title: Role of nitric oxide synthase isoforms for ophthalmic artery reactivity in mice.
abstract: Nitric oxide synthases (NOS) are involved in regulation of ocular vascular tone and blood flow. While endothelial NOS (eNOS) has recently been shown to mediate endothelium-dependent vasodilation in mouse retinal arterioles, the contribution of individual NOS isoforms to vascular responses is unknown in the retrobulbar vasculature. Moreover, it is unknown whether the lack of a single NOS isoform affects neuron survival in the retina. Thus, the goal of the present study was to examine the hypothesis that the lack of individual nitric oxide synthase (NOS) isoforms affects the reactivity of mouse ophthalmic arteries and neuron density in the retinal ganglion cell (RGC) layer. Mice deficient in one of the three NOS isoforms (nNOS-/-, iNOS-/- and eNOS-/-) were compared to respective wild type controls. Intraocular pressure (IOP) was measured in conscious mice using rebound tonometry. To examine the role of each NOS isoform for mediating vascular responses, ophthalmic arteries were studied in vitro using video microscopy. Neuron density in the RGC layer was calculated from retinal wholemounts stained with cresyl blue. IOP was similar in all NOS-deficient genotypes and respective wild type controls. In ophthalmic arteries, phenylephrine, nitroprusside and acetylcholine evoked concentration-dependent responses that did not differ between individual NOS-deficient genotypes and their respective controls. In all genotypes except eNOS-/- mice, vasodilation to acetylcholine was markedly reduced after incubation with L-NAME, a non-isoform-selective inhibitor of NOS. In contrast, pharmacological inhibition of nNOS and iNOS had no effect on acetylcholine-induced vasodilation in any of the mouse genotypes. Neuron density in the RGC layer was similar in all NOS-deficient genotypes and respective controls. Our findings suggest that eNOS contributes to endothelium-dependent dilation of murine ophthalmic arteries. However, the chronic lack of eNOS is functionally compensated by NOS-independent vasodilator mechanisms. The lack of a single NOS isoform does not appear to affect IOP or neuron density in the RGC layer.
authors.affiliation: Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Laspas
authors.affiliation: Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
authors.forename: Evgeny
authors.initials: E
authors.lastname: Goloborodko
authors.affiliation: Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Sniatecki
authors.affiliation: Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
authors.forename: Marcin L
authors.initials: ML
authors.lastname: Kordasz
authors.affiliation: Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Manicam
authors.affiliation: Department of Pharmacology, University Medical Center, Johannes Gutenberg University Mainz, Obere Zahlbacher Str. 67, 55131, Mainz, Germany.
authors.forename: Leszek
authors.initials: L
authors.lastname: Wojnowski
authors.affiliation: Department of Pharmacology, University Medical Center, Johannes Gutenberg University Mainz, Obere Zahlbacher Str. 67, 55131, Mainz, Germany.
authors.forename: Huige
authors.initials: H
authors.lastname: Li
authors.affiliation: Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Patzak
authors.affiliation: Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Pfeiffer
authors.affiliation: Department of Ophthalmology, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany. Electronic address: adrian.gericke@gmx.net.
authors.forename: Adrian
authors.initials: A
authors.lastname: Gericke
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D058646:Adrenergic alpha-1 Receptor Agonists / Q000494:pharmacology; D000818:Animals; D002452:Cell Count; D004730:Endothelium, Vascular / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007429:Intraocular Pressure / Q000502:physiology; D007527:Isoenzymes; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052248:Nitric Oxide Synthase Type I / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II / Q000502:physiology*; D052250:Nitric Oxide Synthase Type III / Q000502:physiology*; D009599:Nitroprusside; D009880:Ophthalmic Artery / Q000201:enzymology / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D012165:Retinal Ganglion Cells / Q000166:cytology; D055351:Retinal Neurons / Q000166:cytology; D014065:Tonometry, Ocular; D014661:Vasoconstriction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D020030:Nitric Oxide Donors; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496321:Nos1 protein, mouse; C496317:Nos2 protein, mouse; C496315:Nos3 protein, mouse; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester
keywords: acetylcholine; knockout mouse; nitric oxide; ophthalmic artery; retinal ganglion cell layer; vasodilation