the characterization of this effect using reserpine pretreatment , propranolol , pargyline , 6-hydroxydopamine or the combination of some of those drugs enable us to conclude that serotonin is an amine of mixed action in the isolated atrium of the hamster , that is , its positive chronotropic effect has a direct component , which is obtained with lower concentrations of agonist and an indirect component through the liberation of endogenous noradrenaline from the sympathetic nerve terminals .
C1372804
positive chronotropic
C0028351
noradrenaline