title: Effect of nitric oxide blockade by NG-nitro-L-arginine on cerebral blood flow response to changes in carbon dioxide tension.
abstract: The importance of nitric oxide (NO) for CBF variations associated with arterial carbon dioxide changes was investigated in halothane-anesthetized rats by using an inhibitor of nitric oxide synthase, NG-nitro-L-arginine (NOLAG). CBF was measured by intracarotid injection of 133Xe. In normocapnia, intracarotid infusion of 1.5, or 7.5, or 30 mg/kg NOLAG induced a dose-dependent increase of arterial blood pressure and a decrease of normocapnic CBF from 85 +/- 10 to 78 +/- 6, 64 +/- 5, and 52 +/- 5 ml 100 g-1 min-1, respectively. This effect lasted for at least 2 h. Raising PaCO2 from a control level of 40 to 68 mm Hg increased CBF to 230 +/- 27 ml 100 g-1 min-1, corresponding to a percentage CBF response (CO2 reactivity) of 3.7 +/- 0.6%/mm Hg PaCO2 in saline-treated rats. NOLAG attenuated this reactivity by 32, 49, and 51% at the three-dose levels. Hypercapnia combined with angiotensin to raise blood pressure to the same level as the highest dose of NOLAG did not affect the CBF response to hypercapnia. L-Arginine significantly prevented the effect of NOLAG on normocapnic CBF as well as blood pressure and also abolished its inhibitory effect on hypercapnic CBF. D-Arginine had no such effect. Decreasing PaCO2 to 20 mm Hg reduced control CBF to 46 +/- 3 ml 100 g-1 min-1 with no further reduction after NOLAG. Furthermore, NOLAG did not change the percentage CBF response to an extracellular acidosis induced by acetazolamide (50 mg/kg).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Clinical Physiology/Nuclear Medicine, Bispebjerg Hospital, Copenhagen, Denmark.
authors.forename: Q
authors.initials: Q
authors.lastname: Wang
authors.forename: O B
authors.initials: OB
authors.lastname: Paulson
authors.forename: N A
authors.initials: NA
authors.lastname: Lassen
mesh_terms: D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects; D002245:Carbon Dioxide / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006935:Hypercapnia / Q000378:metabolism; D016857:Hypocapnia / Q000378:metabolism; D008297:Male; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D019335:Nitroarginine; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002245:Carbon Dioxide; D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine