DIFFERENTIAL CHANGES IN NEUROCHEMICAL MARKERS OF STRIATAL DOPAMINE NERVE-TERMINALS IN IDIOPATHIC PARKINSONS-DISEASE

To determine the extent that different dopamine (DA) neuronal markers provide similar estimates of striatal (caudate and putamen) DA nerve t erminal loss in idiopathic Parkinson's disease (PD), we compared, in p ostmortem striatum of 12 patients with PD and 10 matched controls, lev els of five different DA neuronal markers. These markers included DA i tself, three different estimates of the density of the DA transporter (DAT) ([H-3]GBR 12,935 and [H-3]WIN 35,428 binding; DAT protein immuno reactivity), and one estimate of the vesicular monoamine transporter ( VMAT2; [H-3]DTBZ binding). Striatal levels of all examined DA markers in PD were significantly intercorrelated. However, the magnitude of lo ss relative to controls was unequal (DAT protein = DA > [H-3]WIN 35,42 8 > [H-3]DTBZ > [H-3]GBR 12,935), with the differences more marked in the severely affected putamen. The less severe reduction of binding of the DAT/VMAT2 radioligands relative to DA and DAT protein could be ex plained by differential regulation/degeneration of different DA nerve terminal components or lack of specificity of the radioligands for the DA neuron. These postmortem data may help in interpretation of in viv o neuroimaging studies in PD in which only one radioligand is routinel y employed.