SOMATOSTATIN ENHANCES NEUROFILAMENT EXPRESSION AND NEURITE OUTGROWTH IN CULTURED RAT CEREBELLAR GRANULE CELLS

Somatostatin acid its receptors are transiently expressed at a high le vel in the cerebellum around birth, before declining to adult levels b y 2-3 weeks postnatally, We therefore investigated the neurotrophic ef fects of somatostatin (SS) on rat cerebellar granule cells in culture by measuring the percentage of cells with processes, the content of mR NA and protein for neurofilament (NF) and mRNA for glutaminase, and th e number of viable cells (MTS assay). SS increased the percentage of c ells with processes at 8 h after plating. After 1 day in vitro (DIV), SS caused a 2-fold increase in NF mRNA, and a 23% increase in NF prote in. The mRNA increase was maximal at DIV1 whereas by DIV7 the NF prote in content of control cells reached that of SS-treated cells. SS had n o effect on glutaminase mRNA or on the number of viable neurons from e ither postnatal day 5 or 8 animals. These results demonstrated that SS has a neurotrophic effect on neurite production, including initiation of neurite outgrowth, but no effect on neuronal survival, cell prolif eration, or phenotype differentiation (glutaminase expression), and su pport the possibility that SS plays a role in the differentiation of i mmature cerebellar granule cells during central nervous system develop ment.