Brain's Reward Centers
Catered To By Drugs,
Sex, & Food
(Note - Hear Dr. Wilkie Wilson's remarkable explanation of this discovery
to Jeff in our Archives of 1-19-00)
BRECKENRIDGE, CO (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.


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