CEREBROVASCULAR EFFECTS OF N(G)-NITRO-L-ARGININE METHYLESTER ARE CONSERVED UNDER HALOTHANE ANESTHESIA

The effects of the nitric oxide synthesis inhibitor N(G)-nitro-L-argin ine methylester (L-NAME) on mean arterial blood pressure (MABP) and lo cal cerebral blood flow were determined in conscious and halothane-ana esthetised rats. Thirty minutes post-drug administration in conscious rats L-NAME (30 mg kg-1 i.v.) induced significant hypertension (MABP 1 32 +/- 2 mmHg and 163 +/- 6 mmHg (means +/- S.D.) for saline and L-NAM E groups respectively) and significant hypoperfusion throughout the br ain (mean +/- S.D. reduction in cerebral blood flow 27.3 +/- 5.9% comp ared with controls). In contrast, under halothane anaesthesia, L-NAME did not significantly change MABP but significant reductions in cerebr al blood flow (43.2 +/- 3.7%) were observed. Thus the cerebrovascular response to L-NAME is conserved under halothane anaesthesia despite at tenuation of the peripheral vasoconstrictive action.