Abstract

BACKGROUND: The effect of pituitary adenylate cyclase activating polypeptide (PACAP) during traumatic brain injury (TBI) and whether it can modulate secondary injury has not been reported previously. The present study evaluated the potential protective effects of ventricular infusion of PACAP in a rat model of TBI. METHODS: Male Sprague Dawley rats were randomly divided into 3 treatment groups (n=6, each): sham-operated, vehicle (normal saline)+TBI, and PACAP+TBI. Normal saline or PACAP (1 μg/5 μL) was administered intracerebroventricularly 20 minutes before TBI. Right parietal cortical contusion was produced via a weight-dropping method. Brains were extracted 24 hours after trauma. Histological changes in brains were examined by HE staining. The numbers of CD4+ and CD8+ T cells in blood and the spleen were detected via flow cytometry. RESULTS: In injured brain regions, edema, hemorrhage, inflammatory cell infiltration, and swollen and degenerated neurons were observed under a light microscope, and the neurons were disorderly arrayed in the hippocampi. Compared to the sham group, average CD4+ CD8– lymphocyte counts in blood and the spleen were significantly decreased in rats that received TBI+vehicle, and CD4– CD8+ were increased. In rats administered PACAP prior to TBI, damage was attenuated as evidenced by significantly increased CD4+, and decreased CD8+, T lymphocytes in blood and the spleen. CONCLUSION: Pretreatment with PACAP may protect against TBI by influencing periphery T cellular immune function.

Authors and Affiliations