Phosphodiesterase-4(PDE4), an important component of the cyclic adenosine monophosphate (cAMP) cascade, selectively metabolizes cAMP in the brain to the inactive monophosphate. Their inhibitors may offer novel strategies in the treatment of depression. However, its development as antidepressant drugs has been encumbered by their side effects profile of non-selective PDE inhibitors like nausea, emesis, gastrointestinal...