Spontaneous baroreflex analysis
The sequence method was used to evaluate baroreflex function over the physiological range of fluctuations in arterial pressure without any pharmacological manipulation. For this purpose, the beat-to-beat values of systolic arterial pressure (SAP) and pulse interval (PI) were analysed using CardioSeries v2 software (Lataro, Silva, Silva, Salgado, & Fazan, 2017). The SAP time series were evaluated to find SAP elevations of 4 or more beats that were accompanied by a progressive increase in the R-R interval, which are called UP ramps. DOWN ramps are the opposite and consist of SAP reductions of four or more beats that are accompanied by a progressive decrease in the R-R interval. Spontaneous baroreflex activity was assessed based on the slope (ms/mmHg) of the linear regression between the SAP and PI for UP, DOWN and average (i.e., mean of UP and DOWN sequences) sequences (Di Rienzo et al., 2001). For this experiment, we used a correlation coefficient (r) greater than 0.80. The baroreflex effectiveness index (BEI) was also calculated as the ratio between the number of SAP ramps followed by the reflex PI response and the total number of SAP ramps (Di Rienzo et al., 2001).