Agonist Response of Human Isolated Posterior Ciliary Artery
Investigative Ophthalmology & Visual Science, Vol. 33, No. 1, January 1992 Copyright © Association for Research in Vision and Ophthalmology Agonist Response of Human Isolated Posterior Ciliary Artery Doo-Yi Yu, Valerie A. Alder, Er-Ning Su, Edward M. Mele, Stephen J. Cringle, and William H. Morgan The isometric responses of isolated human posterior ciliary artery to adrenergic agonists, histamine (HIS), and 5-hydroxytryptamine (5-HT) were studied in passively stretched ring segments mounted in a myograph bath. Cumulative dose response curves were measured for nine agonists: HIS, 5-HT, dopamine (DOPA), epinephrine (A), norepinephrine (NA), tyramine (TYR), phenylephrine (PHE), isoproterenol (ISOP), and xylazine (XYL), and the log(molar concentration) at which one half of the maximum active tension was developed (EQo) was estimated. The ring segments were unresponsive to DOPA and XYL; HIS and ISOP produced biphasic responses with a mild relaxation for low concentra- tions and small contractions for high concentrations of the agonist. The remaining agonists caused contractile responses of magnitude listed in the rank order following compared with the maximum active tension in response to 0.124 M K+-Krebs: Kmax > A > 5-HT = PHE > NA > TYR It was concluded that functional HIS, a,-adrenergic, and 5-HT receptors were present on human posterior ciliary artery but that there are no a2-adrenergic receptors. Invest Ophthalmol Vis Sci 33:48-54,1992 The regulation of ocular blood flow to ensure that may affect many aspects of ocular function involving all regions receive an adequate supply despite continu- the outer retina and the optic nerve head, the iris, and ously changing local tissue demands is a complex and the ciliary body.
[Show full text]