Dopamine Hypothesis

• What is the dopamine hypothesis based on?

  the idea that there is too much dopamine in the brain and it leads to schizophrenia
• Why does this theory believe that too much dopamine causes schizophrenia?

  Because psychologists have seen on PET scans that schizophrenics have too many dopamine receptors.
• What does an increased dopamine activity in the Mesolimbic pathway cause?

  positive symptoms
• What does increased dopamine activity in the mesocortical pathway lead to?

  negative symptoms.
• What other type of receptor do schizophrenics have too many of?

  D2 dopamine receptors
• What do D2 dopamine receptors do?

  they are more likely to take up more dopamine than other dopamine receptors.
• What did Lindstroem find in support of the dopamine hypothesis?

  gave L-DOPA to 10 patients with schizophrenia and to 10 patients without schizophrenia- PET scans showed that patients with schizophrenia took up the L-DOPA quicker- due to having more dopamine receptors
• Give an example of an antipsychotic that is a dopamine blocker

  Phenothiazine
• What does Phenothiazine do?

  an anti-psychotic that blocks dopamine receptors which reduces the amount of dopamine that is taken up, and reduces schizophrenia symptoms
• What did Depatie and Lal find that refutes the dopamine hypothesis?

  they gave drugs that increased dopamine to patients and found that it didn’t cause any schizophrenia symptoms- suggests high dopamine levels is not the only cause
• What do PET scans find that refutes the dopamine hypothesis?

  PET scans showed that blocking dopamine receptors didn’t reduce schizophrenia symptoms in patients who had it for 10 or more year even if the dopamine was 90% blocked.