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This Article Full Text Full Text (PDF) All Versions of this Article: 296/1/H202    most recent 00358.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Legramante, J. M. Articles by Galante, A. Search for Related Content PubMed PubMed Citation Articles by Legramante, J. M. Articles by Galante, A.

Investigating feedforward neural regulation of circulation from analysis of spontaneous arterial pressure and heart rate fluctuations in conscious rats

¹Dipartimento di Medicina Interna, Università "Tor Vergata," Roma, ²Medicina d'Urgenza Policlinico Tor Vergata, Roma, ³S. Raffaele Hospital, Velletri, ⁴Stazione per la Tecnologia Animale, Università "Tor Vergata," Roma, and ⁵Dipartimento di Medicina Sperimentale, Università La Sapienza, Roma, Italy

Submitted 5 April 2008 ; accepted in final form 5 November 2008

It has been suggested in anesthetized animals that the occurrence of sequences of consecutive beats characterized by systolic arterial pressure (SAP) and RR or pulse interval (PI) changing in the opposite direction (SAP⁺/RR^– and SAP^–/RR⁺, nonbaroreflex sequences) might represent the expression of neural cardiovascular regulatory mechanisms operating with feedforward characteristics. The aim of the present study was to study nonbaroreflex sequences in a more physiological experimental model, i.e., in conscious freely moving rats. We studied conscious rats before and after 1) complete autonomic blockade (n = 12), 2) sympathetic blockade (n = 10), 3) (n = 7)- and β (n = 8)-adrenergic blockade, and 4) parasympathetic blockade (n = 10). Nonbaroreflex sequences were defined as three or more beats in which SAP and PI of the following beat changed in the opposite direction. Complete autonomic blockade reduced the number of nonbaroreflex sequences (95.6 ± 9.0 vs. 45.2 ± 4.1, P < 0.001), as did sympathetic blockade (80.9 ± 12.6 vs. 30.9 ± 6.1, P < 0.001). The selective -receptor blockade did not induce significant changes (80.9 ± 12.5 in baseline vs. 79.0 ± 14.7 after prazosin), whereas β-receptor blockade significantly reduced nonbaroreflex sequence occurrence (80.9 ± 12.5 in baseline vs. 48.9 ± 15.3 after propranolol). Parasympathetic blockade produced a significant increase of nonbaroreflex sequences (95.1 ± 6.9 vs. 136.0 ± 12.4, P < 0.01). These results demonstrate the physiological role of the nonbaroreflex sequences as an expression of a feedforward type of short-term cardiovascular regulation able to interact dynamically with the feedback mechanisms of baroreflex origin in the neural control of the sinus node.

feedforward mechanisms; negative feedback mechanisms; baroreceptors; nervous system autonomic; nervous system sympathetic