Striatal D₂receptor binding in 22q11 deletion syndrome: An [¹²³ I]IBZM SPECT study

It has been hypothesised that in subjects with 22q11 deletion syndrome (22q11DS) disturbances of the dopamine (DA) system contribute to their increased risk for cognitive deficits and psychiatric problems. However, central DAergic neurotransmission in 22q11DS has not been investigated. We measured striatal D₂ receptor binding potential (D₂R BP_ND) using (S)-(-)-3-iodo-2-hydroxy-6-methoxy-N-[(1-ethyl-2-pyrrolidinyl)methyl] benzamide-single photon emission computed tomography ([¹²³I]IBZM SPECT) in 12 adults with 22q11DS and 12 matched controls. Correlations between D₂R BP_ND and plasma prolactin (pPRL) levels were also determined. 22q11DS subjects and controls had similar D₂R BP _ND. There was a positive correlation between D₂R BP _ND and pPRL values in controls, but no such relation was found in 22q11DS subjects. This study suggests that a 22q11 deletion does not affect striatal DAergic neurotransmission in the living human brain. However, the disturbed relationship between D₂R BP_ND and pPRL values suggests DAergic dysfunction at a different level. Further studies on DAergic function in extra-striatal brain regions and under challenged conditions are needed.