EFFECTS OF LOW-DOSE TRANSDERMAL SCOPOLAMINE ON AUTONOMIC CARDIOVASCULAR CONTROL IN HEALTHY-YOUNG SUBJECTS

We studied how posture influences the effects of transdermal scopolami ne on autonomic cardiovascular regulation in a randomized, double-blin d, placebo-controlled crossover study of 10 healthy young volunteers. We recorded the electrocardiogram and auscultatory sphygmomanometric a nd continuous non-invasive finger arterial pressure (Finapres device) to obtain signals for the beat-by-beat R-R interval and systolic, mean and diastolic pressures. R-R interval and arterial pressure variabili ties were characterized by power spectral analysis. Scopolamine increa sed the mean R-R intervals and reduced arterial pressure in both the s upine and the standing positions, but did not affect blood pressure va riability. Scopolamine increased the total variability of R-R interval and its mid- (0.07-0.15 Hz) and high- (0.15-0.40 Hz) frequency band p ower in the standing position during controlled breathing at 0.25 Hz. In the supine position, scopolamine did not affect R-R interval variab ility. In the deep breathing test, scopolamine increased the maximal e xpiratory-inspiratory R-R interval ratio. This study showed that low-d ose scopola mine increases vagal cardiac inhibition in both supine and standing positions in healthy volunteers. However, scopolamine increa ses heart rate variability only in the standing position during partia l vagal withdrawal. The study also demonstrates that transdermal scopo lamine decreases blood pressure in healthy young subjects.