Increased cerebrospinal fluid cyclo(His-Pro) content in schizophrenia

Cyclo(His-Pro) (CHP) is a peptide endogenous to human brain and cerebrospinal fluid (CSF). In animal studies administration of exogenous CHP augments dopaminergic neurotransmission. To explore the role of this peptide in schizophrenia, a disease characterized by a hyperdopaminergic state, we have measured CSF CHP levels in control, never-medicated schizophrenics and medicated schizophrenics. Our data show a 53% increase in CSF levels of CHP in never-medicated schizophrenics (p = 0.015), and a 25% increase in medicated schizophrenics when compared to controls. We speculate that CHP may contribute to the expression of hyperdopaminergic symptoms in schizophrenia.