Scotoma and fixation patterns using scanning laser ophthalmoscope microperimetry in patients with macular dystrophy

PURPOSE

We used scanning laser ophthalmoscope microperimetry to evaluate the retinal scotoma and the fixation points in the patients with macular dystrophy.

METHODS

We studied 10 eyes of five patients with macular dystrophy (three patients with cone dystrophy and two patients with Stargardt disease). The mean patient age was 37 years (range, 13 to 64 years). An estimation of scotoma and fixation points on the retina was performed using scanning laser ophthalmoscope microperimetry.

RESULTS

All 10 eyes (100%) had one of two types of dense scotoma: type one was a dense ring scotoma (five eyes, 50%), and type two was a dense central scotoma (five eyes, 50%) that included the center of the fovea. In all eyes with a dense ring scotoma, the fixation points were stable and did not shift. In all eyes with a dense central scotoma, the fixation shifted. The logarithm of minimal angle of resolution of the visual acuity in the eyes with the dense central scotoma was significantly worse than that of eyes with the dense ring scotoma type (P =.005).

CONCLUSIONS

Scanning laser ophthalmoscope microperimetry findings demonstrate two types of dense scotoma (dense ring scotoma and dense central scotoma) in the patients with macular dystrophy. The two types of dense scotoma affect the shifting of the fixation points and the stability of fixation and may result in the difference in visual acuity in the patients with macular dystrophy.

Branch retinal vein occlusion in a Japanese patient with neurofibromatosis 1

BACKGROUND

To report an Asian patient with branch retinal vein occlusion secondary to neurofibromatosis 1.

CASE

A 64-year-old woman presented with a loss of vision in her right eye of 9-month duration. A diagnosis of neurofibromatosis 1 was made. A general medical examination showed no abnormalities except the signs of neurofibromatosis 1.

OBSERVATIONS

Fundus examination of the right eye revealed irregularities of the venous caliber, partial sheathing of the corresponding vein and macular edema. Multiple dilated and tortuous collateral channels and an arteriovenous communication bridged the perfused and nonperfused retina. Fundus examination of the left eye showed a tortuous vein in the temporal region of the fovea. Fluorescein angiography of the right eye confirmed delayed filling in a superotemporal artery and in the corresponding vein. The temporal region of the fovea had large areas of capillary loss. The collaterals were tortuous and mimicked a neovascularization. Fluorescein angiography of the left eye confirmed that the vein in the temporal part of the fovea was tortuous and not leaking. A diagnosis of branch retinal vein occlusion of the superotemporal vein was made.

CONCLUSIONS

Neurofibromatosis 1 should be considered in the differential diagnosis of retinal vascular occlusive disease without other risk factors.

Disulfide structure of alfimeprase: a recombinant analog of fibrolase

The disulfide structure of alfimeprase, a recombinant analog of fibrolase, was experimentally determined by a combination of peptide mapping, Edman degradation, and mass spectrometry. The three disulfide bonds were determined to be Cys-116/196, Cys-156 /180, and Cys-158/163 with the residue number system of alfimeprase.

Inhibitory effect of losartan on laser-induced choroidal neovascularization in rats

PURPOSE

To investigate the inhibitory effects of losartan, an angiotensin receptor antagonist, on angiogenesis in a rat model of laser-induced choroidal neovascularization.

METHODS

Experimental study. Fifteen Brown-Norway male rats received losartan (approximately 5 mg/kg/d) in drinking water, and 15 Brown-Norway male rats received unsupplemented drinking water 1 week before photocoagulation, and it was continued to the end of the study. Two weeks after intense laser photocoagulation, choroidal neovascularization was evaluated by fluorescein angiography and histopathologic evaluation.

RESULTS

The incidence of choroidal neovascularization formation was 99.5 +/-.2% (mean +/- standard deviation) in controls and 72.5 +/- 8.8% in losartan-treated rats (P <.01). Quantitative morphometric assessment revealed mean choroidal neovascularization lesion thickness of 54 and 44.8 microm, respectively, in controls and losartan-treated rats (P <.01).

CONCLUSION

Losartan seems to inhibit development of laser-induced choroidal neovascularization. Angiotensin receptor antagonists may be useful as prophylaxis against choroidal neovascularization associated with age-related macular degeneration.

Expression of beta-synuclein in normal human astrocytes

Although alpha- and beta-synucleins are expressed predominantly in presynaptic nerve terminals, recent studies have demonstrated that alpha-synuclein is also expressed in cultured astrocytes and oligodendrocytes. We determined whether beta-synuclein might be expressed in astrocytes. Beta-synuclein mRNA and protein were detected in normal human astrocytes in culture, and immunofluorescent staining showed that beta-synuclein protein was expressed within the cytoplasm and nucleus. Furthermore, beta-synuclein immunoreactivity was present in astrocytes, but not in oligodendrocytes, in normal human brain tissues. Ultrastructurally, beta-synuclein immunoreactivity was found in the cytoplasm of astrocytes, in association with the plasma membrane, ribosomes, rough endoplasmic reticulum and the nuclear outer membrane. The novel expression of beta-synuclein in astrocytes may provide an important insight about the role of this protein.

Stereo acuity in patients with unilateral macular hole and after unilateral macular hole surgery

PURPOSE

To investigate stereo acuity levels in patients with unilateral idiopathic macular hole and after surgical intervention.

METHODS

In 31 consecutive patients with a unilateral macular hole and 46 consecutive patients who underwent successful unilateral macular hole surgery, complete ocular examinations, including orthoptic examinations and microperimetry using the scanning laser ophthalmoscope, were performed.

RESULTS

A significantly positive correlation was found between VA and stereo acuity (r = 0.87, P < 0.01). After successful surgery, stereo acuity also correlated with the presence or absence of absolute and/or relative scotoma, and was best in eyes without scotomata. Patients with unilateral idiopathic macular hole, suppression, and symptom duration of 24 months or longer had no stereoscopic vision.

CONCLUSIONS

The results indicated that in patients with unilateral idiopathic macular hole and after surgery, stereo acuity correlated with VA. Patients with unilateral macular hole should be operated upon as early as possible, resulting in better VA and better stereo acuity.

Effect of acetazolamide on outward permeability of blood-retina barrier using differential vitreous flyorophotometry

PURPOSE

To measure fluorescein (F) and fluorescein monoglucuronide (FG) concentrations in the vitreous and evaluate the effect of acetazolamide (AZM) on the outward permeability of the blood-retina barrier (BRB) using differential vitreous fluorophotometry (DVF).

METHODS

DVF was performed 180 minutes after intravenous injection of AZM (5 mg/kg) and 50 mg of sodium fluorescein in six rabbits (AZM group). DVF also was performed in six rabbits injected intravenously with only 50 mg of sodium fluorescein (control group). The F/FG ratio was calculated based on the concentrations of F and FG obtained by DVF. DVF also was performed 180 minutes after 50 mg of intravenous injection of sodium fluorescein in five rabbits given probenecid (150 mg/kg) intraperitoneally (probenecid group).

RESULTS

The average F/FG ratio was 0.36 +/- 0.17 (range, 0.22-0.66) in the AZM group, which was significantly smaller than the control value of 0.74 +/- 0.22 (range, 0.50-1.60). The average F/FG ratio at 180 minutes after injection was 1.51 +/- 0.46 (range, 0.94-2.00) in the probenecid group, which was significant higher (p < 0.05) than that of the AZM or control group.

CONCLUSIONS

This study showed that the F/FG ratio might be a good indicator of the estimated outward permeability of the BRB using DVF and that AZM may accelerate the outward active transport function of the BRB.

Dynamic observation of selective accumulation of a photosensitizer and its photodynamic effects in rat experimental choroidal neovascularization

PURPOSE

The authors investigated the selective accumulation of a photosensitizer, ATX-S10(Na), in experimental choroidal neovascularization (CNV) in rats using a highly sensitive colorchromatic charge coupled device (CCD) camera.

METHODS

To detect the development of experimental CNV in 30 rats, the animals were followed weekly with simultaneous fluorescein and indocyanine green angiography. After injecting ATX-S10(Na), the authors detected fluorescence from the photosensitizer using a highly sensitive color CCD camera. The camera was connected to a surgical microscope, under which rat fundi were observed through a coverglass in contact with the cornea. The retinas were excited with 405-435 nm light, and the light emitted from the photosensitizer passed through a 680-nm bandpass filter before being detected by the CCD camera.

RESULTS

Immediately after injection, fluorescence appeared in the retinal vessels and then the entire retina. Thirty minutes postinjection, the intensity of the fluorescence was still strong from the whole retina, and the CNV was not detected. One hour after injection, retinal fluorescence was weak but still observable; 1.5 hours postinjection, retinal fluorescence was undetectable but fluorescence was strong from the CNV. Under the optimum therapeutic conditions, CNV was effectively occluded.

CONCLUSION

ATX-S10(Na) selectively accumulates in the CNV in rats. The optimum therapeutic timing is approximately 1.5 hours postinjection of the dye in this CNV model.

'In vivo perfusion Turnbull's reaction' for Fe(II) histochemistry in non-anoxic/non-ischemic and anoxic/ischemic cat brains

We developed a simple but ingenious histochemical method, 'in vivo perfusion-Turnbull's reaction', for the visualization of non-heme Fe(II) of the brain; in situ release of Fe(2+) ions was coupled with formation of insoluble reaction product (Turnbull's blue) by in vivo perfusion of acid ferricyanide through the abdominal (non-anoxic/non-ischemic brain) or ascending (anoxic/ischemic brain) aorta in the deeply anesthetized adult cats. Frozen sections of the brain were treated according to the method of Nyguen-Legros et al. [12] to intensify Turnbull's reaction. The method revealed that cytoplasmic Fe(III) was reduced to Fe(II) in oligodendroglias in anoxic/ischemic (for 20 min) brains, and that Fe(II) was concentrated in the neuronal and glial cell nuclei regardless of the presence or absence of blood supply impairment.

Constitutive nitric oxide synthase is associated with retinal vascular permeability in early diabetic rats

AIMS/HYPOTHESIS

We investigated the association between vascular permeability and constitutive nitric oxide synthase in rats with diabetes for a short duration (2 weeks).

METHODS

Retinal vascular permeability was evaluated in rats with diabetes induced by streptozotocin using vitreous fluorophotometry and a small animal adapter. We carried out in situ hybridization and semi-quantitative reverse transcription-polymerase chain reaction to study the expression of endogenous constitutive nitric oxide synthase mRNA in diabetic retinas. We also examined changes in the protein expression of constitutive nitric oxide synthase in diabetic retinas using immunohistochemistry and Western blotting.

RESULTS

Retinal vascular permeability was significantly higher in diabetic rats (median, 1.09 arbitrary unit) compared with control rats (median, 0.69 arbitrary unit) (p < 0.05). The expression of both neuronal nitric oxide synthase (NOS) and endothelial nitric oxide synthase mRNA was higher in diabetic retinas than in the retinas of control rats as determined by in situ hybridization and reverse transcription-polymerase chain reaction. Immunohistochemistry and Western blotting also showed that neuronal nitric oxide synthase increased in diabetic retinas. The immunohistochemistry of endothelial nitric oxide synthase indicated that non-vessel tissues increased in diabetic retinas while retinal vessels weakened. Western blotting showed that the amount of endothelial nitric oxide synthase increased.

CONCLUSION/INTERPRETATION

These results suggest that increases in both constitutive NOSs (nNOS and eNOS) could be associated with retinal vascular permeability and that NOS is associated with clinical vascular dysfunction in the early stages of diabetes.

Expression of alpha-synuclein in a human glioma cell line and its up-regulation by interleukin-1beta

Although alpha-synuclein is expressed primarily in neurons, it is a major component of oligodendroglial and astrocytic inclusions in several neurodegenerative diseases. Recent study has further demonstrated that alpha-synuclein is expressed in cultured rat oligodendrocytes. We determined whether alpha-synuclein might be expressed in astrocytic cells. alpha-Synuclein mRNA and protein were detected in U251 human astrocytic glioma cells and normal human astrocytes, and the levels were increased in the former, but not in the latter, by stimulation with interleukin-1beta in a time- and concentration-dependent manner. Serum deprivation also led to an increase of alpha-synuclein mRNA and protein in U251 cells. Immunofluorescent staining confirmed the cell-associated alpha-synuclein. These findings suggest that human astrocytes can produce alpha-synuclein in culture and that certain inflammatory cytokines and cell stress increase alpha-synuclein expression.

Factors affecting pulsatile ocular blood flow in normal subjects

BACKGROUND

The factors that influence pulsatile ocular blood flow (POBF) were evaluated in normal subjects.

METHODS

POBF was measured in 80 normal subjects using Langham OBF computerised tonometry. The effect of age, systolic and diastolic blood pressure, refractive error, intraocular pressure, and axial length on POBF was evaluated using multiple regression analysis.

RESULTS

The mean (SD) POBF value was 593.3 (203.6) microl/min (range 290.7-1201.6). Of all the independent variables in the model, only the axial length was statistically significant (p = 0.008). The regression coefficient was negative, indicating that the axial length decreased with increasing POBF.

CONCLUSIONS

These data suggest that, in normal subjects, the POBF decreases as axial length increases. Choroidal blood flow may decrease as the axial length increases. The axial length may therefore be a major factor affecting POBF.

Pulsatile ocular blood flow study: decreases in exudative age related macular degeneration

BACKGROUND

Pulsatile ocular blood flow (POBF) is a parameter for evaluating choroidal blood flow. POBF in the patients with non-exudative and exudative age related macular degeneration (AMD) was investigated.

METHODS

POBF, pulse amplitude (PA), systolic and diastolic blood pressures, intraocular pressure (IOP), refractive error, and axial length were compared among 10 patients with non-exudative AMD, 11 patients with exudative AMD, and 69 age matched controls. A Langham OBF computerised tonometer was used with the participants in the sitting position to measure POBF and PA.

RESULTS

No significant differences were found in age, systolic and diastolic blood pressures, IOP, or refractive error between patients with exudative and non-exudative AMD and the control subjects. In the patients with exudative AMD the POBF (median, 372.7 microl/min) and PA (median, 1.2 mm Hg) were significantly lower than in the patients with non-exudative AMD (median, 607.0 microl/min (p = 0.02) and 2.2 mm Hg (p = 0.04), respectively) and control subjects (median, 547.4 microl/min (p = 0.01) and 2.0 mm Hg (p = 0.01), respectively).

CONCLUSIONS

These data show that the POBF and PA in the patients with exudative AMD are lower than in the patients with non-exudative AMD and normal subjects. Decreased choroidal blood flow may have a role in the development of choroidal neovascularisation in AMD.

Corneal advanced glycation end products increase in patients with proliferative diabetic retinopathy

OBJECTIVE

To evaluate corneal advanced glycation end product (AGE) fluorescence in patients with diabetes and in healthy control subjects.

RESEARCH DESIGN AND METHODS

Corneal autofluorescence was measured in 26 eyes of 26 patients with type 2 diabetes (mean age 57.0 years; mean disease duration 12.2 years; mean HbA1c 7.1%) and 13 eyes of 13 healthy age-matched control subjects (mean age 57.9 years). The patients with type 2 diabetes were divided into the following groups: patients without diabetic retinopathy (DR), patients without proliferative diabetic retinopathy (PDR), and patients with PDR. Corneal autofluorescence was measured by fluorophotometry with the wavelength that is characteristic of AGE fluorescence (excitation and emission 360-370 nm and 430-450 nm, respectively). We defined peak corneal autofluorescence levels as corneal AGE fluorescence values. We compared the corneal AGE fluorescence values in the four groups.

RESULTS

In the PDR group (11.9 +/- 3.9 arbitrary units [mean +/- SD]), the corneal AGE fluorescence values were significantly higher compared with the control subjects (6.9 +/- 1.3 arbitrary units), the patients without DR (7.4 +/- 2.1 arbitrary units), and the patients without PDR (6.9 +/- 2.2 arbitrary units) (P < 0.05).

CONCLUSIONS

We found that corneal AGEs may increase in patients with diabetes and PDR compared with control subjects, patients without DR, and patients without PDR. In the patients with PDR, increased corneal AGEs may play a role in diabetic keratopathy.

Cardiac contusion in blunt chest trauma: a combined study of transesophageal echocardiography and cardiac troponin I determination

BACKGROUND

The role of cardiac troponin I (cTnI) is well established in acute myocardial ischemia. However, its role in myocardial contusion remains to be clarified. Since transesophageal echocardiography (TEE) appears, at present, to be the best method for the diagnosis of myocardial contusion, the aim of this study was to measure the concentration of cTnI in patients with blunt chest trauma studied using TEE.

METHODS

Thirty-two patients (27 males, 5 females, mean age 44+/-20 years), admitted to the Trauma Center of our Institution with clinical and/or radiological signs of acute blunt chest trauma, underwent biplane TEE within 24 hours of injury; serial blood samples were taken to measure cTnI levels (normal values < 0.4 ng/ml), using fluorimetric enzyme immunoassay.

RESULTS

Abnormal levels of cTnI were found in 17 patients (53%): 7 patients had levels of cTnI between 0.4 and 1 ng/ml, whereas 10 patients had levels > 1 ng/ml. Segmental wall motion abnormalities consistent with myocardial contusion could be identified by echocardiography in 6/10 patients with cTnI levels > 1 ng/ml (60%) but in no patients with normal cTnI levels or with titers between 0.4 and 1 ng/ml; mean cTnI levels showed a significant difference between the two groups of patients with and without echocardiographic signs of myocardial contusion (2.6+/-1.6 vs 0.6+/-1.4 ng/ml, p < 0.001).

CONCLUSIONS

Abnormal titers of cTnI suggesting myocardial contusion may be found in more than half of patients with blunt chest trauma; however, myocardial injury can be detected by TEE only for cTnI levels > 1 ng/ml; cTnI concentrations ranging between 0.4 and 1 ng/ml might be indicative of myocardial microlesions, not detectable by echocardiography, even if TEE is used; cTnI assay could therefore be suggested as a screening test before performing TEE after blunt chest trauma.

"Natural histories" of mitral valve prolapse. Influence of patient selection on cardiovascular event rates

BACKGROUND

In previous studies the reported incidence of cardiovascular events among mitral valve prolapse patients has differed more than 10 fold. We endeavored to determine the relation between the clinical features and mode of ascertainment of mitral valve prolapse and the resulting event rate.

METHODS

Between January 1979 and August 1996, 275 patients (129-47% men, 146-53% women, mean age 43 +/- 19 years), were followed for a mean of 98 months after evaluation in a referral center for valvular heart disease. Comparative data were obtained from a separate, less selected population consisting of 316 patients.

RESULTS

A total of 65 events occurred (2.9/100 patient-years): 46 (2.0/100 patient-years) mitral surgery, 12 cardiac deaths (0.5/100 patient-years), 6 neurologic ischemia (0.26/100 patient-years), and 1 infective endocarditis (0.04/100 patient-years). The overall event rate varied significantly according to demographic, clinical and echocardiographic variables (all p < 0.0001). It was higher among males (odds ratio-OR 2.1), subjects > or = 45 years of age (OR 14.7), those with a holosystolic murmur (OR 25.9), an enlarged left ventricle (OR 13.5) or left atrium (OR 34.9) and those with 3-4+ mitral regurgitation at color Doppler echocardiography (OR 40.0). It was lower in those with an audible mid-systolic click (OR 0.05). These ORs closely resembled those we reported previously in a less selected population. At multivariate analysis, male gender (p = 0.013), severe Doppler mitral regurgitation (p = 0.0048), and left atrial enlargement (p = 0.046) were all independent predictors of events.

CONCLUSIONS

In a population of mitral valve prolapse patients, including many with significant mitral regurgitation at baseline, we identified similar predictors of events but an overall event rate nearly 3 times higher than that we previously reported for relatively unselected patients or family members in New York City (1/100 patient-years). Therefore, the impact of patient selection on the prevalence of mitral regurgitation, older age and male gender strongly affects the adversity of the "natural history" of mitral valve prolapse.

[Hemorrhages of dorsal root ganglia and sensory disturbance in congenitally hydrocephalic HTX rats]

Recently we reported the frequent occurrence of hemorrhages in the dorsal root ganglia of congenitally hydrocephalic HTX rats, an animal model of human congenital hydrocephalus. Therefore, we hypothesized that sensory disturbance might be present in these rats. In order to evaluate the sensory abnormality quantitatively, we injected 50 microliters of 5% formalin into the footpad of the left hind paw of hydrocephalic (n = 5) and non-hydrocephalic HTX rats (n = 5) and Wistar rats (n = 5) on postnatal days 17-23, and then recorded the licking response time for 60 min after injection. The mean licking time in the early (0-10 min) and late (10-60 min) phases was significantly longer in hydrocephalic HTX rats than in non-hydrocephalic HTX and Wistar rats (P < 0.05). Histologically, hemorrhages in the dorsal root ganglia were found in all five hydrocephalic animals, of which two had shown thalamic degeneration. These findings suggest that lesions in the dorsal root ganglia and thalamus may correspond to the sensory disturbance observed in congenitally hydrocephalic HTX rats.

[A case of bilateral coronal craniosynostosis with the P250R mutation in FGFR3 gene]

Recently, the substitution of proline 250 by arginine in the fibroblast growth factor receptor 3 (FGFR3) gene, has been identified in patients with craniosynostosis and defines a new syndrome on a molecular basis. We report a 1-year-1-month-old female with bilateral coronal craniosynostosis who had the P250R mutation in FGFR3 gene detected by DNA sequencing. She had brachycephaly, temporal bossing, high and flat forehead, hypertelorism, mild proptosis, low set ears and no digital abnormalities. She underwent surgical repair at 7 months and her cosmetic problems were improved. Her development was normal up to 13 months of age. DNA analysis from her parents showed that her father had the same mutation. The phenotypes of the P250R mutation in the FGFR3 syndrome are variable even within the same family, but main characteristic clinical features are follows, 1) lateral or bilateral coronal craniosynostosis, 2) mild hand and foot anomalies, and 3) sensory deafness. In FGFR3 syndrome the diagnosis of P250R mutation by polymerase chain reaction (PCR) is very easy and important for early diagnosis and genetic counseling.

Convulsive effects of thiophene, a heterocyclic hydrocarbon: behavioral, electrographic and c-Fos immunocytochemical studies

The behavioral, electrographic and histopathological changes induced by the heterocyclic hydrocarbon thiophene were investigated in rats following intramuscular injection of 0.3 mL thiophene for 5 days. Generalized convulsions were noted in 29 out of 34 animals (85%) between 1 and 28 h after the final dose. Electroencephalography revealed that the discharges in the hippocampus and forebrain occurred simultaneously, although epileptic activity emerged more strongly from the hippocampus than from any other region. Neuron damage was detected histologically in the temporal and parietal neocortex, piriform gyrus, amygdaloid nucleus and cerebellar cortex, but not in the hippocampus. In contrast, c-Fos was induced widely in the cerebral cortex and hippocampus, and was most marked in the dentate gyrus. These findings suggest that the hippocampus plays a crucial role in seizure onset following thiophene injection.

Thiophene, a sulfur-containing heterocyclic hydrocarbon, causes widespread neuronal degeneration in rats

Thiophene is a sulfur-containing heterocyclic hydrocarbon that has been detected in a number of environmental sources as various derivatives. Previous studies with rats have shown that thiophene induces selective degeneration of granule cells in the cerebellum, as observed with methyl mercury. To study the neurotoxicity of thiophene, Wistar rats received daily intramuscular injections of 0.2 mL thiophene for 3 days. Ataxia and convulsions were noted in all animals within 24 h after the final dose. Histologically, multiple foci of necrosis were observed in the cerebellum, predominantly in the granular layer. Neuronal damage was also found in the cerebral cortex, inferior colliculus and inferior olive. These findings suggest that thiophene causes widespread neuronal degeneration in rats and that the regional distribution of brain lesions induced by thiophene is different from that caused by methyl mercury poisoning.

Endothelin-3 regulation of retinal hemodynamics in nondiabetic and diabetic rats

PURPOSE

To investigate the mechanisms of action of endothelin (ET)-3 on the regulation of retinal hemodynamics in diabetic and nondiabetic rats.

METHODS

Retinal blood flow changes were measured using video fluorescein angiography. Measurements were made before and after intravitreal injections of different ET-3 concentrations in nondiabetic rats and rats with streptozotocin (STZ)-induced diabetes. The effect of ET-3 on retinal blood flow was also investigated in nondiabetic rats after pretreatment with N:(G)-monomethyl-L-arginine (L-NMMA), a nitric oxide synthase (NOS) inhibitor; BQ-788, an ET receptor B (ETB) antagonist; and BQ-123, an ET receptor A (ETA) antagonist. Control animals were injected intravitreally with vehicle alone.

RESULTS

In nondiabetic rats, ET-3 induced a dose-dependent rapid increase in retinal blood flow 2 minutes after intravitreal injection (maximal at 10(-)(8) M, P < 0. 01) followed 15 and 30 minutes after ET-3 injection by dose-dependent decreases in retinal blood flow (maximal effect at 10(-)(6) M, P < 0.05). The ET-3-stimulated retinal blood flow increase was inhibited by 10(-)(4) M BQ-788 (P < 0.01) and 10(-)(3) M L-NMMA (P < 0.05). The ET-3-stimulated decrease in retinal blood flow at later times (15 minutes) was inhibited (P < 0.03) by 10(-4) M BQ-123. In diabetic rats, baseline retinal blood flows were decreased compared with nondiabetic rats (P < 0.01), showed dose-dependent increases 2 minutes after ET-3 injection (P < 0.03), and at later times remained significantly increased (P < 0.05) in contrast to flows in nondiabetic rats.

CONCLUSIONS

The ET-3-induced initial rapid retinal blood flow increase in nondiabetic rats is mediated by the ET-3/ETB and NOS action. The subsequent retinal blood flow decrease is mediated by ET-3/ETA action. Diabetic rats showed comparable ET-3-induced retinal blood flow increases indicating normal ET-3/ETB action. However, at later times, retinal blood flow remained increased, suggesting an abnormal ET-3/ETA action.