Endothelin‐1 effects on spontaneous oscillations in choroidal arterioles

Delgado, Esmeralda; Marques-Neves, Carlos; Rocha, Isabel; Sales-Luís, José; Silva-Carvalho, L

doi:10.1111/j.1755-3768.2009.01537.x

Cited by 10 publications

(9 citation statements)

References 13 publications

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“…In our study, L -NAME induced the opposite effect of NO, i.e. vasoconstriction, and stimulated the spontaneous oscillations in the same way as ET-1 [17] , increasing their frequency and decreasing their amplitude. Both L-NAME 10 mg/ml L-NAME 20 mg/ml L-NAME 30 mg/ml L-Arg 100 mg/ml drugs ( L -NAME and ET-1) elicit strong vasoconstricting effects and strongly influence vasomotion characteristics.…”

Section: Discussionmentioning

confidence: 83%

“…We have previously investigated the effects upon both perfusion pressure and periodic oscillations at the rabbit external ophthalmic artery of adrenergic drugs [16] , endothelin (ET) 1 [17] and amlodipine [18] . Vasomotion refers to periodic oscillations in vascular tone that allow fine control of the capillary blood and facilitate exchange of metabolites, being a phenomenon described in practically all vascular beds.…”

Section: Introductionmentioning

confidence: 99%

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L-Arginine and L-Nitroarginine Methylester Effects on Vasomotion in Isolated Rabbit Eyes

Delgado¹,

Marques-Neves²,

Rocha³

et al. 2009

Ophthalmic Res

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Background/Aims: Although nitric oxide (NO) has been shown to be essential for maintaining the basal blood flow in the retina and optic nerve head, its exact role in vasomotion is still controversial. This study investigated L-arginine (L-Arg) and N-nitro-L-arginine methylester (L-NAME) effects on vascular reactivity in a model of isolated rabbit eye. Methods: Rabbit external ophthalmic arteries (n = 12) in a head-mounted preparation were cannulated and perfused with warmed Tyrode solution. The effect of intraluminal pressure as a measure of total vascular resistance was assessed. Response curves to intra-arterial injections of 3 growing concentrations of L-Arg (n = 6) and L-NAME (n = 6) were obtained. Results: Without any drug administration, spontaneous oscillations were observed in all the models. L-Arg (NO precursor) induced vasodilation and decreased both frequency and amplitude of the periodic oscillations. L-NAME (NO synthase inhibitor) produced a strong vasoconstrictor tone and stimulated vasomotion, causing a faster rate of pulsatility. Conclusion:L-Arg and L-NAME acted as modulators of ocular vascular tone. L-Arg elicited vasodilation and decreased vasomotion while L-NAME produced a strong vasoconstrictor tone and caused a faster rate of pulsatility. These findings justify the need to investigate NO precursors and antagonists as possible alternative therapeutics in vascular eye diseases.

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Section: Discussionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

L-Arginine and L-Nitroarginine Methylester Effects on Vasomotion in Isolated Rabbit Eyes

Delgado¹,

Marques-Neves²,

Rocha³

et al. 2009

Ophthalmic Res

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show abstract

“…In a study of spontaneous oscillations in choroidal arterioles in rabbits, ET-1 was found to increase vasomotion [29]. In this model of in situ-perfused isolated rabbit eyes, ET-1 induced an initial short and weak vasodilating effect followed by a strong and long-lasting vasoconstrictor tone.…”

Section: Discussionmentioning

confidence: 98%

Endothelin-induced changes in blood flow in STZ-diabetic and non-diabetic rats: relation to nitric oxide synthase and cyclooxygenase inhibition

Granstam

2011

J Physiol Sci

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In this study, using the microsphere method, the hemodynamic response to endothelin-1 (ET-1) in healthy and streptozotocin (STZ)-diabetic rats was evaluated as well as the influences of inhibition of nitric oxide (NO)-synthase using L-NAME (Nω-nitro-l-arginine methyl ester) and the cyclooxygenase inhibitor indomethacin. Blood flow (Q) was measured in tissues of interest for vascular complications in diabetes such as kidney, eye, brain, heart and skeletal muscle with the main focus on ophthalmic circulation. Under resting conditions, evidence for renal vasoconstriction was found in diabetic animals. In both groups, administration of L-NAME reduced Q in all investigated tissues indicating a basal NO influence. In the normal rats, ET-1 induced a significant increase in blood pressure and intense vasoconstriction in all tissues except in the choroid of the eye and in the brain, where it induced an increased Q. In the STZ-diabetic rats, effects of ET-1 were less pronounced. Pretreatment with L-NAME, but not the cyclooxygenase inhibitor, abolished the ET-1-induced vasodilation in the choroid of both groups. Administration of ET A receptor antagonist BQ-123 reduced the ET-1-induced vasodilation in the choroid only in diabetic animals. In conclusion, evidence for altered vascular endothelial response to ET-1 in STZ-diabetic animals was found particularly in the ophthalmic circulation. The findings suggest differential involvement of receptors in the response to ET-1 in normal and STZ-diabetic animals.

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“…In the decomposition of the signal obtained in the ex vivo models, there were no bands present in the HF or LF region due to abolition of autonomic influences, so the myogenic vascular responses were due to autoregulatory mechanisms as has been demonstrated elsewhere [13,14,15]. …”

Section: Discussionmentioning

confidence: 96%

Myogenic Oscillations in Rabbit Ocular Vasculature Are Very Low Frequency

Delgado

Marques-Neves²,

Rocha³

et al. 2013

Ophthalmic Res

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Background/Aims: In a previously described model of isolated rabbit eye, we detected myogenic intrinsic vascular tone of unknown origin in the ophthalmic artery. In order to better understand the origin of these low frequency oscillations, we analyzed their spectral characteristics using fast Fourier. Methods: Hybrid New Zealand rabbits of either sex (n = 24) were used; they were divided into 2 groups according to age. The spectral characteristics of the myogenic behaviour of the rabbit external ophthalmic artery were analyzed using the fast Fourier algorithm. Results: The frequency of the oscillations of the myogenic activity seen in the rabbit external ophthalmic artery varied between 0.033 and 0.066 Hz (mean 0.045 ± 0.012 Hz), all in the region of very low frequency (VLF) oscillations (VLF <0.07 Hz for the rabbit). The frequency of spontaneous oscillations was higher in younger animals. Conclusion: Fast Fourier analysis proved to be an adequate mathematical tool to analyze the myogenic tone oscillations, which were all in the range of VLF in the model we used. These results indicate that myogenic vascular function of ocular blood flow is composed of VLF oscillations, and they provide a new explanation for the origin of VLF in arterial spectra. They also suggest that the ocular local myogenic vascular function observed is more efficient in younger animals.

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Endothelin‐1 effects on spontaneous oscillations in choroidal arterioles

Cited by 10 publications

References 13 publications

<i>L</i>-Arginine and <i>L</i>-Nitroarginine Methylester Effects on Vasomotion in Isolated Rabbit Eyes

<i>L</i>-Arginine and <i>L</i>-Nitroarginine Methylester Effects on Vasomotion in Isolated Rabbit Eyes

Endothelin-induced changes in blood flow in STZ-diabetic and non-diabetic rats: relation to nitric oxide synthase and cyclooxygenase inhibition

Myogenic Oscillations in Rabbit Ocular Vasculature Are Very Low Frequency

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