(A) Both wild type (Pde11a+/+) and knockout (Pde11a−/−) animals respond with suppression of their corticosterone levels to dexamethasone; however, the Pde11a−/− mice fail to suppress significantly in response to low dose dexamethasone; they suppressed, comparable to Pde11a+/+, in response to high-dose dexamethasone. Overall, there are no significant differences between Pde11a+/+ and Pde11a−/− mice. *p = 0.001 and p < 0.001 in low and high doses respectively. **p = 0.08 and p < 0.001 in low and high doses respectively. (B) ACTH responses to low and high dose dexamethasone: ACTH levels were suppressed as expected, however following high dose dexamethasone treatment in Pde11a−/− mice, suppression did not reach statistical significance (*p < 0.01, **p = 0.3) (C) Total adrenal PKA activity at baseline and after the addition of cAMP (D) in Pde11a+/+ and Pde11a−/− animals; knockout mice have higher PKA activity, but the difference only approached tendency to be significant after the addition of cAMP (p = 0.14).