Kiel J W, Reitsamer H A, Walker J S, Kiel F W
Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, USA.
Exp Eye Res. 2001 Sep;73(3):355-64. doi: 10.1006/exer.2001.1050.
A prior study found that inhibition of nitric oxide synthase with L-NAME causes a large, rapid decrease in IOP in anesthetized rabbits. In this follow-up study we sought to determine if this hypotensive effect was due to decreased aqueous production, possibly caused by ciliary vasoconstriction. Two protocols were performed in anesthetized rabbits. In the first protocol, mean arterial pressure (MAP) and IOP were measured by direct cannulation, and aqueous flow was measured by fluorophotometry, before and after L-NAME (5 mg kg(-1), i.v., n = 7). In the second protocol, ciliary blood flow was measured transclerally by laser Doppler flowmetry while MAP was varied mechanically over a wide range before and after L-NAME (5 mg kg(-1), i.v., n = 8). L-NAME caused a significant increase in MAP and decreases in IOP, ciliary blood flow and aqueous flow. L-NAME also caused a significant downward shift in the ciliary pressure-flow relation over the entire pressure range examined. The results indicate that L-NAME causes ciliary vasoconstriction and decreases aqueous production, suggesting that the L-NAME ocular hypotensive effect may be due in part to a blood flow-dependent decrease in aqueous production. However, assuming no uveoscleral outflow and constant episcleral venous pressure and outflow facility, the decrease in aqueous flow accounts for 66% of the drop in IOP, suggesting an additional effect of L-NAME on aqueous outflow.
先前的一项研究发现，用L-硝基精氨酸甲酯（L-NAME）抑制一氧化氮合酶会使麻醉兔的眼压大幅、迅速降低。在这项后续研究中，我们试图确定这种降压作用是否归因于房水生成减少，这可能是由睫状血管收缩引起的。在麻醉兔身上进行了两个实验方案。在第一个方案中，在注射L-NAME（5 mg kg⁻¹，静脉注射，n = 7）前后，通过直接插管测量平均动脉压（MAP）和眼压，并通过荧光光度法测量房水流量。在第二个方案中，在注射L-NAME（5 mg kg⁻¹，静脉注射，n = 8）前后，当通过机械方式在很宽范围内改变MAP时，用激光多普勒血流仪经巩膜测量睫状血流。L-NAME导致MAP显著升高，眼压、睫状血流和房水流量降低。L-NAME还使在所检查的整个压力范围内睫状压力-流量关系显著向下偏移。结果表明，L-NAME引起睫状血管收缩并减少房水生成，这表明L-NAME的眼降压作用可能部分归因于依赖血流的房水生成减少。然而，假设没有葡萄膜巩膜流出且巩膜静脉压和流出率恒定，房水流量的减少占眼压下降的66%，这表明L-NAME对房水流出还有额外作用。
