The Effect of A2A Adrenoceptor Stimulation on the Diameter of Retinal Arterioles During Hypoxia in Vivo
试验速览
- 阶段
- 2 期
- 入组人数
- 20
- 试验地点
- 1
- 主要终点
- Diameter responses of retinal arterioles
研究概览
简要总结
The purpose is to investigate how the adenosine affects the diameter regulation of retinal arterioles during changes in oxygen tension. A deeper understanding of the mechanisms involved in diameter regulation of retinal arterioles during changes in oxygen tension can be used to obtain a more detailed understanding of diseases where changes in the diameter regulation of retinal vessels are involved in the disease pathogenesis and possibly point to new therapeutic options for patients with retinal vascular disease, such as diabetic retinopathy and retinal vein thrombosis.
Preliminary, a routine ophthalmological evaluation, measurement of blood pressure, and electrocardiogram will be preformed to insure that only healthy test persons are included in the study.
The test persons will be randomly allocated to two groups, one group in which protocol 1 is followed by protocol 2, and the other group with the two protocols performed in the reverse order.
Protocol 1: Using the DVA, a video recording will capture the diameter of retinal vessels and the changes occurring during stimulation with flickering light. The recording lasts 4.5 minutes and is preformed before and after intravenous injection of adenosine.
Protocol 2: The procedures are similar to those of protocol 1 but are performed during breathing of a gas mixture with a reduced oxygen tension to 12,5 %, which results in a reduced oxygen saturation in the blood to 85-90 %.
详细描述
Background:
Occlusion of the retinal vessels leading to retinal ischaemia and hypoxia is an important element in the pathophysiology of the major vision threatening diseases in the Western World. The hypoxic areas release vasodilating factors that induce vasodilatation in adjacent retinal areas in order to increase blood flow and retinal oxygenation. An understanding of the mechanisms underlying this vasodilatation may help identifying new therapeutic principles for modulating retinal blood flow during changes in retinal blood flow secondary to hypoxia and other diseases.
The present study:
Two working hypotheses will be tested: 1) That systemic administration of an A2A adrenoceptor agonist affects retinal blood flow independently of its systemic effects. 2) That the vasodilating effect of A2A adrenoceptor stimulation and the vasodilating effects of systemic hypoxia and increased retinal metabolism induced by flicker stimulation are additive.
Methods:
研究设计
- 研究类型
- Interventional
- 分配方式
- Na
- 干预模型
- Single Group
- 主要目的
- Basic Science
- 盲法
- None
入排标准
- 年龄范围
- 20 Years 至 35 Years（Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •Age 20-35
- •Healthy, both current and prior
- •Normal echocardiogram
- •Signed and informed consent
排除标准
- •Former or current cardiovascular disease or high blood pressure
- •Lung diseases incl. asthma or chronic obstructive pulmonary disease (COPD)
- •Known eye disease or previously treated for an eye disease, particularly glaucoma and cataracts
- •People taking medication, except birth control pills
- •Persons who have or who have had epilepsy
- •Pregnant or breast-feeding women
- •Allergies to the constituent substance of the medication used in the study
研究组 & 干预措施
Healthy person
The purpose is to investigate the effect of A2A adrenoceptor stimulation using the drug regadenoson (Rapiscan) on the diameter of retinal arterioles during hypoxia in vivo.
干预措施: Hypoxia (Biological)
Healthy person
The purpose is to investigate the effect of A2A adrenoceptor stimulation using the drug regadenoson (Rapiscan) on the diameter of retinal arterioles during hypoxia in vivo.
干预措施: Regadenoson (Drug)
结局指标
主要结局
Diameter responses of retinal arterioles
时间窗: 11 minutes
The main outcome variable of the DVA is the width measurement of the selected vessel(s), expressed in units of measurement (UM). In a normal Gullstrand eye, 1 UM is equivalent to 1 µm. For the stimulation with flicker light, the outcome is defined as the percent change from baseline.
次要结局
- Intraocular pressure(The intraocular pressure is measured before and after the drug administration (time point 280 and 350 sec) and after the second DVA examination is terminated (time point 670 sec).)
- Blood pressure(The blood pressure is measured during the last 40 seconds in each phase using an oscillometric technique on the left arm.)
- Systemic arterial saturation(The systemic arterial saturation is registered at the beginning and half way through each examination phase and during the 2 min break where the drug Regadenoson is injected.)