PACAP crosses the blood brain barrier and can be administered intravenously to decrease damage in several models of ischemia and is effective even when administered several hours after the ischemic episode (Uchida et al. 1996; Reglodi et al. 2000; Chen et al. 2006; Ohtaki et al. 2008). This evidence concerns the gene ADCYAP1 and ischemia.