DAT Scan Radiopharmaceutical Binding Target
The radiopharmaceutical used in a dopamine transporter (DAT) scan binds specifically to the dopamine transporter (DAT), not to D4 receptors, vesicular monoamine transporter-2 (VMAT2), or other dopamine receptors. 1, 2
Mechanism and Binding Specificity
I-123 ioflupane (DaTscan) binds selectively to presynaptic dopamine transporters (DAT) located on dopaminergic neurons in the striatum. This allows visualization of nigrostriatal dopaminergic neuronal integrity. 1, 2
The radiotracer does NOT bind to dopamine receptors (including D4 receptors), VMAT2, or other receptor subtypes. The binding is highly specific to the dopamine transporter protein on the presynaptic membrane. 1, 2
DAT is the carrier protein that transports dopamine across the presynaptic membrane and terminates dopamine action in the synapse via reuptake. 3
Clinical Distinction from VMAT2
VMAT2 is a completely different target from DAT. VMAT2 is located on vesicular membranes within the presynaptic terminal and packages dopamine into synaptic vesicles, while DAT is on the plasma membrane and reuptakes dopamine from the synaptic cleft. 4, 5
Different radiotracers are used to image VMAT2 (such as [11C]PE2I for research purposes), but clinical DAT scans use I-123 ioflupane which binds exclusively to DAT. 6, 7
While both DAT and VMAT2 can serve as presynaptic markers of dopaminergic function, they are distinct molecular targets with different cellular locations and functions. 5
Imaging Pattern
Decreased radiotracer uptake in the striatum indicates loss of nigrostriatal dopaminergic neurons, typically progressing from posterior putamen to anterior caudate regions. 1, 2
The scan visualizes presynaptic dopaminergic terminals specifically through DAT binding, making it abnormal in all neurodegenerative Parkinsonian syndromes (PD, MSA, PSP, CBD) but normal in essential tremor and drug-induced parkinsonism. 1, 2, 8