Figure 3. Average data for muscle sympathetic nerve activity (MSNA) burst frequency in three groups. Compared with baseline MSNA values (18.4 +/-1.8 burst/min), significant increases in MSNA (peak 34.4 +/-3.3 bursts/min) were observed in ten subjects during left stellate ganglion block with mepivacaine. There was no significant increase in MSNA burst frequency except for a transient increase in MSNA burst frequency 2 min after saline injection in five subjects after saline injection into the left stellate ganglion. There was no significant increase in MSNA burst frequency in five subjects after mepivacaine injection into the left deltoid muscle. Data are mean+/-SEM. *P < 0.05 compared with baseline value.