Inhibition of beta-1 receptor but not vagotomy can abolish the L-NAME evoked bradycardia in anesthetized rat.

We reported previously that the nitric oxide synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) decreases cardiac output. Several studies have shown that inhibition of nitric oxide synthesis decreases the heart rate. In the present study, we investigated the effect of a single bolus administration of L-NAME on blood pressure and heart rate monitored for one hour in anesthetized rats and the influence of vagotomy and beta1-receptor blocker metoprolol on the L-NAME induced bradycardia.