Dopamine Hypothesis Description

Question 1

Research 1950’s

Answer 1

Focused on role of dopamine in Parkinson
Discovered drug levodopa increased dopamine levels in brain and reduced symptoms of parkinsons
H/o- symptoms of schiz appeared
Initial link between dop and schz

Question 2

Initial Hypothesis:

Answer 2

Basic concept= too much dop= symptoms of schz
Griffith et al induced psychosis into volunteers by giving drug dextro-ampethamine (inc lvls of dop in brain)
Vol demonstrated sudden onset of paranoid delusions and detatched emotional responses
Issue was that drugs that reduced lvls of dopamine had little/no effect on individuals suffering w negative symptoms of schz

Question 3

Identification of role of limbic system:

Answer 3

Identified different subtypes of dop receptors across cerebral cortex and subcortex in the limbic system
Seeman & Lee: demonstrated impact of antipsychotic drugs on d2 receptors- d2 receptors mostly found in subcortical regions, therefore limbic system became main focus

Question 4

Revised Hypothesis:

Answer 4

Mesolimbic Path: Carries signals from VTA to NA, too much dop in this area causes overstim of the D2 receptors and ultimately pos symptoms of schz. Antipsychotic drugs reduce dopaminergic neurotransmission reducing dop activity and therefore pos symptoms
Mesocortical Path: Carries signals from the VTA to the FL. This path= important for emotional responses, motivation and cognition. Davis et al suggests that too little dop is evident in the D1 receptors in the FL of individuals w neg symptoms of schz.