(Circulation. 1999;99:1760-1766.)
© 1999 American Heart Association, Inc.
Basic Science Reports |
Investigating Feed-Forward Neural Regulation of Circulation From Analysis of Spontaneous Arterial Pressure and Heart Rate Fluctuations
From the Dipartimento di Medicina Interna, Cattedra di Fisiopatologia Medica, Università di Roma "Tor Vergata," Roma, Italia.
Correspondence to Dr Jacopo M. Legramante, Dipartimento Medicina Interna, Università di Roma "Tor Vergata," Via O Raimondo, snc, 00173 Rome, Italy. E-mail legramante{at}med.uniroma2.it
Background—Analysis of spontaneous fluctuations in systolic arterial pressure (SAP) and pulse interval (PI) reveals the occurrence of sequences of consecutive beats characterized by SAP and PI changing in the same (+PI/+SAP and -PI/-SAP) or opposite (-PI/+SAP and +PI/-SAP) direction. Although the former reflects baroreflex regulatory mechanisms, the physiological meaning of -PI/+SAP and +PI/-SAP is unclear. We tested the hypothesis that -PI/+SAP and +PI/-SAP "nonbaroreflex" sequences represent a phenomenon modulated by the autonomic nervous system reflecting a feed-forward mechanism of cardiovascular regulation.
Methods and Results—We studied anesthetized rabbits
before and after (1) complete autonomic blockade
(guanethidine+propranolol+atropine, n=13; CAB), (2)
sympathetic blockade (guanethidine+propranolol, n=15; SB),
(3) parasympathetic blockade (atropine, n=16), (4) sinoaortic
denervation (n=10; SAD), and (5) controlled respiration (n=10; CR).
Nonbaroreflex sequences were defined as 
3 beats in which SAP and PI
of the following beat changed in the opposite direction. CAB reduced
the number of nonbaroreflex sequences (19.1±12.3 versus 88.7±36.6,
P<0.05), as did SB (25.3±11.7 versus 84.6±23.9,
P<0.001) and atropine (11.2±6.8 versus 94.1±32.4,
P<0.05). SB concomitantly increased baroreflex
sensitivity (1.18±0.11 versus 0.47±0.09 ms/mm Hg,
P<0.01). SAD and CR did not significantly affect their
occurrence.
Conclusions—These results suggest that nonbaroreflex sequences represent the expression of an integrated, neurally mediated, feed-forward type of short-term cardiovascular regulation able to interact dynamically with the feedback mechanisms of baroreflex origin in the control of heart period.
Key Words: nervous system, autonomic • baroreceptors
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