Figure 4.

PDE activity in the brain stem of PDE4D-deficient (a) and PDE4B-deficient (b) mice and their wild-type littermates. PDE activity was determined using 1 μM cAMP as substrate in the absence (total activity) or presence (rolipram-insensitive activity) of 10 μM rolipram. The rolipram-sensitive activity (PDE4 activity) was obtained by subtracting the rolipram-insensitive activity from the total PDE activity. Values were corrected for the amount of protein added to the assay. Results are expressed as mean ± SEM (n = 3–9). *Significantly different at P < 0.05.