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At least 19 recordsLinked to original sources
PubMed1998

The effect of NO donors on bovine retinal small arteries and posterior ciliary arteries.

PURPOSE: This study was designed to investigate the effect of nitric oxide (NO) donors on isolated bovine retinal and ciliary arteries. METHODS: Bovine retinal and short posterior ciliary arteries were mounted on a dual-wire myograph for isometric tension recordings. The relaxation induced by increasing concentrations of the following NO donors was compared: 0.1 nM to 10 microM nitroglycerin, 0.1 nM to 0.1 mM isosorbide dinitrate, 0.1 microM to 1 mM sodium nitrite, 1 nM to 0.1 mM sodium nitroprusside, and 0.1 microM to 10 microM N-carboxy-3-morpholinosydnonimine ethyl ester (Sin-1) applied to vessels after precontraction with 1 microM thromboxane A2 mimetic (U46619). The effects of 1 microM and 10 microM nitric oxide; 1 mM 8-bromo-cyclic guanosine monophosphate (cGMP), a stable cGMP analogue; and 0.1 mM papaverine were also studied. RESULTS: The NO donors elicited a swift and concentration-dependent relaxation of the ciliary arteries. The retinal small arteries were resistant to these drugs. Even at high concentrations, only moderate relaxation was elicited. The cGMP analogue 8-bromo-cGMP also induced significantly more relaxation of the posterior ciliary arteries than of the retinal small arteries. Papaverine almost completely relaxed both vessels. CONCLUSIONS: Nitric oxide donors exert only a moderate relaxing effect on retinal arteries. A weak influence of cGMP-dependent mechanisms on the retinal arterial tone is thought to be responsible.

Animals↗
PubMed1992

A new look at the blood supply of the retro-ocular space. Three-dimensional analysis of the arterial pattern of the posterior ciliary artery.

A study of the arterial architecture of the orbit, especially the ophthalmic artery and the course of the posterior ciliary artery in the retroocular space, was carried out in 198 cadavers by three-dimensional arteriographic analysis. The posterior ciliary arteries were classified into three types: lateral posterior ciliary, medial posterior ciliary, and accessory posterior ciliary arteries. Both the lateral and medial posterior ciliary arteries reach the eyeball in three ways: (1) they run antero-inferiorly in a winding course to the posterior margin of the eyeball, then shift upward vertically at a 60-90 degree angle and reach the eyeball, where they divide into several ciliary branches (69%); (2) after a similar course, others branch to the eyeball from the superior side (29.3%); or (3) they reach the eyeball in an almost straight course along the optic nerve (1.7%). The fundamental characteristics of these three types of posterior ciliary artery pattern also exist in subhuman primates.

Adult↗
PubMed2004

[Effect of pentoxifylline on Doppler blood flow parameters in the central retinal artery and the short posterior ciliary arteries in adolescents with progressive myopia].

PURPOSE: To evaluate the effect of pentoxifylline on blood flow in the central retinal artery and the short posterior ciliary arteries in patients with progressive myopia. MATERIAL AND METHODS: 48 eyes of 24 healthy patients aged between 12 and 18 years (mean 15.1 years) with myopia from -5.0 to -12.75 Dsph (mean -7.56 Dsph), were examined using color Doppler ultrasonography. The examination was performed before and after 10 days of intravenous administration of 200 mg of pentoxifylline. The peak-systolic, end-diastolic flow velocities, pulsatility, resistance and systolic/diastolic ratios were measured. RESULTS: The use of pentoxifylline significantly increased PSV and EDV in the central retinal artery and in the short posterior ciliary arteries (p=0.0001) in patients with progressive myopia and in the same time decreased PI, RI and S/D (p=0.0001). There was no correlation between Doppler blood flow parameters and dioptres or axial length. CONCLUSIONS: pentoxifylline increases retinal and choroidal blood flow in young patients with progressive myopia.

Adolescent↗
PubMed1975

Optic nerve circulation and ocular pressure: contribution of central retinal artery and short posterior ciliary arteries and the effect on oxygen tension.

Blood-flow rate in the optic nerve of the rhesus monkey 4 mm. behind the globe monitored by the heated thermocouple and tissue p02 measurement is found to be influenced by ocular pressure level. Ligation of central retinal artery reduced flow rate to 79 per cent of normal but did not influence the effect of IOP on blood-flow rate. Ligation of short posterior ciliary arteries reduced blood-flow rate to 21 per cent of normal and virtually eliminated the IOP effect. Raising IOP to above systolic arterial pressure level reduced blood-flow rate to 17 per cent of normal. At IOP levels greater than 50 mm. Hg, the reduction in blood-flow rate and in Po becomes marked and may be sufficient to produce primary lesions at this site.

Animals↗
PubMed1991

Central retinal and posterior ciliary artery occlusion after particle embolization of the external carotid artery system.

A 15-year-old boy underwent neuroradiologic embolization of the left internal maxillary artery with polyvinyl alcohol to stop traumatic epistaxis after failure of surgical clipping and nasal packing. Selective catheterization of the external carotid artery before embolization showed a faint choroidal blush. Although the procedure provided hemostasis, embolization to the central retinal artery and ciliary arteries resulted in loss of vision. The route of the emboli to the eye was via the anastomotic network of the lacrimal artery supplied by the external carotid artery system. Neuroradiologic embolization of the external carotid artery is an effective mode of therapy for dural-cavernous fistulas when fed by the external carotid artery system. Because the blood flow to the brain and eye is predominantly supplied by the internal carotid artery, embolization of the external carotid artery is considered relatively safe. The authors document the importance of recognition of the choroidal blush during selective external carotid artery angiography as a sign of collateral blood flow to the eye. Physicians and patients need to be aware of the risk of blindness as a complication of external carotid artery embolization when this sign is present.

Adolescent↗
PubMed1975

Ischemia of ciliary arterial circulation from ocular compression.

Two patients developed unilateral central retinal artery and posterior ciliary artery occlusions related to ocular compression during general anesthesia. One patient had evidence of extensive choroidal ischemia with diffuse hypopigmentation, pigmentary mottling of the posterior pole, and disc edema. Electroretinography showed diminution of the A and B waves. The other patient showed patchy choroidal ischemia with subsequent development of wedge-shaped areas of pigmentary atrophy and mottling in the midperiphery. Iridocyclitis and prolonged hypotony were also present. Retinal and posterior ciliary artery occlusion (perhaps at the level of the ophthalmic artery) can occur as a result of ocular compression by a face mask or an improperly positioned headrest. Systemic hypotension is a factor in many cases. Proper positioning of the head on an adequate headrest and avoidance of ocular compression will prevent the occurrence of retinal and choroidal occlusion during general anesthesia.

Anesthesia, General↗
PubMed2002

Effect of melatonin on vascular responses of porcine ciliary arteries.

PURPOSE: To investigate the effect of melatonin on isolated porcine ciliary arteries. METHODS: Isolated porcine ciliary arteries were suspended in myograph chambers filled with modified Krebs-Ringer solution (37 degrees C; 95% O2/5% CO2) for isometric tension recording. RESULTS: In quiescent porcine ciliary arteries with endothelium, melatonin (10(-11)--10(-5) M) evoked no change in vascular tone. The highest concentration of melatonin (10(-4 ) M) evoked a small but significant contraction. In vessels precontracted with U-46619 (10(-7) M), increasing concentrations of melatonin (10(-11)--10(-5) M) did not evoke a response. In precontracted arteries with endothelium, contractile response of vascular smooth muscle to increasing concentrations of serotonin (10(-10)--10(-5) M) and noradrenaline (10(-10)--10(-5) M) was reduced after preincubation with melatonin (10(-4) M). Melatonin (10(-4) M) did not alter the response to endothelin-1 (10(-10)--10( -7) M) and U-46619 (10(-10)--10(-6 ) M) in precontracted arteries with endothelium. CONCLUSION: These findings demonstrate that melatonin attenuates the effect of serotonin and noradrenaline and is itself a mild vasoconstrictor in porcine ciliary arteries. The role of melatonin in human ocular circulation remains to be established.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1996

Actions of imidazolines on bovine ciliary artery.

A segment of bovine ciliary artery exhibits nonlinear biphasic contractile responses to agonists. The maximal responses of oxymetazoline (OMZ) and norepinephrine (NE) were 55% and 45%, respectively (KCl = 100%). The relative potency comparison based on the ED50 of the first component of the dose-response curve was OMZ; 1 > NE; 1/7 > phenylephrine; 1/72. At equipotent doses of NE and OMZ, the t1/2 duration of response of the latter agonist was 43 times greater than that of the former and, after 3 hrs, responses were 95% reproducible. Naphazoline, tetrahydrozoline and para-aminoclonidine did not produce significant contraction of the blood vessel but did antagonize the action of the agonists. As compared to that of NE, naphazoline was selective in blocking responses of OMZ. Phentolamine blocking action of NE was greater than that of OMZ. Nifedipine, 100 nM, reduced the second component of OMZ response. Although the vascular action of NE was blocked by prazosin, the contractile action of OMZ was totally resistant to block by 1 microM of prazosin. These results indicate that ciliary artery contains a subtype of alpha-adrenoceptors (alpha 11) with low sensitivity to prazosin. The tissue also contains a unique OMZ sensitive site or imidazoline receptors which exhibit low affinity to alpha-adrenoceptor blockers.

Adrenergic alpha-Agonists↗
PubMed2001

Potent alpha(2A)-adrenoceptor-mediated vasoconstriction by brimonidine in porcine ciliary arteries.

PURPOSE: An investigation into whether alpha(2)-adrenoceptor agonists induce contractions in the porcine ciliary arteries and to characterize the functional receptor subtype mediating these responses. METHODS: Isolated arteries from the intraocular part of the porcine ciliary artery were suspended in microvascular myographs for isometric tension recording. The segments were contracted with the alpha(2)-adrenoceptor agonists brimonidine, apraclonidine, and oxymetazoline. To determine which subtypes of the alpha(2)-adrenoceptor mediate this contraction, antagonists subselective for the different alpha(2)-adrenoceptors were added to the vessel bath before concentration-response curves for brimonidine were obtained. The following alpha(2)-adrenoceptor antagonists were applied: BRL44408 (alpha(2A)-selective), ARC239 (alpha(2B)- and alpha(2C)-selective), and prazosin (alpha(2B)- and alpha(2C)-selective). RESULTS: The alpha(2)-adrenoceptor agonists induced vasoconstriction in the porcine ciliary artery with the following potency order (EC(50)) expressed in nanomolar: brimonidine 2.11, oxymetazoline 5.26, and apraclonidine 13.0. As a reference, noradrenaline was tested, and its EC(50) was determined to be 247 nM in the ciliary artery. In the porcine ciliary arteries BRL44408, ARC239, and prazosin caused concentration-dependent and parallel rightward shifts of the concentration-response curves for brimonidine. Schild analyses for the antagonists against brimonidine yielded regression lines with slopes of unity and functional antagonist potencies (pK(B)) for BRL44408 (7.8), ARC 239 (5.8) and for prazosin (6.0) suggesting the presence of functional alpha(2A)-adrenoceptors. Moreover, there was a good correlation of pK(B) with ligand-binding affinity (pK(i)) of the alpha(2A)-adrenoceptor in the porcine eye tissue. CONCLUSIONS: The alpha(2)-adrenoceptor agonists brimonidine, apraclonidine, and oxymetazoline are potent vasoconstrictors in the porcine ciliary artery. In the present work, it was shown for the first time that the alpha(2A)-adrenoceptor subtype mediates this contraction.

Adrenergic alpha-Agonists↗
PubMed2006

Effect and mechanism of betaxolol and timolol on vascular relaxation in isolated rabbit ciliary artery.

PURPOSE: In order to clarify the vasodilatory mechanism of betaxolol and timolol, we studied the effects of these drugs in isolated rabbit ciliary arteries. METHODS: Rabbit ciliary artery specimens were mounted in a double myograph system, and betaxolol, timolol, or another agent was introduced into the organ chamber. The mechanical response of the arteries was studied using an isometric tension recording method. The intracellular free calcium concentration [Ca2+]i was also measured using fluorescence photometry. RESULTS: Betaxolol and timolol induced dose-dependent relaxation in the rabbit ciliary arteries precontracted by high-K+ Krebs solution. The minimum concentrations required to cause relaxation were 10 microM of betaxolol, and 30 microM of timolol. At the maximum concentration of 1 mM, betaxolol induced almost complete relaxation of the ciliary arteries, whereas timolol induced approximately 70% relaxation. These actions were not inhibited by pretreatment with 100 microM NG-nitro-l-arginine methylester (L-NAME), a nitric oxide synthase inhibitor, or by denudation of the vascular endothelium. However, 300 microM of betaxolol or timolol decreased the [Ca2+]i of the vascular smooth muscle, an action similar to that of diltiazem, a typical L-type voltage calcium-channel blocker. CONCLUSIONS: Betaxolol, a selective beta1-adrenoceptor antagonist, and timolol, a nonselective beta-adrenoceptor antagonist, both frequently used in the medical management of glaucoma, decrease [Ca2+]i by acting as Ca2+ channel blockers, thus causing relaxation of isolated rabbit ciliary artery.

Adrenergic beta-Antagonists↗
PubMed2002

Nipradilol induces vasodilation of canine isolated posterior ciliary artery via stimulation of the guanylyl cyclase-cGMP pathway.

We examined the effect of nipradilol on contraction of the posterior ciliary artery induced by high potassium or norepinephrine and on cyclic GMP (cGMP) levels in the posterior ciliary artery of dogs. Nipradilol caused dose-dependent relaxation of KCl-and norepinephrine-induced contractions of posterior ciliary artery. The relaxant effect of nipradilol on norepinephrine-contracted ciliary artery was significantly greater than that on KCl-contracted ciliary artery. In KCl-contracted ciliary artery, N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME, 10(-4) M) did not alter the relaxant effect of nipradilol, whereas 1H-1,2,4-oxadiazolo-4,3-a-quinoxalin-1-one (ODQ, 10(-6) M) significantly inhibited this effect. Ethacrynic acid at 10(-5) M, sulfasalazine at 10(-4) M and S-decylglutathione at 10(-4) M (glutathione S-transferase inhibitors) did not inhibit the relaxant effect of nipradilol. In addition, nipradilol produced dose-dependent increases in cGMP levels in the canine posterior ciliary artery. These findings indicate that nipradilol-induced vasorelaxation in the canine posterior ciliary artery occurs via stimulation of the guanylyl cyclase-cGMP pathway.

Adrenergic beta-Antagonists↗
PubMed1996

Effect of dipyridamole on vascular responses of porcine ciliary arteries.

This study investigated the effects of dipyridamole in isolated porcine ciliary arteries (diameter 200-250 microns). Isolated porcine ciliary arteries were suspended in myograph chambers filled with modified Krebs-Ringer solution (37 degrees C; 95% O2/5% CO2) for isometric tension recording. Dipyridamole induced concentration-dependent relaxations of porcine ciliary arteries with endothelium precontracted with thromboxane analogue U-46619 (10(-6)M), KCl (50 mM), or endothelin-1 (10(-8)M). Removal of the endothelium of the ciliary vessels and preincubation of the arteries with L-NAME (10(-5)M), or indomethacin (10(-5)M), or the combination of the two drugs significantly reduced the relaxation to dipyridamole (p = 0.002-0.03). Similar vascular responses could be observed in a time-dependent analysis of the effect of a single concentration dipyridamole (10(-4)M). The stimulator of cAMP forskolin also caused relaxations. Endothelin-1 (10(-12)-10(-7)M) and U-46619 (10(-10)-10(-6)M) induced potent contractions of porcine ciliary arteries. Preincubation with dipyridamole (10(-5)M) reduced contractions to endothelin-1 as compared to control (p < 0.004), while contractions to U-46619 were only slightly affected under these conditions (n.s.). These findings demonstrate that dipyridamole is a vasodilator in porcine ciliary arteries. Endothelial nitric oxide and prostacyclin contribute importantly to the effects of dipyridamole. Further studies are required to show whether these properties of dipyridamole may also occur in vivo and offer clinical use in patients with ocular vasospasms and other ophthalmic vascular dysfunctions.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2004

Pharmacological vascular reactivity in isolated hypercholesterolemic rabbit ciliary artery.

We have investigated functional and morphological changes occurring in the wall of the hypercholesterolemic rabbit ciliary artery. A mutant rabbit with hypercholesterolemia and atherosclerosis was created by serial breeding. Ciliary arteries from hypercholesterolemic, age-matched control and young control rabbits' eyes were mounted in a myograph system. The effects of phenylephrine (PE), carbachol and electrical field stimulation on this artery were investigated using isometric tension recording methods. The arteries were also examined morphologically. PE caused dose-dependent contraction in young control, age-matched control and hypercholesterolemic rabbits. The EC(50) values were 1.0 microm (0.2-2.1, n = 6), 1.4 microm (0.4-2.4, n = 6) and 4.7 microm (1.8-7.7, n = 8) in the young, age-matched controls and in the Kurosawa and Kusanagi-hypercholesterolemic (KHC) rabbits, respectively. The EC(50) values of the KHC rabbit were significantly different from those of control. Electrical field stimulation evoked contraction only in the control rabbits. On the other hand, electrical field stimulation evoked relaxation when the ciliary artery was pre-contracted by 10 microm histamine in each type of rabbit equally. Carbachol also induced approximately equal dose-dependent relaxation after pre-contraction. The morphological findings of KHC rabbit ciliary artery revealed irregular contours on the internal elastic lamina and deformation of the shape of the medial smooth muscle cells with irregularity in size and widening of the intercellular spaces. However, the endothelial cells were well preserved. Compared with the ciliary artery, typical atherosclerotic changes existed in the intima, not the media, in the KHC rabbit aorta. In the hypercholesterolemic rabbit ciliary artery, the vasoconstricting function was reduced but vasodilatation was well preserved. Morphological findings supported this. The pharmacological vascular reactivity in the hypercholesterolemic rabbit ciliary artery is quite different from that of the large arteries.

Animals↗
PubMedDate not supplied

[Color Doppler ultrasonography of short para-optic ciliary arteries in vascular glaucoma].

PURPOSE: To study color Doppler imaging in orbital vessels, especially para-optic short ciliary arteries, in patients with vascular glaucoma. PATIENTS AND METHODS: Twenty vascular normal or moderate elevated pressure glaucoma patients (6 with bilateral glaucoma, 9 with unilateral glaucoma et 5 with asymmetric glaucoma) underwent a color Doppler imaging (Accusson 128XP) in orbital arteries: common carotid, ophthalmic artery, central retinal artery, short para-optic ciliary arteries. Systolic and diastolic blood flow velocities were measured, and resistance index of Pourcelot and ratios between different parameters were calculated. RESULTS: In patients with unilateral glaucoma, ratios of systolic velocities between para-optic ciliary artery and common carotid, and ratio of Pourcelot index between para-optic ciliary artery and ophthalmic artery were increased in glaucomatous eyes. And Pourcelot index were statistically significant increased in all glaucomatous patients of the study compared with normal subjects. DISCUSSION AND CONCLUSION: Comparison of Pourcelot index and ratios between parameters makes color Doppler imaging more reliable, especially when analyse short para-optic ciliary arteries, which vascularize optic nerve. In these arteries Pourcelot index was increased in vascular glaucoma patients. Vascular risk factor should be taken into consideration in this form of glaucoma.

Aged↗