Cortical somatostatinergic system not affected in Alzheimer's and Parkinson's diseases.

A reduction in the levels of somatostatin-like immunoreactivity (SLI) and somatostatin binding sites in the cerebral cortex has been previously reported to occur in Alzheimer's disease (AD) and Parkinson's disease with associated dementia. In the present study, the levels of both SLI and high affinity [3H]somatostatin binding sites have been measured in the frontal (Brodmann area 9) and temporal (Brodmann area 21) cortices in patients with presenile and senile Alzheimer's disease, and in mentally normal and cognitively impaired cases of Parkinson's disease. The results were compared with those obtained from a group of normal patients matched for age and postmortem delay. No significant changes in SLI or somatostatin binding in the frontal and temporal cortex were found between any of the disease groups. These results suggest that involvement of the somatostatinergic system in AD or Parkinson's disease is not a consistent or primary neurochemical feature of these diseases.