AJP - Heart and Circulatory Physiology, Vol 269, Issue 3 923-H933, Copyright © 1995 by American Physiological Society
Cardiac rhythmicity among NTS neurons and its relationship to sympathetic outflow in rabbits
L. F. Hayward and R. B. Felder
Cardiovascular Center, University of Iowa College of Medicine, Iowa City 52242, USA.
The caudal nucleus tractus solitarius (NTS) is the primary termination site
for baroreceptor afferents, but distinct pulse phasic activity is rarely
recorded from NTS neurons. In the present study cross-correlation analysis
was used to identify pulse phasic activity in NTS neurons in the
anesthetized rabbit. Cross-correlation analysis demonstrated that 19 of 38
pressure-sensitive neurons had activity that correlated with the cardiac
cycle, including 5 of 11 neurons activated by aortic depressor nerve
stimulation, and 12 of 28 pressure-sensitive NTS neurons had activity that
correlated with renal sympathetic nerve activity. Autocorrelation analysis
identified 17 of 38 pressure-sensitive neurons that had rhythmic activity
not related to the cardiac cycle (mean frequency 14.1 +/- 2 Hz). The
results indicate that many NTS neurons do have pulse phasic activity
consistent with baroreceptor input, but this activity is difficult to
detect because it is distributed throughout the cardiac cycle.
