I tried Neuro fuel to boost long-term potentiation and to encode long-term memory in my brain. Artichoke Extract is the safest and most effective PDE4 inhibitor. And Forskolin is the only nootropic known to naturally increase cAMP levels. However I felt the effects are very subtle and mental clarity was not as good as i expected. It also cause me to have diahorrea due to side effect with Forskolin with just 2 pills. because increased cAMP affects the smooth muscle in your gastrointestinal tract. Things move through your intestines faster with Forskolin.