Carbon monoxide regulates cerebral blood flow in epileptic seizures but not in hypercapnia.
Carbon monoxide (CO) is an endogenously produced gas sharing many properties with nitric oxide (NO), notably activating soluble guanylate cyclase and relaxing blood vessels. The brain can generate high quantities of CO from a constitutive enzyme, haem oxygenase (HO-2). To determine whether CO is involved in the regulatory mechanisms of cerebral blood flow (CBF), two conditions associated with a reproducible CBF increase were studied in rats: epileptic seizures induced by kainate, and hypercapnia. The HO inhibitor tin protoporphyrin (Sn-PP) did not modify the basal level of CBF, significantly reduced the increase in CBF during status epilepticus, and did not affect the cerebrovascular response to hypercapnia. It is concluded that CO participates in the regulation of CBF in specific conditions, notably those associated with glutamate release.
Laboratoire de Recherches Cérébrovasculaires, CNRS UPR 646, IFR 6, University of Paris 7, France.
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Montécot
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Seylaz
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Pinard
D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002248:Carbon Monoxide / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004569:Electroencephalography / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004827:Epilepsy / Q000139:chemically induced / Q000503:physiopathology*; D006207:Half-Life; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000139:chemically induced / Q000503:physiopathology*; D007608:Kainic Acid; D008297:Male; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D010100:Oxygen / Q000097:blood; D011524:Protoporphyrins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D004791:Enzyme Inhibitors; D011524:Protoporphyrins; D002245:Carbon Dioxide; D002248:Carbon Monoxide; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D006419:Heme Oxygenase (Decyclizing); D010100:Oxygen; D007608:Kainic Acid