Dopamine hypothesis


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  • Movie clip: house (ao2 points …… ethics & side effects of biological model approach)
  • Dopamine hypothesis

    2. 2. LEARNING OBJECTIVESYou must:• Describe the role of Dopamine (DA) in schizophreniaYou should:• Outline evidence to support the hypothesisYou could:• Evaluate the Dopamine Hypothesis
    3. 3. Lets remind ourselves how neurotransmitters work
    4. 4. Lets remind ourselves how neurotransmitters work
    5. 5. DOPAMINE HYPOTHESISThe Dopamine hypothesis states that the brain of schizophrenic patients produces more dopamine than normal brains. –Evidence comes from –studies with drugs –post mortems –pet scans
    6. 6. Elevated Level of Normal Level of Dopamine In The Brain of a Dopamine In The Schizophrenic Patient Human Brain (specifically the D2 receptor) Neurons that use the transmitter ‘dopamine’ fire too often and transmit too many messages or too often. Certain D2 receptors are known to play a key role in guiding attention. Lowering DA activity helps remove the symptoms of schizophrenia
    7. 7. ROLE OF DRUGS–Amphetamines (agonists) lead to increase in DAlevels–Large quantities lead to delusions andhallucinations–If drugs are given to schizophrenic patients theirsymptoms get worse
    8. 8. Parkinson’s disease • Parkinson’s sufferers have low levels of dopamine • L-dopa raises DA activity • People with Parkinsons develop schizophrenic symptoms if they take too much L-dopa–Chlorphromazine (given to schizophrenics) reducesthe symptoms by blocking D2 receptors
    9. 9. POST MORTEMFalkai et al 1988 Autopsies have found that people with schizophrenia have a larger than usual number of dopamine receptors. Increase of DA in brain structures and receptor density (left amygdala and caudate nucleus putamen)• Concluded that DA production is abnormal for schizophrenia
    10. 10. PET SCANSLindstroem et al (1999)• Radioactively labelled a chemical L-Dopa• administered to 10 patients with schizophrenia and 10 with no diagnosis• L-Dopa taken up quicker with schizophrenic patients• Suggests they were producing more DA than the control group
    11. 11. hatch from eggs, but a Which Came First? mother chicken The Chicken or the Egg? must keepan egg warmin order for it to hatch Schizophrenia or Faulty Chemicals? Faulty chemicals causeschizophrenia but schizophrenia may cause faulty chemicals Drugs may influence other systems that impact on schizophrenia so cant be 100% sure about their effects
    12. 12. ACTIVITY• Use the evaluation points to write effective AO2 commentary for the studies on the handout• You must comment on how the evidence you use supports orchallenges the DA hypothesis.• You should comment on evidence both for and against thehypothesis.• You could use your own skills and knowledge to makeadditional critical and evaluative points.
    13. 13. EVALUATION POINTS• There is a lack of correspondence between taking the drugs and signs of clinical effectiveness. It takes 4 weeks to see any sign that the drugs are working when they begin to block dopamine immediately. We can not seem to explain this time difference.• It could be that the development of receptors in one part of the brain may inhibit the development in another.• Type 1 cases respond well to conventional anti-psychotic drugs. Drugs such as CHLOPROMAZINE: Only effective at relieving the Positive Symptoms of the Illness.• Not good at explaining negative symptoms. Therefore suggested that Type 2 is related to a different kind of abnormality such as brain structure.• PET scans have suggested that drugs did not reduce symptoms of patients diagnosed with disorder for 10 yrs or more• There may be other neurotransmitters involved.• Possible that social and environmental factors trigger the condition.