Department of Clinical Pharmacology, Medical University of Vienna, Vienna, Austria.
Invest Ophthalmol Vis Sci. 2013 Mar 15;54(3):1964-70. doi: 10.1167/iovs.12-11406.
We determined whether administration of a nitric oxide synthase (NOS) inhibitor alters optic nerve head blood flow (ONHBF) regulation during isometric exercise in healthy subjects.
Our study was done in a randomized, placebo-controlled, double-masked, three-way crossover design. A total of 18 healthy subjects was randomized to receive either placebo, phenylephrine, or an inhibitor of NOS (L-NMMA) on three different study days. ONHBF was measured with laser Doppler flowmetry while the study participants performed isometric exercise (squatting). This was done before drug administration and during infusion of the study drugs. Mean arterial pressure (MAP) and IOP were measured noninvasively, and ocular perfusion pressure (OPP) was calculated as 2/3 MAP - IOP.
The response in ONHBF to isometric exercise was less pronounced than the response in OPP, indicating for some autoregulatory capacity in the ONH. Administration of L-NMMA significantly decreased ONHBF at rest (P < 0.01). In contrast, inhibition of NOS did not alter the pressure-flow relationship in the ONH during an experimental increase in OPP compared to phenylephrine and placebo (P = 0.37 between groups).
The data of our study support previous findings that ONHBF is autoregulated during an experimental increase in OPP. Nitric oxide has an important role in basal ONHBF regulation, but seems not to be involved in the autoregulatory response during an increase in OPP induced by isometric exercise. (ClinicalTrials.gov number, NCT00806741.).
我们旨在确定一氧化氮合酶（NOS）抑制剂的给药是否会改变健康受试者等长运动期间视神经头血流（ONHBF）的调节。
我们的研究采用随机、安慰剂对照、双盲、三向交叉设计进行。总共 18 名健康受试者随机分为三组，分别接受安慰剂、苯肾上腺素或 NOS 抑制剂（L-NMMA）。在进行等长运动（深蹲）时，使用激光多普勒血流仪测量 ONHBF。在给药前和研究药物输注期间进行此操作。通过非侵入性测量平均动脉压（MAP）和眼压（IOP），并计算眼灌注压（OPP）为 2/3 MAP - IOP。
ONHBF 对等长运动的反应不如 OPP 反应明显，表明 ONH 具有一定的自动调节能力。L-NMMA 的给药显著降低了静息时的 ONHBF（P < 0.01）。相比之下，与苯肾上腺素和安慰剂相比，NOS 抑制在实验性 OPP 增加期间并未改变 ONH 中的压力-流量关系（组间 P = 0.37）。
我们研究的数据支持先前的发现，即在实验性 OPP 增加期间，ONHBF 是自动调节的。一氧化氮在基础 ONHBF 调节中具有重要作用，但似乎不参与等长运动引起的 OPP 增加期间的自动调节反应。（ClinicalTrials.gov 编号，NCT00806741）。
