Figure 4.

Effects of 8Br-cAMP or NE on β-actin and APP mRNA. Astrocytes were prepared as in Fig. 1. (A) Representative Northern blot indicates an increase in APP mRNA with increasing concentrations (50, 100, or 250 μM) of 8Br-cAMP. G3PDH mRNA was unaffected by 8Br-cAMP treatments. Subsequent experiments showed that 250 μM was the most effective and reliable 8Br-cAMP concentration for stimulating APP synthesis. (B) Representative Northern blot shows that 8Br-cAMP (250 μM) or NE (50 μM) treatment for 24 h increased APP mRNA and decreased β-actin mRNA levels. Three independent experiments produced similar effects.