Upregulation of putaminal dopamine D2 receptors in early Parkinson's disease: a comparative PET study with [11C] raclopride and [11C]N-methylspiperone.
Dopamine D2 receptor function was assessed in a PET study with 2 dopamine D2 receptor PET ligands, [11C]raclopride (RAC) and [11C]N-methylspiperone (NMSP), in early Parkinson's disease.


METHODS
Seven patients with early Parkinson's disease and 5 healthy volunteers were studied. Each underwent PET both with reversible [11C]RAC and with irreversible [11C]NMSP.


RESULTS
Upregulation of dopamine D2 receptors in the putamen contralateral to the predominant symptoms of Parkinson's disease was confirmed using both [11C]RAC and [11C]NMSP. Uptake of [11C]RAC in the contralateral putamen was 105% of uptake in the opposite putamen (P = 0.020). For [11C]NMSP, uptake in the contralateral putamen was 105% of uptake in the ipsilateral putamen (P = 0.011). No significant differences between Parkinson's disease patients and healthy volunteers were detected in any of the studied brain regions using either [11C]RAC or [11C]NMSP. No significant differences between [11C]RAC and [11C]NMSP uptake were detected in the striatum, whereas in the extrastriatal regions, [11C]NMSP showed significantly higher uptake than [11C]RAC both in healthy volunteers and in Parkinson's disease patients.


CONCLUSIONS
This study confirms an increase in dopamine D2 receptors in the putamen contralateral to the predominant symptoms, compared with the ipsilateral putamen, in early Parkinson's disease. This increase was seen both with reversible ligand [11C]RAC and with irreversible ligand [11C]NMSP and thus does not seem a consequence of depleted endogenous dopamine.
Kaasinen
V
V
Department of Neurology, University of Turku, Finland.
Ruottinen
H M
HM
Någren
K
K
Lehikoinen
P
P
Oikonen
V
V
Rinne
J O
JO
D002250:Carbon Radioisotopes; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000000981:diagnostic imaging* / Q000378:metabolism; D011699:Putamen / Q000000981:diagnostic imaging* / Q000378:metabolism; D020891:Raclopride; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D013134:Spiperone / Q000031:analogs & derivatives*; D014055:Tomography, Emission-Computed; D015854:Up-Regulation / Q000502:physiology
D002250:Carbon Radioisotopes; D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; D020891:Raclopride; D013134:Spiperone; C039167:3-N-methylspiperone