Document Detail


Paradoxical effect of phentolamine on aqueous flow in the rabbit.
MedLine Citation:
PMID:  17341146     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
PURPOSE: The aim of this study was to assess the effects of acute systemic, nonselective alpha-adrenergic blockade on aqueous flow.
METHODS: This study used pentobarbital-anesthetized rabbits (n=7), in which the following parameters were measured: mean arterial pressure, carotid blood flow, heart rate, intraocular pressure (IOP), orbital venous pressure (OVP), ciliary blood flow, and aqueous flow (AqFlow). Measurements were made before and after an intravenous administration of phentolamine (0.1 mg/kg).
RESULTS: Phentolamine caused significant decreases in IOP -23%+/-2%; P<0.01), OVP (-28%+/-12%; P<0.05), and AqFlow (-33%+/-6%; P<0.01). The other parameters were not significantly altered. The rapidity of the OVP and IOP responses were noteworthy, being essentially complete 60 s after the phentolamine injection.
CONCLUSIONS: A subpressor dose of phentolamine has complex effects on ocular hydrodynamics. The initial IOP decrease is too fast to be explained by aqueous dynamics or ocular rigidity, and so is most likely a result of the disgorgement of choroidal blood volume caused by decreased venous pressure outside the eye. The more prolonged ocular hypotensive effect is explained by the decrease in AqFlow, and perhaps a decrease in episcleral venous pressure or increase in uveoscleral outflow. However, the inhibition of aqueous production is odd, as lost prejunctional inhibition of norepinephrine release and unopposed beta-receptor activation should have increased aqueous production.
Authors:
Jeffrey W Kiel; Herbert A Reitsamer
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of ocular pharmacology and therapeutics : the official journal of the Association for Ocular Pharmacology and Therapeutics     Volume:  23     ISSN:  1080-7683     ISO Abbreviation:  J Ocul Pharmacol Ther     Publication Date:  2007 Feb 
Date Detail:
Created Date:  2007-03-07     Completed Date:  2007-06-25     Revised Date:  2013-01-31    
Medline Journal Info:
Nlm Unique ID:  9511091     Medline TA:  J Ocul Pharmacol Ther     Country:  United States    
Other Details:
Languages:  eng     Pagination:  21-6     Citation Subset:  IM    
Affiliation:
Department of Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA. kiel@uthscsa.edu
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MeSH Terms
Descriptor/Qualifier:
Adrenergic alpha-Antagonists / pharmacology*
Animals
Aqueous Humor / drug effects*,  physiology
Blood Flow Velocity / drug effects
Blood Pressure / drug effects
Carotid Body / blood supply,  drug effects
Ciliary Body / blood supply,  drug effects
Female
Heart Rate / drug effects
Intraocular Pressure / drug effects
Male
Phentolamine / pharmacology*
Rabbits
Regional Blood Flow / drug effects
Venous Pressure / drug effects
Grant Support
ID/Acronym/Agency:
EY09702/EY/NEI NIH HHS; R01 EY009702/EY/NEI NIH HHS
Chemical
Reg. No./Substance:
0/Adrenergic alpha-Antagonists; 50-60-2/Phentolamine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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