Volume 13 Supplement 1

18th Scientific Symposium of the Austrian Pharmacological Society (APHAR)

Open Access

The role of nitric oxide and endothelin on optic nerve head blood flow autoregulation

  • Doreen Schmidl1,
  • Agnes Boltz1, 2,
  • Semira Kaya1,
  • René Werkmeister2,
  • Reinhard Told1, 2,
  • Stefan Palkovits1,
  • Gabriele Fuchsjäger-Mayrl3,
  • Gerhard Garhöfer1 and
  • Leopold Schmetterer1, 2Email author
BMC Pharmacology and Toxicology201213(Suppl 1):A28

DOI: 10.1186/2050-6511-13-S1-A28

Published: 17 September 2012

Background

Autoregulation is defined as the ability of a vascular bed to keep its blood flow constant despite changes in perfusion pressure. While several studies have investigated choroidal blood flow regulation, only few data are available for the optic nerve head (ONH). The aim of the present study was to explore the potential role of a potent vasodilator (nitric oxide) and a potent vasoconstrictor (endothelin-1) in ONH autoregulation.

Methods

Two randomized, double-blind, placebo-controlled, cross-over studies were performed. Eighteen subjects received either a nitric oxide synthase (NOS) inhibitor (L-NMMA) or placebo. Fifteen subjects received either an endothelin ETA receptor antagonist (BQ-123) or placebo on two trial days. Isometric exercise (squatting) was performed to increase ocular perfusion pressure (OPP). ONH blood flow (ONHBF) was measured continuously by means of laser Doppler flowmetry. OPP was calculated as https://static-content.springer.com/image/art%3A10.1186%2F2050-6511-13-S1-A28/MediaObjects/40360_2012_Article_34_IEq1_HTML.gif × (mean arterial pressure) − (intraocular pressure).

Results

During all experiments the response in ONHBF was less pronounced than the response in OPP indicating autoregulation. L-NMMA had no influence on the response of ONHBF to isometric exercise (p = 0.27). When BQ-123 was administered the increase in ONHBF during squatting was more pronounced than during placebo (p < 0.01) leading to a left-shift of the pressure/flow curve.

Conclusions

The present data confirm previously published observations that ONHBF shows some autoregulatory capacity during changes in OPP. Nitric oxide does not seem to be involved in the regulatory mechanisms during isometric exercise. In contrast, endothelin-1 seems to provide some of the vasoconstrictor tone that counteracts the increase in OPP during isometric exercise.

Declarations

Acknowledgements

This work was supported by the Austrian Science Fund (project no. P21406).

Authors’ Affiliations

(1)
Department of Clinical Pharmacology, Medical University of Vienna
(2)
Center for Medical Physics and Biomedical Engineering, Medical University of Vienna
(3)
Department of Ophthalmology and Optometry, Medical University of Vienna

Copyright

© Schmidl et al; licensee BioMed Central Ltd. 2012

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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