Role of PDE9 in Cognition.

Inhibition of phosphodiesterases (PDEs) has been demonstrated to enhance performance of animals in various cognition tasks and accordingly PDE inhibitors have been proposed as new approach for treatment of cognitive dysfunction (Reneerkens et al. Psychopharmacology 202:419-443, 2009; Schmidt Curr Top Med Chem 10(2):222-230, 2010). One of the eleven PDE isoforms, showing expression in cognition relevant brain regions across species, is PDE9, which hydrolyzes cGMP only. Furthermore, it is well established that the nitric oxide (NO)/cGMP pathway and NMDA receptor signaling has a crucial function in synaptic plasticity and cognitive function. In this chapter, we will provide an overview on PDE9, its expression and function in the brain, and hence, its relevance for synaptic plasticity and cognitive performance. Moreover, the recent advances of PDE9 inhibition as potential therapeutic approach for treatment of cognitive dysfunction in CNS disorders will be discussed.