In Advance

Web-Based Activities

Activity Number	Web Version
Activity 1	Yes
Activity 2	No
Activity 3	Yes

Photocopies

For the class	For each student
1 transparency of Master 3.1, Cocaine Alters Neurotransmission 1 transparency of Master 3.2, Methamphetamine and Nicotine Disrupt Neurotransmission 1 transparency of Master 3.3, How Does Alcohol Affect Neurotransmission? 1 transparency of Master 3.7, What Should the Doctor Do?	1 copy of Master 3.4, Parent Letter 1 copy of Master 3.5, Caffeine: How Does Your Heart Respond? 1 copy of Master 3.6, How Do Drugs Get In the Body?

Material

Activity Number	Materials
Activity 1	overhead projector computers
Activity 2	soft drinks, caffeinated and caffeine-free (see Preparation) 1 watch or classroom clock with a second hand
Activity 3	computers

Preparation

Arrange for students to have access to computers for Activities 1 and 3.

At least one week before conducting Activity 2, send a copy of Master 3.4, Parent Letter, home with each student to inform parents of the activity and get permission for the students to consume a caffeinated or a caffeine-free soft drink during science class. You can also use the letter to ask each student to bring in his or her own can of the designated soft drink.

Decide on a brand of soft drink that is available with and without caffeine to use in the activity. Students should drink the same brand of soft drink because each brand contains a different amount of caffeine. If students drank different brands or flavors, the results would be difficult to interpret because each student who drank a caffeinated soft drink would ingest a different dose. You will need approximately half of the students to drink a caffeinated soft drink and half the students to drink a caffeine-free soft drink. Students who do not get parental permission can participate by drinking water, thereby providing a comparison to the control group. You may obtain the necessary soft drinks through one of the following ways:

• purchase all the soft drinks yourself through your school budget,
• ask for parent or business donations to cover the cost, or
• request that each student bring in one can of soft drink, labeled with his or her name, for his or her consumption only. (If you use this approach, you will need to specify which drink each student brings to class.)

Before the day of Activity 2, have students practice taking a resting heart rate so they are used to finding their pulse, counting the beats for 15 seconds, and multiplying that number by four to get a resting heart rate for one minute (see Activity 2).

Procedure

ACTIVITY 1: DRUGS ALTER NEUROTRANSMISSION

Content Standard A: Formulate and revise scientific explanations and models using logic and evidence.

Content Standard C: Cell functions are regulated. Content Standard C: Organisms have behavioral responses to internal changes and to external stimuli.

1. Review neurotransmission with the students. It may be helpful to have the class watch the Web site animation of neurotransmission to refresh their memories. Have students refer to their summary of neurotransmission that they completed on Master 2.5.

Open the Web site in your browser (see Using the Web Site). From the main page, click on Web Portion of Student Activities, then select Lesson 2—Neurons, Brain Chemistry, and Neurotransmission.

2. Create a chart with the following headings on the board:

Change in neurotransmission

Effect on neurotransmitter release or availability

3. Ask students if they think there are ways that neurotransmission could be altered. As students propose ideas, fill in the chart on the board. Probe for ideas by asking questions such as:

• What would happen if certain components in the process increased or decreased in amount?
• How would that change affect the response in the responding neuron?

Students may suggest a variety of ways in which neurotransmission can be altered. For example, maybe less neurotransmitter gets released, which would result in reduced (fewer) firings in the responding (postsynaptic) neuron. The postsynaptic neuron might have either more or fewer receptors; changing the number of receptors would cause an increased or decreased chance of postsynaptic neuron firing. The following chart outlines potential changes and their responses. Omit the third column on the chart at this time; you will complete that part in Step #4.

Change in neurotransmission	Effect on neurotransmitter release or availability	Drug that acts this way
increase the number of impulses	increased neurotransmitter release	nicotine alcohol* opiates*
release neurotransmitter from vesicles with or without impulses	increased neurotransmitter release	amphetamines methamphetamine
release more neurotransmitter in response to an impulse	increased neurotransmitter release	nicotine
block reuptake	more neurotransmitter present in synaptic cleft	cocaine amphetamine
produce less neurotransmitter	less neurotransmitter in synaptic cleft	probably doesn't work this way
prevent vesicles from releasing neurotransmitter	less neurotransmitter released	no drug example
block receptor with another molecule or the neurotransmitter cannot bind to its receptor on postsynaptic neuron	no change in amount of neurotransmitter released	LSD caffeine
*These drugs cause an increase in dopamine release. However, both alcohol and opiates act indirectly. See Steps 10 and 11 for a more complete explanation of their actions.

4. When you have the first two columns completed on the chart, inform students that certain drugs may cause the changes in the neurons that they have suggested. Write the name of the drug next to the change as indicated in the third column on the previous chart.

Students will begin to see that drugs of abuse interfere with and disrupt the process of neurotransmission. When neurons do not communicate normally, the brain does not function normally, either.

5. Display a transparency of Master 3.1, Cocaine Alters Neurotransmission, showing cocaine's effect on dopamine neurotransmission. Point out that cocaine blocks the dopamine transporters. Ask the following questions:

• How does this blocking action of cocaine affect dopamine levels?
• What is the effect on the responding postsynaptic neuron?

Cocaine blocks the dopamine reuptake pumps (also called dopamine transporters). Students should recall that transporters carry neurotransmitter, dopamine in this case, back into the presynaptic neuron, where it is repackaged into new vesicles. If the reuptake pumps cannot function, more dopamine will be present in the synaptic space, where it can cause a greater stimulation of the postsynaptic neuron.

6. After the students understand how blocking the dopamine transporters alters neurotransmission, show the Web site animation on cocaine's effect on neurotransmission to the class.

Open the Web site in your browser (see Using the Web Site). From the main page, click on Student Activities, then select Drugs Change the Way Neurons Communicate. This brings up the page, How Does Cocaine Alter Neurotransmission? Click the watch video button to view the animation.

7. Discuss the actions of another type of drug, methamphetamine, with the class. Display a transparency of Master 3.2, Methamphetamine and Nicotine Disrupt Neurotransmission (top half only). Explain that methamphetamine can act similarly to cocaine in blocking dopamine transporters (reuptake pumps). Methamphetamine also acts in another way to alter neurotransmission. Methamphetamine passes directly through the neuron cell membrane and is carried to the axon terminals. In the terminals, methamphetamine enters the vesicles that contain dopamine. This then triggers the vesicles to be released, even without an electrical signal (action potential) to cause vesicle release. Ask students how this affects the postsynaptic neuron.

Methamphetamine acts in two ways to change dopamine neurotransmission. Both actions lead to an increase in the amount of dopamine in the synaptic cleft. When more dopamine is present in the synaptic cleft, it is more likely to bind to the dopamine receptors on the postsynaptic neuron.

8. Continue to assess the students' understanding of how drugs can alter neurotransmission by asking them to consider how nicotine interferes with dopamine neurotransmission in the brain. Display a transparency of Master 3.2 (bottom half). Explain that nicotine binds to receptors on the transmitting (presynaptic) neuron and causes the neuron to release more neurotransmitter each time an electrical impulse (action potential) occurs. How does this affect the activity of the postsynaptic (receiving) neuron?

Nicotine binds to nicotine receptors on the presynaptic neuron. The binding of nicotine to its receptor stimulates the generation of action potentials in the neuron that cause dopamine to be released from the neuron. The released dopamine can then bind to its receptor on the postsynaptic neuron. Nicotine also changes the amount of dopamine that is released. When the presynaptic neuron fires an action potential, more dopamine is released than normal. The increased amount of dopamine in the synaptic cleft will bind to dopamine receptors on the postsynaptic neuron.

9. Display a transparency of Master 3.3, How Does Alcohol Affect Neurotransmission? Inform students that alcohol is an inhibitory signal and point out that alcohol acts on the dendrites of the presynaptic neuron. Ask students what other inhibitory signal they have learned.

Now that students have expanded their understanding of neurotransmission to include how drugs of abuse can alter the process, they should be able to determine how another drug, alcohol, changes neurotransmission.

This exercise is similar to Activity 4 in Lesson 2. Although the activity in Lesson 2 limited the signal molecules to being neurotransmitters, drugs can also be signal molecules that affect neuron activity.

Students may benefit from reviewing their work on Masters 2.7 and 2.8. Students have learned previously that GABA is an inhibitory neurotransmitter.

10. Ask students to use what they have learned about neurotransmission to answer the following questions:

• How does alcohol affect the activity of the presynaptic neuron?
  
  Alcohol is an inhibitory signal, so it reduces the activity of the presynaptic neuron.
  
  
• If the presynaptic neuron releases GABA as its neurotransmitter, does the amount of GABA that is released increase or decrease when alcohol is present in the body?
  
  If the activity of the presynaptic neuron is decreased, it releases less neurotransmitter.
  
  
• How does this affect the release of dopamine from the postsynaptic neuron?
  
  Because GABA is an inhibitory neurotransmitter, smaller quantities of it in the synaptic space create less inhibition of the postsynaptic neuron. Therefore, the activity of the postsynaptic neuron increases and more dopamine is released when alcohol is present.
  
  If you complete a line for alcohol on the chart like that on Master 2.8, it would appear as follows:

Does the signal molecule excite or inhibit Neuron #1?	Does the activity of Neuron #1 increase or decrease?	Does the amount of neurotransmitter released from Neuron #1 increase or decrease?	What is the name of the neuro-transmitter released from Neuron #1?	Is the neuro-transmitter released from Neuron #1 excitatory or inhibitory?	Does the activity of Neuron #2 increase or decrease?	Does the amount of dopamine released from Neuron #2 increase or decrease?
inhibit			GABA	inhibitory

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