Striatal dopamine nerve terminal markers but not nigral cellularity are reduced in spinocerebellar ataxia type 1

We previously reported markedly reduced (−76%) dopamine (DA) levels in the putamen of seven patients with spinocerebellar ataxia type 1 (SCA1) who had no evidence of nigral cell loss or parkinsonism. To determine whether the DA reduction was accompanied by loss of DA nerve terminals, we measured levels of the DA transporter ([ 3 H]WIN, 35,428 binding; DA transporter protein) and the vesicular monoamine transporter ([ 3 H]DTBZ binding) in the putamen of these patients. As compared with the controls (n = 14), mean putamen concentrations of [ 3 H]WIN 35,428 binding (−45%), dopamine transporter protein (−61%), and [ 3 H]DTBZ binding (−48%) were significantly reduced in this SCAl subgroup. We conclude that the degeneration in nigrostriatal DA neurons begins at the nerve ending in SCA1.