50 msec by 30% (p <0.002), decreased the root-mean-square successive difference by 17% (p <0.02), and decreased the natural logarithm of high-frequency power by 6% (p < 0.03). The significant heart rate increase and HPV decreases demonstrate vagolytic effects of LZ in healthy subjects during 24 hours of normal physiologic activity. (J Clin Psychopharmacol 1996;16:449-453).