June 2011
Volume 52, Issue 7
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Physiology and Pharmacology  |   June 2011
Functional Role of α1-Adrenoceptor Subtypes in Murine Ophthalmic Arteries
Author Affiliations & Notes
  • Adrian Gericke
    From the Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany;
  • Marcin L. Kordasz
    From the Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany;
  • Andreas Steege
    the Department of Internal Medicine II, University Medical Center Regensburg, Regensburg, Germany;
  • Atsushi Sanbe
    the Department of Pharmacotherapeutics, School of Pharmacy, Iwate Medical University, Iwate, Japan; and
  • Evgeny Goloborodko
    From the Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany;
  • Jan M. Vetter
    From the Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany;
  • Andreas Patzak
    the Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
  • Norbert Pfeiffer
    From the Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Mainz, Germany;
  • Corresponding author: Adrian Gericke, Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55101 Mainz, Germany; adrian.gericke@gmx.net  
Investigative Ophthalmology & Visual Science June 2011, Vol.52, 4795-4799. doi:10.1167/iovs.11-7516
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      Adrian Gericke, Marcin L. Kordasz, Andreas Steege, Atsushi Sanbe, Evgeny Goloborodko, Jan M. Vetter, Andreas Patzak, Norbert Pfeiffer; Functional Role of α1-Adrenoceptor Subtypes in Murine Ophthalmic Arteries. Invest. Ophthalmol. Vis. Sci. 2011;52(7):4795-4799. doi: 10.1167/iovs.11-7516.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose.: To identify the α1-adrenoceptor (α1-AR) subtypes mediating vascular adrenergic responses in murine ophthalmic arteries.

Methods.: Expression of mRNA was quantified for individual α1-AR subtypes in murine ophthalmic arteries using real-time PCR. To assess the functional relevance of α1-ARs for mediating vascular responses, ophthalmic arteries from mice deficient in one of the three α1-AR subtypes (α1A-AR−/−, α1B-AR−/−, and α1D-AR−/−, respectively) and wild-type controls were isolated, cannulated with micropipettes, and pressurized. Changes in luminal artery diameter in response to the α1-AR agonist phenylephrine, the sympathetic transmitter noradrenaline, and to the nonadrenergic vasoconstrictor arginine vasopressin (AVP) were measured by video microscopy.

Results.: Using real-time PCR, mRNA for all three α1-AR subtypes was detected in ophthalmic arteries from wild-type mice. In functional studies, phenylephrine and noradrenaline produced dose-dependent constriction of ophthalmic arteries that was similar in wild-type, α1B-AR−/−, and α1D-AR−/− mice. Strikingly, responses to phenylephrine and noradrenaline were almost completely abolished in α1A-AR−/− mice. In contrast, the nonadrenergic agonist AVP produced dose-dependent vasoconstrictor responses that did not differ between any of the mouse genotypes tested.

Conclusions.: These findings provide evidence that the α1A-AR subtype mediates adrenergic vasoconstriction in murine ophthalmic arteries.

Disturbances in ocular perfusion have been implicated in the pathophysiology of various eye diseases, including diabetic retinopathy, nonarteritic anterior ischemic optic neuropathy, and glaucoma. 1 6 The α1-adrenoceptor (α1-AR) family plays a critical role in regulating ocular vascular tone and blood flow by mediating vasoconstrictor responses of catecholamines in the ocular circulation. 7 11  
Pharmacologic studies and molecular cloning techniques have revealed the existence of three α1-AR subtypes: α1A, α1B, and α1D. 12 16 All three receptor subtypes are expressed in blood vessels and can mediate vasoconstriction via Gq/11 protein–mediated increases of inositol phosphates and intracellular calcium in vascular smooth muscle cells. 17 However, the expression pattern of individual α1-AR subtypes and their role in mediating vascular responses to catecholamines differs considerably between individual vascular beds. 18,19 Based on these findings, selective pharmacologic activation or blockade of individual α1-AR subtypes may provide a useful tool to selectively modulate perfusion of various organs, including the eye. Thus, we designed this study to identify the α1-AR subtypes that mediate adrenergic vascular responses in ophthalmic arteries. Since the expression pattern of α1-ARs is unknown in ocular vessels, we used real-time (RT) PCR to quantify mRNA expression of individual α1-AR subtypes in murine ophthalmic arteries. Due to the lack of highly selective agonists and antagonists for individual α1-AR subtypes, we used gene-targeted mice deficient in one of the three α1-ARs (α1A-AR−/−, α1B-AR−/−, α1D-AR−/−, respectively) to determine the role of each receptor subtype in mediating adrenergic vasoconstriction in ophthalmic arteries. 
Materials and Methods
Animals
All studies were performed in accordance with the ARVO statement for the Use of Animals in Ophthalmic and Vision Research and were approved by the local government. The generation of α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice has been described previously. 20 22 Each genotype has been backcrossed with C57BL/6Slc mice for more than eight times and maintained on a C57BL/6Slc background. For experiments, male mice at the age of 7 to 9 months were used. Mice were fed with standard mouse chow and allowed free access to tap water. 
Real-Time PCR Analysis
Expression of α1-AR mRNA was quantified in isolated ophthalmic arteries from wild-type mice (C57BL/6Slc) using RT-PCR. After mice had been killed by CO2 inhalation, the eyes were immediately removed together with the retrobulbar tissue and placed in ice-cold PBS (Invitrogen, Karlsruhe, Germany). Then, ophthalmic arteries were isolated by the use of fine-point tweezers under a dissecting microscope, transferred into a 1.5-mL tube, and immediately snap frozen. To increase the RNA yield, arteries were pooled from three mice. Subsequently, vessels were homogenized in lysis buffer using a homogenizing device (Schwingmühle MM 300; Retsch GmbH, Haan, Germany; Lysing Matrix D MP, MP Biomedicals, Illkirch, France). After homogenization, total RNA was extracted with a kit (Absolutely RNA Nanoprep; Stratagene, La Jolla, CA) according to the manufacturer's protocol. After complete DNA digestion, the RNA was reverse transcribed with the use of a reverse transcription kit and random hexamers (High Capacity cDNA Reverse Transcription Kit; Applied Biosystems, Darmstadt, Germany). Quantitative PCR analysis was performed (GeneAmp StepOne Plus; Applied Biosystems). Nucleic acid stain (SYBR Green; Bioline, Luckenwalde, Germany) was used for the fluorescent detection of DNA generated during PCR. The PCR reaction was performed in a total volume of 12.5 μL with 0.4 pmol/μL of each primer and ready-to-use 2× reaction mix (ImmoMix; Bioline); 2 μL cDNA corresponding to 10 ng RNA was used as a template. Published sequences for mouse α1A-AR (NM_013461), α1B-AR (NM_007416), and α1D-AR (NM_013460) were used to design primers for PCR amplification. Primer sequences were α1A-AR sense 5′-TGC GAG GAC TGA AGG TCC GCT-3′ and antisense 5′-CAG GGA CGC TGG GCG AAT GG-3′; α1B-AR sense 5′-TCC AGG GAA AAG AAA GCA GCC AA-3′ and antisense 5′-GGG TAG ATG ATG GGG TTG AGG CA-3′; α1D-AR sense 5′-TAA GGC TGC TCA AGT TTT CCC GC-3′ and antisense 5′-TGA GCG GGT TCA CAC AGC TAT TGA-3′; ß-actin sense 5′-CAC CCG CGA GCA CAG CTT CTT T-3′ and antisense 5′-AAT ACA GCC CGG GGA GCA TC-3′. The expression levels of α1A-AR, α1B-AR, and α1D-AR mRNA were normalized to ß-actin using the ΔCt method. Parallelism of standard curves was confirmed. 
Measurements of Vascular Reactivity
Mice were killed by CO2 inhalation and the eyes were rapidly removed, together with the retrobulbar tissue, and placed in ice-cold Krebs buffer with the following ionic composition (in mM): 118.3 NaCl, 4.7 KCl, 2.5 CaCl2, 1.2 MgSO4, 1.2 KH2PO4, 25 NaHCO3, and 11 glucose (Carl Roth GmbH, Karlsruhe, Germany). Then, ophthalmic arteries were isolated under a dissecting microscope, placed in an organ chamber filled with cold Krebs solution, and cannulated and sutured onto micropipettes, as described previously. 23 Vessels were pressurized via the micropipettes to 50 mm Hg under no-flow conditions using two reservoirs filled with Krebs solution and imaged using a video camera mounted on an inverted microscope; video sequences were captured to a personal computer for offline analysis. The organ chamber was continuously circulated with oxygenated and carbonated Krebs buffer at 37°C and pH 7.4. Arteries were allowed to equilibrate for 30 to 40 minutes before study. During this time, ophthalmic arteries of all groups developed spontaneous myogenic tone by constricting to 86% to 81% of initial diameter recorded immediately after pressurization. Reduction in luminal artery diameter during the equilibration period was similar in all four mouse genotypes. Viability of vessels was assessed as satisfactory when at least 50% constriction from stabilized resting diameter in response to high KCl solution (100 mM) was achieved. Then, cumulative concentration–response curves were obtained to phenylephrine (1 nM to 300 μM), a non-subtype–selective α1-AR agonist; to noradrenaline (1 nM to 300 μM), a major neurotransmitter of sympathetic nerves; and to arginine vasopressin (AVP, 1 pM to 300 nM), a nonadrenergic receptor agonist, which induces vasoconstricton via V 1a-receptor–mediated increases of inositol phosphates and intracellular calcium in vascular smooth muscle. Responses to noradrenaline (10 μM) were also compared before and after addition of prazosin (100 nM), a competitive non-subtype–selective α1-AR antagonist. 
Statistical Analysis
Data are presented as mean ± SE and n represents the number of mice per group. Vascular responses are presented as percentage of change in diameter from stabilized resting diameter. Comparisons of concentration–response curves were made using the Brunner test for nonparametric analysis of longitudinal data. 24 The Bonferroni adjustment was used to correct for multiple comparisons. To compare vascular responses to noradrenaline before and after prazosin treatment, the Wilcoxon signed-rank test was used. Comparisons of α1-AR mRNA expression levels were made using the Kruskal–Wallis test. The level of significance was set at 0.05. 
Results
α1-Adrenoceptor mRNA Expression in Ophthalmic Arteries
Expression of α1-AR mRNA was determined in ophthalmic arteries (five pooled samples) from wild-type mice (n = 15) by the use of quantitative RT-PCR. Remarkably, mRNA of all three α1-AR subtypes was found to be expressed at high levels, although there was no difference between mRNA expression levels of individual receptor subtypes (Fig. 1). 
Figure 1.
 
Relative mRNA expression of individual α1-AR subtypes (α1A, α1B, and α1D) normalized to β-actin transcripts in ophthalmic arteries from wild-type mice. Values are averages of five independent experiments and are expressed as mean ± SE.
Figure 1.
 
Relative mRNA expression of individual α1-AR subtypes (α1A, α1B, and α1D) normalized to β-actin transcripts in ophthalmic arteries from wild-type mice. Values are averages of five independent experiments and are expressed as mean ± SE.
Responses of Ophthalmic Arteries
Baseline luminal diameters of ophthalmic artery segments (after development of stable myogenic tone) were (in μm) 118 ± 13, 130 ± 9, 125 ± 8, and 132 ± 10 in α1A-AR−/−, α1B-AR−/−, α1D-AR−/−, and wild-type mice and did not differ between individual mouse genotypes (P > 0.05, one-way ANOVA, n = 8–10 per genotype). To identify the α1-AR subtypes that mediate adrenergic vasoconstriction of ophthalmic arteries, we compared vascular responses from α1A-AR−/−, α1B-AR−/−, α1D-AR−/−, and wild-type mice to the non-subtype–selective α1-AR agonist phenylephrine. Phenylephrine elicited concentration-dependent vasoconstriction in arteries from wild-type, α1B-AR−/−, and α1D-AR−/− mice that was similar in the three groups (Fig. 2). Maximal reduction in luminal diameter in response to phenylephrine was 41% ± 6%, 43% ± 8%, and 38% ± 4% in wild-type (n = 10), α1B-AR−/− (n = 8), and α1D-AR−/− (n = 10) mice, respectively. The pD2 values (mean negative log of the vasoconstrictor concentration producing 50% of maximal response) were 5.79 ± 0.16, 5.75 ± 0.19, and 5.68 ± 0.19 in wild-type, α1B-AR−/−, and α1D-AR−/− mice, respectively. In contrast, phenylephrine-induced vasconstriction was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice (n = 8), differing significantly from responses of all other genotypes. Maximal reduction in luminal diameter to phenylephrine was only 6% ± 5% in this group (Fig. 2). 
Figure 2.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the α1-AR agonist phenylephrine. Vasoconstriction to phenylephrine was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice. In contrast, deletion of α1B-AR and α1D-AR genes had no significant effect on vascular reactivity. Values are expressed as mean ± SE (#P < 0.01, α1A-AR−/− mice versus all other groups, n = 8 to 10 per concentration and genotype).
Figure 2.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the α1-AR agonist phenylephrine. Vasoconstriction to phenylephrine was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice. In contrast, deletion of α1B-AR and α1D-AR genes had no significant effect on vascular reactivity. Values are expressed as mean ± SE (#P < 0.01, α1A-AR−/− mice versus all other groups, n = 8 to 10 per concentration and genotype).
Moreover, we examined responses to the sympathetic transmitter noradrenaline that, apart from α1-ARs, can also activate α2-ARs and β-ARs. Noradrenaline also produced concentration-dependent vasoconstriction in ophthalmic arteries from wild-type, α1B-AR−/−, and α1D-AR−/− mice that did not differ between the three genotypes. Maximal constriction to noradrenaline was 42% ± 7%, 52% ± 7%, and 44% ± 5% in wild-type (n = 10), α1B-AR−/− (n = 8), and α1D-AR−/− (n = 10) mice, respectively. The pD2 values were 5.97 ± 0.20, 5.75 ± 0.17, and 5.91 ± 0.17 in wild-type, α1B-AR−/−, and α1D-AR−/− mice, respectively. In α1A-AR−/− mice (n = 8), however, maximal reduction in luminal artery diameter in response to noradrenaline was negligible and differed significantly from responses of all other genotypes. Maximal reduction in luminal diameter was only 1% ± 3% in this group (Fig. 3A). After incubation with the competitive non-subtype–selective α1-AR antagonist prazosin (100 nM), responses to noradrenaline (10 μM) were negligible in all groups of mice (Fig. 3B). 
Figure 3.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the sympathetic transmitter noradrenaline. (A) Vasoconstriction to noradrenaline was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice. In contrast, deletion of α1B-AR and α1D-AR genes had no significant effect on vascular reactivity. Values are expressed as mean ± SE (#P < 0.01, α1A-AR−/− mice versus all other groups, n = 8 to 10 per concentration and genotype). (B) Vasoconstrictor responses to noradrenaline (10−5 M) were virtually abolished after incubation with prazosin (10−7 M). Values are expressed as mean ± SE (*P < 0.05, prazosin-treated versus nontreated arteries, n = 6 per genotype).
Figure 3.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the sympathetic transmitter noradrenaline. (A) Vasoconstriction to noradrenaline was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice. In contrast, deletion of α1B-AR and α1D-AR genes had no significant effect on vascular reactivity. Values are expressed as mean ± SE (#P < 0.01, α1A-AR−/− mice versus all other groups, n = 8 to 10 per concentration and genotype). (B) Vasoconstrictor responses to noradrenaline (10−5 M) were virtually abolished after incubation with prazosin (10−7 M). Values are expressed as mean ± SE (*P < 0.05, prazosin-treated versus nontreated arteries, n = 6 per genotype).
The nonadrenergic vasoconstrictor AVP elicited concentration-dependent vasoconstricton in ophthalmic arteries from all four mouse genotypes, which did not differ between individual groups (Fig. 4). Maximal constriction to AVP was 48% ± 8%, 49% ± 8%, 52% ± 8%, and 45% ± 7% in wild-type (n = 10), α1A-AR−/− (n = 8), α1B-AR−/− (n = 8), and α1D-AR−/− (n = 10) mice, respectively. The pD2 values were 9.28 ± 0.17, 9.30 ± 0.20, 9.17 ± 0.25, and 9.06 ± 0.27 in wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice, respectively. 
Figure 4.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the nonadrenergic vasoconstrictor AVP. Deletion of α1A-AR, α1B-AR, or α1D-AR genes did not affect responses to AVP. Values are expressed as mean ± SE (n = 8 to 10 per concentration and genotype).
Figure 4.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the nonadrenergic vasoconstrictor AVP. Deletion of α1A-AR, α1B-AR, or α1D-AR genes did not affect responses to AVP. Values are expressed as mean ± SE (n = 8 to 10 per concentration and genotype).
Discussion
The purpose of the present study was to identify the α1-AR subtypes that mediate adrenergic responses in ophthalmic arteries. Using RT-PCR, we found mRNA of all three α1-AR subtypes to be expressed at similar levels in ophthalmic arteries of wild-type mice. Since highly selective agonists and antagonists are not available for all three subtypes, we used mice with targeted disruption of single α1-AR subtype genes to assess the functional relevance of each receptor subtype. Strikingly, ophthalmic arteries from mice deficient in the α1A-AR gene showed almost no reactivity to phenylephrine and noradrenaline. The α1-AR antagonist prazosin almost completely abolished noradrenaline-induced responses, indicative of the predominant involvement of α1-ARs in adrenergic vasoconstriction of ophthalmic arteries. Deletion of either receptor subtype did not affect vasoconstriction induced by AVP, suggesting that the lack of a single α1-AR subtype does not affect the downstream signaling cascades that ultimately mediate vasoconstriction. 
Previous studies using electrical stimulation of sympathetic nerve pathways and intravenous application of α1-AR antagonists demonstrated that α1-ARs mediate neurogenic vasoconstriction in the anterior choroid of rats and in long posterior ciliary arteries of cats. 8,10 Another study using transmural electrical stimulation in isolated vascular strips showed that α1-ARs contributed to neurogenic vasoconstriction in dog short posterior ciliary and ophthalmic arteries. 9 The present study is the first to demonstrate that adrenergic vasoconstriction of murine ophthalmic arteries is mediated predominantly by the α1A-AR subtype. 
Earlier pharmacologic studies making use of subtype-selective agents and functional studies in gene-targeted mice lacking one or more α1-AR subtypes revealed that the contribution of individual α1-AR subtypes to adrenergic vasoconstrictor responses differs considerably depending on the vascular bed. Based on these studies, the α1A-AR is significantly involved in adrenergic vasoconstriction of rat and mouse small mesenteric and tail arteries, but plays only a minor role in α1-AR–mediated contraction of large vessels, such as aorta, iliac, and carotid arteries. 18,19,25 27 In contrast, the α1D-AR was shown to play a major vasoconstrictor role in large vessels, but was also suggested to participate in α1-AR–mediated vasoconstriction of some small arteries, such as coronary and femoral small arteries. 19,27 30 The α1B-AR was shown to play only a minor role in adrenergic vasoconstriction. In vivo studies have demonstrated that blood pressure responses to phenylephrine and to noradrenaline are reduced in gene-targeted mice lacking the α1B-AR. However, no differences in resting blood pressure between α1B-AR knockout and respective wild-type mice were detected. 21 Moreover, several in vitro studies using α1-AR subtype-selective antagonists and mice with targeted disruption of the α1B-AR gene revealed only a minor contribution of the α1B-AR subtype to vasoconstrictor responses in mouse aorta, carotid, mesenteric, and tail arteries. 18,21,25  
Studies of mRNA and protein expression revealed diverse distribution of α1-AR receptor subtypes among vascular beds. 18,19,31 Some of these studies reported that the mRNA expression levels of individual α1-AR subtypes were in fairly good agreement with their protein levels or their contribution to adrenergic vasoconstrictor responses. 18,19,31,32 Other studies, however, demonstrated that the presence of mRNA or even protein for a particular α1-AR subtype does not ensure its participation in vasoconstriction. 33,34 This can be explained either by differences in the efficiency of individual α1-AR subtypes to accumulate intracellular inositol phosphate and calcium or by a different extent of receptor subtype expression in intracellular compartments, preventing them from interaction with the hydrophilic natural ligands. 34 36 Although we found mRNA of all three α1-AR subtypes to be expressed at similar levels in ophthalmic arteries, adrenergic vasoconstriction was predominantly mediated by the α1A-AR, raising a question about the physiologic role of α1B- and α1D-ARs. A growing body of evidence suggests that each receptor subtype can activate independent signaling pathways, resulting in different physiologic functions. 15 For example, the α1D-AR was shown to mediate generation of reactive oxygen species and induction of apoptosis in human aortic smooth muscle cells. 37,38 Moreover, the α1B-AR was reported to mediate trophic effects of catecholamines in mouse arteries, whereas the α1D-AR does not appear to be involved in this process. 39,40 Thus, although our data indicate that α1B- and α1D-ARs do not significantly contribute to adrenergic vasoconstricton in murine ophthalmic arteries, both receptor subtypes may be involved in regulation of other physiologic or pathophysiologic actions. 
In conclusion, our data provide evidence that the α1A-AR subtype mediates adrenergic vasoconstriction in murine ophthalmic arteries. From a clinical point of view, selective α1A-AR antagonists may become therapeutically useful to increase ocular perfusion in certain pathologic conditions, such as diabetic retinopathy and glaucoma. 1,2,5,6  
Footnotes
 Supported in part by a grant from the Gertraud Maria Rzehulka Foundation.
Footnotes
 Disclosure: A. Gericke, None; M.L. Kordasz, None; A. Steege, None; A. Sanbe, None; E. Goloborodko, None; J.M. Vetter, None; A. Patzak, None; N. Pfeiffer, None
The authors thank Paul C. Simpson (Cardiology Section, San Francisco Veterans Affairs Medical Center; Department of Medicine, Cardiology Division, University of California, San Francisco, CA), Susanna Cotecchia (Department of General and Environmental Physiology, University of Bari, Italy, and Department of Pharmacology and Toxicology, University of Lausanne, Switzerland), and Akito Tanoue (Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan) for making α1A-, α1B-, and α1D-AR knockout mice, respectively, available for this study; and Ulrike Neumann (Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany) for expert technical assistance with real-time PCR experiments. 
References
Dimitrova G Kato S Yamashita H . Relation between retrobulbar circulation and progression of diabetic retinopathy. Br J Ophthalmol. 2003;87:622–625. [CrossRef] [PubMed]
Savage HI Hendrix JW Peterson DC Young H Wilkinson CP . Differences in pulsatile ocular blood flow among three classifications of diabetic retinopathy. Invest Ophthalmol Vis Sci. 2004;45:4504–4509. [CrossRef] [PubMed]
Arnold AC . Pathogenesis of nonarteritic anterior ischemic optic neuropathy. J Neuroophthalmol. 2003;23:157–163. [CrossRef] [PubMed]
Hayreh SS . Ischemic optic neuropathy. Prog Retin Eye Res. 2009;28:34–62. [CrossRef] [PubMed]
Mozaffarieh M Grieshaber MC Flammer J . Oxygen and blood flow: players in the pathogenesis of glaucoma. Mol Vis. 2008;14:224–233. [PubMed]
Garhofer G Fuchsjager-Mayrl G Vass C Pemp B Hommer A Schmetterer L . Retrobulbar blood flow velocities in open angle glaucoma and their association with mean arterial blood pressure. Invest Ophthalmol Vis Sci. 2010;51:6652–6657. [CrossRef] [PubMed]
Ferrari-Dileo G Davis EB Anderson DR . Response of retinal vasculature to phenylephrine. Invest Ophthalmol Vis Sci. 1990;31:1181–1182. [PubMed]
Kawarai M Koss MC . Sympathetic vasoconstriction in the rat anterior choroid is mediated by alpha1-adrenoceptors. Eur J Pharmacol. 1998;363:35–40. [CrossRef] [PubMed]
Toda M Okamura T Ayajiki K Toda N . Neurogenic vasoconstriction as affected by cholinergic and nitroxidergic nerves in dog ciliary and ophthalmic arteries. Invest Ophthalmol Vis Sci. 1999;40:1753–1760. [PubMed]
Koss MC . Effects of sympathetic nerve stimulation on long posterior ciliary artery blood flow in cats. J Ocul Pharmacol Ther. 2002;18:115–125. [CrossRef] [PubMed]
Ichikawa M Okada Y Asai Y Hara H Ishii K Araie M . Effects of topically instilled bunazosin, an alpha1-adrenoceptor antagonist, on constrictions induced by phenylephrine and ET-1 in rabbit retinal arteries. Invest Ophthalmol Vis Sci. 2004;45:4041–4048. [CrossRef] [PubMed]
Hein P Michel MC . Signal transduction and regulation: are all alpha1-adrenergic receptor subtypes created equal? Biochem Pharmacol. 2007;73:1097–1106. [CrossRef] [PubMed]
Koshimizu TA Tanoue A Tsujimoto G . Clinical implications from studies of alpha1 adrenergic receptor knockout mice. Biochem Pharmacol. 2007;73:1107–1112. [CrossRef] [PubMed]
Perez DM . Structure-function of alpha1-adrenergic receptors. Biochem Pharmacol. 2007;73:1051–1062. [CrossRef] [PubMed]
Cotecchia S . The alpha1-adrenergic receptors: diversity of signaling networks and regulation. J Recept Signal Transduct Res. 2010;30:410–419. [CrossRef] [PubMed]
Docherty JR . Subtypes of functional alpha1-adrenoceptor. Cell Mol Life Sci. 2010;67:405–417. [CrossRef] [PubMed]
Graham RM Perez DM Hwa J Piascik MT . alpha 1-adrenergic receptor subtypes. Molecular structure, function, and signaling. Circ Res. 1996;78:737–749. [CrossRef] [PubMed]
Hosoda C Tanoue A Shibano M . Correlation between vasoconstrictor roles and mRNA expression of alpha1-adrenoceptor subtypes in blood vessels of genetically engineered mice. Br J Pharmacol. 2005;146:456–466. [CrossRef] [PubMed]
Marti D Miquel R Ziani K . Correlation between mRNA levels and functional role of alpha1-adrenoceptor subtypes in arteries: evidence of alpha1L as a functional isoform of the alpha1A-adrenoceptor. Am J Physiol Heart Circ Physiol. 2005;289:H1923–H1932. [CrossRef] [PubMed]
Rokosh DG Simpson PC . Knockout of the alpha 1A/C-adrenergic receptor subtype: the alpha 1A/C is expressed in resistance arteries and is required to maintain arterial blood pressure. Proc Natl Acad Sci USA. 2002;99:9474–9479. [CrossRef] [PubMed]
Cavalli A Lattion AL Hummler E . Decreased blood pressure response in mice deficient of the alpha1b-adrenergic receptor. Proc Natl Acad Sci U S A. 1997;94:11589–11594. [CrossRef] [PubMed]
Tanoue A Nasa Y Koshimizu T . The alpha(1D)-adrenergic receptor directly regulates arterial blood pressure via vasoconstriction. J Clin Invest. 2002;109:765–775. [CrossRef] [PubMed]
Gericke A Mayer VG Steege A . Cholinergic responses of ophthalmic arteries in M3 and M5 muscarinic acetylcholine receptor knockout mice. Invest Ophthalmol Vis Sci. 2009;50:4822–4827. [CrossRef] [PubMed]
Brunner E Puri M . Nonparametric methods in factorial designs. Stat Papers. 2001;42:1–52. [CrossRef]
Daly CJ Deighan C McGee A . A knockout approach indicates a minor vasoconstrictor role for vascular alpha1B-adrenoceptors in mouse. Physiol Genomics. 2002;9:85–91. [CrossRef] [PubMed]
Martinez-Salas SG Campos-Peralta JM Pares-Hipolito J Gallardo-Ortiz IA Ibarra M Villalobos-Molina R . Alpha1A-adrenoceptors predominate in the control of blood pressure in mouse mesenteric vascular bed. Auton Autacoid Pharmacol. 2007;27:137–142. [CrossRef] [PubMed]
Methven L Simpson PC McGrath JC . Alpha1A/B-knockout mice explain the native alpha1D-adrenoceptor's role in vasoconstriction and show that its location is independent of the other alpha1-subtypes. Br J Pharmacol. 2009;158:1663–1675. [CrossRef] [PubMed]
Turnbull L McCloskey DT O'Connell TD Simpson PC Baker AJ . Alpha 1-adrenergic receptor responses in alpha 1AB-AR knockout mouse hearts suggest the presence of alpha 1D-AR. Am J Physiol Heart Circ Physiol. 2003;284:H1104–H1109. [CrossRef] [PubMed]
Chalothorn D McCune DF Edelmann SE . Differential cardiovascular regulatory activities of the alpha 1B- and alpha 1D-adrenoceptor subtypes. J Pharmacol Exp Ther. 2003;305:1045–1053. [CrossRef] [PubMed]
Zacharia J Hillier C Tanoue A . Evidence for involvement of alpha1D-adrenoceptors in contraction of femoral resistance arteries using knockout mice. Br J Pharmacol. 2005;146:942–951. [CrossRef] [PubMed]
Rudner XL Berkowitz DE Booth JV . Subtype specific regulation of human vascular alpha(1)-adrenergic receptors by vessel bed and age. Circulation. 1999;100:2336–2343. [CrossRef] [PubMed]
Jensen BC Swigart PM Laden ME DeMarco T Hoopes C Simpson PC . The alpha-1D is the predominant alpha-1-adrenergic receptor subtype in human epicardial coronary arteries. J Am Coll Cardiol. 2009;54:1137–1145. [CrossRef] [PubMed]
Piascik MT Guarino RD Smith MS Soltis EE Saussy DLJr Perez DM . The specific contribution of the novel alpha-1D adrenoceptor to the contraction of vascular smooth muscle. J Pharmacol Exp Ther. 1995;275:1583–1589. [PubMed]
Hrometz SL Edelmann SE McCune DF . Expression of multiple alpha1-adrenoceptors on vascular smooth muscle: correlation with the regulation of contraction. J Pharmacol Exp Ther. 1999;290:452–463. [PubMed]
Theroux TL Esbenshade TA Peavy RD Minneman KP . Coupling efficiencies of human alpha 1-adrenergic receptor subtypes: titration of receptor density and responsiveness with inducible and repressible expression vectors. Mol Pharmacol. 1996;50:1376–1387. [PubMed]
Chalothorn D McCune DF Edelmann SE Garcia-Cazarin ML Tsujimoto G Piascik MT . Differences in the cellular localization and agonist-mediated internalization properties of the alpha(1)-adrenoceptor subtypes. Mol Pharmacol. 2002;61:1008–1016. [CrossRef] [PubMed]
García-Cazarín ML Smith JL Olszewski KA . The alpha1D-adrenergic receptor is expressed intracellularly and coupled to increases in intracellular calcium and reactive oxygen species in human aortic smooth muscle cells. J Mol Signal. 2008;3:Art. 6.
Garcia-Cazarin ML Smith JL Clair DK Piascik MT . The alpha1D-adrenergic receptor induces vascular smooth muscle apoptosis via a p53-dependent mechanism. Mol Pharmacol. 2008;74:1000–1007. [CrossRef] [PubMed]
Vecchione C Fratta L Rizzoni D . Cardiovascular influences of alpha1b-adrenergic receptor defect in mice. Circulation. 2002;105:1700–1707. [CrossRef] [PubMed]
Zhang H Cotecchia S Thomas SA Tanoue A Tsujimoto G Faber JE . Gene deletion of dopamine beta-hydroxylase and alpha1-adrenoceptors demonstrates involvement of catecholamines in vascular remodeling. Am J Physiol Heart Circ Physiol. 2004;287:H2106–H2114. [CrossRef] [PubMed]
Figure 1.
 
Relative mRNA expression of individual α1-AR subtypes (α1A, α1B, and α1D) normalized to β-actin transcripts in ophthalmic arteries from wild-type mice. Values are averages of five independent experiments and are expressed as mean ± SE.
Figure 1.
 
Relative mRNA expression of individual α1-AR subtypes (α1A, α1B, and α1D) normalized to β-actin transcripts in ophthalmic arteries from wild-type mice. Values are averages of five independent experiments and are expressed as mean ± SE.
Figure 2.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the α1-AR agonist phenylephrine. Vasoconstriction to phenylephrine was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice. In contrast, deletion of α1B-AR and α1D-AR genes had no significant effect on vascular reactivity. Values are expressed as mean ± SE (#P < 0.01, α1A-AR−/− mice versus all other groups, n = 8 to 10 per concentration and genotype).
Figure 2.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the α1-AR agonist phenylephrine. Vasoconstriction to phenylephrine was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice. In contrast, deletion of α1B-AR and α1D-AR genes had no significant effect on vascular reactivity. Values are expressed as mean ± SE (#P < 0.01, α1A-AR−/− mice versus all other groups, n = 8 to 10 per concentration and genotype).
Figure 3.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the sympathetic transmitter noradrenaline. (A) Vasoconstriction to noradrenaline was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice. In contrast, deletion of α1B-AR and α1D-AR genes had no significant effect on vascular reactivity. Values are expressed as mean ± SE (#P < 0.01, α1A-AR−/− mice versus all other groups, n = 8 to 10 per concentration and genotype). (B) Vasoconstrictor responses to noradrenaline (10−5 M) were virtually abolished after incubation with prazosin (10−7 M). Values are expressed as mean ± SE (*P < 0.05, prazosin-treated versus nontreated arteries, n = 6 per genotype).
Figure 3.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the sympathetic transmitter noradrenaline. (A) Vasoconstriction to noradrenaline was almost completely abolished in ophthalmic arteries from α1A-AR−/− mice. In contrast, deletion of α1B-AR and α1D-AR genes had no significant effect on vascular reactivity. Values are expressed as mean ± SE (#P < 0.01, α1A-AR−/− mice versus all other groups, n = 8 to 10 per concentration and genotype). (B) Vasoconstrictor responses to noradrenaline (10−5 M) were virtually abolished after incubation with prazosin (10−7 M). Values are expressed as mean ± SE (*P < 0.05, prazosin-treated versus nontreated arteries, n = 6 per genotype).
Figure 4.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the nonadrenergic vasoconstrictor AVP. Deletion of α1A-AR, α1B-AR, or α1D-AR genes did not affect responses to AVP. Values are expressed as mean ± SE (n = 8 to 10 per concentration and genotype).
Figure 4.
 
Responses of ophthalmic arteries from wild-type, α1A-AR−/−, α1B-AR−/−, and α1D-AR−/− mice to the nonadrenergic vasoconstrictor AVP. Deletion of α1A-AR, α1B-AR, or α1D-AR genes did not affect responses to AVP. Values are expressed as mean ± SE (n = 8 to 10 per concentration and genotype).
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