Diminution of preprosomatostatin-mRNA in cerebral cortex of the aged rat

The aim of the present study was to examine the effect of normal aging on somatostatin neurotransmission. Somatostatin gene expression was analysed in several regions of the cerebral cortex and hippocampus in 3, 7 and 21 month-old Sprague-Dawley rats using quantitative in situ hybridization with a 48mer oligodeoxynucleotide antisense probe. Furthermore the distribution of 125I-Tyr11 somatostatin receptor binding sites was studied using quantitative receptor autoradiography. The results demonstrated a significant reduction of preprosomatostatin-mRNA in the frontal cortex of the aged (21 month) group compared with the young (3 month) and the middle-aged (7 month) groups. The receptor binding densities of the aged (21 month) group tended to be lower, compared to the other groups although no significant region-specific changes were evident. These results indicate neurochemical changes in somatostatin-containing neurons in the frontal cortex during aging.