Abstract | BACKGROUND AND PURPOSE: The role of nitric oxide in cerebrovascular response to changes in PCO2 is unclear. In the present study, we assessed responses at two levels of hypercapnia in a primate model before and after blockade of nitric oxide synthesis. METHODS: RESULTS: Before L-NAME administration, hypercapnia increased flow in all regions (eg, forebrain, high-CO2 group 69 +/- 10 to 166 +/- 15 mL.min-1.100 g-1; moderate-CO2 group, 49 +/- 7 to 93 +/- 15 mL.min-1.100 g-1) and decreased cerebral vascular resistance (high-CO2, 1.1 +/- 0.1 to 0.4 +/- 0.1 mm Hg.mL-1.min.100 g; moderate-CO2, 1.4 +/- 0.1 to 0.7 +/- 0.1 mm Hg.mL-1.min.100 g). During normocapnia, L-NAME decreased cerebral blood flow (high-CO2, 37 +/- 9%; moderate-CO2, 40 +/- 6%) and increased cerebral vascular resistance (high-CO2, 93 +/- 33%; moderate-CO2, 88 +/- 20%). After L-NAME, hypercapnia still increased blood flow in all regions (eg, forebrain: high-CO2, 56 +/- 7 to 128 +/- 3 mL.min-1.100 g-1, moderate-CO2, 36 +/- 5 to 57 +/- 8 mL.min-1.100 g-1) and decreased vascular resistance (high-CO2, 1.5 +/- 0.1 to 0.6 +/- 0.1 mm Hg.mL-1.min.100 g; moderate-CO2, 2.0 +/- 0.3 to 1.2 +/- 0.1 mm Hg.mL-1.min.100 g). In both groups L-NAME attenuated hypercapnia hyperemia by approximately 30% in cortex but not in other regions. CONCLUSIONS:
Nitric oxide contributes to basal vascular tone but is not a major contributor to the mechanism of hypercapnia-induced cerebral vasodilation, except in cortex, in primates.
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Authors | R W McPherson, J R Kirsch, R F Ghaly, R J Traystman |
Journal | Stroke
(Stroke)
Vol. 26
Issue 4
Pg. 682-7
(Apr 1995)
ISSN: 0039-2499 [Print] United States |
PMID | 7535954
(Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)
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Chemical References |
- Carbon Dioxide
- Arginine
- Nitric Oxide Synthase
- Amino Acid Oxidoreductases
- Oxygen
- NG-Nitroarginine Methyl Ester
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Topics |
- Amino Acid Oxidoreductases
(antagonists & inhibitors)
- Animals
- Arginine
(analogs & derivatives, pharmacology)
- Carbon Dioxide
(blood)
- Cerebrovascular Circulation
(drug effects)
- Haplorhini
- Hypercapnia
(enzymology)
- Male
- NG-Nitroarginine Methyl Ester
- Nitric Oxide Synthase
- Oxygen
(blood)
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