Effect of controlled cortical impact on the passage of pituitary adenylate cyclase activating polypeptide (PACAP) across the blood-brain barrier
Injuries to the central nervous system can affect the blood-brain barrier (BBB), including disruption and influencing peptide transport across the BBB. Pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) is a potent neurotrophic and neuroprotective peptide currently being investigated for its therapeutic role following injury to the central nervous system and can cross the BBB in a saturable manner. The goal of the current study was to investigate for the first time PACAP38 uptake by the brain following traumatic brain injury (TBI). Using radioactively labeled PACAP38, we measured the levels of PACAP38 present in the injured, ipsilateral cortex in Sham-treated mice compared to mice receiving a controlled cortical impact (CCI), a model of TBI. Experiments were conducted at 6 different time points (from 2 h up to 4 weeks) following CCI to determine temporal changes in PACAP38 transport. PACAP38 uptake was increased at 2 and 72 h post-CCI compared to Sham. We did not detect changes in PACAP38 uptake in the contralateral cortex and cerebellum between Sham and CCI-treatment. The rate of PACAP38 transport into the ipsilateral cortex following CCI was increased 3.6-fold 72 h after compared to 2 h post-CCI. In addition, the rate of transport into the cerebellum was greater than that of the cortices. The data presented here shows PACAP38 transport is temporally altered following CCI-treatment and PACAP38 uptake is greater in the cerebellum compared to the cortices.