The invention provides for novel benzonaphthyridine derivatives and compositions comprising novel benzonaphthyridine derivatives. In some embodiments, the compounds are phosphodiesterase inhibitors. The invention further provides for methods for inhibition of phosphodiesterase comprising contacting phosphodiesterase with novel benzonaphthyridine derivatives or compositions comprising novel benzonaphthyridine derivatives. The invention further provides for methods for treatment of neurodegenerative diseases, increasing memory or long term potentiation with novel benzonaphthyridine derivatives or compositions comprising novel benzonaphthyridine derivatives. In some embodiments, the phosphodiesterase is PDE5.