title: Intravenous angiotensin II does not affect dynamic baroreflex characteristics of the neural or peripheral arc.
abstract: Although the elevation of angiotensin II (Ang II) associated with cardiovascular diseases has been considered to suppress the arterial baroreflex function, how Ang II affects dynamic arterial pressure (AP) regulation remains unknown. The aim of the present study was to elucidate the acute effects of Ang II on dynamic AP regulation by the arterial baroreflex. In seven anesthetized Japanese white rabbits, we randomly perturbed intra-carotid sinus pressure (CSP) according to a binary white noise sequence while recording renal sympathetic nerve activity (RSNA) and AP. We estimated the neural arc transfer function from CSP to RSNA and the peripheral arc transfer function from RSNA to AP before and after 30-min intravenous administration of Ang II (100 ng/kg/min). Ang II increased mean AP from 75.7 +/- 3.1 to 95.5 +/- 5.1 mmHg (p < 0.01), while it did not affect mean RSNA (from 5.9 +/- 1.3 to 5.7 +/- 1.2 a.u.). The neural arc transfer functions did not differ before or after Ang II administration (dynamic gain: -0.94 +/- 0.04 vs. -0.94 +/- 0.13, corner frequency: 0.06 +/- 0.01 vs.0.06 +/- 0.01 Hz, pure delay: 0.16 +/- 0.01 vs. 0.17 +/- 0.02 s). The peripheral arc transfer function did not differ before or after Ang II administration (dynamic gain: 1.18 +/- 0.05 vs. 1.06 +/- 0.11, natural frequency: 0.07 +/- 0.01 vs. 0.08 +/- 0.01 Hz, damping ratio: 1.19 +/- 0.06 vs. 1.24 +/- 0.19, pure delay: 0.83 +/- 0.06 vs. 0.78 +/- 0.05 s). Intravenous Ang II hardly affects the dynamic characteristics of neural and peripheral arc around the physiological operating pressure.
authors.affiliation: Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, 565-8565, Japan. kasihara@ri.ncvc.go.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Kashihara
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Kaori
authors.initials: K
authors.lastname: Chatani
authors.forename: Toru
authors.initials: T
authors.lastname: Kawada
authors.forename: Can
authors.initials: C
authors.lastname: Zheng
authors.forename: Meihua
authors.initials: M
authors.lastname: Li
authors.forename: Masaru
authors.initials: M
authors.lastname: Sugimachi
authors.forename: Kenji
authors.initials: K
authors.lastname: Sunagawa
mesh_terms: D000465:Algorithms; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002346:Carotid Sinus / Q000502:physiology; D002490:Central Nervous System / Q000502:physiology*; D003627:Data Interpretation, Statistical; D003714:Denervation; D001330:Electronic Data Processing; D004594:Electrophysiology; D007668:Kidney / Q000294:innervation / Q000502:physiology; D017933:Peripheral Nervous System / Q000502:physiology*; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D014662:Vasoconstrictor Agents; D000804:Angiotensin II