Role of PACAP in neural stem/progenitor cell and astrocyte--from neural development to neural repair.

After central nervous system (CNS) injury, reactive astrocytes display opposing functions, inducing neural repair and axonal regeneration via the release of growth factors, or forming a glial scar which acts as a barrier to axonal regeneration. Endogenous neural stem/progenitor cells have also recently been identified at the site of CNS injury, where they have been shown to differentiate into mature neurons in an animal model of ischemia. However, the pathophysiological mechanisms underpinning the contribution of reactive astrocytes and neural stem/progenitor cells to neural repair are still to be fully elucidated. Pituitary adenylate cyclase activating polypeptide (PACAP) is widely expressed in the CNS, where it has been shown to exert numerous biological effects. This review will summarize the current state of knowledge regarding the expression of PACAP and its receptors during neural development, as well as the involvement of PACAP in astrocytes and neural stem/progenitor cell biology. In addition, we will also discuss emerging evidence that implicates PACAP in neurogenesis and neural repair in response to brain pathophysiology.