Physiological Society Symposium — Vagal Control: From Axolotl to Man

Wang, Tobias; Warburton, Stephen J.; Abe, Augusto Shinya; Taylor, Ted K.

doi:10.1111/j.1469-445x.2001.tb00044.x

Cited by 50 publications

(12 citation statements)

References 38 publications

(21 reference statements)

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“…However, in turtles, central vascular shunting is possible (Hicks et al, 1996), which would cause an air/ blood mismatch that would serve to alter gas uptake or removal even in the inflated lung (Farhi, 1967;Farhi and Yokoyama, 1967;West, 1962). Although pulmonary blood flow can be significantly reduced, and even abolished in freshwater turtles or rattlesnakes during diving and vagal stimulation (Milsom et al, 1977;Taylor et al, 2009;Wang, 2011;Wang et al, 2001), the well-developed sphincter appears unique to sea turtles and allows for complete pulmonary bypass solely by regulation of the tone on the extrinsic portion of the pulmonary artery. The PASp in particular, and also the LP, contracts under parasympathetic tone.…”

Section: Discussionmentioning

confidence: 99%

“…The undivided chelonian heart provides for intracardiac shunts, and it is well established that pulmonary blood flow is reduced during diving, causing R-L shunts, while pulmonary flow increases during intermittent ventilation, where a L-R shunt may dominate (Burggren, 1977;Shelton and Burggren, 1976;Wang et al, 1997Wang et al, , 2001). The changes in pulmonary blood flow are mediated by the parasympathetic innervation, where increased tone elevates pulmonary vascular resistance through vagal innervation of the smooth muscle within the wall of the pulmonary artery (Burggren, 1977;Hicks, 1998;Shelton and Burggren, 1976;Wang et al, 1997Wang et al, , 2001. Our observation that the pulmonary vessels from sea turtles exhibit intense vasoconstriction when exposed to 5HT and ACh suggests that the PASp is an important anatomical vasomotor structure driving the cardiac shunt in sea turtles.…”

Section: Discussionmentioning

confidence: 99%

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Deciphering function of the pulmonary arterial sphincters in loggerhead sea turtles (Caretta caretta)

García-Párraga

Lorenzo

Wang

et al. 2018

Journal of Experimental Biology

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To provide new insight into the pathophysiological mechanisms underlying gas emboli (GE) in bycaught loggerhead sea turtles (Caretta caretta), we investigated the vasoactive characteristics of the pulmonary and systemic arteries, and the lung parenchyma (LP). Tissues were opportunistically excised from recently dead animals for in vitro studies of vasoactive responses to four different neurotransmitters: acetylcholine (ACh; parasympathetic), serotonin (5HT), adrenaline (Adr; sympathetic) and histamine. The significant amount of smooth muscle in the LP contracted in response to ACh, Adr and histamine. The intrapulmonary and systemic arteries contracted under both parasympathetic and sympathetic stimulation and when exposed to 5HT. However, proximal extrapulmonary arterial (PEPA) sections contracted in response to ACh and 5HT, whereas Adr caused relaxation. In sea turtles, the relaxation in the pulmonary artery was particularly pronounced at the level of the pulmonary artery sphincter (PASp), where the vessel wall was highly muscular. For comparison, we also studied tissue response in freshwater sliders turtles (Trachemys scripta elegans). Both PEPA and LP from freshwater sliders contracted in response to 5HT, ACh and also Adr. We propose that in sea turtles, the dive response (parasympathetic tone) constricts the PEPA, LP and PASp, causing a pulmonary shunt and limiting gas uptake at depth, which reduces the risk of GE during long and deep dives. Elevated sympathetic tone caused by forced submersion during entanglement with fishing gear increases the pulmonary blood flow causing an increase in N 2 uptake, potentially leading to the formation of blood and tissue GE at the surface. These findings provide potential physiological and anatomical explanations on how these animals have evolved a cardiac shunt pattern that regulates gas exchange during deep and prolonged diving.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Deciphering function of the pulmonary arterial sphincters in loggerhead sea turtles (Caretta caretta)

García-Párraga

Lorenzo

Wang

et al. 2018

Journal of Experimental Biology

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“…2 atria and 1 ventricle, which allows some intraventricular mixing of systemic and pulmonary blood flow (Shelton & Burggren 1976, Wang et al 2001. All sea turtles also have vascular adaptations for shunting during diving, including muscular sphincters within the pulmonary arteries and an anastomosis between the left and right aorta (White 1976, Wyneken et al 2013.…”

Section: Hypothetical Patho-physiological Mechanismmentioning

confidence: 99%

“…Additionally, heart rate and pulmonary blood flow in turtles often increase immediately before breathing starts, which is suggestive of central mechanisms based on elevated sympathetic tone. This effect could also be induced by catecholamine release during the fight-or-flight response resulting from capture (White & Ross 1966, Shelton & Burggren 1976, West et al 1992, Wang et al 2001.…”

Section: Hypothetical Patho-physiological Mechanismmentioning

confidence: 99%

“…Although speculative, the shunting ability in diving reptiles may not only represent a mechanism for regulating metabolism through modulation of oxygen supply to the tissue , Wang et al 1997, 2001), but also could minimize nitrogen solubility in blood and subsequent risk of DCS. Sea turtles and sea snakes have the highest shunting capabilities (White 1976, Lillywhite & Donald 1989, Wyneken 2009.…”

Section: Hypothetical Patho-physiological Mechanismmentioning

confidence: 99%

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Decompression sickness (‘the bends’) in sea turtles

García-Párraga¹,

Crespo-Picazo²,

Quirós³

et al. 2014

Dis. Aquat. Org.

106

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Distribution and innervation of putative peripheral arterial chemoreceptors in the red‐eared slider (Trachemys scripta elegans)

Reyes

Fong

Milsom

2015

J of Comparative Neurology

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Peripheral arterial chemoreceptors have been isolated to the common carotid artery, aorta, and pulmonary artery of turtles. However, the putative neurotransmitters associated with these chemoreceptors have not yet been described. The goal of the present study was to determine the neurochemical content, innervations, and distribution of putative oxygen-sensing cells in the central vasculature of turtles and to derive homologies with peripheral arterial chemoreceptors of other vertebrates. We used tract tracing together with immunohistochemical markers for cholinergic cells (vesicular acetylcholine transporter [VAChT]), tyrosine hydroxylase (TH; the rate-limiting enzyme in catecholamine synthesis), and serotonin (5HT) to identify putative oxygen-sensing cells and to determine their anatomical relation to branches of the vagus nerve (Xth cranial nerve). We found potential oxygen-sensing cells in all three chemosensory areas innervated by branches of the Xth cranial nerve. Cells containing either 5HT or VAChT were found in all three sites. The morphology and size of these cells resemble glomus cells found in amphibians, mammals, tortoises, and lizards. Furthermore, we found populations of cholinergic cells located at the base of the aorta and pulmonary artery that are likely involved in efferent regulation of vessel resistance. Catecholamine-containing cells were not found in any of the putative chemosensitive areas. The presence of 5HT- and VAChT-immunoreactive cells in segments of the common carotid artery, aorta, and pulmonary artery appears to reflect a transition between cells containing the major neurotransmitters seen in fish (5HT) and mammals (ACh and adenosine).

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Physiological Society Symposium — Vagal Control: From Axolotl to Man

Cited by 50 publications

References 38 publications

Deciphering function of the pulmonary arterial sphincters in loggerhead sea turtles (Caretta caretta)

Deciphering function of the pulmonary arterial sphincters in loggerhead sea turtles (Caretta caretta)

Decompression sickness (‘the bends’) in sea turtles

Distribution and innervation of putative peripheral arterial chemoreceptors in the red‐eared slider (Trachemys scripta elegans)

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