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Neuropharmacology: Affective Disorders

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Lecture 20 from a college level neuropharmacology course taught in the spring 2012 semester by Brian J. Piper, Ph.D. ([email protected]) at Willamette University. Focus is on the pharmacological treatment of depression.

Text of Neuropharmacology: Affective Disorders

  • 1. Affective DisordersBrian J. Piper, Ph.D., M.S.
  • 2. Goals Serotonin (5-HT) Major Depressive Disorder Bipolar Disorder
  • 3. Major Depressive Disorder Five + (1 or 2) causing significant social or occupational impairment not due to medical condition 1) Depressed mood most of the day, nearly every day 2) Marked diminished interest or pleasure, in activities 3) Significant weight loss/gain (+5%/month) 4) Insomnia/hypersomnia 5) Fatigue or loss of energy 6) Diminished ability to think or concentrate 7) recurrent thoughts of death, suicidal attempt/planAnna M. Kring, Ph.D. Lecture 14, 19:38-23:08
  • 4. Edvard Munch (1863-1944) Vincent van Gogh (1853-1890)Despair (1894) Sorrowing Old Man (At Eternitys Gate) 1890
  • 5. MDD Episode = 6 months Female: Males (2:1) Age of Onset (younger)
  • 6. HeritabilityBMJ 1999; 319 : 37
  • 7. Biosynthesis HO: hydroxyl COOH: carboxyl
  • 8. BiosynthesisTryptophan: yogurt, milk, fish, nutsTryptophan hydroxylase: rate limitingstep
  • 9. Role of 5-HT in MDD Methods: 15 un-medicated women with a history of 2+ episodes of depression were on a low protein diet for 1 week, then randomly assigned to receive: Tryptophan + : L-tryptophan (1.9 g), L-alanine (4.6 g) L-arginine (4.1 g) Tryptophan - : L-alanine (4.6 g) L-arginine (4.1 g)
  • 10. Hamilton Depression Inventory http://www.psy-world.com/online_hamd.htm
  • 11. Ham-D Max Hamilton 1912-1988http://www.psy-world.com/online_hamd.htm
  • 12. Smith et al. (1997). Lancet, 349, 915-919.
  • 13. Smith et al. (1997). Lancet, 349, 915-919.
  • 14. 5-HT & Aggression Para-chlorophenylalanine (PCPA): irreversible tryptophan hydroxylase inhibitor PCPA treated rats were tested for muricide Killers Non-killers Control 0 13 PCPA 14 4Paxinos et al. (1977). Pharmacology, Biochemistry, Behavior, 6, 439-447.
  • 15. 5-HT & Aggression muricide: mouse killing PCPA: aggression PCPA + 5-HTP: no aggressionPaxinos et al. (1977). Pharmacology, Biochemistry, Behavior, 6, 439-447.
  • 16. Serotonergic Projects Cell bodies in Raphe Projections throughout CNS
  • 17. 5-HT Functions Brain stem NauseaSpinal Cord Sexual dysfunction Modified from Stahl (2001) p. 182
  • 18. 5-HT Functions Limbic AnxietyBrain stem Insomnia Modified from Stahl (2001) p. 182
  • 19. 5-HT FunctionsFrontal Cortex MoodHypothalamus Appetite (Bulimia?) Modified from Stahl (2001) p. 182
  • 20. Fenfluramine Fenfluramine is a 5-HT releaser that was used with phentermine for weight control Animal studies indicate fenfluramine causes 5-HT axotomy Methods: Former fenfluramine users (N=15) and controls (N=17) completed PET imaging McCann et al. (2007). Molecular Imaging & Biology, 9, 151-157.
  • 21. 5-HT Receptors Postsynaptic 1A 1B 2A 2C 4 5 6 7 Presynaptic 1A
  • 22. 5-HT1A Agonist: 8-OH-DPAT Example#1: Rats received MDMA from age 35 to 60 A 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin) challenge was administered at age 67Piper et al. (2006) JPET, 317, 838-849.
  • 23. 5-HT2A Agonist: DOI Example #2: Rats received MDMA from age 35 to 60 A DOI (di-methoxy-4-iodophenyl)- 2-aminopropane) challenge was administered at age 67Biezonski et al. (2009) Brain Research, 1252, 87-93.
  • 24. MAO-Is Monoamine Oxidase (MAO) is an enzyme that breaks down 5-HT, NE, & DA
  • 25. MAO-Is Monoamine Oxidase (MAO) is an enzyme that breaks down 5-HT, NE, & DA; peak use in 1970s Food Interactions: Tyramine: amino acid breakdown product of tyrosine, doesnt cross BBB but causes norepinephrine release Tyramine rich foods (aged cheese, beer, wine) + MAO-I results in increased blood pressure & headaches (cheese effect)
  • 26. MAO-Is Monoamine Oxidase (MAO) is an enzyme that breaks down 5-HT, NE, & DA Food Interactions: tyramine foods (aged cheese, beer, wine) results in increased norepinephrine (blood pressure) Drug Interactions: increased activity of drugs that elevated 5- HT, NE, DA (cocaine, hypericum, ritalin) 1st generation were irreversible inhibitors (1960s), 2nd generation are reversible inhibitors
  • 27. Tricyclic Antidepressants Developed from antipsychotic drugs Have 3 ringed structure
  • 28. SERT & NET Blockade+
  • 29. Serotonin Reuptake Inhibitors Prozac (fluoxetine) was the original SRI Greater affinity for SERT than NET Not Selective (sigma receptors, CYP2D6) Anorgasmia
  • 30. Comparison MAO-Is TCA SSRIsEfficacy Moderate Moderate LowSide-effects cheese effect, orthostatic Sexual, many drug hypertension, OD Discontinuation interactions SyndromePrevalence very low low highMechanism 5-HT, NE, DA 5-HT & NE 5-HTTherapeutic Lag Yes Yes Yes
  • 31. Other Mechanisms of Antidepressants 5-HT2 Intracellelar (e.g. cAMP) Brain Derived Neurotrophic Factor
  • 32. Cortisol The Hypothalamus-Pituitary-Adrenal (HPA) axis control release of the stress hormone cortisol. As many as half of depressed patients show elevations in cortisol. Drugs that turn off the HPA axis are ineffective. Belmaker & Agam (2008). New England Journal of Medicine, 358, 55-68.
  • 33. Structural Changes following Elevated Cortisol? Rat research indicate that persistent increases in cortisol are toxic to hippocampal neurons. Studies examining the volume of the hippocampus in MDD were inconsistent. A meta-analysis showed that the left (-4.5%) and right hippocampus (-4.0%) showed reductions. Cole et al. (2011). J of Affective Dis 134, 483-487.
  • 34. Antidepressants & Neurogenesis New neurons are produced in the hippocampus in adultsECS: electroconvulsive therapy; TCP: trancyclpromine (MAO-I), or Reboxetine (SNRI)Mahlberg (2000). J Neurosciece, 20, 9104-9110.
  • 35. Electroconvulsive Therapy The most effective treatment for MDD (especially high suicide risk) Controversial! Potential memory loss George, David T. (2011). Electroconvulsive therapy. Starts at 54:50: http://videocast.nih.gov/Summary.asp?File=16674
  • 36. Cognitive Behavioral Therapy Short, evidence based, therapy Developed

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