Pressure-Dependent Elevation of Vasoactive Intestinal Peptide Level in Chicken Choroid

Evgeny Privalov; Matthias Zenkel; Ursula Schloetzer-Schrehardt; Stefanie Kuerten; Antonio Bergua; Bettina Hohberger

doi:10.3390/biology12040495

Pressure-Dependent Elevation of Vasoactive Intestinal Peptide Level in Chicken Choroid

Biology (Basel). 2023 Mar 24;12(4):495. doi: 10.3390/biology12040495.

Authors

Evgeny Privalov¹, Matthias Zenkel¹, Ursula Schloetzer-Schrehardt¹, Stefanie Kuerten², Antonio Bergua¹, Bettina Hohberger¹

Affiliations

¹ Department of Ophthalmology, Universität of Erlangen-Nürnberg, Friedrich-Alexander-University-Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany.
² Institute of Neuroanatomy, Medical Faculty, University of Bonn, 53115 Bonn, Germany.

Abstract

Purpose: Autonomic control is important in maintaining ocular integrity. As recent data suggested that intrinsic choroidal neurons (ICN), an intrinsic choroidal autonomic control, may regulate choroidal thickening via release of the vasodilative vasoactive intestinal peptide (VIP), it was the aim of the study to investigate the level of choroidal VIP (VIP_chor) in the presence of an increased atmospheric pressure in a chicken model.

Methods: Chicken choroidal whole mounts were exposed to ambient pressure (n = 20) and 40 mm Hg (n = 20) in a PC-controlled, open chamber system for 24 and 72 h, respectively. The VIP concentration was analyzed by ELISA, and the total protein concentration was measured by the BCA assay. Statistical analysis was done using an unpaired two-tailed t-test.

Results: The pressurization systems enabled choroidal whole mount pressurization (40 mm Hg) with humidifying, pressure, temperature, and gas exchange. Overall, the VIP_chor level concentration was significantly increased at 40 mmHg compared to the ambient pressure (30.09 ± 7.18 pg vs. 20.69 ± 3.24 pg; p < 0.0001). Subgroup analysis yielded a significantly increased VIP_chor level at 40 mmHg compared to the ambient pressure after 24 h (28.42 ± 6.03 pg vs. 20.76 ± 4.06 pg; p = 0.005) and 72 h (31.77 ± 7.82 pg vs. 20.61 ± 2.12 pg; p = 0.002), respectively. The VIP_chor elevation at 40 mm Hg ranged between 1.37- (24 h) and 1.54-fold (72 h) compared to the ambient pressure. No difference was observed between the VIP_chor level at 24 h and 72 h (p > 0.05).

Conclusions: The increase of the total choroidal VIP level, representing the intracellular VIP content, in the presence of an increased ambient pressure argues for a retention of VIP within the neurons, decreasing both vasodilatation and, consequently, choroid thickness. This finding might be a passive or even active function of ICN in the regulation of choroidal thickness, ocular integrity and IOP.

Keywords: ICN; choroid; glaucoma; intraocular pressure; tissue pressurization; vasoactive intestinal peptide.

Grants and funding

This research received no external funding.