title: The effect of i.v. L-NG methylarginine hydrochloride (L-NMMA: 546C88) on basal and acetazolamide (Diamox) induced changes of blood velocity in cerebral arteries and regional cerebral blood flow in man.
abstract: The aim of this study was to estimate the effect of Nitric Oxide synthase (NOS)-inhibition (L-NMMA) on the diameter of the middle cerebral artery (MCA) and on regional cerebral blood flow (rCBF). Furthermore, to assess the effect of L-NMMA on acetazolamide induced increases in MCA blood velocity (Vmean) and rCBF. In an open crossover design 12 healthy subjects attended the laboratory twice. The first day 6 mg/kg L-LNMMA i.v. over 15 min preceded 1 g acetazolamide i.v. over 5 min. Eight days later only acetazolamide was given. V(mean) in MCA was determined with transcranial Doppler (TCD) and rCBF with Xe-133 inhalation SPECT at baseline, after L-NMMA and 25 and 55 min after acetazolamide infusion. After L-NMMA the decrease in rCBF(MCA) was 6.8% (+/- 7.4) (P < 0.019, n = 12), whereas V(mean) was not affected (P = 0.83, n = 8). The change in MCA diameter was estimated to - 1.3% (P = 0.44, n = 8). L-NMMA did not affect acetazolamide increases in Vmean (P = 0.67, n = 8) nor rCBF (P = 0.29, n = 12). The percentage increase of V(mean) was 1.5 times that of rCBF (n = 8). Our data suggest that the basal tone of human cerebral arterioles but not of conduit arteries is NO-dependent. The action of acetazolamide in man is not NO-dependent.
authors.affiliation: Department of Neurology, Glostrup Hospital, University of Copenhagen, Glostrup, Denmark. l.h.lassen@dadlnet.dk
authors.forename: L h
authors.initials: Lh
authors.lastname: Lassen
authors.forename: B
authors.initials: B
authors.lastname: Sperling
authors.forename: A r
authors.initials: Ar
authors.lastname: Andersen
authors.forename: J
authors.initials: J
authors.lastname: Olesen
mesh_terms: D000086:Acetazolamide / Q000008:administration & dosage*; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D002536:Cerebral Arteries / Q000187:drug effects* / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects* / Q000502:physiology; D018592:Cross-Over Studies; D004347:Drug Interactions / Q000502:physiology; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D019323:omega-N-Methylarginine / Q000008:administration & dosage*
chemical_list: D019323:omega-N-Methylarginine; D000086:Acetazolamide