High-hormone phase of contraceptive use increased baseline MSNA burst incidence (P=0.03) and frequency (P=0.02), but responses to severe chemoreflex stimulation were greater in the low-hormone phase.
Observational (n=7)
Does the high-hormone phase of contraceptive use alter muscle sympathetic nerve activity at rest and during chemoreflex stimulation compared to the low-hormone phase in healthy young women?
Hormonal contraceptive phase influences sympathetic nerve activity, with higher baseline activity in the high-hormone phase but greater sympathetic responses to severe chemoreflex stimulation in the low-hormone phase.
p-value: p=0.03
Hormone fluctuations in women may influence muscle sympathetic nerve activity (MSNA) in a manner dependent on the severity of the sympathoexcitatory stimulus. This study examined MSNA patterns at rest and during chemoreflex stimulation in low- (LH) vs. high-hormone (HH) phases of contraceptive use in healthy young women (n = 7). We tested the hypothesis that MSNA would be greater in the HH phase at baseline and in response to chemoreflex stimulation. MSNA recordings were obtained through microneurography in LH and HH at baseline, during rebreathing causing progressive hypoxia and hypercapnia, and during a hypercapnic-hypoxic end-inspiratory apnea. Baseline MSNA burst incidence (P = 0.03) and burst frequency (P = 0.02) were greater in the HH phase, while MSNA burst amplitude distributions and hemodynamic measures were similar between phases. Rebreathing elicited increases in all MSNA characteristics from baseline (P < 0.05), but was not associated with hormone phase-dependent changes to MSNA patterns. Apnea data were considered in two halves, both of which caused large increases in all MSNA variables from baseline in each hormone phase (P < 0.01). Increases in burst incidence and frequency were greater in LH during the first half of the apnea (P = 0.03 and P = 0.02, respectively), while increases in burst amplitude and total MSNA were greater in LH during the second half of the apnea (P < 0.05). These results indicate that change in hormone phase brought on through use of hormonal contraceptives influences MSNA patterns such that baseline MSNA is greater in the HH phase, but responses to severe chemoreflex stimulation are greater in the LH phase.
Usselman et al. (Fri,) conducted a observational in Healthy young women using hormonal contraceptives (n=7). High-hormone phase of contraceptive use vs. Low-hormone phase was evaluated on Muscle sympathetic nerve activity (MSNA) burst incidence and frequency at baseline (p=0.03). High-hormone phase of contraceptive use increased baseline MSNA burst incidence (P=0.03) and frequency (P=0.02), but responses to severe chemoreflex stimulation were greater in the low-hormone phase.