title: Menstrual cycle and sex effects on sympathetic responses to acute chemoreflex stress.
abstract: This study aimed to examine the effects of sex (males vs. females) and sex hormones (menstrual cycle phases in women) on sympathetic responsiveness to severe chemoreflex activation in young, healthy individuals. Muscle sympathetic nerve activity (MSNA) was measured at baseline and during rebreathing followed by a maximal end-inspiratory apnea. In women, baseline MSNA was greater in the midluteal (ML) than early-follicular (EF) phase of the menstrual cycle. Baseline MSNA burst incidence was greater in men than women, while burst frequency and total MSNA were similar between men and women only in the ML phase. Chemoreflex activation evoked graded increases in MSNA burst frequency, amplitude, and total activity in all participants. In women, this sympathoexcitation was greater in the EF than ML phase. The sympathoexcitatory response to chemoreflex stimulation of the EF phase in women was also greater than in men. Nonetheless, changes in total peripheral resistance were similar between sexes and menstrual cycle phases. This indicates that neurovascular transduction was attenuated during the EF phase during chemoreflex activation, thereby offsetting the exaggerated sympathoexcitation. Chemoreflex-induced increases in mean arterial pressure were similar across sexes and menstrual cycle phases. During acute chemoreflex stimulation, reduced neurovascular transduction could provide a mechanism by which apnea-associated morbidity might be attenuated in women relative to men.
authors.affiliation: Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada;
authors.forename: Charlotte W
authors.initials: CW
authors.lastname: Usselman
authors.affiliation: Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada;
authors.forename: Tamara I
authors.initials: TI
authors.lastname: Gimon
authors.affiliation: Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada;
authors.forename: Chantelle A
authors.initials: CA
authors.lastname: Nielson
authors.affiliation: Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada;
authors.forename: Torri A
authors.initials: TA
authors.lastname: Luchyshyn
authors.affiliation: Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada;
authors.forename: Nicole S
authors.initials: NS
authors.lastname: Coverdale
authors.affiliation: Department of Medicine, Western University, London, Ontario, Canada; Lawson Health Research Institute, Western University, London, Ontario, Canada; and.
authors.forename: Stan H M
authors.initials: SH
authors.lastname: Van Uum
authors.affiliation: Neurovascular Research Laboratory, School of Kinesiology, Western University, London, Ontario, Canada; Department of Physiology and Pharmacology, Western University, London, Ontario, Canada kshoemak@uwo.ca.
authors.forename: J Kevin
authors.initials: JK
authors.lastname: Shoemaker
mesh_terms: D000200:Action Potentials; D000328:Adult; D015415:Biomarkers / Q000097:blood; D002628:Chemoreceptor Cells / Q000378:metabolism*; D005260:Female; D006439:Hemodynamics; D006801:Humans; D006935:Hypercapnia / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D000860:Hypoxia / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008597:Menstrual Cycle / Q000097:blood / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000294:innervation*; D012018:Reflex; D012737:Sex Factors; D013312:Stress, Physiological; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers
keywords: hypercapnia; hypoxia; menstrual cycle; muscle sympathetic nerve activity; sex differences