Correlative single photon emission computed tomography imaging of [123I]altropane binding in the rat model of Parkinson's

IntroductionThis study used the dopamine transporter (DAT) probe, [123I]-2β-carbomethoxy-3β-(4-fluorophenyl)-N-(3-iodo-E-allyl)nortropane ([123I]altropane), to assess the DAT levels in the 6-hydroxydopamine rat model of Parkinson's disease. We sought to assess if the right to left [123I]altropane striatal ratios correlated with dopamine content in the striatum and substantia nigra and with behavioural outcomes.Methods[123I]altropane images taken pre- and postlesion were acquired before and after the transplantation of neural stem/progenitor cells. The images obtained using [123I]altropane and single photon emission computed tomography (SPECT) were compared with specific behavioural tests and the dopamine content assessed by high-performance liquid chromatography.Results[123I]altropane binding correlated with the content of dopamine in the striatum; however, [123I]altropane binding did not correlate with the dopamine content in the substantia nigra. There was a significant correlation of altropane ratios with the cylinder test and the postural instability test, but not with amphetamine rotations. The low coefficient of determination (r2) for these correlations indicated that [123I]altropane SPECT was not a good predictor of behavioural outcomes.ConclusionOur data reveal that [123I]altropane predicts the integrity of the striatal dopamine nerve terminals, but does not predict the integrity of the nigrostriatal system. [123I]altropane could be a useful marker to measure dopamine content in cell replacement therapies; however, it would not be able to evaluate outcomes for neuroprotective strategies.