PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Hormone levels in women using contraception affect nerve activity involved in vessel constriction

2013-11-07
(Press-News.org) Contact information: Donna Krupa
dkrupa@the-aps.org
American Physiological Society
Hormone levels in women using contraception affect nerve activity involved in vessel constriction Bethesda, Md. (Nov. 6, 2013)—After menopause, women's levels of estrogen and progesterone fall. Their formerly lower risk for heart disease equals, even surpasses, men's risk. One possible contributing explanation for the change in risk is that sex hormones affect the sympathetic nervous system (SNS), which controls constriction of blood vessels and participates in the fight or flight response.

A new study by researchers at Western Ontario University is among the first to look at the hormone/SNS relationship in young women taking hormone contraceptives. It is the first to observe differences in the frequency of firings of the SNS neurons between high and low hormone phases of the menstrual cycle. It is also the first to examine how the SNS responds to chemoreflex stress (in this study, several moments of rebreathing oxygen-depleted air, then a breath held as long as possible). The study also examined the rarely studied strength of nerve firings, called burst amplitude. Using this unique approach, results that had been ambiguous or conflicting in other studies became clearer. The findings also provide new insight into mechanisms through which lower hormone levels may make the body more susceptible to damage caused by stress and the chronic elevation of the fight or flight response. A pattern consistent with these findings is observed in postmenopausal women.

The article is entitled "Hormone phase-dependency of neural responses to chemoreflex-drive sympatho-excitation in young women using hormonal contraceptives." It appears in the online edition of the Journal of Applied Physiology, published by the American Physiological Society. The article is available online at http://bit.ly/18ZvwPI.

Methodology

Study participants were 10 women between the ages of 22 and 26 (average age 24). All were healthy nonsmokers of normal weight, who exercised regularly. All were taking some form of hormone contraception. The women were studied once during the first four days of menses (low hormone phase) and again between day 20-24 (high hormone phase). For these studies, each woman was connected to an instrument that measures the amount of oxygen in the lungs. Lying down, each breathed normally through a special mouthpiece. After five minutes, a valve on the mouthpiece changed room air to that in a bag with air earlier expired by the woman. Rebreathing used air resulted in lower oxygen and higher carbon dioxide levels in the blood. This chemoreflex stressor maximized response of the SNS. When oxygen levels fell to a specific point, the woman was asked to hold her breath as long as she could. Throughout the breathing sequence, investigators also monitored heart rate, blood pressure, and cardiac output. Tiny needles inserted into a nerve in the woman's leg measured frequency and "bursts" of SNS activity.

Results

Hormone contraception affected the regulation of muscle sympathetic nerve activity differently, depending on sex hormone levels and on the presence and severity of chemoreflex stress.

When the women were at rest, they experienced more frequent nerve firings during phases of their cycle when their hormone levels were highest. There was no difference in the amplitude (the scientific term for magnitude or size) of neural bursts between high and low hormone phases. During episodes of stress, however, the women experienced greater increases in the number and amplitude of nerve bursts when their hormone levels were lowest. The more severe and long-lasting the stress was, the higher the amplitude was.

Importance of the Findings

The study findings show that the SNS uses different methods to control blood flow to the muscles. Depending on hormone levels and stress, the SNS alters the frequency and amplitude of nerve firings. The effect of these alterations helps explain how higher hormone levels in younger, premenopausal women protect against damage to the cardiovascular system through greater ability to control the SNS. The findings also suggest how stress can elevate the SNS in ways that, in the presence of lower hormones, may make the cardiovascular system more susceptible to the damage caused by chronic elevation of the fight or flight response. A pattern consistent with these findings is observed in postmenopausal women, where chronically low hormone levels are associated with increases in cardiovascular disease.

This more precise understanding about the relationship of hormones and the SNS also helps explain the mystery of why, as is known, males and females have different SNS responses while at rest and different responses to stress.

Study Team

First author is Charlotte W. Usselman, a doctoral student of Kevin Shoemaker, School of Kinesiology, and Department of Physiology and Pharmacology, Western University, London, Ontario. Dr. Shoemaker's Neurovascular Research Laboratory explores the pathways in the brain associated with recruitment of sympathetic nerve activity and the physiological effects of these different pathways. The study team also includes Torri A. Luchyshyn and Chantelle A. Nielson, both master degree students; undergraduate Tamara I. Gimon; and endocrinologist Stan H M. Van Uum, Department of Medicine, Western University.

INFORMATION:

Physiology is the study of how molecules, cells, tissues, and organs function in health and disease. Established in 1887, the American Physiological Society (APS) was the first US society in the biomedical sciences field. The Society represents more than 11,000 members and publishes 14 peer-reviewed journals with a worldwide readership.

NOTE TO EDITORS: To schedule an interview with a member of the research team, please contact Donna Krupa at dkrupa@the-aps.org, @Phyziochick, or 301.634.7209. The article is available online at http://bit.ly/18ZvwPI.

END



ELSE PRESS RELEASES FROM THIS DATE:

'Please feed me': The power of putting a human face on social causes

2013-11-07
'Please feed me': The power of putting a human face on social causes Companies often put a personal face on products in an attempt to reach a deeper connection with consumers. New research suggests the same idea can be applied to social ...

CWRU study finds mending ruptures in client-therapist relationship has positive benefits

2013-11-07
CWRU study finds mending ruptures in client-therapist relationship has positive benefits In order for prolonged exposure therapy, an evidence-based psychotherapy for post traumatic stress disorder (PTSD), to reach its full potential, any misperceptions ...

Mothers' relationships can influence adolescent children's relationships, MU study finds

2013-11-07
Mothers' relationships can influence adolescent children's relationships, MU study finds COLUMBIA, Mo. – Until now, little research has been conducted on the association between parents' friendships and the emotional well-being of their adolescent ...

UC's SmartLight more than a bright idea, it's a revolution in interior lighting ready to shine

2013-11-07
UC's SmartLight more than a bright idea, it's a revolution in interior lighting ready to shine The innovative solar technology 'would change the equation for energy,' according to UC researchers A pair of University of Cincinnati researchers has seen the light ...

Georgia Tech warns of threats to cloud data storage, mobile devices in latest 'emerging cyber threat'

2013-11-07
Georgia Tech warns of threats to cloud data storage, mobile devices in latest 'emerging cyber threat' As more businesses find their way into the cloud, few engage in security measures beyond those provided by the associated cloud storage firm, a new report ...

From 1 collapsing star, 2 black holes form and fuse

2013-11-07
From 1 collapsing star, 2 black holes form and fuse Black holes—massive objects in space with gravitational forces so strong that not even light can escape them—come in a variety of sizes. On the smaller end of the scale are the stellar-mass black holes that ...

Addicts may be seeking relief from emotional lows more than euphoric highs

2013-11-07
Addicts may be seeking relief from emotional lows more than euphoric highs Rutgers study could lead to a better understanding of human addiction -- alcohol, tobacco and food -- as well as substance abuse Cocaine addicts may become trapped in drug binges – not because of the euphoric ...

Early childhood educators hold the key to children's communication skills

2013-11-07
Early childhood educators hold the key to children's communication skills High-quality interactions between children and adults foster growth Researchers at UNC's Frank Porter Graham Child Development Institute have completed ...

US media consumption to rise to 15.5 hours a day -- per person -- by 2015

2013-11-07
US media consumption to rise to 15.5 hours a day -- per person -- by 2015 New study issued by SDSC researcher with USC Marshall School of Business A new study by a researcher at the San Diego Supercomputer Center (SDSC) at the University of California, San ...

Movin' on out

2013-11-07
Movin' on out Support of parents and peers vital for millennials leaving home: New study from Concordia University This news release is available in French. Montreal, November 6, 2013 — Leaving home is an important milestone that signals entry into ...

LAST 30 PRESS RELEASES:

MSU team develops scalable climate solutions for agricultural carbon markets

Playing an instrument may protect against cognitive aging

UNM study finds link between Grand Canyon landslide and Meteor Crater impact

Ultra-hot Jupiter’s death spiral could reveal stellar secrets

You only get one brain! The best helmet material for protecting your noggin

Neurodegeneration and stroke after GLP-1RAs in diabetes and obesity

Pediatric COVID-19 hospitalization trends by race and ethnicity, 2020-2023

Research spotlight: New genetic roadmap offers insights into obesity and diabetes

Fred Hutch leads new Vanguard Study for Cancer Screening Research Network

‘Mismatched’ transplants now safe, effective for blood cancer patients, study finds

New research helps narrow down uncertainties in near-term precipitation projections for the Asian Water Tower

AI tool accurately detects tumor location on breast MRI

Researchers use OCT imaging to uncover how the fallopian tube transports embryos

PolyU secures RGC theme-based research scheme funding to develop cost-effective and sustainable Co-GenAI model

Van Andel Institute scientists develop technique for high-resolution single cell epigenetic analysis

The Lundquist Institute wins multi-year NIH grant exceeding $11 million to transform diagnosis and treatment of deadly mucormycosis

Review suggests ending adult boosters for tetanus, diphtheria

ESMT Berlin welcomes Rebecca Schaumberg to faculty

Blocking a little-known protein may offer new hope for devastating lung disease

Medieval medicine was smarter than you think – and weirdly similar to TikTok trends

FAU receives NIH grant to investigate amphetamine addiction

Realizing on-site carbon nanotube photo-thermoelectric imaging

Most of us love memes. But are they a form of comics?

Novel biosensor allows real-time monitoring of sucrose uptake in plants

Korea University researchers reveal revealing how WEE1 drives cancer resistance to immunotherapy

Pusan National University researchers develop breakthrough deep learning model that enhances handheld 3D medical imaging

SLAS Discovery and SLAS Technology demonstrate research impact with 2024 impact factors

Disease-causing bacteria can deal with stink as long as they get a meal

Mapping the metabolism of blood stem cells

UK air quality improved since 2015 but targets still missed

[Press-News.org] Hormone levels in women using contraception affect nerve activity involved in vessel constriction