Schizophrenia: Neurotransmitters as an explanation

Question 1

What is a neurotransmitter?

3

Answer 1

• Brain chemicals released from synaptic vesicles
• Excitatory/inhibitory
• Relay signals from 1 neuron to next across synapse

Question 2

What did Davis et al. (1991) suggest?

2

Answer 2

• +Symp of schizo = hyperdopaminergia in mesolimbic pathway

- -Symp = hypodopaminergia (low activity) in mesocortical pathway

Question 3

What did Howes and Kapur propose - most recent version of dopamine hypothesis?
3

Answer 3

• Dopa dysregulation in striatum = prone to psychosis
• Attention to ^presynaptic dopa
• Believe dopa hypothesis = psychosis proneness not schizo

Question 4

What does clozapine bind to?

3

Answer 4

• D1 and D4 dopa receptors
• Weakly to D2 receptors
• Sero receptors to >+/- symptoms

Question 5

What does the drug clozapine (antipsychotic) treat?

1

Answer 5

• Schizo, +/- symp

Question 6

What was thought negative symptoms were caused by (clozapine)?
1

Answer 6

• Irregular serotonergic activity

Question 7

What is the role of serotonin?

1

Answer 7

• Regulates dopa in areas e.g. mesolimbic pathway

Question 8

Why were schizophrenic symptoms linked to high levels of dopamine? (1950 earliest)
3

Answer 8

• Chlorpromazine and reserpine (antipsychotics) alleviate symptoms of schizo
• Both also induced tremors
• Side effects similar of Parkinson’s, caused by >dopa

Question 9

What are the main explanations of excess dopamine levels?

2

Answer 9

1) >Beta hydroxylase (enzyme that breaks down dopa) - synapse
2) Proliferation of D2 dopa receptors on postsynaptic cells = ^chance of summation

Question 10

Evaluate neurotransmitters as an explanation of schizophrenia?
3

Answer 10

Tenn et al. found rats given 9 amphetamine injections over 3 weeks = schizo symp e.g. stereotypical movements, or as rates are social animals = social withdrawal. Dopa antagonists (block D1 receptors) successful in reversing these effects

Veling et al. showed Moroccan immigrants = ^likely to be diagnosed w schizo than Turkish immigrants. Correlated w actual/perceived discrimination faced by each group. Environmental factors (stress)

Snyder found chlorpromazine = antagonist at many dopa receptors has antipsychotic effect. Haloperidol = dopa antagonist w narrower biochemical effects, yet ^effective in >schizo symp. Specific dopa receptors