Decreased transcription of neuronal polyadenylated RNA during senescence in nuclei from rat brain cortex.

Neuronal and glial cell-enriched nuclei were prepared from the brain cortex of rats of different ages for study of alterations in the synthesis of cellular RNA with age. RNA synthesis by isolated neuronal nuclei was substantially reduced in senescent rats, whereas that of glial nuclei remained constant throughout development. The nuclear content of polyadenylic acid-containing RNA in neurons was particularly decreased in old rats. The results show that the activity of the chromatin-bound neuronal RNA polymerase declines during senescence, an observation indicating an age-related reduction in template activity in neuronal nuclei. The activity of nuclear poly(adenylate) polymerase also progressively decreases in aging neurons. The decrease in the transcription and polyadenylation of nuclear RNA may contribute to the decline in neuronal protein synthesis observed in old animals.