ADCYAP1 and systemic inflammatory response syndrome: Concerning the source of the extra amount of PACAP in the aforementioned biological fluids of these patients compared to the normal controls they hypothesized that the trauma related endogenous overproduction, the damage of the blood-brain barrier, the secondary CNS injuries, the systemic inflammatory response syndrome and the elevated ceruloplasmin (PACAP-binding protein in the serum) concentration together can be responsible for the observed prolonged elevation.