Structural requirements of flavonoids for increment of ocular blood flow in the rabbit and retinal function recovery in rat eyes.

PURPOSE: We have recently reported that the effect of a flavonoid on ocular blood flow depends upon the number of hydroxy (OH) groups in its backbone structure. To elucidate the structural features on the number and type of functional groups present in the flavonoid molecule plus the number of OH groups, flavonoids with four to five OH groups, with or without methoxy groups, were studied on their effects to affect the ocular blood flow and the retinal function recovery. METHODS: A colored microsphere technique was used to determine the ocular blood flow in albino rabbit eyes and electroretinography was used to measure the retinal function recovery. RESULTS: Flavonols with four free OH groups produced no effects on the ocular blood flow (fisetin, kaempferol), whereas flavanone and flavones with four free OH groups and without the C2-C3 double bond produced the rapid increment on ocular blood flow (dihydrofisetin and luteolin, respectively). Similarly, flavonols with five free OH groups produced no effects on the ocular blood flow (morin, quercetin). Yet, flavanone with five free OH groups and without the C2-C3 double bond produced the rapid increment on ocular blood flow (dihydroquercetin). Flavanols with five free OH groups and without the C2-C3 double bond and the carbonyl group produced no effects on the ocular blood flow (catechin). Flavonols with four free OH groups and a methoxy group on the 7 position produced no effects on the ocular blood flow (Rhamnetin). Flavonols with four free OH groups and a methoxy group at the 5 (5-methylquercetin) or 3' position (isorhamnetin) produced positive effects on the ocular blood flow also. Flavonol with five methoxy groups but no OH group produced positive effects on the ocular blood flow (pentamethylquercetin). Flavonols with an excessive number of OH groups, having both a catechol-like structure in the C ring and a catechol at the B ring, produced no effect on the ocular blood flow (rhamnetin, quercetin). Parallel results were obtained on retinal function recovery after ischemic insult. CONCLUSION: The presence of OH groups at certain positions and the double bond at C2-C3 in the flavonoid molecules, which produces lipophilic action, can affect the increment on ocular blood flow and retinal function recovery. O-methylation can increase ocular blood flow and retinal function recovery as well.     

天然类黄酮分子中羟基基团在兔眼缺血损伤后眼球血流量和视网膜功能恢复的作用

目的:我们最近已报告有些天然类黄酮可影响眼球血流量。为阐明黄酮分子中羟基(OH)的作用,选择黄酮含1-4个羟基基团、附有或无糖、有或无甲氧基团,观察对眼球血流量和视网膜功能恢复的作用。方法:采用彩色微珠技术测定兔眼球血流量,视网膜电图监测视网膜功能的恢复。结果:黄酮含4个游离的羟基基团(毛地黄黄酮),似乎有增加眼球血流量和促进视网膜功能恢复的作用。含3个羟基基团(5,7,4'-三羟基黄酮)可迅速增加眼球血流量和恢复视网膜功能。少于2个羟基基团的黄酮(Chrysin),对眼球血流量无增加作用。黄酮附着有芦丁糖,并含2个游离的羟基和甲氧基团(Diosmin),对眼球血流量和视网膜功能均无作用,但是,含儿茶酚的黄酮附着有葡萄糖时(毛地黄黄酮-7-糖苷),会影响眼球血流量。黄酮附着有甲氧基,并含2个游离羟基基团(Acacetin),均影响缺血损伤后眼球血流量和视网膜功能的恢复。结论:黄酮分子中羟基基团数量的增加,可显著提高眼球血流量和促进视网膜功能的恢复,而在黄酮分子B环上有7个羟基基团和儿茶酚基团时,其作用最显著。     

Effects of dihydrogenation of flavones and number of hydroxy groups in the molecules on ocular blood flow in rabbits and retinal function recovery in rats.

PURPOSE: It has been found that the number of hydroxy groups in the molecule of flavones and flavanones affect the ocular blood flow significantly. However, the effects of dihydrogenation of flavones into flavanones on ocular blood flow and retinal function recovery have not been studied and required investigation. METHODS: The colored microsphere technique and electroretinography method were used for the study of ocular blood flow and retinal function, respectively. RESULTS: Maximum effects on ocular blood flow were obtained when there were 3 hydroxy groups in the molecule of flavones and flavanones. Dihydrogenation of flavones to flavanones increased the ocular blood flow further. The same is true for retinal function recovery after ischemic insult. CONCLUSION: These results indicate that hydrogenation is an excellent way to convert natural flavones into more potent compounds of flavanones.     

Timolol increased retrobulbar flow velocities in untreated glaucoma eyes but not in ocular hypertension

PURPOSE: To investigate retrobulbar blood flow velocities and the effects of topical timolol treatment in eyes with newly detected, previously untreated open angle glaucoma or ocular hypertension. METHODS: Fifteen eyes with open angle glaucoma (OAG) and 12 eyes with ocular hypertension (OH), in the same number of patients, all untreated and newly detected, were examined with colour Doppler imaging of retrobulbar vessels before and after 1 month of topical timolol treatment (0.5% Timoptic BID). RESULTS: Baseline central retinal artery end diastolic velocity was lower (48%, p=0.0002) and resistive index higher (7.6%, p=0.018) in the OAG group than in the OH group. In the glaucoma group mean end diastolic velocity increased by 41%, (p=0.006) while resistive index decreased by 5.8%, (p=0.02) on treatment, while no significant changes were seen in the OH group. Blood flow velocities in the ophthalmic artery did not change with treatment. Baseline IOP and IOP reduction did not differ between OAG and OH group. CONCLUSION: Peripheral resistance to blood flow was found to be increased in untreated glaucoma eyes as compared to a similar group of eyes with ocular hypertension. Timolol treatment diminished resistance significantly in the glaucoma group, but not in the ocular hypertension group. Thus the two groups responded differently to timolol treatment. The reaction to IOP lowering treatment could indicate defective autoregulation in the glaucoma group.     

Effects of naringenin on ocular blood flow and choroidal neovascularization in experimental animals

AIM: To investigate the effects of naringenin on laser- induced experimental choroidal neovascularization (CNV) in rat models, ocular blood flow and retinal function recovery after ischemic insults in rat eyes. METHODS: Male Brown Norway rats were treated to break the Bruch's membrane. Naringenin 10g/L (20mg/kg) was given once per day through intraperitoneal injection for 4 weeks after laser treatment. The development of CNV was determined by fluorescein angiography (FA) performed on week 2 and 4. The colored microsphere technique and electroretinography method were used for the study of ocular blood flow and retinal function recovery, respectively. RESULTS: The choroidal blood flow in elevated intraocular pressure (IOP) rabbit eyes was significantly increased by 10g/L naringenin solution as compared to control group (P < 0.05). The retinal function recovery after ischemic insults in rat eyes indicated significant increase of b-wave recovery in treated group, as compared to control group (P <0.05). The intensity of fluorescein leakage from the photocoagulated lesions significantly decreased in treated group, compared to the control group (75.8%-95.0%, P <0.01). CONCLUSION: Naringenin could prevent the development of CNV on laser-induced experimental rat models, increase the choroidal blood flow in elevated IOP rabbit eyes and be beneficial on retinal function recovery in ischemic rat eyes.     

柚皮素对大鼠眼血流和脉络膜新生血管的作用(英文)

目的:研究柚皮素对激光诱发大鼠脉络膜新生血管形成(CNV)、高眼压兔眼血流和缺血大鼠眼视网膜功能恢复的作用。方法:选择雄性棕色挪威大鼠,采用激光诱发Bruch膜破裂后,予10g/L(20mg/kg)柚皮素,1次/d,持续4wk;光凝后2,4wk分别做眼底荧光血管造影,评估CNV的形成。采用彩色微球技术、眼电生理技术检测兔眼血流和大鼠视网膜功能恢复。结果:与对照组比较,10g/L柚皮素能明显增加高眼压兔眼脉络膜血流(P<0.05),能明显增加缺血大鼠眼视网膜功能恢复(P<0.05),能明显减轻光凝点荧光素渗漏(75.8%～95.0%,P<0.01)。结论:柚皮素能抑制激光诱发大鼠络膜新生血管形成;增加高眼压兔眼脉络膜血流;增加缺血大鼠眼视网膜功能恢复。     

右旋噻吗洛尔滴眼液临床观察及与其左旋异构体的比较

目的：评价右旋噻吗洛尔（D－timolol）治疗青光眼的疗效。方法：36名原发性开角型青光眼或高眼压病人随机分为两组,分别滴用1％D-timolol和0.5％左旋噻吗心安（L－timolol）。观察用药前后眼压、视野和眼血流的变化及副作用发生率。结果：两组单次滴药眼压均显著降低;长期用药眼压日曲线较用药前降低;随诊3个月降压幅度无显著差异;且D组降压幅度与用药前眼压呈线性相关。用药前后,两组眼血流无显著变化;视野平均光敏感D组显著上升而L组无显著改变。用药后的副作用轻微。结论：1％D-timolol是有效安全的抗青光眼药物。     

Effect of topical levobunolol on retinal, optic nerve head, and choroidal circulation in normal volunteers]

PURPOSE: Using three different techniques of ocular blood flow measurement, we evaluated the effects of topical levobunolol on retinal, optic nerve head, and choroidal circulation. METHODS: Twenty normal volunteers received one drop of levobunolol in one eye and one drop of placebo in the fellow eye. Retinal venous blood flow was measured using multiple scattering laser velocimetry. Retinal capillary blood flow and optic nerve head blood flow were measured by Heidelberg Retina Flowmeter. Pulsatile ocular blood flow was measured by ocular blood flow tonography. Changes in blood pressure, heart rate, retinal venous blood flow, retinal capillary blood flow, optic nerve head blood flow, intraocular pressure and pulsatile ocular blood flow were detected from measurements taken at baseline and at 90 to 120 minutes following the instillation. RESULTS: Intraocular pressure decreased significantly in both eyes. Retinal capillary blood flow increased significantly in both eyes. Optic nerve head blood flow increased significantly in treated eyes but remained unchanged in placebo eyes. There were no significant changes in retinal venous blood flow or pulsatile ocular blood flow in either eyes. CONCLUSION: Our results suggest that one administration of levobunolol may increase the retinal and optic nerve circulation but does not decrease the choroidal circulation.     

瞬间性高眼压对视网膜血流量的影响

本研究主要观察瞬间性高眼压对视网膜血流量的影响。实验对象为１２只新西兰白兔（１２只眼），观察发现，瞬间性高眼压持续的时间不同，视网膜及其它眼组织的血流量改变的差异具有显著性。该研究表明，瞬间性高眼压及其持续时间可以影响视网膜及其它眼组织血流量的改变和恢复。     

Effects of some natural flavonoids on retinal function recovery after ischemic insult in the rat.

PURPOSE: There are six natural flavonoids studied recently and their effects on ocular blood flow measured with colored microsphere technique. It was found that three out of six compounds showed strong positive effects in increasing the ocular blood flow. In this study, we tried to find out whether these results can be translated on their effects to improve retinal function recovery after ischemic insult. METHODS: Electroretinography was used to measure the b-wave recovery as an indication of retinal function recovery. RESULTS: Naringenin, hesperetin, and rutin were found to produce marked positive effects on b-wave recovery, whereas naringin, hesperidin, and quercetin showed poor recovery of b-wave after ischemic insult of the retina. CONCLUSION: It was found that the compounds that showed strong increase of ocular blood flow also showed marked increase of retinal function recovery, whereas those that showed poor increase of ocular blood flow also showed poor effects on the retinal function recovery.     

Color Doppler imaging of the orbital vessels in Behçet's disease

OBJECTIVE: To investigate blood flow velocity changes, pulsatility and resistivity index values of orbital vessels in Beh?et's disease with or without ocular involvement (groups I and II) and healthy volunteers (group III). METHODS: Twenty-five eyes in the first group, 24 eyes in the second group and 24 eyes in the third group were examined by using color Doppler imaging. Peak systolic and end-diastolic blood flow velocity measurements, pulsatility and resistivity index values were measured in ophthalmic, central retinal, nasal and temporal ciliary arteries and the central retinal vein. RESULTS: The end-diastolic blood flow velocity measurements in all arteries were significantly higher in groups II and III than in group I, but resistivity and pulsatility indexes of all arteries were higher in group I than the other two groups. There was no significant difference in blood flow velocity of the central retinal vein in the three groups. CONCLUSION: Detection of increased vascular resistance of orbital vessels may predict the diagnosis of ocular involvement in Beh?et's disease.     

Retinal vessel reaction to short-term IOP elevation in ocular hypertensive and glaucoma patients

PURPOSE: Regulation of ocular blood flow might be impaired in glaucoma patients. We compared the reaction of retinal vessels to a short-term increase of intraocular pressure (IOP), using a retinal vessel analyzer (RVA), in normal volunteers, ocular hypertensive patients (OH) and primary open angle glaucoma patients (POAG). METHODS: Ten healthy subjects (56+/-8 years, IOP 13.7+/-1.6 mmHg), 10 OH patients (55+/-12 years, IOD 23.4+/-4.1 mmHg) and 11 POAG patients (60+/-11 years, IOP 23.3+/-1.95 mmHg) were evaluated. Arterial and venous retinal vessel diameter was measured continuously before, during and after raising IOP to suprasystolic values by the suction cup method, described as ocular oscillo-dynamography. RESULTS: The change in vessel diameter after the IOP rise differed in its temporal sequence and in absolute values depending on the group examined. In the retinal branch veins the reduction of vessel diameter during the IOP rise was significantly different in POAG (0%+/-6.7) and volunteers (-6.7%+/-8.5; p = 0.06) and in POAG and OH (-6.7%+/-7.0; p = 0.04). At 70-130 sec after IOP increase a dilatation occurred, again differing significantly in POAG (+5.8%+/-3.9) and volunteers (+9.7%+/-4.3; p = 0.03). Systemic blood pressure did not show any significant differences between groups or during the course of the examination. DISCUSSION: At short-term rise in IOP leads to less retinal vessel reaction in POAG patients than in volunteers and OH. This might be due to impaired autoregulation to ocular perfusion changes in POAG patients.     

Ocular perfusion pressure and visual field indice modifications induced by alpha-agonist compound (clonidine 0.125%, apraclonidine 1.0% and brimonidine 0.2%) topical administration. An acute study on primary open-angle glaucoma patients

OBJECTIVE: The aim of this study was to verify the acute effects of alpha-adrenoreceptor agonist eyedrop administration on visual field parameters and ocular perfusion pressure (OPP) in patients affected by primary open-angle glaucoma. METHODS: A prospective, randomized double-blind study was carried out. Sixty-four glaucomatous subjects were enrolled in the clinical trial and subsequently separated into four study groups, of 16 patients each, to compare the systemic and ocular effects of placebo, clonidine 0.125%, apraclonidine 1.0% and brimonidine 0.2%. RESULTS: No significant variations in the ocular or systemic parameters were observed after placebo administration. All the alpha-adrenoreceptor agonist compounds induced a significant reduction of the intraocular pressure. Clonidine induced significant modifications of mean blood pressure, OPP and visual field indices. The acute administration of apraclonidine did not affect both mean blood pressure and OPP, but a worsening of the visual field was nevertheless recorded. The analyzed parameters did not significantly vary after brimonidine instillation. CONCLUSIONS: The present findings demonstrate that the lack of effects on the blood flow and the absence of vasomotor activity at the level of the posterior pole exhibited by brimonidine is related to its alpha-2 selectivity, as appears by comparing this compound with the other alpha-agonists available for the management of glaucoma.     

Assessment of blood flow in orbital arteries in ocular sarcoidosis

PURPOSE: Posterior uveitis in ocular sarcoidosis is characterized by obliterative arteriolitis, so-called "microangiopathy", in sarcoidosis that may affect blood flow in ocular arteries. This study was performed to evaluate blood flow velocity in orbital arteries in patients with ocular sarcoidosis. METHODS: This study is a case-control study. Thirty-two patients with posterior uveitis diagnosed on the basis of pathological or clinical findings as having ocular sarcoidosis functioned as cases and 24 healthy volunteers as controls. Pulse rate and blood flow velocities were measured in central retinal arteries, ophthalmic arteries, or short posterior ciliary arteries by the pulsed Doppler method. Laser flaremetry was also performed. Blood flow velocities were compared in patients with sarcoidosis and controls and the correlation coefficients between flare intensity values and flow velocities were evaluated using Student's t-test. RESULTS: Blood flow velocities in orbital arteries in eyes with sarcoidosis were significantly lower than those in normal eyes. The resistance index (RI) of peripheral vessels, which is calculated as (maximal velocity - minimal velocity)/maximal velocity, was significantly higher in patients with sarcoidosis. No association was found between flare intensity values and flow velocities. CONCLUSIONS: Patients with ocular sarcoidosis have impairment in ocular circulation. We speculate that changes in orbital blood flow resulted from inflammatory changes in fundus vasculature.     

The response of retrobulbar vasculature to hypercapnia in primary open-angle glaucoma and ocular hypertension

PURPOSE: To evaluate the physiological effects of hypercapnia on the retrobulbar vasculature in ocular hypertension (OH) and open-angle glaucoma (OAG). METHODS: Peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistive index (RI) of the ophthalmic (OA) and central retinal arteries (CRA) were evaluated in 12 eyes with OH and 8 eyes with OAG using color Doppler imaging. Measurements were taken before and during hypercapnia. RESULTS: Patients with OAG were found to have increased EDV (p < 0.035) of the CRA, and decreased PSV (p < 0.097) and EDV (p < 0.098) of the OA, during hypercapnia. Patients with OH had increased PSV (p < 0.062) and EDV (p < 0.072) of the CRA during hypercapnia. Patients with OH also demonstrated a greater percent change in the calculated RI (p < 0.065) of the CRA in response to hypercapnia when compared to OAG. The mean RI of the CRA decreased during hypercapnia. DISCUSSION: Patients with OH were found to have a normal vasodilatory response within the retrobulbar vasculature during hypercapnia resulting in increased volumetric blood flow to the retina while patients with OAG did not, suggesting there is vasospasm at or downstream from the CRA resulting in decreased volumetric blood flow to the retina.     

Effects of pentoxifylline and alprostadil on ocular hemodynamics in healthy humans

PURPOSE: Alprostadil, a prostaglandin (PG)E(1) analogue and pentoxifylline, an alkylxanthine derivate, have been shown to exert vasodilatory effects in several vascular beds. The purpose of the present study was to investigate the effect of PGE(1) and pentoxifylline on the ocular circulation. METHODS: A placebo-controlled, double-masked, three-way, crossover study was performed in 15 healthy male subjects. Subjects received pentoxifylline (300 mg), PGE(1) (alprostadil 60 mug), or placebo intravenously over 2 hours on three trial days. Choroidal red blood cell flow was assessed with laser Doppler flowmetry and pulsatile choroidal blood flow with laser interferometric measurement of fundus pulsation amplitude (FPA). Retinal blood cell flow was calculated based on the measurements of maximum erythrocyte velocity in a retinal vein assessed with bidirectional laser Doppler velocimetry, and diameter measurements of retinal vessels were obtained with a retinal vessel analyzer. RESULTS: Pentoxifylline increased FPA by 15.4% +/- 1.1% (P < 0.001 versus placebo and baseline). Alprostadil tended to increase FPA, but this effect did not reach the level of significance (P = 0.07 versus placebo). Choroidal blood flow as measured with laser Doppler flowmetry tended to increase during pentoxifylline and PGE(1) infusion by 8.9% +/- 2.9% (P = 0.062) and 4.5% +/- 6.2% (P = 0.29), respectively, but none of these effects was significant. The drugs under study had no effect on mean red blood cell velocity in retinal veins, on retinal vessel diameters, intraocular pressure, blood pressure, or pulse rate. CONCLUSIONS: PGE(1) did not alter the parameters of retinal or choroidal circulation in healthy subjects. Pentoxifylline increased FPA, but did not change choroidal blood flow as measured with laser Doppler flowmetry and did not affect retinal blood flow parameters. Accordingly, neither pentoxifylline nor PGE(1) appears to be suitable to improve ocular blood flow in healthy subjects. Whether long-term treatment with alprostadil would improve choroidal blood flow in patients with vascular disease remains to be established.     

Effect of dorzolamide and timolol on ocular blood flow in patients with primary open angle glaucoma and ocular hypertension

BACKGROUND: There is evidence that perfusion abnormalities of the optic nerve head are involved in the pathogenesis of glaucoma. There is therefore considerable interest in the effects of topical antiglaucoma drugs on ocular blood flow. A study was undertaken to compare the ocular haemodynamic effects of dorzolamide and timolol in patients with primary open angle glaucoma (POAG) or ocular hypertension (OHT). METHODS: One hundred and forty patients with POAG or OHT were included in a controlled, randomised, double blind study in two parallel groups; 70 were randomised to receive timolol and 70 to receive dorzolamide for a period of 6 months. Subjects whose intraocular pressure (IOP) did not respond to either of the two drugs were switched to the alternative treatment after 2 weeks. Scanning laser Doppler flowmetry was used to measure blood flow in the temporal neuroretinal rim and the cup of the optic nerve head. Pulsatile choroidal blood flow was assessed using laser interferometric measurement of fundus pulsation amplitude. RESULTS: Five patients did not respond to timolol and were changed to the dorzolamide group, and 18 patients changed from dorzolamide treatment to timolol. The effects of both drugs on IOP and ocular perfusion pressure were comparable. Dorzolamide, but not timolol, increased blood flow in the temporal neuroretinal rim (8.5 (1.6)%, p<0.001 versus timolol) and the cup of the optic nerve head (13.5 (2.5)%, p<0.001 versus timolol), and fundus pulsation amplitude (8.9 (1.3)%, p<0.001 versus timolol). CONCLUSIONS: This study indicates augmented blood flow in the optic nerve head and choroid after 6 months of treatment with dorzolamide, but not with timolol. It remains to be established whether this effect can help to reduce visual field loss in patients with glaucoma.     

The effects of sildenafil on ocular blood flow

PURPOSE: To investigate the effects of sildenafil, a popular new drug in the treatment of erectile dysfunction, on ocular blood flow. METHODS: This study was designed as a prospective, double-blind, placebo-controlled study. Twenty participants with erectile dysfunction were given a single oral dose of 100 mg sildenafil, while 10 participants with erectile dysfunction were given placebo. All the participants underwent routine systemic and ophthalmological examinations. Intraocular pressure, systolic and diastolic blood pressure and ocular blood flow (ophthalmic, central retinal, short posterior ciliary arteries) were measured in both eyes before and 1 hour after the dose of sildenafil or placebo. Ocular blood flow measurements were performed using colour Doppler ultrasonography. RESULTS: None of the parameters were significantly different between the groups before study drug intake. Although central retinal artery velocities were not changed, ophthalmic artery and short posterior ciliary artery peak systolic velocity, end-diastolic velocity, and mean velocity values were significantly increased 1 hour after drug intake in the sildenafil group compared to the placebo group (p < 0.05). CONCLUSION: Sildenafil causes a significant increase in blood flow in these arteries. A possible role of inhibition of phosphodiesterase-5 in vascular smooth muscles by sildenafil is implicated. Further studies are needed to investigate the effects of sildenafil on ocular blood flow in patients with senile macular degeneration, diabetic retinopathy and glaucoma.     

Effect of isometric exercise on choroidal blood flow in type I diabetic patients

BACKGROUND: In healthy subjects, choroidal blood flow is regulated when the mean ocular perfusion pressure increases. Since capillary vascular beds are altered in diabetic patients, the regulation of choroidal blood flow could be affected by this pathology. PATIENTS AND METHODS: 10 type I diabetic patients without retinopathy (DNR group) and 7 type I diabetic patients with retinopathy (DR group) participated in the study. In NDR and DR groups, choroidal blood flow was measured while patients raised their mean arterial blood pressure by squatting. The results were compared to those of a previous study in normals. Pupillometry was performed at rest on the two diabetic groups and on seven normals during a modification of illumination (white/black screen transition). RESULTS: In the NDR and DR groups, mean ocular perfusion pressure raised by 61 and 50 % during squatting, respectively. Consecutively, choroidal blood flow did not change in NDR as in normals, but increased linearly in DR patients. The white/black screen transition produced an increase of the pupil diameter of 52 and 49 % in normals and NDR patients, respectively, while it increased by only 16 % in the DR patients. CONCLUSIONS: As already shown in healthy subjects, choroidal blood flow is regulated in NDR patients when the ocular perfusion pressure increases. In DR patients, the absence of this control could be due to a failure of the autonomic nervous system, as suggested by pupillometry results.     

Possible role for nitric oxide releasing nerves in the regulation of ocular blood flow in the rat

AIM—To investigate the role of nitrergic nerves in the regulation of ocular blood flow.
METHODS—Conscious, lightly restrained rats were treated with either the neuronal nitric oxide synthase inhibitor 7-nitroindazole (7-NI), or the non-selective inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), and ocular blood flow was measured ex vivo from tissue samples, using the fully quantitative [14C]-iodoantipyrine technique.
RESULTS—In the peripheral circulation, L-NAME produced an increase in arterial blood pressure (+22%) while 7-NI had no effect. In contrast, both 7-NI and L-NAME produced significant decreases in ocular blood flow (−31% and −59% respectively). The ocular vascular resistance calculated from ocular blood flow and mean arterial blood pressure increased by 29% following 7-NI, but by 130% following L-NAME.
CONCLUSIONS—Nitric oxide releasing neurons may play an important contributory role in regulating ocular blood flow.

Keywords: nitric oxide; neuronal nitric oxide synthase; 7-nitroindazole; NG-nitro-L-arginine methyl ester; ocular blood flow