Huntington's disease is accompanied by changes in the distribution of somatostatin-containing neuronal processes.

The distribution of somatostatin-like immunoreactivity in the caudate, putamen, globus pallidus and ventral mesencephalon of the normal human brain has been studied with immunocytochemical techniques, and compared to that seen in Huntington's disease. Within the normal striatum, sparsely distributed varicose fibers and a population of medium-sized neurons were stained. In Huntington's disease, somatostatin immunoreactive striatal neurons appear to degenerate in proportion to the loss of striatal tissue, but there is an increase in the density of immunostained varicose fibers. In contrast, the pattern and amount of fiber staining in the substantia nigra appeared virtually unchanged from that seen in the normal brain. The morphology of striatal perikarya containing somatostatin-like immunoreactivity and the patterns of fiber staining in normal and Huntington's disease pallidum and substantia nigra suggest that striatal neurons containing somatostatin-like immunoreactivity are local circuit neurons.