Input-size dependence of the baroreflex neural arc transfer characteristics.
Static characteristics of the baroreflex neural arc from pressure input to sympathetic nerve activity (SNA) show sigmoidal nonlinearity, whereas its dynamic characteristics approximate a derivative filter where the magnitude of SNA response becomes greater as the input frequency increases. To reconcile the static nonlinear and dynamic linear components, we examined the effects of input amplitude on the apparent linear transfer function of the neural arc. In nine anesthetized rabbits, we perturbed isolated carotid sinus pressure by using binary white noise while varying the input amplitude among 5, 10, 20, and 40 mmHg. With increasing input amplitude, the transfer gain at 0.01 Hz decreased from 1.21 +/- 0.27 to 0.49 +/- 0.28 arbitrary units/mmHg (P < 0.01). Moreover, the slope of the transfer gain between 0.03 and 0.3 Hz decreased from 14.3 +/- 3.7 to 6.5 +/- 2.5 dB/decade (P < 0.01). We conclude that the model consisting of a sigmoidal component following rather than preceding a derivative component explains the observed results and thus can be used as a first approximation of the overall neural arc transfer characteristics.
Kawada
Toru
T
Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan. torukawa@res@ncvc.go.jp
Yanagiya
Yusuke
Y
Uemura
Kazunori
K
Miyamoto
Tadayoshi
T
Zheng
Can
C
Li
Meihua
M
Sugimachi
Masaru
M
Sunagawa
Kenji
K
D000161:Acoustic Stimulation / Q000379:methods; D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002346:Carotid Sinus / Q000502:physiology; D004525:Efferent Pathways / Q000502:physiology; D005583:Fourier Analysis; D066298:In Vitro Techniques; D016014:Linear Models; D008955:Models, Cardiovascular; D009622:Noise; D011817:Rabbits; D013564:Sympathetic Nervous System / Q000502:physiology*