Major role for neuronal NO synthase in curtailing choroidal blood flow autoregulation in newborn pig
| Autor: | P. Hardy, Daniel Abran, Daya R. Varma, Sylvain Chemtob, D. Lamireau, Anne Monique Nuyt, Isabelle Dumont, Xin Hou |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
medicine.medical_specialty
Nitric Oxide Synthase Type III Swine Physiology Nuclease Protection Assays Ganglionic blocker Hemodynamics Nitric Oxide Synthase Type I Biology Endothelial NOS Nitric oxide chemistry.chemical_compound Physiology (medical) Internal medicine medicine Animals Homeostasis Autoregulation RNA Messenger Cyclic GMP Retinal Vessels Anatomy Nitric oxide synthase Autonomic nervous system Endocrinology Animals Newborn chemistry Regional Blood Flow Choroid Plexus biology.protein Hexamethonium Blood Gas Analysis Nitric Oxide Synthase |
| Zdroj: | Journal of Applied Physiology. 91:1655-1662 |
| ISSN: | 1522-1601 8750-7587 |
| DOI: | 10.1152/jappl.2001.91.4.1655 |
| Popis: | We examined whether nitric oxide (NO) generated from neuronal NO synthase (nNOS) contributes to the reduced ability of the newborn to autoregulate retinal blood flow (RBF) and choroidal blood flow (ChBF) during acute rises in perfusion pressure. In newborn pigs (1–2 days old), RBF (measured by microsphere) is autoregulated over a narrow range of perfusion pressure, whereas ChBF is not autoregulated. NG-nitro-l-arginine methyl ester (l-NAME) or specific nNOS inhibitors 7-nitroindazole, 3-bromo-7-nitroindazole, and 1-(2-trifluoromethyl-phenyl)imidazole as well as ganglionic blocker hexamethonium, unveiled a ChBF autoregulation as observed in juvenile (4- to 6-wk old) animals, whereas autoregulation of RBF in the newborn was only enhanced byl-NAME. All NOS inhibitors and hexamethonium prevented the hypertension-induced increase in NO mediator cGMP in the choroid. nNOS mRNA expression and activity were three- to fourfold higher in the choroid of newborn pigs than in tissues of juvenile pigs. It is concluded that increased production of NO from nNOS curtails ChBF autoregulation in the newborn and suggests a role for the autonomic nervous system in this important hemodynamic function, whereas, for RBF autoregulation, endothelial NOS seems to exert a more important contribution in limiting autoregulation. |
| Databáze: | OpenAIRE |
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