Exploring Dihexa: A Peptide for Cognitive Function Dihexa (also known as PNB 0408) is an experimental small molecule derived from angiotensin IV. It was engineered to cross the bloodbrain barrier and has shown synaptogenic effects in preclinical models. The often quoted You're sleeping eight hours and still waking up in a fog. It's not about the hours. It's about what's happening while you're asleep. For me it was a peptide called DSIP UT Austin Dell Pediatric Research Institute Hensel Phelps