Liu John H K, Li Ruixia, Nelson Thomas R, Weinreb Robert N
Hamilton Glaucoma Center and Department of Ophthalmology, University of California-San Diego, La Jolla, CA 92039-0946, USA.
J Ocul Pharmacol Ther. 2007 Apr;23(2):103-9. doi: 10.1089/jop.2006.0098.
The aim of this study was to investigate the resistance to blood flow in the ophthalmic artery of rabbits receiving topical treatment with timolol.
Eight (8) New Zealand albino rabbits received 20 mul of timolol treatment (vehicle, 0.1%, 0.33%, 1%, and 3.3%) on the right eye. Blood-flow velocity in the ophthalmic artery was determined in the treated eye using color Doppler imaging (CDI) with a 12-MHz linear ultrasound transducer prior to the treatment and at 0.5, 1, 1.5, 2, and 3 h after the treatment. Intraocular pressure (IOP) was measured in both eyes, using a pneumatonometer at the same time points. Pourcelot's resistive index of blood flow was calculated, using the peak systolic velocity and the end diastolic velocity. A control experiment was performed with CDI obtained from the right eye when the left eye was treated with 1% timolol.
In the eye treated with 1% and 3.3% timolol, a dose-dependent increase in the resistive index of blood flow occurred in the ophthalmic artery. No change in the resistive index occurred when the contralateral eye was treated with 1% timolol. Changes of IOP were not different between the two eyes under all the experimental conditions. Timolol, at all concentrations, caused a significant reduction of heart rate. A similar reduction of heart rate occurred when either eye was treated with 1% timolol.
Topical treatment with timolol in rabbits can increase the resistance to blood flow in the ophthalmic artery. This effect is caused by a mechanism local to the eye and is not dependent on an IOP change.
本研究旨在调查接受噻吗洛尔局部治疗的家兔眼动脉的血流阻力。
8只新西兰白化兔右眼接受20微升噻吗洛尔治疗（溶媒、0.1%、0.33%、1%和3.3%）。在治疗前以及治疗后0.5、1、1.5、2和3小时，使用12兆赫线性超声换能器通过彩色多普勒成像（CDI）测定治疗眼的眼动脉血流速度。在相同时间点使用气动眼压计测量双眼的眼压。使用收缩期峰值速度和舒张末期速度计算普尔索洛特血流阻力指数。当左眼用1%噻吗洛尔治疗时，对右眼进行CDI对照实验。
在接受1%和3.3%噻吗洛尔治疗的眼中，眼动脉血流阻力指数呈剂量依赖性增加。当对侧眼用1%噻吗洛尔治疗时，阻力指数无变化。在所有实验条件下，两眼间眼压变化无差异。所有浓度的噻吗洛尔均导致心率显著降低。当任一眼用1%噻吗洛尔治疗时，心率出现类似降低。
家兔局部应用噻吗洛尔可增加眼动脉的血流阻力。这种作用是由眼部局部机制引起的，不依赖于眼压变化。
