None listed
Conditions
Brief summary
The role of the sympathetic nervous system in the regulation of brain blood flow in humans remains controversial and incompletely understood. There is some evidence from human studies that activation of the sympathetic nerves can reduce brain blood flow and/or constrict brain blood vessels. We will test the hypothesis that the sympathetic nervous system modifies the brain blood flow responses to neuronal activation by visial stimulation (known as neurovascular coupling). These investigations will provide new insights into brain blood flow regulation in healthy individuals, with broader implications to relevant patient groups (e.g., people with high blood pressure).
Interventions
This is a non-therepeutic mechanistic physiological study.
Participants will undertake on initial familarisation visit and one experimental visit. At the familarisation visit participants will complete a general health questionnaire and have their height and weight measured. For the experimental visit participants will rest in a supine position on a comfortable hospital bed in a custom built airtight box up to the level of the iliac crest (i.e. a lower body negative pressure chamber). They wil
This is a non-therepeutic mechanistic physiological study. Participants will undertake on initial familarisation visit and one experimental visit. At the familarisation visit participants will complete a general health questionnaire and have their height and weight measured. For the experimental visit participants will rest in a supine position on a comfortable hospital bed in a custom built airtight box up to the level of the iliac crest (i.e. a lower body negative pressure chamber). They will be instrumented for the measurement of brain blood flow (transcranaial Doppler ultrasound), blood pressure (finger photoplethysmography and automated sphygmomanometer), breathing rate (spirometer, gas analyser). After a 10 min baseline, three experimental conditions will then be undertaken in a randomised order, namely; 1) neurovascular coupling test with no lower body negative pressure, 2) neurovascular coupling test with -20 mmHg lower body negative pressure, and 3) neurovascular coupling test with -40 mmHg lower body negative pressure. Each trial will last 10 min. Trials will be separated by 30 min. Neurovacular coupling will be assessed (5 cycles, of 20 s eyes closed and 40 s of reading) during each trial. All sessions will be conducted by a University student (registered for a PhD in Exercise Science) and supervised by an Assoc Prof of Physiology. The mode of administration is one-to-one for all activities. A check list will be use to monitor adherence to the intervention.
Sponsors
University of Auckland
Study design
Allocation
Randomised controlled trial
Primary purpose
Diagnosis
Eligibility
Sex/Gender
All
Age
18 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
•Healthy individuals •Not taking any prescription or over-the-counter medications (other than oral contraceptive pill) •Body mass index < 30 kg/m2 •No history of syncope (fainting) •Not hypotensive (e.g., have a resting blood pressure >90/60 mmHg)
Exclusion criteria
•Cardiovascular disease (e.g., coronary heart disease, hypertension) •Severe respiratory disease (e.g., chronic obstructive pulmonary disease) •Smokers •Metabolic disease (e.g., type II diabetes) •Cancer •Connective tissue or inflammatory disease •Neurological disease •Infection or pyrexial illness •Thyroid disorders •Hepatic or renal impairment •Pregnancy •Underlying medical conditions, which in the opinion of the Investigator place the participant at unacceptably high risk for participating in the study •Inability to fully or appropriately provide consent
Outcome results
None listed