Which MAO-B inhibitor is used to treat canine cognitive dysfunction (old dog dementia)?

• A. Fluoxetine
• B. Diazepam
• C. Selegiline
• D. Enalapril

Answer: (C)

The concept being tested is how boosting dopamine in the brain can help manage canine cognitive dysfunction. Selegiline is the drug that does this by selectively inhibiting MAO-B, the enzyme that breaks down dopamine. With MAO-B blocked, dopamine levels stay higher in brain circuits involved in learning, memory, and behavior, which can improve cognitive function and daily activities in older dogs. It’s a targeted approach that works well for CCD because it directly addresses the dopaminergic deficit seen with aging brains, and at therapeutic doses it has fewer dietary interaction risks than non-selective MAO inhibitors.

Other options don’t act on this dopaminergic mechanism. Fluoxetine is an antidepressant affecting serotonin, not an MAO-B inhibitor for CCD. Diazepam is a benzodiazepine that sedates and can worsen some CCD symptoms. Enalapril is an ACE inhibitor used for cardiovascular conditions and has no role in treating CCD.