Evaluation of the sequence method as a tool to assess spontaneous baroreflex in reptiles

Filogonio, Renato; Orsolini, Karina F.; Castro, Samanta Aparecida; Oda, Gustavo M.; Rocha, Gabriella Campos; Tavares, Driele; Abe, Augusto Shinya; Leite, Cléo A. C.

doi:10.1002/jez.2273

Cited by 11 publications

(27 citation statements)

References 39 publications

(61 reference statements)

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“…We utilized the sequence method to assesses the baroreflex at the operating point (G op ) based on the average of the slopes from spontaneous baroreflex sequences (i.e. minimum of three cardiac cycles displaying sequential increases or decreases in P s followed by concomitant modulation of PI [27,28,36]). Baroreflex gain obtained was then normalized for P m and PI to allow for meaningful comparisons between temperatures [37,38]:…”

Section: Discussionmentioning

confidence: 99%

“…Baroreflex effectiveness index (BEI) was calculated as a ratio between the number of baroreflex sequences and the total number of ramps, which comprise both baroreflex and non-baroreflex sequences [27,28]:…”

Section: Discussionmentioning

confidence: 99%

“…Before surgical procedures, lizards were sedated with elevated levels of CO 2 until complete loss of righting reflexes [28,[30][31][32][33]. Individuals underwent tracheal intubation and were mechanically ventilated with isoflurane (2-5%; 5 breaths × min -1 ; tidal volume of 30 ml × kg -1 ; SAR-830/P Ventilator) throughout the entire surgical procedure.…”

Section: Instrumentationmentioning

confidence: 99%

“…These calculations were performed with CardioSeries software (v2.4, www.danielpenteado. com) utilizing a minimum of 300 cardiac cycles and delay 1 [28].…”

Section: Bei ¼ Number Of Baroreflex Sequences Total Number Of Ramps ð2þmentioning

confidence: 99%

“…gain at the point of the baroreflex sigmoidal curve correspondent to the P m operating point [26]) and baroreflex effectiveness index (BEI; i.e. the capacity of the baroreflex to overcome concomitant stimuli modulating f H [27,28]) to investigate the responses of the cardiac branch. Since longer PI at lower T b enables pressure to decay…”

Section: Introductionmentioning

confidence: 99%

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Baroreflex gain and time of pressure decay at different body temperatures in the tegu lizard, Salvator merianae

et al. 2020

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Ectotherms may experience large body temperature (Tb) variations. Higher Tb have been reported to increase baroreflex sensitivity in ectotherm tetrapods. At lower Tb, pulse interval (PI) increases and diastolic pressure decays for longer, possibly resulting in lower end-diastolic pressures and mean arterial pressures (Pm). Additionally, compensatory baroreflex-related heart rate modulation (i.e. the cardiac branch of the baroreflex response) is delayed due to increased PI. Thus, low Tb is potentially detrimental, leading to cardiovascular malfunctioning. This raises the question on how Pm is regulated in such an adverse condition. We investigated the baroreflex compensations that enables tegu lizards, Salvator merianae, to maintain blood pressure homeostasis in a wide Tb range. Lizards had their femoral artery cannulated and pressure signals recorded at 15°C, 25°C and 35°C. We used the sequence method to analyse the heart rate baroreflex-related corrections to spontaneous pressure fluctuations at each temperature. Vascular adjustments (i.e. the peripheral branch) were assessed by calculating the time constant for arterial pressure decay (τ)—resultant from the action of both vascular resistance and compliance—by fitting the diastolic pressure descent to the two-element Windkessel equation. We observed that at lower Tb, lizards increased baroreflex gain at the operating point (Gop) and τ, indicating that the diastolic pressure decays at a slower rate. Gop normalized to Pm and PI, as well as the ratio τ/PI, did not change, indicating that both baroreflex gain and rate of pressure decay are adjusted according to PI lengthening. Consequently, pressure parameters and the oscillatory power fraction (an index of wasted cardiac energy) were unaltered by Tb, indicating that both Gop and τ modulation are crucial for cardiovascular homeostasis.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Instrumentationmentioning

confidence: 99%

“…These calculations were performed with CardioSeries software (v2.4, www.danielpenteado. com) utilizing a minimum of 300 cardiac cycles and delay 1 [28].…”

Section: Bei ¼ Number Of Baroreflex Sequences Total Number Of Ramps ð2þmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Baroreflex gain and time of pressure decay at different body temperatures in the tegu lizard, Salvator merianae

et al. 2020

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The nonpharmacological sequence method provides a reliable evaluation of baroreflex sensitivity in fish

et al. 2021

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The most commonly used technique to study the barostatic regulation of blood pressure in ectothermic vertebrates consists of determining the heart rate response to pharmacological manipulations of blood pressure, the so‐called “Oxford method.” Although well established, the Oxford method has some important limitations, such as induction of hypervolemia in small animals and undesired effects of vasoactive drugs on central and peripheral baroreflex components. As an alternative, the sequence method, which consists in the computerized evaluation of naturally‐occurring baroreflex adjustments of heart rate without the need for pharmacological administrations, was developed to study baroreflexes. In the present study, we compare this sequence method with the Oxford technique in two teleost species with different life styles, and we assess the optimal software configuration for the employment of the sequence method in fish. Calculation of baroreflex gain through the sequence method was adequate and reliable when the software was configured to search for baroreflex sequences with a minimum length of three cardiac cycles with a delay of one cardiac cycle between fluctuations in mean ventral aortic blood pressure and reflex changes in pulse interval. When properly configured, the sequence and the Oxford methods yielded similar determinations of the baroreflex gain in fish.

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A comparison of four common mathematical models to assess baroreflex sensitivity

Filogonio

Leite

2023

J Exp Zool Pt A

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Different methods have been used to assess baroreflex gain in experiments where changes in the carotid sinus pressure or the arterial blood pressure using different techniques provoke a baroreflex response, usually a rapid variation of heart rate. Four mathematical models are most used in the literature: the linear regression, the piecewise regression, and two different four‐parameter logistic equations: equation 1, Y = (A1–D1)/[1 + eB1(X – C1)] + D1; equation 2, Y = (A2–D2)/[1 + (X/C2)B2] + D2. We compared the four models regarding the best fit to previously published data in all vertebrate classes. The linear regression had the worst fit in all cases. The piecewise regression generally exhibited a better fit than the linear regression, though it returned a similar fit when no breakpoints were found. The logistic equations showed the best fit among the tested models and were similar to each other. We demonstrate that equation 2 is asymmetric and the level of asymmetry is accentuated according to B2. This means that the baroreflex gain calculated when X = C2 is different from the actual maximum gain. Alternatively, the symmetric equation 1 returns the maximum gain when X = C1. Furthermore, the calculation of baroreflex gain using equation 2 disregards that baroreceptors may reset when individuals experience different mean arterial pressures. Finally, the asymmetry from equation 2 is a mathematical artifact inherently skewed to the left of C2, thus bearing no biological meaning. Therefore, we suggest that equation 1 should be used instead of equation 2.

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Evaluation of the sequence method as a tool to assess spontaneous baroreflex in reptiles

Cited by 11 publications

References 39 publications

Baroreflex gain and time of pressure decay at different body temperatures in the tegu lizard, Salvator merianae

Baroreflex gain and time of pressure decay at different body temperatures in the tegu lizard, Salvator merianae

The nonpharmacological sequence method provides a reliable evaluation of baroreflex sensitivity in fish

A comparison of four common mathematical models to assess baroreflex sensitivity

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