Striosomal organization of substance P-like immunoreactivity in parkinsonian patients.

We designed this study to evaluate the expression of substance P (SP) in the striatum and the globus pallidus in normal controls, idiopathic Parkinson's disease (PD), and striatonigral degeneration (SND). We determined immunohistochemically the expression of SP in formalin-fixed, paraffin-embedded brain tissues using the free-floating method. In normal controls, we observed SP-like immunoreactivity in the internal segment of the globus pallidus, where the SP-positive fibers showed typical "woolly fiber" patterns. SP expression in the striatum had the characteristic patchwork of striosomes. Patients with PD showed the normal distribution pattern of SP. By comparison, in patients with SND, there was a striking diminution of SP in the putamen, while the SP-positive patches persisted in the caudate nucleus. This study represents the first unequivocal immunohistochemical demonstration of SP-positive striosomes in the human striatum.