The effect of sex on sympathetic transduction during an acute pain stimulus

Previously, we have noted sex differences in beat-by-beat fluctuations in blood pressure following sequences of muscle sympathetic nerve activity (MSNA; i.e. sympathetic transduction) during acute sympatho-inhibition but not at rest. However, sex differences in sympathetic transduction during sympatho-excitation have yet to be examined. Therefore, we tested the hypothesis that sympathetic transduction during acute sympatho-excitation and recovery from sympatho-excitation are greater in men than women. We tested healthy women (n=5) and men (n=5) of similar age (26±4 vs 23±2y, respectively; P=0.3). Integrated MSNA (microneurography; NeuroAmp, ADInstruments) and beat-by-beat blood pressure (finger photoplethysmography; Finometer MIDI) were assessed during 10 minutes of supine rest, an acute pain stimulus (6-minute cold pressor test; CPT), and recovery (6-minutes). Custom software was used to calculate sympathetic transduction: beat-by-beat changes in mean arterial pressure (MAP) were tracked for 15 subsequent cardiac cycles (expressed relative to the cardiac cycle associated with the final burst or non-burst in the sequence). Like sequences were overlaid and averaged. Prevailing MSNA and MAP were not different between women and men at rest (9±8 vs 8±5 bursts/min, P=0.8; 88±6 vs 97±6 mmHg, P=0.06) or during the CPT (21±10 vs 16±6 bursts/min, P=0.3; 98±5 vs 104±6 mmHg, P=0.1). However, during recovery, MSNA was greater in women than men (21±8 vs 10±4 bursts/min, P=0.03), despite similar MAP (95±5 vs 99±6 mmHg, P=0.3). Peak and nadir changes in sympathetic transduction following burst and non-burst sequences were not different between women and men at rest (burst: 1.55±0.46 vs 1.67±0.27mmHg, P=0.6; non-burst: -2.21±1.88 vs -2.26±0.36mmHg, P=0.9) or during the CPT (burst: 1.06±0.32 vs 0.45±0.47mmHg, P=0.08; non-burst: -3.24±1.44 vs 1.90±0.46mmHg, P=0.1). Sympathetic transduction following a burst of MSNA did not differ between the sexes during recovery (1.73±0.34 vs 1.65±0.23mmHg, P=0.7), while nadir decreases in MAP following non-burst sequences during recovery were more pronounced in women than men (-2.81±0.75 vs -1.56±0.91mmHg, P=0.04). Taken together, although sympathetic transduction did not differ between the sexes during the CPT, these data suggest that women may require heightened MSNA during recovery from acute stress to maintain equivalent blood pressure. This project was funded by McGill University, FRQS, and NSERC. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.