Effect of nimodipine on the autoregulation of cerebral blood flow studied by laser-Doppler flowmetry.
The present work examines whether nimodipine impairs autoregulation of CBF during hypotension. The CBF of 16 anesthetized rabbits was measured with a laser-Doppler flowmetry probe placed on the external surface of a plexiglas window, chronically inserted in the skull. Autoregulation was triggered by aortic bleeding. First, the effects of three doses of nimodipine (1, 3 and 10 micrograms/kg) and the solvent were studied in 10 rabbits in which MABP was maintained at 50 mmHg for one minute. Second, 10 micrograms/kg i.v. nimodipine was administered to 6 rabbits in which MABP was kept at 30 mmHg for one minute. Before bleeding, the 10 micrograms/kg dose significantly decreased MABP (from 96 +/- 11 mmHg to 81 +/- 11 mmHg, P < 0.01) and increased CBF (from 104 +/- 20% to 147 +/- 25%, P < 0.01) as compared to the solvent. In the first set of experiments, only the 10 micrograms/kg dose suppressed the autoregulatory vasodilation, but CBF was not different from control (84 +/- 17% versus 87 +/- 12%), probably because of the previous induced vasodilation. In the second set of experiments, active vasodilation occurred and the CBF during hypotension was not different from control (72 +/- 26% versus 65 +/- 11%). We conclude that under nimodipine the triggering of the active autoregulatory vasodilation is dependent on both the severity of hypotension and the previous nimodipine-induced vasodilation.
Florence
G
G
Centre d'Etudes et de Recherches de Médecine Aérospatiale, Section de Physiologie Comparée, Brétigny sur Orge, France.
Bonvento
G
G
Roucher
P
P
Charbonne
R
R
Seylaz
J
J
D000818:Animals; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D006470:Hemorrhage / Q000503:physiopathology; D006706:Homeostasis / Q000187:drug effects; D017078:Laser-Doppler Flowmetry; D008297:Male; D009553:Nimodipine / Q000494:pharmacology*; D011817:Rabbits
D009553:Nimodipine