Bezold-Jarisch reflex attenuates dynamic gain of baroreflex neural  arc

Although acute myocardial ischemia or infarction may induce the Bezold-Jarisch (BJ) reflex through the activation of serotonin receptors on vagal afferent nerves, the mechanism by which the BJ reflex modulates the dynamic characteristics of arterial pressure (AP) regulation is unknown. The purpose of this study was to examine the effects of the BJ reflex induced by intravenous phenylbiguanide (PBG) on the dynamic characteristics of the arterial baroreflex. In seven anesthetized rabbits, we perturbed intracarotid sinus pressure (CSP) according to a white noise sequence while renal sympathetic nerve activity (RSNA), AP, and heart rate (HR) were recorded. We estimated the transfer function from CSP to RSNA (neural arc) and from RSNA to AP (peripheral arc) before and after 10 min of intravenous administration of PBG (100 μg · kg–1 · min–1). The intravenous PBG decreased mean AP from 84.5 ± 4.0 to 68.2 ± 4.7 mmHg ( P < 0.01), mean RSNA to 76.2 ± 7.0% ( P < 0.05), and mean HR from 301.6 ± 7.7 to 288.4 ± 9.0 beats/min ( P < 0.01). The intravenous PBG significantly decreased neural arc dynamic gain at 0.01 Hz (1.06 ± 0.08 vs. 0.59 ± 0.17, P < 0.05), whereas it did not affect that of the peripheral arc (1.20 ± 0.12 vs. 1.18 ± 0.41). In six different rabbits without intravenous PBG, the neural arc transfer function did not change between two experimental runs with intervening interval of 10 min, excluding the possibility that the cumulative effects of anesthetics had altered the neural arc transfer function. In conclusion, excessive activation of the BJ reflex during acute myocardial ischemia may exert an adverse effect on AP regulation, not only by sympathetic suppression, but also by attenuating baroreflex dynamic gain.

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Contrasting open-loop dynamic characteristics of sympathetic and vagal systems during baroreflex-mediated heart rate control in rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00231.2019 ◽

2019 ◽

Vol 317 (6) ◽

pp. R879-R890 ◽

Cited By ~ 2

Author(s):

Toru Kawada ◽

Hiromi Yamamoto ◽

Yohsuke Hayama ◽

Takuya Nishikawa ◽

Kunihiko Tanaka ◽

...

Keyword(s):

Heart Rate ◽

Transfer Function ◽

Dynamic Characteristics ◽

Carotid Sinus ◽

Gaussian White Noise ◽

Open Loop ◽

Model Parameters ◽

Before And After ◽

Dynamic Gain ◽

Sinus Pressure

Although heart rate (HR) is governed by the sympathetic and parasympathetic nervous systems, a head-to-head comparison of the open-loop dynamic characteristics of the total arc from a baroreceptor pressure input to the HR response has yet to be performed. We estimated the transfer function from carotid sinus pressure input to the HR response ( HCSP→HR) before and after bilateral vagotomy ( n = 7) as well as before and after the administration of a β-blocker propranolol ( n = 8) in anesthetized male Wistar-Kyoto rats. The carotid sinus pressure was perturbed according to a Gaussian white noise signal so that the input power spectra were relatively flat between 0.01 and 1 Hz. The gain plot of HCSP→HR was V-shaped. Vagotomy reduced the dynamic gain at 1 Hz (0.0598 ± 0.0065 to 0.0025 ± 0.0004 beats·min−1·mmHg−1, P < 0.001) but not at 0.01 or 0.1 Hz. β-Blockade reduced the dynamic gain at 0.01 Hz (0.247 ± 0.069 to 0.077 ± 0.017 beats·min−1·mmHg−1, P = 0.020) but not at 0.1 or 1 Hz. We also estimated the efferent limb transfer function from electrical vagal efferent stimulation to the HR response ( HVN→HR) under β-blockade conditions. We associated the model parameters of HVN→HR with the mean HR and the standard deviation of HR so that HVN→HR could be estimated based only on the HR data. We finally estimated the neural arc transfer function from a pressure input to efferent vagal nerve activity by dividing HCSP→HR by HVN→HR. The mathematically determined vagal neural arc showed derivative characteristics with its phase near zero radians at the lowest frequency.

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Effects of neuronal norepinephrine uptake blockade on baroreflex neural and peripheral arc transfer characteristics

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00527.2003 ◽

2004 ◽

Vol 286 (6) ◽

pp. R1110-R1120 ◽

Cited By ~ 13

Author(s):

Toru Kawada ◽

Tadayoshi Miyamoto ◽

Kazunori Uemura ◽

Koji Kashihara ◽

Atsunori Kamiya ◽

...

Keyword(s):

Transfer Function ◽

Sympathetic Nerve ◽

Neuronal Uptake ◽

Arterial Baroreflex ◽

Exogenous Disturbance ◽

Sympathetic Regulation ◽

White Noise Sequence ◽

Noise Sequence ◽

Normalized Gain ◽

Sinus Pressure

Neuronal uptake is the most important mechanism by which norepinephrine (NE) is removed from the synaptic clefts at sympathetic nerve terminals. We examined the effects of neuronal NE uptake blockade on the dynamic sympathetic regulation of the arterial baroreflex because dynamic characteristics are important for understanding the system behavior in response to exogenous disturbance. We perturbed intracarotid sinus pressure (CSP) according to a binary white noise sequence in anesthetized rabbits, while recording cardiac sympathetic nerve activity (SNA), arterial pressure (AP), and heart rate (HR). Intravenous administration of desipramine (1 mg/kg) decreased the normalized gain of the neural arc transfer function from CSP to SNA relative to untreated control (1.03 ± 0.09 vs. 0.60 ± 0.08 AU/mmHg, mean ± SE, P < 0.01) but did not affect that of the peripheral arc transfer function from SNA to AP (1.10 ± 0.05 vs. 1.08 ± 0.10 mmHg/AU). The normalized gain of the transfer function from SNA to HR was unaffected (1.01 ± 0.04 vs. 1.09 ± 0.12 beats·min−1·AU−1). Desipramine decreased the natural frequency of the transfer function from SNA to AP by 28.7 ± 7.0% (0.046 ± 0.007 vs. 0.031 ± 0.002 Hz, P < 0.05) and that of the transfer function from SNA to HR by 64.4 ± 2.2% (0.071 ± 0.003 vs. 0.025 ± 0.002 Hz, P < 0.01). In conclusion, neuronal NE uptake blockade by intravenous desipramine administration reduced the total buffering capacity of the arterial baroreflex mainly through its action on the neural arc. The differential effects of neuronal NE uptake blockade on the dynamic AP and HR responses to SNA may provide clues for understanding the complex pathophysiology of cardiovascular diseases associated with neuronal NE uptake deficiency.

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Dynamic characteristics of baroreflex neural and peripheral arcs are preserved in spontaneously hypertensive rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00540.2010 ◽

2011 ◽

Vol 300 (1) ◽

pp. R155-R165 ◽

Cited By ~ 21

Author(s):

Toru Kawada ◽

Shuji Shimizu ◽

Atsunori Kamiya ◽

Yusuke Sata ◽

Kazunori Uemura ◽

...

Keyword(s):

Transfer Function ◽

Dynamic Characteristics ◽

Spontaneously Hypertensive Rats ◽

Transfer Functions ◽

Carotid Sinus ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

Carotid Sinus Baroreflex ◽

Low Pass ◽

Dynamic Gain

Although baroreceptors are known to reset to operate in a higher pressure range in spontaneously hypertensive rats (SHR), the total profile of dynamic arterial pressure (AP) regulation remains to be clarified. We estimated open-loop transfer functions of the carotid sinus baroreflex in SHR and Wistar Kyoto (WKY) rats. Mean input pressures were set at 120 (WKY120 and SHR120) and 160 mmHg (SHR160). The neural arc transfer function from carotid sinus pressure to efferent splanchnic sympathetic nerve activity (SNA) revealed derivative characteristics in both WKY and SHR. The slope of dynamic gain (in decibels per decade) between 0.1 and 1 Hz was not different between WKY120 (10.1 ± 1.0) and SHR120 (10.4 ± 1.1) but was significantly greater in SHR160 (13.2 ± 0.8, P < 0.05 with Bonferroni correction) than in SHR120. The peripheral arc transfer function from SNA to AP showed low-pass characteristics. The slope of dynamic gain (in decibels per decade) did not differ between WKY120 (−34.0 ± 1.2) and SHR120 (−31.4 ± 1.0) or between SHR120 and SHR160 (−32.8 ± 1.3). The total baroreflex showed low-pass characteristics and the dynamic gain at 0.01 Hz did not differ between WKY120 (0.91 ± 0.08) and SHR120 (0.84 ± 0.13) or between SHR120 and SHR160 (0.83 ± 0.11). In both WKY and SHR, the declining slope of dynamic gain was significantly gentler for the total baroreflex than for the peripheral arc, suggesting improved dynamic AP response in the total baroreflex. In conclusion, the dynamic characteristics of AP regulation by the carotid sinus baroreflex were well preserved in SHR despite significantly higher mean AP.

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Abstract 711: Diagnosis of Acute Myocardial Ischemia by Speckle Tacking Echocardiography -A Comparative Animal Study-

Circulation ◽

10.1161/circ.118.suppl_18.s_604-a ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Aya Ebihara ◽

Katsu Takenaka ◽

Koichi Kimura ◽

Kansei Uno ◽

Katsuhito Fuju ◽

...

Keyword(s):

Myocardial Ischemia ◽

Strain Rate ◽

Roc Curve ◽

Radial Strain ◽

Posterior Wall ◽

Acute Myocardial Ischemia ◽

Roc Curve Analysis ◽

2D Echocardiography ◽

Before And After ◽

Diagnostic Values

Since the subendocardium is known to be more vulnerable to ischemia than the subepicardium, indexes of subendocardial function are expected to be more sensitive than indexes of whole LV wall. The aim of our study is to compare the diagnostic values of systolic and diastolic indexes measured by 2D speckle tracking echocardiography in an animal experiment. The proximal left circumflex coronary artery was balloon-occluded for 3 minutes in 14 pigs. LV short-axis view was recorded at rest and 30 minutes after release of the occlusion by transthoracic 2D echocardiography except for one pig with ventricular fibrillation. Peak circumferential and radial strain (CR, RS), peak systolic and diastolic strain rate (CSR-S′ and CSR-E′), time from QRS to peak CS and RS, time from QRS to E′, and the incidence of post-systolic shortening (PSS) were measured in the subendocardium of the LV posterior wall. ROC curve analysis of these indexes was done for the diagnosis of acute myocardial ischemia followed by reperfusion. Only 5 indexes showed significant change before and after the occlusion. ROC curve revealed that CSR-E′ had the highest predictive value for detecting the ischemic memory, followed by peak CS, and CSR-S′. Peak early diastolic circumferential strain rate of the subendocardium was the most powerful index for diagnosing ischemic memory after acute coronary occlusion. Table. Results of meaurement (mean±SD)

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Heparin from Intestine and Lung Source Administered in Large Dose to Dogs with Acute Myocardial Ischemia

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648674 ◽

1978 ◽

Vol 40 (02) ◽

pp. 407-417

Author(s):

Michael J Saliba ◽

Richard J Pavalec

Keyword(s):

Coronary Artery ◽

Myocardial Ischemia ◽

Adenosine Triphosphate ◽

Intestinal Mucosa ◽

Large Dose ◽

Acute Myocardial Ischemia ◽

Ischemic Myocardium ◽

Atp Levels ◽

Initial Control ◽

The Difference

SummaryIntestinal mucosa heparin (IMH) and beef lung heparin (BLH) were infused into dogs subjected to myocardial ischemia by intermittent coronary artery occlusions. The IMH was from a mixture of beef, sheep, and pig intestinal mucosa. Initial control occlusion and recovery was followed by a second occlusion with 60,000 units of IMH or BLH added. Electrocardiographic S-T segment elevations (ST) were measured acutely. There were no significant differences in ST in non-ischemic myocardium before occlusions or with occlusions. In ischemic myocardium, IMH significantly lowered control ST 84% in amount (t = 6.1 p <0.00005), and 76% in number (t = 11.6 p <0.00001). BLH lowered control ST a significant, lesser, 36% in amount (t = 3.6 p <0.008), and 35% in number (t = 3.2 p <0.01). The difference between IMH and BLH in ischemic myocardium was a significant 48% in amount (t = 4.0 p <0.0007), and 41% in number (t = 2.0 p <0.06). Myocardial adenosine triphosphate (ATP) levels were assayed after 90 min. ATP levels were 31% higher in both ischemic and non-ischemic myocardium in IMH-treated dogs than in BLH- treated. It was concluded that IMH and BLH are functionally different, and IMH was significantly more effective.

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