicit drugs
appear to share brain pathways that spell "reward," which may explain why it is
possible to become addicted to these things. At the 33rd annual Winter
Conference on Brain Research, a panel of experts discussed animal studies that
show "a degree of interchangeability between eating food, engaging in mating,
and self-administering drugs."
"Common neurochemicals mediate food and drug response," said Dr. Marilyn
Carroll of the University of Minnesota. Neurochemicals are substances in the
brain. "In animal studies, sweet and fat preferences predict alcohol
self-administration. Giving preferred foods blocks drug self-administration. In
humans, cigarette abstinence results in weight gain and ethanol abstinence is
associated with eating more sweets."
Carroll's research showed that monkeys on food-restrictive diets use more
cocaine than monkeys given ample food. Giving monkeys glucose solution instead
of plain water also reduces their cocaine use. Relapse after withdrawal is
greater in food-restricted animals. She concluded that in animals, food and
sweets decrease first-time drug use by 40% to 50%.
"We're trying very hard to find medications that help in drug addiction,"
said Carroll. "Some medications work a little, but none work very well. A
combination of food and medication decreases drug use 80% to 90% in animals.
Medicine combined with other rewards works best in humans."
Dr. Philippe DeWitte of the University of Lourain in Belgium studied the
effect of exercise on alcohol use. A substance called taurine, which regulates
calcium efflux and influx, increases after running. Runners have higher levels
of taurine after a marathon or a 100-kilometer run.
"Heavily alcoholized rats have increased taurine," said DeWitte. "As do
extreme runners. We can use aerobic exercise to increase taurine and reduce
alcohol use," he added.
Dr. Elaine Hull, from the State University of New York at Buffalo, has
studied the effect of the neurotransmitters dopamine and serotonin on sexual
behavior in male rats. Her research shows that dopamine facilitates and
serotonin inhibits sex in male rats. She noted that studies in humans show that
drugs that affect serotonin levels also affect sexual function.
"Anti-depressants like Prozac or Zoloft cause a decrease in libido and the
ability to have orgasms," Hull pointed out. "It's a side effect of serotonin."
Dr. Sara Leibowitz of the Rockefeller University studied the effect of the
peptide galanin on fat intake. "There is a positive feedback loop," she said.
"Galanin shifts our preference to more fat intake. A high-fat diet in turn
stimulates galanin release."
"If we found a small molecule to bind the galanin active site, then we
could reduce fat intake," Leibowitz added. "In women at puberty, a high-fat diet
stimulates estrogen and progesterone production. These steroids in turn
stimulate galanin release, which then stimulate more steroids."
Understanding the similarities and the differences involved in the
pathways of the brain that control eating, mating and drug taking will help in
the development of therapies aimed at treating different types of addiction, the
panel concluded.
