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Rhythmic Aortic Contractions Induced by Electrical Stimulation In Vivo in the Rat.

Sahibzada N, Mangel AW, Tatge JE, Dretchen KL, Franz MR, Virmani R, Gillis RA - PLoS ONE (2015)

Bottom Line: In response to pulsatile pressure changes, the vessels undergo a 'passive' elastic dilatation-contraction cycle, described as a "Windkessel" effect.However, Mangel and colleagues have presented evidence that is contrary to this view.Electrical stimulation of the aorta evoked contractions that occur at a rate that is in the range of the animal's heartbeat and are suppressed by tetrodotoxin and the alpha-adrenergic receptor blocker, phentolamine.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology & Physiology, Georgetown University School of Medicine, 3900 Reservoir Road, NW, Washington, DC, 20007, United States of America.

ABSTRACT
For over a century, the behavior of the aorta and other large arteries has been described as passive elastic tubes in which no active contraction occurs in the smooth muscle wall. In response to pulsatile pressure changes, the vessels undergo a 'passive' elastic dilatation-contraction cycle, described as a "Windkessel" effect. However, Mangel and colleagues have presented evidence that is contrary to this view. They reported that in the rabbit, the aorta undergoes rhythmic 'active' (contraction) during the cardiac cycle; but these findings have been largely ignored. In the present study, we observed spontaneous contractions in synchrony with the heartbeat in another species (rat). In addition we demonstrate that aorta contractions are of neurogenic origin. Electrical stimulation of the aorta evoked contractions that occur at a rate that is in the range of the animal's heartbeat and are suppressed by tetrodotoxin and the alpha-adrenergic receptor blocker, phentolamine. Altogether, these findings indicate that aortic contractions are under neural control from the heart.

No MeSH data available.


Related in: MedlinePlus

Effect of varying stimulation voltage on magnitude of the contractile response of the aorta.Voltage was varied from 0.25–7.5V, whereas frequency and pulse duration were kept constant at 5Hz and 2ms, respectively. (A) Representative tracing of electrically induced contractions of the aorta in response to varying voltage stimuli (two/voltage; bars) and peak parameters (a') of a 10V induced single contraction and (a") the mean ± SEM of 5 contractions per aorta in three animals (arrow; TR = rise time, TF = fall time, SlopeL = leading slope, W50% = half-width, AUC = area under the curve). (B) Graph showing the stimulus-response profile of aortic contractions in relationship to the percent change in amplitude elicited by 10V (n = 4).
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pone.0130255.g002: Effect of varying stimulation voltage on magnitude of the contractile response of the aorta.Voltage was varied from 0.25–7.5V, whereas frequency and pulse duration were kept constant at 5Hz and 2ms, respectively. (A) Representative tracing of electrically induced contractions of the aorta in response to varying voltage stimuli (two/voltage; bars) and peak parameters (a') of a 10V induced single contraction and (a") the mean ± SEM of 5 contractions per aorta in three animals (arrow; TR = rise time, TF = fall time, SlopeL = leading slope, W50% = half-width, AUC = area under the curve). (B) Graph showing the stimulus-response profile of aortic contractions in relationship to the percent change in amplitude elicited by 10V (n = 4).

Mentions: To consistently induce single contractions of the aorta, we employed frequencies of 1.7 Hz (to approximate a heart rate of 100 beats/min) and 5 Hz (to approximate a heart rate of 300 beats/min). These stimulation rates did not change the basal tone of the aorta. Fig 2 illustrates a stimulation-response curve that was derived using a 5 Hz frequency with varying voltages (0.25V-10V). The typical profile of electrically-evoked neurally mediated contraction had a relatively fast rise-time and recovery compared to that reported for direct muscle-stimulated vascular contraction [12]. For our studies, to assess the effect of drugs on stimulation-induced contractions, we utilized the 10V stimulation strength because it elicited repeatable aortic contractions of similar amplitudes. Fig 2: Effect of varying stimulation voltage on magnitude of the contractile response of the aorta.


Rhythmic Aortic Contractions Induced by Electrical Stimulation In Vivo in the Rat.

Sahibzada N, Mangel AW, Tatge JE, Dretchen KL, Franz MR, Virmani R, Gillis RA - PLoS ONE (2015)

Effect of varying stimulation voltage on magnitude of the contractile response of the aorta.Voltage was varied from 0.25–7.5V, whereas frequency and pulse duration were kept constant at 5Hz and 2ms, respectively. (A) Representative tracing of electrically induced contractions of the aorta in response to varying voltage stimuli (two/voltage; bars) and peak parameters (a') of a 10V induced single contraction and (a") the mean ± SEM of 5 contractions per aorta in three animals (arrow; TR = rise time, TF = fall time, SlopeL = leading slope, W50% = half-width, AUC = area under the curve). (B) Graph showing the stimulus-response profile of aortic contractions in relationship to the percent change in amplitude elicited by 10V (n = 4).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4489007&req=5

pone.0130255.g002: Effect of varying stimulation voltage on magnitude of the contractile response of the aorta.Voltage was varied from 0.25–7.5V, whereas frequency and pulse duration were kept constant at 5Hz and 2ms, respectively. (A) Representative tracing of electrically induced contractions of the aorta in response to varying voltage stimuli (two/voltage; bars) and peak parameters (a') of a 10V induced single contraction and (a") the mean ± SEM of 5 contractions per aorta in three animals (arrow; TR = rise time, TF = fall time, SlopeL = leading slope, W50% = half-width, AUC = area under the curve). (B) Graph showing the stimulus-response profile of aortic contractions in relationship to the percent change in amplitude elicited by 10V (n = 4).
Mentions: To consistently induce single contractions of the aorta, we employed frequencies of 1.7 Hz (to approximate a heart rate of 100 beats/min) and 5 Hz (to approximate a heart rate of 300 beats/min). These stimulation rates did not change the basal tone of the aorta. Fig 2 illustrates a stimulation-response curve that was derived using a 5 Hz frequency with varying voltages (0.25V-10V). The typical profile of electrically-evoked neurally mediated contraction had a relatively fast rise-time and recovery compared to that reported for direct muscle-stimulated vascular contraction [12]. For our studies, to assess the effect of drugs on stimulation-induced contractions, we utilized the 10V stimulation strength because it elicited repeatable aortic contractions of similar amplitudes. Fig 2: Effect of varying stimulation voltage on magnitude of the contractile response of the aorta.

Bottom Line: In response to pulsatile pressure changes, the vessels undergo a 'passive' elastic dilatation-contraction cycle, described as a "Windkessel" effect.However, Mangel and colleagues have presented evidence that is contrary to this view.Electrical stimulation of the aorta evoked contractions that occur at a rate that is in the range of the animal's heartbeat and are suppressed by tetrodotoxin and the alpha-adrenergic receptor blocker, phentolamine.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology & Physiology, Georgetown University School of Medicine, 3900 Reservoir Road, NW, Washington, DC, 20007, United States of America.

ABSTRACT
For over a century, the behavior of the aorta and other large arteries has been described as passive elastic tubes in which no active contraction occurs in the smooth muscle wall. In response to pulsatile pressure changes, the vessels undergo a 'passive' elastic dilatation-contraction cycle, described as a "Windkessel" effect. However, Mangel and colleagues have presented evidence that is contrary to this view. They reported that in the rabbit, the aorta undergoes rhythmic 'active' (contraction) during the cardiac cycle; but these findings have been largely ignored. In the present study, we observed spontaneous contractions in synchrony with the heartbeat in another species (rat). In addition we demonstrate that aorta contractions are of neurogenic origin. Electrical stimulation of the aorta evoked contractions that occur at a rate that is in the range of the animal's heartbeat and are suppressed by tetrodotoxin and the alpha-adrenergic receptor blocker, phentolamine. Altogether, these findings indicate that aortic contractions are under neural control from the heart.

No MeSH data available.


Related in: MedlinePlus