A Simple Method for Generating a Blood Pressure‐Unit Activity Relationship for Central Cardiovascular Neurons in the Rat

Cividjian, Andrei; Rentero, N.; McAllen, Robin M.; Quintin, Luc

doi:10.1113/eph8702410

Cited by 4 publications

(6 citation statements)

References 17 publications

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“…The systolic upswing of the arterial pulse wave triggers a burst of activity in the arterial baroreceptors, which in turn activates CVM, giving cardiac rhythmicity to their discharge (8,32,40). CVM activity was maximal around the systolic peak in arterial pressure, as shown by the neuron illustrated in Fig.…”

Section: Ratsmentioning

confidence: 91%

“…3, A and B), following established methods and criteria (8,32,40). As reported, clonidine (100 g/kg) decreased arterial pressure and HR, while increasing CVM activity (Fig.…”

Section: Ratsmentioning

confidence: 99%

“…Rats were paralyzed with metocurine iodide (0.2 mg iv; Metubine, Lilly, Indianapolis, IN) and mechanically ventilated (ϳ72/min; 40% O 2; end-tidal CO2, ϳ30 -35 mmHg). A percutaneous transluminal coronary angioplasty (PTCA) catheter with a balloon at its tip (2-3 mm; Boston Scientific, Galway, Ireland) was introduced through the right femoral artery up to the thoracic aorta to monitor BP and to generate BP rises when inflated (8). An infusion of saline (Ͻ3 ml/h) through the PTCA catheter prevented hypovolemia (39) and clotting.…”

Section: Ratsmentioning

confidence: 99%

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Effect of clonidine on cardiac baroreflex delay in humans and rats

Cividjian

Toader

Wesseling

et al. 2011

American Journal of Physiology-Regulatory, Integrative and Comp

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Cividjian A, Toader E, Wesseling KH, Karemaker JM, McAllen R, Quintin L. Effect of clonidine on cardiac baroreflex delay in humans and rats. Am J Physiol Regul Integr Comp Physiol 300: R949-R957, 2011. First published January 26, 2011 doi:10.1152/ajpregu.00438.2010The delay between rising systolic blood pressure (SBP) and baroreflex bradycardia has been found to increase when vagal tone is low. The ␣2-agonist clonidine increases cardiac vagal tone, and this study tested how it affects . In eight conscious supine human volunteers clonidine (6 g/kg po) reduced , assessed both by cross correlation baroreflex sensitivity and sequence methods (both P Ͻ 0.05). Experiments on urethane-anaesthetized rats reproduced the phenomenon and investigated the underlying mechanism. Heart rate (HR) responses to increasing SBP produced with an arterial balloon catheter showed reduced (P Ͻ 0.05) after clonidine (100 g/kg iv). The central latency of the reflex was unaltered, however, as shown by the unchanged timing with which antidromically identified cardiac vagal motoneurons (CVM) responded to the arterial pulse. Testing the latency of the HR response to brief electrical stimuli to the right vagus showed that this was also unchanged by clonidine. Nevertheless, vagal stimuli delivered at a fixed time in the cardiac cycle (triggered from the ECG R-wave) slowed HR with a 1-beat delay in the baseline state but a 0-beat delay after clonidine (n ϭ 5, P Ͻ 0.05). This was because clonidine lengthened the diastolic period, allowing the vagal volleys to arrive at the heart just in time to postpone the next beat. Calculations indicate that naturally generated CVM volleys in both humans and rats arrive around this critical time. Clonidine thus reduces not by changing central or efferent latencies but simply by slowing the heart. sequences; lag; latency; cardiac vagal motoneurons; ␣ 2-agonist THE GAIN OF THE ARTERIAL baroreceptor-heart rate reflex (cardiac baroreflex) has been calculated from the relationship between spontaneous (10, 13) or drug-induced (47) increases in systolic blood pressure (SBP) and the accompanying decrease in heart rate (HR). In humans, the best correlations were initially obtained by relating cardiac intervals to the preceding SBP (delay ϭ 1 beat) (47), although later studies (14, 38) found a delay of 0 beat was appropriate in subjects with lower initial HRs. In unanesthetized rats, delays of between 2 and 14 beats gave the best correlation for spontaneous baroreflex measurements (35); the best fit for tachycardic responses was 2 to 3 beats longer than that for bradycardic responses (35). The sequence technique of baroreflex sensitivity (sBRS) (13) traditionally uses a constant delay ϭ 1 beat to measure spontaneous baroreflex slope in humans, although the method may be applied using delays of any whole number of beats. This approach has been expanded to give a near-continuous assessment of the slope of the cardiac baroreflex [time-domain cross-correlation BRS (xBRS)] (56). The algorithm of xBRS (56) adjusts in seconds...

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Section: Ratsmentioning

confidence: 91%

“…3, A and B), following established methods and criteria (8,32,40). As reported, clonidine (100 g/kg) decreased arterial pressure and HR, while increasing CVM activity (Fig.…”

Section: Ratsmentioning

confidence: 99%

Section: Ratsmentioning

confidence: 99%

See 1 more Smart Citation

Effect of clonidine on cardiac baroreflex delay in humans and rats

Cividjian

Toader

Wesseling

et al. 2011

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

show abstract

“…The right femoral vein was catheterized. A percutaneous transluminal coronary angioplasty catheter with an inflatable balloon at its tip (PTCA catheter 2-3 mm; Boston Scientific, Galway, Ireland) was introduced through the right femoral artery up to the thoracic level to monitor BP and generate pressure rises [25] ('balloon inflation'). A slow infusion (<3 ml/h) through the arterial lumen of the PTCA catheter prevented hypovolemia [26] and clotting.…”

Section: Methodsmentioning

confidence: 99%

Cardioinhibitory actions of clonidine assessed by cardiac vagal motoneuron recordings

Toader

Cividjian

Rentero

et al. 2008

Journal of Hypertension

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“…To assess RBF and ChBF BP responses in rats using MRI in the present study, a transient increase in BP inside the scanner was achieved by mechanically inflating a balloon catheter to occlude the descending aorta near the diaphragm (Cividjian et al, 2002; Kiel, 1999). This method can induce transient hypertension above the occluder without pharmacologic manipulation that would confound the vascular responses being investigated.…”

Section: Introductionmentioning

confidence: 99%

MRI study of cerebral, retinal and choroidal blood flow responses to acute hypertension

Shih

Kiel

et al. 2013

Experimental Eye Research

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Blood flow (BF) in many tissues is stable during significant fluctuations in systemic arterial blood pressure or perfusion pressure under normal conditions. The regulatory mechanisms responsible for this non-passive BF behavior include both local and neural control mechanisms. This study evaluated cerebral BF (CBF), retinal BF (RBF) and choroidal BF (ChBF) responses to acute blood pressure increases in rats using magnetic resonance imaging (MRI). A transient increase in blood pressure inside the MRI scanner was achieved by mechanically inflating a balloon catheter to occlude the descending aorta near the diaphragm. We verified the rat model of mechanical occlusion and MRI approach by first measuring blood-flow regulatory responses to changing BP in the brain under normoxia and hypercapnia where the phenomenon is well documented. Retinal and choroidal blood-flow responses to transient increased arterial pressure were then investigated. In response to an acute increase in blood pressure, RBF exhibited autoregulatory behavior and ChBF exhibited baroregulation similar to that seen in the cerebral circulation. This approach may prove useful to investigate retinal and choroidal vascular dysregulation in rat models of retinal diseases with suspected vascular etiology.

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A Simple Method for Generating a Blood Pressure‐Unit Activity Relationship for Central Cardiovascular Neurons in the Rat

Cited by 4 publications

References 17 publications

Effect of clonidine on cardiac baroreflex delay in humans and rats

Effect of clonidine on cardiac baroreflex delay in humans and rats

Cardioinhibitory actions of clonidine assessed by cardiac vagal motoneuron recordings

MRI study of cerebral, retinal and choroidal blood flow responses to acute hypertension

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