INCREASED EXPRESSION OF PREPRONEUROPEPTIDE-Y AND PREPROSOMATOSTATIN MESSENGER-RNA IN STRIATUM AFTER SELECTIVE SEROTONINERGIC LESIONS IN RATS

The levels of neuropeptide Y and somatostatin may change when serotoni nergic neurotransmission is altered in different brain regions. To ass ess whether serotonin regulates the synthesis of these peptides, we me asured the levels of preproneuropeptide Y (ppNPY) and preprosomatostat in (ppSOM) mRNA in different brain regions after intracerebroventricul ar injection of 5,7-dihydroxytryptamine (5,7-DHT), a selective seroton in neurotoxin. The mRNA of these peptides significantly increased in t he striatum but not in hippocampus and frontal cortex. It thus appears that serotonin has an inhibitory effect on the biosynthesis of neurop eptide Y and somatostatin in striatum whereas it probably acts by stim ulating the release of these peptides in hippocampus and frontal corte x.