Graduation Semester and Year

2020

Language

English

Document Type

Thesis

Degree Name

Master of Science in Exercise Science

Department

Kinesiology

First Advisor

Unknown

Abstract

Cerebral vasodilatory responsiveness is blunted in older adults (~45-70 yrs) with depressive disorders and thought to contribute to the link between depressive symptomology and increased risk for neurocognitive (e.g., dementia) and cerebral vascular (e.g., stroke) diseases. In young adults with major depressive disorder (MDD), peripheral vascular endothelial dysfunction is evident; however, to date, limited investigations have examined cerebral vasodilatory function in young healthy adults with MDD. We tested the hypothesis that cerebral vasodilatory responsiveness to a hypercapnic stimulus would be blunted in healthy young adults with MDD compared to healthy non-depressed adults (HA). Fourteen HA (22 ± 3yrs) and 14 adults with MDD (22 ± 3yrs; n=9 tested with moderate to severe depressive symptoms) participated. Beatto-beat mean arterial pressure (MAP; finger photoplethysmography), middle cerebral artery blood velocity (MCAv; transcranial Doppler ultrasound), internal carotid artery (ICA) diameter and blood flow (Doppler ultrasound), and end-tidal carbon dioxide concentration (PETCO2;capnograph) were continuously measured during baseline (i.e., normocapnia) and rebreathing induced hypercapnia. Cerebral vascular conductance index (CVCi=MCAv•MAP -1) and ICA blood flow (Vmean• ��(��•20-1)2•60) and conductance (CVC=ICA blood flow•MAP -1) were calculated at baseline and at the highest common magnitude of hypercapnia achieved by all subjects during rebreathing (∆9 mmHg PETCO2). At baseline and hypercapnia, there were no differences between groups (p>0.05 ). MAP (HA: 91 ± 9mmHg; MDD: 90 ± 7mmHg), MCAv (HA: 101 ± 17 cm·s-1 ; MDD: 103 ± 18 cm·s-1), absolute CVCi (HA: 1.11 ± 0.21 cm·s-1·mmHg1; MDD: 1.15 ± 0.21 cm·s-1·mmHg-1) relative CVCi %baseline (HA: 36.5 ± 12.5%; MDD: 31.0 ± 13.9%). There were also no group differences in ICA diameter (HA: 4.8 ± 0.8mm; MDD: 5.0 ± 0.7mm) or blood flow responses (HA: 550.0 ± 144.1 mL·min-1; MDD: 563.8 ± 168.61 mL·min-4 1), absolute CVC (HA: 6.13 ± 1.72 mL·min-1·mmHg-1; MDD: 6.17 ± 1.55 mL·min-1·mmHg-1) or relative CVC %baseline (HA: 33.9 ± 23.3%; MDD: 33.0 ± 19.0%). These data suggest that cerebrovascular function in young adults with MDD is preserved, intimating a protective mechanism that may not be present in older adults with MDD.

Keywords

Major depressive disorder, Middle cerebral artery, Young adults

Disciplines

Kinesiology | Life Sciences

Comments

Degree granted by The University of Texas at Arlington

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