THE LONG-TERM INCREASE OF BASELINE AND REFLEXLY AUGMENTED LEVELS OF HUMAN VAGAL-CARDIAC NERVOUS ACTIVITY INDUCED BY SCOPOLAMINE

The hypothesis that transdermal scopolamine increases vagal-cardiac nervous outflow over the long term was tested in 16 healthy young men. Twenty-four hours after application of 1 scopolamine patch, the average RR interval was increased by 13% and the average SD of the RR interval (taken as an index of the level of vagal-cardiac nervous activity) was increased by 31%. Baroreceptor-cardiac reflex responsiveness (as reflected by prolongation of RR interval provoked by graded neck suction) also was increased substantially. These findings suggest that vagal-cardiac nervous activity can be augmented pharmacologically in a man on a long-term basis. Since vagal outflow influences cardiac electrical properties in an important way, these findings may have therapeutic implications.