Afferent and efferent nerve activity of arterial baroreceptor reflex undernonpulsatile systemic circulation

We studied the changes in arterial baroreceptor reflex (ABR) afferent activ ity and efferent activity induced by nonpulsatile systemic circulation (NC) during total left heart bypass (TLHB) in rabbits. To evaluate the influenc e of the circuit priming fluid and exposure to NC, we directly measured aor tic depressor nerve activity (ADNA) (n = 5) and renal sympathetic nerve act ivity (RSNA) (n = 5) before the start of partial left heart bypass (PLHB) ( Before), after PHLB (After), and 5 min after the start of TLHB (During THLB ) while maintaining the mean aortic pressure. The circuit priming fluid did not affect the ABR. ADNA exhibited periodic discharge at Before and After, but at During THLB, this periodic discharge transformed into a continuous discharge, and ADNA increased significantly. However, there were no signifi cant differences in RSNA. Our results suggested that in the acute phase und er NC, the ABR differed from that under natural circulation.