Table 3.
The PET studies of dopaminergic function in individuals at increased risk of schizophrenia
| Study | Medication status MN/MF/M/HC | Phenotype | Radiotracer | Study type | Findings (standard effect size) |
|---|---|---|---|---|---|
| Bloemen et al. 2013b | 14/0/0/15 | UHR | [123I]IBZM | Dopamine depletion | - |
| Howes et al. 2009 | 23/0/1/12 | UHR | [18F]-DOPA | Synthesis capacity | ↑ (0.75) |
| Howes et al. 2011ba | 30/0/0/29 | UHR | [18F]-DOPA | Synthesis capacity | ↑ (1.18) |
| Mizrahi et al. 2013 | 12/0/0/12 | UHR | [11C]-+-PHNO | MIST induced dopamine release | ↑ (0.98) |
| Suridjan et al. 2013 | 12/0/0/12 | UHR | [11C]-+-PHNO | D2high/D3 receptor availability | - |
| Abi-dargham et al. 2004 | 13/0/0/13 | Schizotypal | [123I]IBZM | Amphetamine induced dopamine release | ↑ (0.93) |
| Howes et al. 2012 | 16/0/0/16 | Auditory hallucinations (otherwise healthy) | [18F]-DOPA | Synthesis capacity | - |
| Huttunen et al. 2008 | 17/0/0/17 | First degree relatives of patients with schizophrenia | [18F]-DOPA | Synthesis capacity | ↑ |
| Shotbolt et al. 2011 | 6/0/0/20 | Twins of patients with schizophrenia | [18F]-DOPA | Synthesis capacity | - |
| Soliman et al. 2008c | 16/0/0/10 | “Potential schizotype” | [11C] raclopride | MIST induced dopamine release | ↑ |
↑ = significantly higher in patient group; ↓ = significantly lower level in patient group; - = no significant difference
[123I]IBZM - [123I](S)-(-)-3-iodo-2-hydroxy-6-methoxy-N- [(1-ethyl-2-pyrrolidinyl)methyl]benzamide; [11C]-+-PHNO - [11C]-(+)-4-propyl-9-hydroxynaphthoxazine; [18F]-DOPA- 6-[18F]fluoro-L-Dihydroxyphenylalanine; MIST – Montreal Imaging Stress Task; D1, D2, D3= Dopamine receptor sub-type 1, 2 and 3 respectively
MN- antipsychotic naïve; HC – healthy control; M – currently taking antipsychotic medication; MF- antipsychotic free; UHR – Ultra high risk for psychosis
Synthesis capacity increased only in subgroup that transitioned to psychosis (n=9)
No significant differences between controls and UHR but correlation between receptor occupancy by dopamine and positive symptoms
MIST leads to significant decrease in tracer binding in subgroup characterized as ‘potential schizotype’ on the basis that subjects scored >1.95 SD on the negative subscale of Chapman schizotypy questionnaire.