Immunocytochemical studies of substance P and leucine-enkephalin in Huntington's disease

The distribution of substance P and leucine-enkephalin in selected regions of brain obtained postmortem from patients with Huntington's disease and from neurologically normal persons has been studied with immunocytochemical techniques. In the normal brain, substance P immunoreactivity was identified in medium-sized neurons in the neostriatum, in neurons of the external segment of the globus pallidus, and in fine fibers in teh neostriatum, inner segment of the globus pallidus, and in the pars reticulata of the substantia nigra. Huntington's disease brains all exhibited a marked decrease in substance P fiber density in the substantia nigra and globus pallidus. A few medium-sized neurons with substance P immunoreactivity remained in the neostriatal remnant. Leucine-enkephalin immunoreactive processes were present throughout the neostriatum of normal brain, and were densely packed in the external segment of the globus pallidus and in the substantia nigra. A uniform population of medium-sized neurons containing immunoreactive leucine-enkephalin was present in the caudate and putamen. By contrast, in the Huntington's disease brains there was a marked diminution of fiber staining in the globus pallidus and substantia nigra. A few medium-size neurons and sparse fibers with leucine-enkephalin immunoreactivity persisted in the atrophic neostriatum. These observations are consistent with previous reports of regional peptide concentrations in both normal and Huntington's disease brain. Cells containing substance P and leucine-enkephalin immunoreactivity persist in the basal ganglia in brains from patients with Huntington's disease, and we have no evidence that cellular content of one or the other peptide is associated with disproportionate cell death or survival.