Effect of treatment with L-dopa/carbidopa or L-selegiline on striatal dopamine transporter SPECT imaging with [123I]beta-CIT.
The effect of subchronic treatment with L-dopa/carbidopa or L-selegiline on striatal dopamine transporters (DAT) was examined in patients with idiopathic Parkinson's disease with SPECT (single photon emission computed tomography) using [123I]beta-CIT (2beta-carbomethoxy-3beta-[4-iodophenyl]tropane) as the radiotracer. Patients who were not currently being treated with these medications were given either 750 mg L-dopa/carbidopa per day (n = 8) or 10 mg L-selegiline per day (n = 8). [123I]beta-CIT imaging was performed three times in each patient: at baseline before treatment, while on medication and after 4-6 weeks of drug treatment, and following withdrawal from medication (approximately 1 week for L-dopa/carbidopa and 9 weeks for L-selegiline). Comparison of scans 2 and 3 provided a measure of drug occupancy of the [123I]beta-CIT binding site; comparison of scans 1 and 2 provided a measure of both up- or downregulation of DAT levels and drug occupancy following subchronic drug treatment. DAT levels were assessed from an image acquired approximately 22 hours after radiotracer injection as a ratio of regional brain activities: (striatum - occipital)/occipital. Striatal DAT levels were not significantly different when any two of the three scans were compared for both drug treatments. These results suggest that typical clinical doses of L-dopa/carbidopa and L-selegiline do not induce significant occupancy of the [123I]beta-CIT binding site and that 4-6 weeks of treatment causes no significant modulation of DAT levels. These results support the validity of measuring DAT levels with [123I]beta-CIT without the need to withdraw patients from medication treatment.
Innis
R B
RB
Department of Psychiatry, Yale University School of Medicine, VA Connecticut at West Haven 06516, USA.
Marek
K L
KL
Sheff
K
K
Zoghbi
S
S
Castronuovo
J
J
Feigin
A
A
Seibyl
J P
JP
D000368:Aged; D000978:Antiparkinson Agents / Q000627:therapeutic use*; D001692:Biological Transport; D002230:Carbidopa / Q000627:therapeutic use*; D003042:Cocaine / Q000031:analogs & derivatives*; D003342:Corpus Striatum / Q000000981:diagnostic imaging* / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D007980:Levodopa / Q000627:therapeutic use*; D008297:Male; D008995:Monoamine Oxidase / Q000378:metabolism; D009778:Occipital Lobe / Q000378:metabolism; D010300:Parkinson Disease / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D012642:Selegiline / Q000494:pharmacology / Q000627:therapeutic use*; D015899:Tomography, Emission-Computed, Single-Photon; D016896:Treatment Outcome
D000978:Antiparkinson Agents; D007457:Iodine Radioisotopes; D012642:Selegiline; D007980:Levodopa; C069723:2beta-carbomethoxy-3beta-(4-iodophenyl)tropane; D008995:Monoamine Oxidase; D003042:Cocaine; D002230:Carbidopa; D004298:Dopamine