Sex Differences in Sympathetic Vascular Reactivity at High Altitude
NCT ID: NCT05525416
Last Updated: 2024-09-19
Study Results
The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.
Basic Information
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COMPLETED
NA
17 participants
INTERVENTIONAL
2022-07-28
2023-02-05
Brief Summary
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Detailed Description
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The main purpose of this study is to examine the differences between men and women in the sympathetic nervous system control of blood vessels during exposure to low oxygen. To study this question, the investigators will test how blood vessels respond to stressors in both men and women. Participants will be recruited at the Canadian sites, and the investigators will test them while they breathe low oxygen for a short amount of time at low altitude. The investigators will also perform assessments on the same participants during a two week stay at high altitude at White Mountain, CA, which is at an altitude of 3,800m. These data will have implications in the basic understanding of differences between male and female physiology. Specifically, to males and females living or travelling to high altitude.
Conditions
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Study Design
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NON_RANDOMIZED
CROSSOVER
BASIC_SCIENCE
NONE
Study Groups
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Low Altitude
Participants will be assessed at an altitude of \<1050m.
Sodium Nitroprusside
A bolus injection of sodium nitroprusside will be given to lower blood pressure and evaluate baroreflex function.
Phenylephrine Hydrochloride
A bolus injection of phenylephrine will be given to raise blood pressure and evaluate baroreflex function immediately following the sodium nitroprusside infusion.
Phenylephrine Hydrochloride
Investigators will give three incremental doses via brachial artery catheter to observe α1-adrenoreceptor mediated vasoconstriction. This will occur three times throughout the protocol.
Norepinephrine
Investigators will give three incremental doses via brachial artery catheter to observe adrenoreceptor activation. This will occur three times throughout the protocol.
Isometric Handgrip and Post-Exercise Circulatory Occlusion
Participants will perform 2 minutes of isometric handgrip at 30% maximal voluntary contraction followed by 2 minutes of post-exercise circulatory occlusion to assess the reactivity of the blood vessels to exercise and the metaboreflex.
Rhythmic Handgrip
Participants will perform 3 minutes of rhythmic handgrip at 25% maximal voluntary contraction to assess the reactivity of blood vessels to dynamic exercise.
Cold Pressor Test
Standardized sympathetic stressor involving submersion of the hand in ice-cold water for 3-minutes, aiming to elicit endogenous neurotransmitter release and blood pressure increases.
Propranolol Hydrochloride
Local infusion via brachial artery catheterization will occur continuously for the remainder of the study. Propranolol is a beta-adrenergic antagonist and will allow investigation of the role of beta receptors in responses to various stressors. The above phenylephrine, norepinephrine, isometric handgrip, post-exercise circulatory occlusion, and rhythmic handgrip protocols will be repeated under propranolol infusion.
Phentolamine Mesylate
Local infusion via brachial artery catheterization will occur continuously for the remainder of the study. Phentolamine is an alpha-adrenergic antagonist and will allow investigation the role of alpha receptors in responses to various stressors. It will be continuously infused with propranolol. The above phenylephrine, norepinephrine, isometric handgrip, post-exercise circulatory occlusion, and rhythmic handgrip protocols will be repeated under propranolol infusion.
High Altitude
Participants will be assessed on a high-altitude expedition at an elevation of 3,800m.
Sodium Nitroprusside
A bolus injection of sodium nitroprusside will be given to lower blood pressure and evaluate baroreflex function.
Phenylephrine Hydrochloride
A bolus injection of phenylephrine will be given to raise blood pressure and evaluate baroreflex function immediately following the sodium nitroprusside infusion.
Phenylephrine Hydrochloride
Investigators will give three incremental doses via brachial artery catheter to observe α1-adrenoreceptor mediated vasoconstriction. This will occur three times throughout the protocol.
Norepinephrine
Investigators will give three incremental doses via brachial artery catheter to observe adrenoreceptor activation. This will occur three times throughout the protocol.
Isometric Handgrip and Post-Exercise Circulatory Occlusion
Participants will perform 2 minutes of isometric handgrip at 30% maximal voluntary contraction followed by 2 minutes of post-exercise circulatory occlusion to assess the reactivity of the blood vessels to exercise and the metaboreflex.
Rhythmic Handgrip
Participants will perform 3 minutes of rhythmic handgrip at 25% maximal voluntary contraction to assess the reactivity of blood vessels to dynamic exercise.
Cold Pressor Test
Standardized sympathetic stressor involving submersion of the hand in ice-cold water for 3-minutes, aiming to elicit endogenous neurotransmitter release and blood pressure increases.
Propranolol Hydrochloride
Local infusion via brachial artery catheterization will occur continuously for the remainder of the study. Propranolol is a beta-adrenergic antagonist and will allow investigation of the role of beta receptors in responses to various stressors. The above phenylephrine, norepinephrine, isometric handgrip, post-exercise circulatory occlusion, and rhythmic handgrip protocols will be repeated under propranolol infusion.
Phentolamine Mesylate
Local infusion via brachial artery catheterization will occur continuously for the remainder of the study. Phentolamine is an alpha-adrenergic antagonist and will allow investigation the role of alpha receptors in responses to various stressors. It will be continuously infused with propranolol. The above phenylephrine, norepinephrine, isometric handgrip, post-exercise circulatory occlusion, and rhythmic handgrip protocols will be repeated under propranolol infusion.
Interventions
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Sodium Nitroprusside
A bolus injection of sodium nitroprusside will be given to lower blood pressure and evaluate baroreflex function.
Phenylephrine Hydrochloride
A bolus injection of phenylephrine will be given to raise blood pressure and evaluate baroreflex function immediately following the sodium nitroprusside infusion.
Phenylephrine Hydrochloride
Investigators will give three incremental doses via brachial artery catheter to observe α1-adrenoreceptor mediated vasoconstriction. This will occur three times throughout the protocol.
Norepinephrine
Investigators will give three incremental doses via brachial artery catheter to observe adrenoreceptor activation. This will occur three times throughout the protocol.
Isometric Handgrip and Post-Exercise Circulatory Occlusion
Participants will perform 2 minutes of isometric handgrip at 30% maximal voluntary contraction followed by 2 minutes of post-exercise circulatory occlusion to assess the reactivity of the blood vessels to exercise and the metaboreflex.
Rhythmic Handgrip
Participants will perform 3 minutes of rhythmic handgrip at 25% maximal voluntary contraction to assess the reactivity of blood vessels to dynamic exercise.
Cold Pressor Test
Standardized sympathetic stressor involving submersion of the hand in ice-cold water for 3-minutes, aiming to elicit endogenous neurotransmitter release and blood pressure increases.
Propranolol Hydrochloride
Local infusion via brachial artery catheterization will occur continuously for the remainder of the study. Propranolol is a beta-adrenergic antagonist and will allow investigation of the role of beta receptors in responses to various stressors. The above phenylephrine, norepinephrine, isometric handgrip, post-exercise circulatory occlusion, and rhythmic handgrip protocols will be repeated under propranolol infusion.
Phentolamine Mesylate
Local infusion via brachial artery catheterization will occur continuously for the remainder of the study. Phentolamine is an alpha-adrenergic antagonist and will allow investigation the role of alpha receptors in responses to various stressors. It will be continuously infused with propranolol. The above phenylephrine, norepinephrine, isometric handgrip, post-exercise circulatory occlusion, and rhythmic handgrip protocols will be repeated under propranolol infusion.
Other Intervention Names
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Eligibility Criteria
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Inclusion Criteria
* No medical history of cardiovascular, respiratory, nervous system, or metabolic disease
* Females must be pre-menopausal
Exclusion Criteria
* Having travelled above 2,000m within 1 month of testing at low and high altitude
* Females who are pregnant, confirmed by a pregnancy test
* Females who are post-menopausal
* Participants that are classified as obese (body mass index \> 30kg⋅m²)
* Participants who are current daily smokers
* Those with a known allergy to sulfites
* Participants taking monoamine oxidase (MAO) inhibitors or tricyclic antidepressants or other medications that have contraindications with the study drugs
* Participants who are still within the washout period from participating in other studies involving drugs.
18 Years
45 Years
ALL
Yes
Sponsors
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University of Alberta
OTHER
Responsible Party
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Principal Investigators
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Sean van Diepen, MD, MSc
Role: PRINCIPAL_INVESTIGATOR
University of Alberta
Craig D Steinback, PhD
Role: PRINCIPAL_INVESTIGATOR
University of Alberta
Locations
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University of Alberta
Edmonton, Alberta, Canada
University of British Columbia - Okanagan
Kelowna, British Columbia, Canada
Countries
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References
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Hart EC, Charkoudian N, Wallin BG, Curry TB, Eisenach JH, Joyner MJ. Sex differences in sympathetic neural-hemodynamic balance: implications for human blood pressure regulation. Hypertension. 2009 Mar;53(3):571-6. doi: 10.1161/HYPERTENSIONAHA.108.126391. Epub 2009 Jan 26.
Mazzeo RS, Child A, Butterfield GE, Mawson JT, Zamudio S, Moore LG. Catecholamine response during 12 days of high-altitude exposure (4, 300 m) in women. J Appl Physiol (1985). 1998 Apr;84(4):1151-7. doi: 10.1152/jappl.1998.84.4.1151.
Purdy GM, James MA, Rees JL, Ondrus P, Keess JL, Day TA, Steinback CD. Spleen reactivity during incremental ascent to altitude. J Appl Physiol (1985). 2019 Jan 1;126(1):152-159. doi: 10.1152/japplphysiol.00753.2018. Epub 2018 Nov 21.
Usselman CW, Gimon TI, Nielson CA, Luchyshyn TA, Coverdale NS, Van Uum SH, Shoemaker JK. Menstrual cycle and sex effects on sympathetic responses to acute chemoreflex stress. Am J Physiol Heart Circ Physiol. 2015 Mar 15;308(6):H664-71. doi: 10.1152/ajpheart.00345.2014. Epub 2014 Dec 19.
Other Identifiers
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Pro00096808
Identifier Type: -
Identifier Source: org_study_id
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