Effects of N-omega-nitro-L-arginine methyl ester on the cerebral circulation of newborn piglets quantified in vivo by near-infrared spectroscopy.
The effects of N-omega-nitro-L-arginine methyl ester (L-NAME) on basal cerebral vascular tone, the vasodilatory effects of acetylcholine (ACh), and the cerebrovascular response to alterations in arterial carbon dioxide tension (CBVR) were investigated using near-infrared spectroscopy. Seven newborn piglets were anesthetized and mechanically ventilated; mean arterial blood pressure (MAP) was monitored and near-infrared spectroscopy used to measure changes in total cerebral Hb concentration. At the beginning of the experiment, CBVR was measured and then 10, 20, 30, and 100 mg.kg-1 L-NAME were administered sequentially; ACh (1, 2, 3, and 5 micrograms) was given before and after each injection of L-NAME. At the end of this sequence, CBVR was measured again and finally sodium nitroprusside (1.5 mg.kg-1) was administered. Ten and 20 mg.kg-1 L-NAME caused a significant decrease in total cerebral Hb concentration of -0.59 (-3.21 to -0.02) and -1.46 (-6.50 to -0.15) mumol.L-1 (median and range), respectively (Wilcoxon p < 0.05), but subsequent injections did not. Ten, 20, and 100 mg.kg-1 L-NAME caused an increase in MAP (Wilcoxon p < 0.05). ACh caused an increase in total cerebral Hb concentration and a decrease in MAP that was impaired but not abolished by L-NAME (ANOVA p < 0.05). CBVR was not affected by L-NAME. Sodium nitroprusside caused a reduction in mean (SD) MAP of 4.7 (1.6) kPa, and a slower rise in [tHb] of 13.44 (2.03) mumol.L-1. Postmortem examination of three animals revealed NADPH-diaphorase staining in neurons, cerebral blood vessels, carotid artery, and jugular vein.(ABSTRACT TRUNCATED AT 250 WORDS)
Takei
Y
Y
Department of Paediatrics, University College and Middlesex School of Medicine, London, UK.
Edwards
A D
AD
Lorek
A
A
Peebles
D M
DM
Belai
A
A
Cope
M
M
Delpy
D T
DT
Reynolds
E O
EO
D000109:Acetylcholine / Q000494:pharmacology; D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D000818:Animals; D000831:Animals, Newborn; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase; D009599:Nitroprusside / Q000494:pharmacology; D013055:Spectrophotometry, Infrared; D013552:Swine; D014664:Vasodilation / Q000187:drug effects*
D009599:Nitroprusside; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester