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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

Schematic illustration of the set-up performing electrical stimulation of the aorta.To elicit aortic contractions, the aorta was directly stimulated with a 5s pulse train at different frequencies (pulse width, 2ms) at a 4 min inter-stimulus train using a constant voltage generator. Once two stable series of contractions were obtained at the same frequency, the aorta was exposed to different drugs by direct application into the thoracic cavity in 1ml increments. That is, an additional 1 ml of drug solution was added to the thoracic cavity. The volume of mineral oil and/or Tyrode's solution placed in the cavity was approximately 5–7 ml. This was followed by a series of stimulations over 5 s that were spread 4 min apart.
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pone.0130255.g001: Schematic illustration of the set-up performing electrical stimulation of the aorta.To elicit aortic contractions, the aorta was directly stimulated with a 5s pulse train at different frequencies (pulse width, 2ms) at a 4 min inter-stimulus train using a constant voltage generator. Once two stable series of contractions were obtained at the same frequency, the aorta was exposed to different drugs by direct application into the thoracic cavity in 1ml increments. That is, an additional 1 ml of drug solution was added to the thoracic cavity. The volume of mineral oil and/or Tyrode's solution placed in the cavity was approximately 5–7 ml. This was followed by a series of stimulations over 5 s that were spread 4 min apart.

Mentions: Proximal to the second ligature placed at the distal end of the aorta (approximately 2cm from the heart), a small incision was made in the aorta, which was cannulated with a 16 gauge gavage needle attached to a silicone tubing. After cannulation, a hooked bipolar electrode was positioned underneath the aorta proximal to the gavage needle. The aorta was then inflated with warm Tyrode’s solution to produce a baseline pressure of 0.8–1.6 kPa (6–12 mmHg), measured by a pressure transducer (sensitivity 5μV/V/mmHg; low pass filter set at 100Hz), which was coupled to a computerized data acquisition system (PowerLab AD Instruments, Colorado Springs, Co.). The thoracic cavity was then filled with warm (approximately 37°C) mineral oil or Tyrode's solution (pH 7.4; 300 mOsm) with the following composition (in mM): 121 NaCl, 2.5 KCl, 26 NaHCO3, 1.25 NaH2PO4, 2 CaCl2, 1 MgCl2, 5 HEPES and 10 glucose. The ECG was recorded as described above. Fig 1 illustrates the rat preparation used for recording aortic contractions.


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)

Schematic illustration of the set-up performing electrical stimulation of the aorta.To elicit aortic contractions, the aorta was directly stimulated with a 5s pulse train at different frequencies (pulse width, 2ms) at a 4 min inter-stimulus train using a constant voltage generator. Once two stable series of contractions were obtained at the same frequency, the aorta was exposed to different drugs by direct application into the thoracic cavity in 1ml increments. That is, an additional 1 ml of drug solution was added to the thoracic cavity. The volume of mineral oil and/or Tyrode's solution placed in the cavity was approximately 5–7 ml. This was followed by a series of stimulations over 5 s that were spread 4 min apart.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0130255.g001: Schematic illustration of the set-up performing electrical stimulation of the aorta.To elicit aortic contractions, the aorta was directly stimulated with a 5s pulse train at different frequencies (pulse width, 2ms) at a 4 min inter-stimulus train using a constant voltage generator. Once two stable series of contractions were obtained at the same frequency, the aorta was exposed to different drugs by direct application into the thoracic cavity in 1ml increments. That is, an additional 1 ml of drug solution was added to the thoracic cavity. The volume of mineral oil and/or Tyrode's solution placed in the cavity was approximately 5–7 ml. This was followed by a series of stimulations over 5 s that were spread 4 min apart.
Mentions: Proximal to the second ligature placed at the distal end of the aorta (approximately 2cm from the heart), a small incision was made in the aorta, which was cannulated with a 16 gauge gavage needle attached to a silicone tubing. After cannulation, a hooked bipolar electrode was positioned underneath the aorta proximal to the gavage needle. The aorta was then inflated with warm Tyrode’s solution to produce a baseline pressure of 0.8–1.6 kPa (6–12 mmHg), measured by a pressure transducer (sensitivity 5μV/V/mmHg; low pass filter set at 100Hz), which was coupled to a computerized data acquisition system (PowerLab AD Instruments, Colorado Springs, Co.). The thoracic cavity was then filled with warm (approximately 37°C) mineral oil or Tyrode's solution (pH 7.4; 300 mOsm) with the following composition (in mM): 121 NaCl, 2.5 KCl, 26 NaHCO3, 1.25 NaH2PO4, 2 CaCl2, 1 MgCl2, 5 HEPES and 10 glucose. The ECG was recorded as described above. Fig 1 illustrates the rat preparation used for recording aortic contractions.

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