Evidence that neurotensin mediates postprandial intestinal hyperemia in the python, Python regius

Self Cite

To accommodate the pronounced metabolic response to digestion, pythons increase heart rate and elevate stroke volume, where the latter has been ascribed to a massive and fast cardiac hypertrophy. However, numerous recent studies show that heart mass rarely increases, even upon ingestion of large meals, and we therefore explored the possibility that a rise in mean circulatory filling pressure (MCFP) serves to elevate venous pressure and cardiac filling during digestion. To this end, we measured blood flows and pressures in anaesthetized Python regius. The anaesthetized snakes exhibited the archetypal tachycardia as well as a rise in both venous pressure and MCFP that fully account for the approximate doubling of stroke volume. There was no rise in blood volume and the elevated MCFP must therefore stem from increased vascular tone, possibly by means of increased sympathetic tone on the veins. Furthermore, although both venous pressure and MCFP increased during volume loading, there was no evidence that postprandial hearts were endowed with an additional capacity to elevate stroke volume. In vitro measurements of force development of paced ventricular strips also failed to reveal signs of increased contractility, but the postprandial hearts had higher activities of cytochrome oxidase and pyruvate kinase, which probably serves to sustain the rise in cardiac work during digestion.

Section: Mean Circulatory Filling Pressure and Volume Loadingsupporting

confidence: 85%

Improved cardiac filling facilitates the postprandial elevation of stroke volume inPython regius

Enok

Leite

et al. 2016

Self Cite

“…As predicted, pythons experience a very large postprandial increase in intestinal blood flow, highlighted by an 11-fold increase in flow through the superior mesenteric artery (Secor and White, 2007). The Burmese python's postprandial intestinal hyperemia appears in part to be mediated (via vasodilatation) by the regulatory peptide neurotensin, whose plasma concentration increases 3.3-fold with feeding (Secor et al, 2001;Skovgaard et al, 2007).…”

Section: An Integrated Effortmentioning

confidence: 99%

Digestive physiology of the Burmese python: broad regulation of integrated performance

Secor

2008

119

132

SummaryAs an apparent adaptation to predictably long episodes of fasting, the sit-and-wait foraging Burmese python experiences unprecedented regulation of gastrointestinal and cardiovascular performance with feeding and fasting. The ingestion of a meal signals the quiescent gut tissues to start secreting digestive acid and enzymes, to upregulate intestinal brush-border enzymes and nutrient transporters, and to grow. An integrated phenomenon, digestion is also characterized by increases in the mass, and presumably the function, of the heart, pancreas, liver and kidneys. Once digestion is complete, the pythonʼs stomach and small intestine rapidly downregulate performance. Much of the modulation of intestinal function can be explained by the 5-fold increase in microvillus length and apical surface area with feeding, and the subsequent shortening of the microvilli after digestion has finished. Digestion for the Burmese python is a relatively expensive endeavor, evident by the as much as a 44-fold increase in metabolic rate and equivalent in cost to as much as 37% of the mealʼs energy. Their large metabolic response is supported by substantial increases in ventilation and cardiac output and the apparent catabolism of glucose and lipids. Unmatched in the magnitude of its numerous physiological responses to feeding, the Burmese python is a very attractive model for examining the capacities and regulatory mechanisms of physiological performance.

“…In support, chemical blockade of the cholinergic and adrenergic receptors revealed for crawling boa constrictors (Boa constrictor) that the increase in heart rate was accompanied by an increase adrenergic tone and decrease cholinergic tone (Wang et al, 2001). Interestingly for the boa constrictor and ball python (Python regius), elevated heart rate during digestion is associated with a decrease in both cholinergic and adrenergic cardiac tone, and for the ball python, a transitory increase in histaminergic tone (Wang et al, 2001;Skovgaard et al, 2007). If this is the case for the Burmese python, then their postprandial tachycardia is apparently triggered by a circulating non-adrenergic, non-cholinergic (NANC) factor being released elsewhere in the body (Wang et al, 2001).…”

Section: Mechanisms Underlying Gastrointestinal Hyperemiamentioning

confidence: 99%

“…Two pieces of evidence suggesting humoral modulation of gut blood flow originate from studies on the ball python, Python regius. First, histamine, possibly released by cardiac mast cells, temporarily stimulate the postprandial heart, and second an administration of neurotensin at physiological levels (1pmolkg -1 ) induces a 150% increase in superior mesenteric blood flow (Skovgaard et al, 2007;Skovgaard et al, 2009).…”

Section: Mechanisms Underlying Gastrointestinal Hyperemiamentioning

confidence: 99%

Prioritizing blood flow: cardiovascular performance in response to the competing demands of locomotion and digestion for the Burmese python,Python molurus

Secor

White

2010

SUMMARYIndividually, the metabolic demands of digestion or movement can be fully supported by elevations in cardiovascular performance, but when occurring simultaneously, vascular perfusion may have to be prioritized to either the gut or skeletal muscles. Burmese pythons (Python molurus) experience similar increases in metabolic rate during the digestion of a meal as they do while crawling, hence each would have an equal demand for vascular supply when these two actions are combined. To determine, for the Burmese python, whether blood flow is prioritized when snakes are digesting and moving, we examined changes in cardiac performance and blood flow in response to digestion, movement, and the combination of digestion and movement. We used perivascular blood flow probes to measure blood flow through the left carotid artery, dorsal aorta, superior mesenteric artery and hepatic portal vein, and to calculate cardiac output, heart rate and stroke volume. Fasted pythons while crawling experienced a 2.7-and 3.3-fold increase, respectively, in heart rate and cardiac output, and a 66% decrease in superior mesenteric flow. During the digestion of a rodent meal equaling in mass to 24.7% of the snake's body mass, heart rate and cardiac output increased by 3.3-and 4.4-fold, respectively. Digestion also resulted in respective 11.6-and 14.1-fold increases in superior mesenteric and hepatic portal flow. When crawling while digesting, cardiac output and dorsal aorta flow increased by only 21% and 9%, respectively, a modest increase compared with that when they start to crawl on an empty stomach. Crawling did triggered a significant reduction in blood flow to the digesting gut, decreasing superior mesenteric and hepatic portal flow by 81% and 47%, respectively. When faced with the dual demands of digestion and crawling, Burmese pythons prioritize blood flow, apparently diverting visceral supply to the axial muscles.