Phosphodiesterase type 5 (PDE5) inhibition improves object recognition memory: Indications for central and peripheral mechanisms

► Vardenafil improved normal memory function and reversed memory deficits. ► UK-343,664 did not affect normal memory function or reverse MK-801 deficits. ► UK-343,664 reversed the scopolamine induced memory deficit. ► Vardenafil crossed the BBB, whereas UK-343,664 did not. ► PDE5-Is improve memory function through central and peripheral mechanisms.