Immunocytochemical Studies of Substance P and Met-Enkephalin in the Globus Pallidus of Progressive Supranuclear Palsy

Abstract

The globus pallidus (GP) is considered to receive the afferent nerve fibers originating mainly from the striatum1 and may play a role in expression of the striatal functions. 2 Substance P(SP) and Met-enkephalin (MEnk) are neuropeptides that have been demonstrated in the basal ganglia and appear to be part of the straitopallidal and striatonigral projections.3 4 A study on the regional distribution of the peptides in the GP showed the internal segment to be rich in SP and an abundance of MEnk in the external segment.3 Based on neurochemical measurements and on immunohistochemical studies, abnormalities in basal ganglia SP and MEnk have been reported in Huntington’s disease (HD)4–7 and Parkinson’s disease (PD).6–8 Progressive supranuclear palsy (PSP), a parkinsonian-like syndrome, is characterized by supranuclear ophthalmoplegia, axial dystonia, and pseudobulbar palsy.9 Histologically, neuronal cell loss, gliosis, and neurofibrillary tangles involve mainly the globus pallidus, subthalamic nucleus, substantia nigra, and other brainstem tegmental nuclei. Few reports have appeared on SP and MEnk in the basal ganglia of PSP. In one study no significant alterations were observed,10 and one case report showed some decrease in SP content in the external segment of the pallidum.11 To ascertain whether some alteration is present in the striatal efferent nerve terminals, we performed an immunohistochemical study on the globus pallidus of PSP patients.