Influence of pressure on VIP concentration within the chick choroid

Abstract <strong>Purpose</strong>: Regulation of intraocular pressure (IOP) is important for ocular integrity and health. A recent study presented vasoactive intestinal peptide (VIP) as potential IOP coregulator. The aim of this study was to investigate VIP levels under increased pressure in an avian model. <strong>Methods</strong>: Forty whole choroid explants were prepared using chicken eyes. Twenty choroids were exposed to increased pressure using a PC-controlled, open pressurized chamber system. Ten choroids were exposed to 40 mmHg for 24 and for 72 hours respectively. VIP concentration was analyzed by ELISA and total protein concentration was measured by BCA assay. Statistical analysis was done using unpaired two-tailed <em>t</em>-test. <strong>Results</strong>: (I) Overall choroidal VIP (chr-VIP) concentration was significantly increased at 40 mmHg compared to controls (30.10 ± 7.2 pg vs 20.70 ± 3.2 pg; p&lt;0.0001). (II) Subgroup analysis yielded a significantly increased chr-VIP level at 40 mmHg after 24 h (28.42 ± 6.0 pg vs 20.76 ± 4.0 pg; p = 0.002) and 72 h (31.77 ± 7.8 pg vs 20.61 ± 2.1 pg; p = 0.005). (III) Chr-VIP elevation at higher atmospheric pressure ranged between 1.37 (24 h) and 1.54-fold (72h). <strong>Conclusions</strong>: Increased chr-VIP concentration argues for a decreased chr-VIP release. Considering the strong vasodilative properties of VIP, this data suggests a potential link of IOP and blood flow via VIP.