Vestibulosympathetic reflex during the early follicular and mid‐luteal phases of the menstrual cycle

Abstract

The influence of the menstrual cycle on the vestibulosympathetic reflex is unknown. We examined muscle sympathetic nerve activity (MSNA), mean arterial pressure (MAP), and heart rate responses to head‐down rotation (HDR) in 10 healthy females during the early follicular (EF) and mid‐luteal (ML) phases of the menstrual cycle. The menstrual cycle had no effect on resting MSNA, MAP, and heart rate (EF: 13±3 bursts/min, 81±3 mmHg, 65±2 beats/min versus ML: 14+3 bursts/min, 83±3 mmHg, 64±3 beats/min). During the EF phase, HDR increased MSNA (Δ3±1 bursts/min; P<0.05), but did not change MAP or heart rate (Δ0±1 mmHg and Δ1±1 beats/min). During the ML phase, HDR increased both MSNA and MAP (Δ4±1 bursts/min and Δ3±1 mmHg; P<0.05) with no change in heart rate (Δ0±1 beats/min). MSNA and heart rate responses to HDR were not different between the EF and ML phases, but MAP responses to HDR were augmented during the ML phase (Interaction, P=0.029). Our results demonstrate that the menstrual cycle does not influence the vestibulosympathetic reflex, but appears to alter MAP responses to HDR during the ML phase. The augmented arterial blood pressure during the ML phase of the menstrual cycle may be due to increased sympathetic transduction to the vascular smooth muscle. Supported by REF‐060605.