Arterial baroreceptor afferent activity in nonpulsatile systemic circulation

We directly measured aortic depressor nerve activity (ADNA) in rabbits to i nvestigate changes in arterial baroreceptor afferent activity (ABAA) in res ponse to nonpulsatile systemic circulation (NC) during total left heart byp ass (TLHB). ADNA was measured before and 5, 20, 30, 40, 50, and 60 min afte r the start of TLHB while maintaining the mean aortic pressure (MAP) at pre established values (n = 10). At 5 min, the ADNA was significantly increased compared to its baseline value. At 30 min, it was significantly decreased compared to its value at 5 min and thereafter remained the same. The ADNA w as then measured before and 5 and 30 min after the start of TLHB under incr eased MAP (n = 10). The results showed that the percentage changes in ADNA during TLHB were significantly less than that observed when the MAP was inc reased before TLHB. We conclude that ABAA acutely adapts to NC 30 min after its initiation, but changes in ABAA are depressed under NC combined with i ncreased MAP.