Drugsandthe Brain Part1 Review


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Drugsandthe Brain Part1 Review

  1. 1. Drugs and the Brain Part 1 Neurotransmitter Review
  2. 2. Spectrum of Neurotransmitters <ul><li>There are at least 50 distinct neurotransmitters that carry messages in the brain </li></ul><ul><li>Only a few have been well studied </li></ul><ul><li>Virtually all drugs used in psychopharmacology today target one of the 5 well studied neurotransmitters </li></ul><ul><li>Neuropharmacology is in its infancy; future developments are likely to be extensive </li></ul>
  3. 3. A Review of Major Neurotransmitters <ul><li>Norepinephrine - </li></ul><ul><ul><li>One of two major catecholamines – transmitter of the sympathetic nerves of the autonomic nervous system which controls emergency responses (fight or flight) </li></ul></ul><ul><li>Dopamine – </li></ul><ul><ul><li>A catecholamine transmitter. A major transmitter in the corpus striatum, a part of the brain regulating motor behavior. Destruction of these neurons causes Parkinson’s. Blockade of actions of dopamine in other brain areas is mode of action of some antischizophrenic drugs. </li></ul></ul><ul><li>Serotonin – </li></ul><ul><ul><li>Transmitter of a group of neurons in the raphe nuclei of the brain stem. Actions of psychedelic drugs are due to changes in activity of serotonin neurons </li></ul></ul>
  4. 4. A Review of Major Neurotransmitters (continued) <ul><li>Acetylcholine – </li></ul><ul><ul><li>Neurotransmitter at neuromuscular junctions for all voluntary muscles, as well as many involuntary synapses. Exact role in brain still unclear </li></ul></ul><ul><li>GABA – </li></ul><ul><ul><li>Occurs almost exclusively in the brain. Inhibitory transmitter that reduces firing of neurons </li></ul></ul><ul><li>Glycine – </li></ul><ul><ul><li>Serves as an inhibitory neurotransmitter in small neurons in the spinal cord and brain stem </li></ul></ul>
  5. 5. A Review of Major Neurotransmitters (continued) <ul><li>Glutamic Acid – </li></ul><ul><ul><li>An amino acid that also functions as a neurotransmitter. Probably the major excitatory neurotransmitter in the brain. Acts at several receptor subtypes. May be responsible for damage associated with stroke. </li></ul></ul><ul><li>Nitric Oxide – </li></ul><ul><ul><li>Transmitter of nerves to the intestines and other organs. May regulate emotional behavior in brain. </li></ul></ul>
  6. 6. A Review of Major Neurotransmitters <ul><li>Endorphins – </li></ul><ul><ul><li>Endogenous morphine-like substances. Any substance that produces opiate-like effects. Includes (& is sometimes a synonym for) enkephalins. </li></ul></ul><ul><li>Enkephalins – </li></ul><ul><ul><li>2 peptides, each containing 5 amino acids, that act at opiate receptors in the brain. Analgesics. </li></ul></ul><ul><li>Substance P – </li></ul><ul><ul><li>A peptide containing 11 amino acids. A major transmitter of sensory neurons which convey pain from the periphery to the spinal cord. Opiates block release. Also found in brain. </li></ul></ul>
  7. 7. How Drugs Effect Neurotransmitters <ul><li>Effects can occur at many stages in the process </li></ul><ul><li>May block the action of an enzyme required to synthesize a neurotransmitter from a precursor molecule </li></ul><ul><ul><li>Many drugs to lower blood pressure work by decreasing synthesis of norepinephrine </li></ul></ul><ul><li>May cause neurotransmitters to leak from synaptic vesicles, where they are degraded by enzyme </li></ul><ul><ul><li>Resperine interferes with storage of norepinephrine this way (tranquilizer, lowers blood pressure) </li></ul></ul>
  8. 8. How Drugs Effect Neurotransmitters (Cont.) <ul><li>May effect the release of transmitters from nerve endings </li></ul><ul><ul><li>Slip into vesicles, pushing neurotransmitters out into the synaptic cleft </li></ul></ul><ul><ul><li>Amphetamines release norepinephrine & dopamine this way </li></ul></ul><ul><li>Other drugs block the release process itself </li></ul><ul><li>Some drugs inhibit enzymes that degrade neurotransmitters, increasing the level of transmitter present in the synapse and facilitating transmission </li></ul><ul><ul><li>Most antidepressants work this way </li></ul></ul><ul><ul><li>MAOI – monoamine oxidase inhibitors inhibit enzyme which degrades transmitters responsible for mood stabilization </li></ul></ul>
  9. 9. How Drugs Effect Neurotransmitters (Cont.) <ul><li>Others block re-uptake </li></ul><ul><ul><li>Tricyclics </li></ul></ul><ul><ul><li>SSRIs & SNRIs </li></ul></ul><ul><li>May influence the neurotransmitter receptor </li></ul><ul><ul><li>May resemble transmitter and mimic effect at the receptor </li></ul></ul><ul><ul><li>May occupy the receptor without causing any 2 nd messenger response in the nerve </li></ul></ul><ul><ul><li>Blocks access of neurotransmitter to receptor </li></ul></ul>
  10. 10. Location of Drug Action <ul><li>Where in the brain a drug acts is critical </li></ul><ul><li>Each transmitter can bind many locations, has multiple effects; side effects can be considerable </li></ul><ul><ul><li>Example: Acetylcholine </li></ul></ul><ul><ul><li>Many insecticides target acetylcholinesterase, the enzyme that breaks down acetylcholine; can cause death in children by stopping breathing </li></ul></ul><ul><ul><li>Belladona – Plant used since ancient times for stomach upset, slows intestinal contractions. Overdose can cause memory loss, death. Active ingredient, atropine, blocks acetylcholine. </li></ul></ul><ul><ul><li>Acetylcholine deficiency is implicated in memory loss. Acetylcholine-rich neurons of the basal nucleus destroyed in Alzheimer’s patients. Drugs that inhibit acetylcholinesterase improve memory & are used in Alzheimer’s patients. </li></ul></ul>