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Sympathetic Neurovascular Transduction: Role of Adrenergic Receptors and Sex Differences (STARS)

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ClinicalTrials.gov Identifier: NCT05997732
Recruitment Status : Recruiting
First Posted : August 18, 2023
Last Update Posted : November 2, 2023
Sponsor:
Information provided by (Responsible Party):
University of Alberta

Study Description
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Brief Summary:

The main purpose of this interventional study is to examine differences in resting blood pressure control between healthy males and females. The main questions it aims to answer are:

  1. Are there sex differences in the communication between the sympathetic nervous system (also known as the "fight or flight" response) and peripheral blood vessels (which influence systemic blood pressure)?
  2. What is the role of specific vascular receptors that respond to sympathetic signals, and is it different between males and females?

Participants will complete one study visit of approximately 3 hours where they will:

  • Have a blood sample taken to measure circulating sex hormone and sympathetic transmitters.
  • Receive very small doses of medications commonly used to adjust blood pressure through an artery in their arm. The effects of these medications will be short-acting and localized to the forearm.
  • Have their sympathetic nervous activity directly measured through two very small needles (similar to acupuncture needles) in the side of their leg.
  • Have their blood pressure and heart rate recorded, and forearm blood flow measured using ultrasound.

Condition or disease Intervention/treatment Phase
Vasoconstriction Vasodilation Drug: Phenylephrine Hydrochloride Drug: Isoproterenol Hydrochloride Drug: Norepinephrine Bitartrate Drug: Propranolol Hydrochloride Drug: Phentolamine Mesylate Phase 4

Detailed Description:

Blood pressure is in part regulated by activity of your sympathetic nervous system (also known as your "fight or flight" response). Sympathetic nerve activity affects the size of your blood vessels, which in turn will affect your blood pressure. This communication between sympathetic impulses and the resulting change in vascular resistance is termed "sympathetic neurovascular transduction". In other words, transduction represents the reactivity of the blood vessels in response to individual sympathetic bursts of activity.

Males and females regulate their blood pressure in different ways; for example, females tend to have lower blood pressure and sympathetic nerve activity than males. Females also appear to have less constriction of their blood vessels in response to stress. This may be due to differences in the receptors which are activated by the sympathetic nervous system. These receptors are called α and β-adrenergic receptors and are located on vascular smooth muscle cells. They respond to sympathetic neurotransmitters such as norepinephrine in opposite directions: α-adrenoreceptors cause vasoconstriction (and an increase in vascular resistance), and β-adrenoreceptors cause vasodilation (and a decrease in vascular resistance) in part through the endothelium-dependent nitric oxide pathway.

Current evidence suggests that β-adrenergic receptors are more sensitive in females and contribute to paradoxical vasodilation when α-adrenergic receptors are stimulated by norepinephrine from sympathetic bursts. It has also been suggested that estrogen interacts with adrenergic receptors, contributing to this sex difference. This study will contribute to the understanding of sex differences in cardiovascular physiology and may have implications for clinical cardiovascular conditions.

Study Design
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Study Type : Interventional  (Clinical Trial)
Estimated Enrollment : 30 participants
Allocation: Non-Randomized
Intervention Model: Crossover Assignment
Intervention Model Description: Participants will complete three pharmacological conditions, and serve as their own controls.
Masking: None (Open Label)
Primary Purpose: Basic Science
Official Title: Sympathetic Neurovascular Transduction: Role of Adrenergic Receptors and Sex Differences
Actual Study Start Date : October 31, 2023
Estimated Primary Completion Date : September 1, 2024
Estimated Study Completion Date : September 1, 2024
Arms and Interventions
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Arm Intervention/treatment
Experimental: Control Condition
Normal saline will be infused through the brachial artery catheter at the same calculated rate as propranolol + phentolamine in the α+β-blockade condition to control for volumetric effects.
 Drug: Phenylephrine Hydrochloride
Participants will receive three incremental doses via the brachial artery catheter to assess α1-adrenoreceptor mediated vasoconstriction.

Drug: Isoproterenol Hydrochloride
Participants will receive four incremental doses via the brachial artery catheter to assess β-adrenoreceptor mediated vasodilation.

Drug: Norepinephrine Bitartrate
Participants will receive three incremental doses via the brachial artery catheter to assess nonspecific adrenoreceptor activation.
Experimental: β-Adrenergic Blockade
β-adrenoreceptors will be blocked locally in the forearm using propranolol. Normal saline will be co-infused at the calculated rate of phentolamine in the α+β-blockade condition to control for volumetric effects.
 Drug: Norepinephrine Bitartrate
Participants will receive three incremental doses via the brachial artery catheter to assess nonspecific adrenoreceptor activation.

Drug: Propranolol Hydrochloride
Propranolol will be continuously infused through the brachial artery catheter to induce β-adrenergic blockade locally in the forearm.
Experimental: α+β-Adrenergic Blockade
α-adrenoreceptors will be blocked locally in the forearm using phentolamine. Propranolol will be co-infused to maintain β-blockade.
 Drug: Phentolamine Mesylate
Phentolamine will be continuously infused through the brachial artery catheter to induce α-adrenergic blockade locally in the forearm.

Drug: Phenylephrine Hydrochloride
Participants will receive one dose via the brachial artery catheter to evaluate the effectiveness of the α-adrenergic blockade.

Drug: Isoproterenol Hydrochloride
Participants will receive one dose via the brachial artery catheter to evaluate the effectiveness of the β-adrenergic blockade.

Drug: Propranolol Hydrochloride
Propranolol will be continuously co-infused with phentolamine to maintain the β-adrenergic blockade.


Outcome Measures
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Primary Outcome Measures :
  1. Forearm blood flow [ Time Frame: 10 minutes per condition + 2 minutes per agonist dose = 60 minutes ]
    Measured during resting baseline; changes during phenylephrine, isoproterenol, and norepinephrine infusion to determine agonist sensitivity.

  2. Forearm vascular resistance [ Time Frame: 10 minutes per condition + 2 minutes per agonist dose = 60 minutes ]
    Measured during resting baseline; changes during phenylephrine, isoproterenol, and norepinephrine infusion to determine agonist sensitivity.

  3. Forearm vascular conductance [ Time Frame: 10 minutes per condition + 2 minutes per agonist dose = 60 minutes ]
    Measured during resting baseline; changes during phenylephrine, isoproterenol, and norepinephrine infusion to determine agonist sensitivity.

  4. Arterial blood pressure [ Time Frame: 10 minutes per condition + 2 minutes per agonist dose = 60 minutes ]
    Measured during resting baseline; changes during phenylephrine, isoproterenol, and norepinephrine infusion to determine agonist sensitivity.

  5. Muscle sympathetic nerve activity [ Time Frame: 10 minutes per condition = 30 minutes ]
    Resting baseline

  6. Circulating sex hormone concentrations [ Time Frame: 2 minutes ]
    Blood samples

  7. Circulating sympathetic neurotransmitter concentrations [ Time Frame: 2 minutes ]
    Blood sample


Secondary Outcome Measures :
  1. Arterial-venous blood gas concentrations [ Time Frame: 2 minutes per sample = 6 minutes ]
    Blood sample during each condition


Eligibility Criteria
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Ages Eligible for Study:   18 Years to 40 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Between ages 18-40 years
  • No diagnosed medical history of cardiovascular, respiratory, nervous system, or metabolic disease.
  • Females must be pre-menopausal.
  • Prior to study visit: abstained from caffeine, alcohol, strenuous exercise, and medication not taken regularly for at least 12 hours.

Exclusion Criteria:

  • Current diagnosis of cardiovascular, respiratory, nervous system, or metabolic disease that may impact blood pressure regulation. This will be assessed on a case-by-case basis by the study physician.
  • Participants with bleeding or clotting disorders, or those currently taking blood thinners.
  • Participants currently taking beta-agonist inhalers i.e. Ventolin (at least not in the last 24 hours).
  • Females who are pregnant, confirmed by a pregnancy test.
  • Females who have are less than 1 year postpartum or are breastfeeding.
  • Females who are post-menopausal.
  • Participants that are classified as obese (body mass index > 30 kg ⋅ m2).
  • Have a history of smoking regularly in the last 6 months (but nicotine substitutes (i.e. patch, gum) are not an exclusion criteria).
  • Those with a known allergy to sulfites, or other components of the supplied solution of study drugs.
  • Participants taking medications that are contraindicated with any of the study drugs, such as monoamine oxidase (MAO) inhibitors or tricyclic antidepressants.
  • Participants who have not adhered to the pre-testing guidelines related to diet, alcohol or exercise will not be excluded, but will be rescheduled for a different day. This is to reduce experimental variability.
Contacts and Locations
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Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT05997732


Contacts
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Contact: Emily Vanden Berg, MSc (780)-492-5553 ervanden@ualberta.ca
Contact: Nicholas Cheung, MSc (780)-492-5553 nkcheung@ualberta.ca

Locations
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Canada, Alberta
University of Alberta Recruiting
Edmonton, Alberta, Canada, T6G 2R3
Contact: Craig Steinback, PhD    (780)492-5553    craig.steinback@ualberta.ca   
Sponsors and Collaborators
University of Alberta
Investigators
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Principal Investigator: Sean van Diepen, MD, MSc University of Alberta
Principal Investigator: Craig Steinback, PhD University of Alberta
More Information
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Publications:

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Responsible Party: University of Alberta
ClinicalTrials.gov Identifier: NCT05997732    
Other Study ID Numbers: Pro00126600
First Posted: August 18, 2023    Key Record Dates
Last Update Posted: November 2, 2023
Last Verified: October 2023

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Studies a U.S. FDA-regulated Drug Product: No
Studies a U.S. FDA-regulated Device Product: No
Keywords provided by University of Alberta:
sympathetic nerve activity
sex differences
adrenergic receptors
neurovascular transduction
Additional relevant MeSH terms:
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Propranolol
Phentolamine
Phenylephrine
Isoproterenol
Oxymetazoline
Norepinephrine
Adrenergic beta-Antagonists
Adrenergic Antagonists
Adrenergic Agents
Neurotransmitter Agents
Molecular Mechanisms of Pharmacological Action
Physiological Effects of Drugs
Anti-Arrhythmia Agents
Antihypertensive Agents
Vasodilator Agents
 Cardiotonic Agents
Mydriatics
Autonomic Agents
Peripheral Nervous System Agents
Sympathomimetics
Vasoconstrictor Agents
Nasal Decongestants
Respiratory System Agents
Adrenergic alpha-1 Receptor Agonists
Adrenergic alpha-Agonists
Adrenergic Agonists
Protective Agents
Adrenergic alpha-Antagonists
Adrenergic beta-Agonists
Bronchodilator Agents