OBJECTIVE To investigate the relationship between diabetes and somatostatin (SOM). METHODS We established a streptozocin-induced diabetic rats model and studied the changes of SOM mRNA in hippocampi of diabetic and normal rats by using in situ hybridication and computer image analysis. We studied the mechanism of chronic diabetes encephalopathy by observing the changes of somatostatin mRNA in the hippocampus of diabetic rats was studied. RESULT The number, light density and average area of positive cells in dentate gyrus area of hippocampus in diabetes model were reduced significantly as compared with normal rats (P < 0.01). CONCLUSION A decline in SOM mRNA expression may play a role in chronic diabetes encephalopathy because of SOM effect in brain.