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Food intake is complex

Food intake is complex. Many brain areas, neurotransmitters, neurohormones , etc. are involved in the process of eating. What happens in reward-related parts of the brain when we eat?. Drugs that are abused act on brain systems that evolved to reinforce natural behaviors (e.g., sex, feeding ).

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Food intake is complex

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  1. Food intake is complex Many brain areas, neurotransmitters, neurohormones, etc. are involved in the process of eating.

  2. What happens in reward-related parts of the brain when we eat? • Drugs that are abused act on brain systems that evolved to reinforce natural behaviors (e.g., sex, feeding). • There are overlaps in the brain pathways activated by palatable foods and drugs of abuse.

  3. Defining an addiction Addiction

  4. Could some people be “addicted” to eating highly-palatable foods rich in sweets and fats in ways that resemble drug addiction? Could such out-of-control eating result in increased body weight and obesity in some individuals?

  5. Comparing and contrasting normal feeding and drug addiction Normal Feeding Drug Addiction • We need food to survive (but not hyperpalatable foods). • Food is not regulated, eating is socially accepted and encouraged, and food is readily available. • Food cues are everywhere (sights, smells, even sounds). • We don’t need drugs of abuse to survive. • Drugs of abuse are illegal, discouraged by society, and hard to procure. • Drug cues and advertisements are not common.

  6. Enhanced locomotion Increased Consumption Assessing Addiction Using Animal Models BINGEING WITHDRAWAL CRAVING Cross-sensitization

  7. Bingeing/Tolerance Rada, Avena, and Hoebel (2005) Daily Intermittent Sucrose and Chow Daily Ad libitum Sucrose and Chow Sucrose Twice

  8. Alterations in Brain Dopamine Levels • Increases in dopamine (DA) release wane with repeated exposure to chow; however, these increases continue in response to sugar. • This effect is only seen in sugar-bingeing rats, not control rats. • This effect is also seen in response to fat (Liang, Hajnal, & Norgren, 2006). • Rats are not overweight. Binge group All rats Rada, Avena and Hoebel (2005)

  9. Sham-feeding while overeating • Does the taste of sucrose repeatedly release accumbensDA?

  10. From Avena, Rada, Moise and Hoebel (2006)

  11. WITHDRAWAL • Sugar bingeing rats show signs of anxiety when given an opioid antagonist (naloxone), or when fasted from all food for 36 h. • Opioid systems are perturbed by overeating, as revealed by increased mu-opioid receptor binding in these animals prior to withdrawal. Colantuoni et al. (2001); Avena, Bocarsly, et al. (2008)

  12. Neural correlates of withdrawal DEPRIVATION Withdrawal from sugar is concurrent with decreases in dopamine and increases in acetylcholine levels in the nucleus accumbens, similar to the pattern seen during drug withdrawal. Avena, Bocarsly, et al. (2008)

  13. Craving • Rats that overeat sugar daily show an increase in intake following a period of abstinence (Avena et al, 2005), and will work harder to access sugar-associated cues (Grimm et al., 2005). • Rats prone to overeat are more likely to cross a shock grid to access palatable food (Oswald, Murdaugh, King & Boggiano, 2011).

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