Baroreceptor influences on cardiac-related sympathetic nerve activity.

We studied the effect of a dropped ventricular beat (i.e. loss of one cycle of pulse synchronous baroreceptor nerve activity) on the centrally generated 2-6 Hz oscillation in postganglionic sympathetic nerve discharge (SND) in cats anesthetized with Dial-urethane. The results indicate that in each cardiac cycle baroreceptor nerve activity can: (1) decrease the rate of recruitment and number of postganglionic fibers that become active and (2) advance the onset of central inhibition responsible for the abrupt decline of SND. These effects are independent of baroreceptor-mediated entrainment of the 2-6 Hz oscillation of SND to the cardiac cycle.