The overall purpose of this research project is to use newly available technology to study the physiology and pharmacology of blood flow in specific areas of the eye. Special emphasis will be on the role of the sympathetic nervous system in ocular vascular control and on the effects of adrenergic drugs. Previous methodologies, such as microsphere and various washout techniques, are non-continuous and are limited to steady-state flow conditions. The best o f these only produces a """"""""snapshot"""""""" of ocular blood flow at one point in time. We will utilize laser-Doppler flowmetry to measure blood flow from the surface of the eye at the limbus (anterior segment) and at the equator (choroidal flow). A newly developed sensitive transit-time ultrasonic flowmeter will be used to directly measure blood flow from one of the two arteries supplying blood to the front of the eye (long posterior ciliary artery). Both of these methodologies provide a continuous, high-frequency response. Laser-Doppler flowmetry has a high degree spatial resolution, whereas ultrasonic flowmetry will produce more global flow of measurements. Using these techniques, determination of the effects of altered perfusion pressures on regional flow will be determined by experimentally increasing or decreasing both intra-ocular pressure and systemic blood pressure. The degree of regional autoregulation and the role of sympathetic neural input will be determined. Adrenergic drugs (both stimulants and blockers) will be used to systematically define the presence of, and relative roles of adrenergic receptor subtypes in these regional vascular beds. In recent years it has become increasingly clear that disruption of normal circulatory function in the eye may directly cause or exacerbate the pathophysiology of such diverse condition as glaucoma, various retinopathies and macular degeneration. In addition, most of the drugs currently used, or proposed for use, in the treatment of glaucoma have pronounced effects on ocular blood vessels. It is hoped that information gained from this research project will enhance our understanding of ocular physiology and pharmacology in general. More specifically, these results should expand our knowledge of specific adrenergic subtypes in these vascular beds and should prove helpful in the design of new therapeutic agents with greater receptor specificity and fewer untoward side effects.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY009344-02
Application #
3266741
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1992-01-01
Project End
1994-12-31
Budget Start
1993-01-01
Budget End
1993-12-31
Support Year
2
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of Oklahoma Health Sciences Center
Department
Type
Schools of Dentistry
DUNS #
937727907
City
Oklahoma City
State
OK
Country
United States
Zip Code
73117
Yu, Yongxin; Koss, Michael C (2005) Rat clonidine mydriasis model: imidazoline receptors are not involved. Auton Neurosci 117:17-24
Yu, Yongxin; Koss, Michael C (2004) Alpha2-adrenoceptors do not mediate reflex mydriasis in rabbits. J Ocul Pharmacol Ther 20:479-88
Koss, M C (2003) Rilmenidine produces mydriasis in cats by stimulation of CNS alpha 2-adrenoceptors. Auton Autacoid Pharmacol 23:51-6
Koss, Michael C (2002) Effects of sympathetic nerve stimulation on long posterior ciliary artery blood flow in cats. J Ocul Pharmacol Ther 18:115-25
Koss, Michael C (2002) Differential neural activation of vascular alpha-adrenoceptors in oral tissues of cats. Eur J Pharmacol 440:53-9
Yu, Y; Kawarai, M; Koss, M C (2001) Histamine H3 receptor-mediated inhibition of sympathetically evoked mydriasis in rats. Eur J Pharmacol 419:55-9
Kawarai, M; Koss, M C (2001) Sympathetic control of nasal blood flow in the rat mediated by alpha(1)-adrenoceptors. Eur J Pharmacol 413:255-62
Koss, M C (2001) Effects of inhibition of nitric oxide synthase on basal anterior segment ocular blood flows and on potential autoregulatory mechanisms. J Ocul Pharmacol Ther 17:319-29
Roberts, Z V; Koss, M C (2001) Nitric oxide regulation of lingual blood flow in the rat. Nitric Oxide 5:271-7
Koss, M C; Yu, Y (2000) Role of nitric oxide in maintenance of basal oral tissue blood flow in anesthetized cats. Gen Pharmacol 35:159-64

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