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Synapses and Drugs

Synapses and Drugs. Raymond S. Broadhead Brooks School MCB/HHMI Summer Camp July, 2005. Objectives. Review the Synapse Discuss some drugs and their effects on the synapse Discuss how the altered synapses may affect the adolescent brain Play “Jeopardy Game” on neurobiology.

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Synapses and Drugs

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  1. Synapses and Drugs Raymond S. Broadhead Brooks School MCB/HHMI Summer Camp July, 2005

  2. Objectives • Review the Synapse • Discuss some drugs and their effects on the synapse • Discuss how the altered synapses may affect the adolescent brain • Play “Jeopardy Game” on neurobiology

  3. Review the Synapse • What is a synapse? • A synapse is the “gap” between the axon of one nerve and the dendrite of the next one. • The average neuron has 1,000 synapses with other neurons.

  4. What does a synapse look like? Electron Micrograph Microscopy with Fluorescent Proteins Microscopy with Fluorescent Proteins Murthy_HHMI_teachers_2005_sub.ppt

  5. Figure 48.12 A chemical synapse

  6. Key to Previous Diagram • Impulse from action potential opens ion channels for Ca++ • The increased Ca++ concentration in the axon terminal initiates the release of the neurotransmitter (NT) • NT is released from its vesicle and crosses the “gap” or synaptic cleft and attaches to a protein receptor on the dendrite

  7. Key to Diagram (cont.) • Interaction of NT and protein receptor open post-synaptic membrane ion channel for Na+ • After transmission the NT is either degraded by an enzyme or taken back into the pre-synaptic membrane by a transporter or reuptake pump

  8. Synapse Animation To see an animation of a synapse, click here. Copyright - Pearson Education

  9. Neurotransmitters • There are dozens of different neurotransmitters (NT) in the neurons of the body. • NTs can be either excitatory or inhibitory • Each neuron generally synthesizes and releases a single type of neurotransmitter • The major neurotransmitters are indicated on the next slide.

  10. Major Neurotransmitters in the Body NIH Publication No. 00-4871

  11. Drugs Interfere with Neurotransmission • Drugs can affect synapses at a variety of sites and in a variety of ways, including: • Increasing number of impulses • Release NT from vesicles with or without impulses • Block reuptake or block receptors • Produce more or less NT • Prevent vesicles from releasing NT

  12. Three Drugs (of many) which affect Neurotransmission Methamphetamine Nicotine Alcohol seattlepi.nwsource.com/ methamphetamines/ science.howstuffworks.com/ alcohol.htm

  13. Methamphetamine alters Dopamine transmission in two ways: 1. Enters dopamine vesicles in axon terminal causing release of NT 2. Blocks dopamine transporters from pumping dopamine back into the transmitting neuron seattlepi.nwsource.com/ methamphetamines/ NIH Publication No. 00-4871

  14. Result: More dopamine in the Synaptic Cleft • This causes neurons to fire more often than normal resulting in a euphoric feeling.

  15. Problems…… • After the drug wears off, dopamine levels drop, and the user “crashes”. The euphoric feeling will not return until the user takes more methamphetamine • Long-term use of methamphetamine causes dopamine axons to wither and die. • Note that cocaine also blocks dopamine transporters, thus it works in a similar manner. • To see an animation on cocaine and brain synapses, click here.

  16. What about Nicotine? • Similar to methamphetamine and cocaine, nicotine increases dopamine release in a synapse. • However, the mechanism is slightly different. • Nicotine binds to receptors on the presynaptic neuron.

  17. NIH Publication No. 00-4871 • Nicotine binds to the presynaptic receptors exciting the neuron to fire more action potentials causing an increase in dopamine release. • Nicotine also affects neurons by increasing the number of synaptic vesicles released.

  18. How does alcohol affect synapses? • Alcohol has multiple effects on neurons. It alters neuron membranes, ion channels, enzymes, and receptors. • It binds directly to receptors for acetylcholine, serotonin, and gamma aminobutyric acid (GABA), and glutamate. • We will focus on GABA and its receptor.

  19. GABA and the GABA Receptor • GABA is a neurotransmitter that has an inhibitory effect on neurons. • When GABA attaches to its receptor on the postsynaptic membrane, it allows Cl- ions to pass into the neuron. • This hyperpolarizes the postsynaptic neuron to inhibit transmission of an impulse.

  20. Alcohol and the GABA Receptor • When alcohol enters the brain, it binds to GABA receptors and amplifies the hyperpolarization effect of GABA. • The neuron activity is further diminished • This accounts for some of the sedative affects of alcohol science.howstuffworks.com/ alcohol.htm

  21. The Adolescent Brain and Alcohol From AMA pub 9416 • The brain goes through dynamic change during adolescence, and alcohol can seriously damage long- and short-term growth processes. • Frontal lobe development and the refinement of pathways and connections continue until age 16, and a high rate of energy is used as the brain matures until age 20. • Damage from alcohol at this time can be long-term and irreversible.

  22. The Adolescent Brain (cont.) • In addition, short-term or moderate drinking impairs learning and memory far more in youth than adults. • Adolescents need only drink half as much as adults to suffer the same negative effects. • To see an animation of GABA receptors and the influence of alcohol, click here.

  23. Drugs That Influence Neurotransmitters NIH Publication No. 00-4871

  24. Review - Jeopardy Game • Click here to play neurobiology jeopardy www.ibiblio.org/.../ greviews/jeop/jeop1.gif

  25. http://www.pbs.org/wnet/closetohome/home.html http://www.biologymad.com/NervousSystem/synapses.htm#drugs http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Synapses.html http://science.education.nih.gov/Customers.nsf/HSBrain?OpenForm Biology, Campbell and Reece, 6th Edition, Benjamin Cummings, San Francisco, 2002 Resources

  26. More Related Websites to Explore • http://faculty.washington.edu/chudler/neurok.html • http://www.teachersdomain.org/ • http://science.nhmccd.edu/biol/ap1int.htm • http://www.hhmi.org/ • http://www.med.harvard.edu/AANLIB/home.html • http://www.med.harvard.edu/publications/On_The_Brain/

  27. Acknowledgements Thank you to all members of the MCB/HHMI Summer Camp for helping to make this a great experience. Special thanks to Tara Bennett, Susan Johnson, and my computer buddy, Katie Horne.

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