DYNAMICS OF GENE-EXPRESSION FOR MICROTUBULE-ASSOCIATED PROTEIN MAP1B, EMBRYONIC ALPHA-TUBULIN AND LATE NEURAL BETA-TUBULIN MESSENGER-RNAS IN THE HIPPOCAMPUS OF AGED RATS

In the present study we characterized the developmental changes in the prevalence of mRNA coding for microtubule-associated protein, MAP1B, embryonic α-tubulin and late neural β-tubulin in rat hippocampus and forebrain from 1 to 720 days of age using RNA gel-blot analysis. We find that (i) the microtubule-associated protein, MAP1B, signal was relatively abundant at early postnatal stages when compared with mature animals. The hybridization signal in the 24-month-old rats was was ∼1.7 times that observed in 6-month-old rats. (ii) Embryonic α-tubulin and late neural β-tubulin were differentially regulated during rat brain development. This regulation is characterized by a dramatic decrease in the amount of α-tubulin after day-1 and a coincident increase in the production of late neural β-tubulin. Both messages became stabilized at moderate levels during the subsequent developmental stages. However, the averaged signal for β-tubulin was then ∼1.8-fold increased in 24- vs. 6-month-old rats. These results are consistent with hypothesis of an age-associated increase in reactive synaptogenesis where the healthy neurons sprout new connections to compensate for neuronal loss occurring in neighboring neurons. © 1992.