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

Abstract

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.

On the accuracy of sequence methods for baroreflex sensitivity estimation

“…Spontaneous data, in this case, is considered spontaneous fluctuations in BP and HR, recorded while the subject is in standing and supine positions, without any external stimulus. The non-invasive methods developed range from spectral analysis methods [ 5 ] to autoregressive methods [ 6 ], and everything in between [ 7 – 9 ], with sequence methods emerging as a popular method [ 10 , 11 ].…”

A comparison of four common mathematical models to assess baroreflex sensitivity

“…Alternatively, another four‐parameter logistic equation originally proposed to analyze the logit( Y ) versus log( X ) nonlinear relationships in radioimmunoassays, immunoradiometric assays, and dose–response curves (DeLean et al, 1978; Rodbard, 1974) is often used to describe the f H responses to oscillations in arterial pressure (Altimiras et al, 1998; Armelin et al, 2021a, 2021b; Crossley et al, 2015; Filogonio et al, 2019; Hagensen et al, 2010; Reid, 1996; Tavares et al, 2022; Wong et al, 1993): $$$Y=\,\frac{A2-D2}{1+({X/C2)}^{B2}}+D2,$$$where A 2, B 2, C 2, and D 2 are analogous to A 1, B 1, C 1, and D 1, respectively (Figure 1b).…”

“…proposed to analyze the logit(Y) versus log(X) nonlinear relationships in radioimmunoassays, immunoradiometric assays, and dose-response curves (DeLean et al, 1978;Rodbard, 1974) is often used to describe the f H responses to oscillations in arterial pressure (Altimiras et al, 1998;Armelin et al, 2021aArmelin et al, , 2021bCrossley et al, 2015;Filogonio et al, 2019;Hagensen et al, 2010;Reid, 1996;Tavares et al, 2022;Wong et al, 1993):…”