Effects of putative cognitive function-enhancing drugs and dopaminergic agents on somatostatin and neuropeptide Y in rat brain.

Reduced levels of somatostatin and neuropeptide Y (NPY) have been demonstrated in the brain of patients with some organic mental disorders. We designed the present study to test whether drugs thought to be effective in improving cognitive functions in these disorders increased the levels of these two peptides. The drugs were given to normal rats for 14 days to examine chronic effects on regional brain somatostatin and NPY levels. Amantadine and bifemelane increased these peptide levels. Idebenone and indeloxazine had little effect. The effect of dopaminergic agents on peptide levels was also tested in rats. 1-Dihydroxyphenylalanine increased somatostatin levels in whole brain, and hypothalamic NPY levels, and reduced NPY levels in the cerebral cortex, hippocampus and striatum. Sulpiride increased the levels of NPY in the striatum and brainstem. 6-Hydroxydopamine decreased cortical somatostatin levels, and increased striatal NPY levels. These findings indicate that some agents used to improve cognitive function impairment in organic mental disorders may increase somatostatin and NPY content in the brain of rats. Also, it is suggest that these peptides are under different influences of the dopaminergic system in the brain.