Abstract
The in situ perfusion of the sinus node artery was performed under a constant pressure of 100mm Hg. Effect of haloperidol on sinus acceleration induced by dopamine and norepinephrine was examined in 7 vagotomized dogs. Doses of more than 3 μg of haloperidol usually induced a negative chronotropic response. The injection of more than 100 μg of haloperi-dol caused frequently sinus arrhythmia. An acceleration response not only to lug of dopamine but also to 0.1 μg of norepinephrine was significantly suppressed by 30 to 100 μg of haloperidol showing no differentiation of blocking activity of haloperidol between dopamine- and norepinephrine-induced positive chronotropic effects.
