Question 10. Why did the scientists who conducted this experiment include Rats B, C, and D in this experiment? How did the data from those rats help scientists understand more about how cocaine acts in the brain?

Rats B, C, and D were used as controls in this experiment. Rat B received a saline injection after pressing the stimulus lever. (The cocaine that Rat A received was dissolved in a saline solution.) Because Rat B's behavior differed from Rat A's behavior, this suggests that the cocaine that Rat A received caused the frequent stimulus-lever-pressing behavior. Because both rats had a canula inserted to deliver the solution, the process of inserting the canula is not sufficient to cause Rat A's behavior.

The data from Rat C reveal that electrical stimulation of the VTA elicits behavior similar to that caused by cocaine injection. Because cocaine is known to act on neurons in the VTA, these data reinforce the findings from Rat A that the cocaine acting on the VTA neurons causes the frequent stimulus-lever-pressing behavior.

Rat D received electrical stimulation in the cerebellum after pressing the stimulus lever. The cerebellum is not part of the reward system. These data show that stimulation to a discrete brain area, the reward system, causes Rat C's behavior. Inserting the electrode into other areas of the brain is not sufficient to elicit the rapid stimulus-lever-pressing behavior observed in Rat C.

Question 11. Do you think that Rats A and C will stop pressing the stimulus lever if they continue to receive the same stimulation each time they press it? Why?

Based on the data, it does not seem likely that Rats A and C would stop pressing the stimulus lever because the number of times it is pressed continues to increase within each five-minute period. Students may notice that Rat A pressed the stimulus lever more times during the last five-minute period of the experiment than it did during the first five-minute period.

Question 12. Based on what you learned from these data, what might this investigation tell you about drug use by humans? Explain your view.

The data from the rat experiment show that the use of addictive drugs is reinforcing. Rats who are given cocaine want more cocaine. Because rats are mammals just as humans are and many of their organs function in ways similar to those in humans, the data suggest that drug use in humans is likely to be reinforcing as well: Humans who take drugs will probably want to continue taking drugs.

5. Have students consider the question, Why do humans continue to abuse drugs?

Drug addicts continue to take drugs in spite of negative consequences. They know that their family, social, or career interactions are disrupted by their drug abuse, but they cannot stop. Drug-taking becomes compulsive. Rats A and C became conditioned to the activation of the reward system by the administration of cocaine or electrictrical stimulation in the VTA in response to a lever press. Those rats continued to press the stimulus bar in their cages and ignored the food lever. The cocaine or electrical stimulation in the VTA was a bigger reward for the rats than was the food. In humans, drugs cause a compulsive need for more drugs.

6. Write the following definition of addiction on the chalkboard or overhead transparency.

• Addiction is the continued compulsive use of drugs in spite of adverse health or social consequences.

7. Ask students to consider what they learned from the data concerning the continued use of cocaine by Rat A and the continued stimulation of the reward pathway in Rat C. Did Rat A and Rat C experience any adverse effects from their treatments? What adverse consequences do human drug addicts experience?

Although it is not appropriate to refer to the rats as addicted to cocaine, those rats would have experienced adverse effects if the experiment continued for a long time. If the experiments continued and the rats continued to push only the stimulus lever, the lack of food and water would lead to adverse health consequences. If the scientists did not stop the experiment, the rats would have continued to press the stimulus lever until they died from a cocaine overdose.

Human addicts are most concerned with their next drug use. Because of this, they often eat little or poorly and consequently suffer the adverse health consequences of poor nutrition.

8. Ask students to consider the distinction between drug abuse and drug addiction in humans.

• When does abuse become addiction?
• What causes abuse to become addiction?
• Does the change from abuse to addiction occur at the same level (amount of drug taken, duration of drug abuse) of drug abuse for different individuals?

Students should be able to use the previously given definition of addiction and the results of the cocaine self-administration experiments with rats to differentiate between drug abuse and addiction. Abuse is voluntary; addiction is the compulsive, continued drug use in spite of adverse health or social consequences.

Scientists do not know what causes a drug abuser to become an addict. Continuing research is attempting to answer this question.

Content Standard F: Personal choice concerning fitness and health involves multiple factors.

ACTIVITY 3: WHEN DOES ABUSE BECOME ADDICTION?

1. Divide the class into groups of three students. Give each group a deck of cards that have been divided into two piles. Tell the students that the small pile contains the face cards and the larger pile has the aces and number cards.

2. Display a transparency of Master 4.4, Playing the Game, showing the instructions for the game. Have students play through the game. Each student in the group will play individually, but the group members share the deck of cards.

Figure 4.4: The arrangement of cards during the game.

3. When all the groups have finished the game, discuss the game and the results of the game with them. The value of this activity lies in the discussion and questions that it may generate. The following sample questions can guide the discussion.

• How many choice cards did each person pick?
  
  Students will draw different numbers of cards before they decide to stop.
  
  
• How many people equaled or went over the value of the switch card?
  
  Some students will decide to play it safe, whereas other students will risk going over the switch value.
  
  
• How does this game relate to drug abuse and drug addiction?
  
  This game relates to abuse and addiction in that each person who continues to abuse drugs will reach some point that, if surpassed, will change the person and the person's brain from a drug abuser to a drug addict. Each person has risk factors, and each person can make choices about abusing drugs.
  
  
• What does the switch card mean in regard to drug addiction?
  
  When a person abuses drugs, there is some point at which the person's brain changes and the individual becomes compulsive about using drugs despite negative consequences. Scientists do not know what factors control the "switch" between drug abuse and addiction.
  
  
• Is everyone's switch level the same?
  
  In the card game, students choose one of three cards, each assigned an arbitrary value, as their switch card. In life, a person does not know when he or she will reach the point where drug abuse switches to drug addiction. For some people, that change will occur earlier in their drug abuse, while other people will abuse drugs extensively before they become addicted.
  
  
• What does the risk card mean?
  
  The risk card symbolizes that there are factors that influence the outcome. An individual does not know what all the risks are or how great their influence is.
  
  
• Is everyone's risk card the same?
  
  Different students will have different risk cards. In life, people who abuse drugs have different risks of becoming addicted.
  
  
• Why is the risk card face down?
  
  The risk card is face down because a person does not know all of the risk factors that help determine if a person becomes addicted.
  
  
• What factors influence a person's risk of becoming addicted to drugs?
  
  Many factors influence whether a person becomes addicted to drugs. Some of these include genetics, family influence, influence of friends, age at which drug abuse begins (a person who begins using drugs early in life is more likely to become addicted), context of drug use, and the development of coping skills.
  
  
• What do the choice cards represent?
  
  Each choice card in this model represents an episode of drug use.
  
  Students likely will try to assign meaning to the numbers on the choice cards. For example, they may equate a 2 with drinking a low-alcohol beer and a 10 with heroin injection. These correlations are difficult to make with any accuracy. For example, a person may smoke a small amount of marijuana believing that it contains a low dose of THC. If that marijuana is of a potent strain that contains a high level of THC, the individual could receive a higher dose than if he or she smoked a larger dose of a less potent strain of marijuana.
  
  Like most models, this one has imperfections. The discussion that this issue may generate among students can be valuable because it causes them to question drug abuse.
  
  
• If a total score that equals or goes over the switch value indicates addiction, did anyone become addicted to drugs with the first drug use?
  
  The point values in the game have been assigned so that the player cannot reach the switch value after drawing one choice card. This correlates with addiction; no one becomes addicted with one episode of drug abuse.
  
  Important note: This is true with the outcome of the game being drug addiction if the switch value is reached. This is not true if the designated outcome is death if the switch value is reached. A person can die from the first episode of drug abuse. After one use, drugs do not change the brain sufficiently to cause addiction. However, drugs can affect other body systems and cause them to fail. See Step #9 for a modification of the game to address this. Also, although a person does not become addicted to drugs after one use, one episode can cause some changes to start occurring in the brain. For example, one use of crack cocaine can cause the abuser to experience cravings for the drug.

Figure 4.5: Sample card hand #1. The player had a moderate switch value (the switch card is a queen). The student elected to draw six choice cards totaling 33 points before finding out that the risk card had a value of 5. The 38-point total put the score over the switch value (35), signifying addiction.

Figure 4.6: Sample card hand #2. The player had a higher switch card (king = 45 points) and elected to draw eight choice cards totaling 36 points. Because the risk card was low (a 2), the 38-point total was still below the switch value, signifying drug abuse.

Figure 4.7: Sample card hand #3. The player elected to draw only one choice card, a 5, to ensure that the total of risk (which turned out to be a 4) and choice cards remained below the switch value of 25 points (jack = 25 points).

Figure 4.8: Sample card hand #4. The player drew a low switch card (a jack = 25 points) and a high risk card (a 10). Because the choice cards have high point values, the total of just two cards totaled more than the switch value, signifying drug addiction.

4. Have the students play the game again now that they can relate the game to the issues of drug abuse and drug addiction.

5. Ask students if they played the game any differently this time. Did they make different choices?

Some students will continue to risk drawing more choice cards and get closer to the switch value. Other students may elect not to draw any choice cards.

Some students might bring up questions relating to a hand containing a high switch card, a low risk card, and some low choice cards so that they can continue to draw more cards. Students may feel that this scenario would lead them to continue to experiment with drugs. You can respond by asking them what choices they would make if they drew a low switch card and a high risk card. (Perhaps the numbers on the cards are lower or higher than the assigned values. For example, what if the switch card had a value of 22 points and the risk card had a value of 12 points? Would this change the decision about drawing additional cards?) This scenario leads into the next step of the activity, in which students consider that the switch point really is unknown.

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