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Nitric oxide and choroidal blood flow regulation
R M Mann1, C E Riva, R A Stone
1Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia 19104, USA.
Investigative Ophthalmology & Visual Science
|April 1, 1995
Summary
Nitric oxide (NO) plays a key role in regulating choroidal blood flow (ChBF). This study shows NO is released by a cholinergic mechanism and helps maintain basal ChBF.
Area of Science:
- Ophthalmology
- Physiology
- Neuroscience
Background:
- Nitric oxide (NO) is an endothelial-derived relaxing factor involved in vasodilation.
- NO is a potential neurotransmitter in choroidal perivascular autonomic fibers.
- The role of NO in regulating choroidal blood flow (ChBF) requires further investigation.
Purpose of the Study:
- To investigate the potential role of nitric oxide (NO) in the regulation of choroidal blood flow (ChBF).
- To explore the involvement of cholinergic mechanisms in NO-mediated ChBF regulation.
Main Methods:
- Choroidal blood flow (ChBF) was measured using laser Doppler flowmetry in anesthetized cats.
- Acetylcholine (ACh), an NO synthesis inhibitor (N omega-nitro-L-arginine, NNL-A), L-arginine, and D-arginine were infused to assess their effects on ChBF and mean arterial pressure (MAP).
Main Results:
- Acetylcholine (ACh) infusion increased ChBF by 68% and decreased MAP by 9%.
- N omega-nitro-L-arginine (NNL-A) attenuated the ACh-induced ChBF increase by 46% and raised MAP by 40%.
- NNL-A alone dose-dependently decreased ChBF and increased MAP, while L-arginine enhanced the ACh-induced ChBF increase, unlike D-arginine.
Conclusions:
- A local vasodilatory cholinergic mechanism in the choroid releases NO.
- NO release in the choroid is crucial for maintaining basal blood flow to the tissue.