Somatostatin immunoreactivity is reduced in Parkinson's disease dementia with Alzheimer's changes.

Somatostatin-like immunoreactivity (SLI) was measured in postmortem brain tissue from 15 control patients, 7 non-demented parkinsonian patients and 7 demented parkinsonian patients who had Alzheimer-type cortical pathology. The non-demented parkinsonian patients had normal concentrations of SLI in the cerebral cortex, hippocampus, amygdala, putamen, caudate or globus pallidus. Demented parkinsonian patients with Alzheimer-type cortical pathology had significantly reduced (approximately 40%) levels of SLI in both the frontal (Brodmann area 6) and temporal (Brodmann area 21) cortex. These findings suggest that parkinsonian dementia with Alzheimer-type pathology like Alzheimer's disease itself, is associated with reduced concentrations of cortical somatostatin.