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This Article Full Text Full Text (PDF) All Versions of this Article: 292/1/H360    most recent 00630.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ito, I. Articles by Knot, H. J Search for Related Content PubMed PubMed Citation Articles by Ito, I. Articles by Knot, H. J

Characteristics of myogenic tone in the rat ophthalmic artery

¹Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida; ²Wake Forest Institute of Regenerative Medicine, Wake Forest University, Winston-Salem, North Carolina; ³Department of Ophthalmology, College of Medicine, Showa University, Tokyo, Japan; and ⁴Danish MyoTechnology, Aarhus, Denmark

Submitted 13 June 2006 ; accepted in final form 15 August 2006

The pressure-induced constriction in the rat ophthalmic artery was characterized. Ophthalmic arteries were isolated, cannulated in an arteriograph, and pressurized. Arteries developed 25% constriction at 70 mmHg of intraluminal pressure. Arteries maintained almost similar diameter over the range of pressures 50–210 mmHg, and forced dilatation was observed at pressures >210 mmHg. Denudation of endothelium increased the sensitivity of arteries to pressure-induced constriction, and significantly higher myogenic tone was observed in the pressure range of 10–100 mmHg. Indomethacin and cyclooxygenase-2 inhibition by SC-236 decreased myogenic tone, whereas cyclooxygenase-1 inhibition by SC-560 potentiated myogenic tone in a lower concentration range and decreased at a higher concentration. Pressure-induced constriction was completely blocked by 1 µM nifedipine. Phospholipase C inhibition by 6 µM U-73122 decreased myogenic tone by 39%, whereas PKC inhibitor GF-109203X (3 µM) had no effect. Constriction to phenylephrine was significantly decreased by U-73122 (1 µM) and GF-109203X (3 µM) at an intraluminal pressure of 10 mmHg. Rho-kinase inhibition by Y-27632 (30 µM) and HA-1077 (30 µM) decreased myogenic tone by 75% and 73%, respectively, and 1 µM Y-27632 significantly decreased myogenic tone developed in response to graded increases in pressure. These results suggest that rat ophthalmic artery has an efficient pressure-dependent autoregulatory function that is modulated by endothelium. Contribution of phospholipase C-activation to myogenic tone is minimal, whereas Rho-kinase activation plays a predominant role in the myogenic reactivity in this artery.

endothelium; phospholipase C; rho kinase