Smad3 deficiency leads to increased MAO-B levels in the ventral midbrain. (A) Smad3-/- mice had higher MAO-B levels in the VM than Smad3+/+ mice. (B) VMAT-2 protein contents are not altered in Smad3-/- mice. Bars represent values normalized to β-tubulin from 6 mice per group, each measured two to three times. **P < 0.01, Student's t- test.