ANALYSIS OF RNA SYNTHESIZED BY AN ISOLATED RAT-BRAIN SYNAPTOSOMAL FRACTION

A synaptosomal fraction derived from rat brain, when incubated in an appropriate medium, incorporated [5-3H]uridine into RNA. On the basis of sedimentation analysis, RNA-DNA hybridization and metabolic inhibitor studies, mitochondrial RNA species appeared to be the major, if not sole, RNA products synthesized by the isolated synaptosomal fraction. EM autoradiographic analysis showed that about 50% of the incorporation of [5-3H]uridine into RNA by this fraction occurred in the presynaptic endings. The capacity of mitochondrial RNA synthesis in isolated nerve endings declined as the age of the animal increased from 10-30 days, and by 60 days of age discrete mitochondrial RNA species were barely detectable.