Cellular distribution of GAP-43 mRNA in hippocampus and cerebellum of adult rat brain by in situ RT-PCR

The growth-associated protein GAP-43 is a presynaptic membrane phosphoprote in that plays a key role in guiding the growth of axons and in modulating t he formation of new synapses. To identify the cells that synthesize GAP-43 mRNA, we applied direct in situ reverse transcription-polymerase chain reac tion (in situ RT-PCR) in cerebellum and hippocampus of adult rat brain. In situ RT-PCR revealed GAP-43 mRNA in cerebellar granule cells, in Purkinje c ells and in some interneurons of the molecular layer. Previous in situ hybr idization studies had demonstrated a dense label throughout the granular la yer of the cerebellar cortex but no labeling of other cerebellar neurons. H ippocampal cells showing distinct GAP-43 mRNA signal after in situ RT-PCR w ere CA1 and CA3 pyramidal neurons, CA4 hilar cells, and dentate gyrus granu le cells, whereas in situ hybridization studies had detected GAP-43 mRNA on ly in CA3 and CA1 pyramidal neurons. our data indicate that GAP-43 mRNA is widely distributed, suggesting that many cell types are potentially involve d in synaptic plasticity events.