Title page for ETD etd-06112009-063109
|Type of Document
||Hickey, Matthew Sean
||Effects of opioid antagonism on thermoregulation during prolonged exercise in the heat
||Master of Science
||Health and Physical Education
|Herbert, William G.
|Lee, John C.
|Rankin, Janet L. Walberg
- Core Temperature
- Forearm Blood Flow
- Prolonged Exercise Thermoregulation.
|Date of Defense
Five adult male volunteers were studied to investigate
the effect of opiate receptor blockade on the physiological
response to a maximum of 60 minutes of stationary cycling at
70% V02peak in a hot (33 0 C/65% RH) environment. Exercise
bouts were conducted following the administration of naloxone
(4mg IV) 5 minutes prior to exercise with a follow-up 4mg dose
at 25 minutes of exercise. In the placebo trial, volume-matched
doses of saline were administered at the same points.
No significant drug effect was observed on rectal or mean skin
temperature during exercise. Post-exercise skin temperature
was significantly (P<.OOl) higher on naloxone versus saline.
Forearm blood flow (FBF) was consistently higher from minute
25 of exercise until test termination, although only the
minute 25 and minute 55 data points were significantly
elevated (P<.05, P<.005, respectively) . The rectal
temperature threshold at which FBF plateaued was higher on
naloxone (P=.054), and the FBF: rectal temperature slope was
higher on naloxone throughout the trial. No significant
changes were observed in heart rate or estimated mean arterial
pressures, although both were consistently lower on naloxone.
Gross sweat response was not altered by the drug. Plasma
Beta-Endorphin was significantly (P<.Ol) higher on naloxone
versus saline, and Beta-Endorphin was significantly elevated
in the naloxone trial only. The observation that FBF was
significantly higher on naloxone without inducing compensatory
heart rate or blood pressure changes suggests that the opioids
may be involved in the blood volume shifts that occur during
prolonged exercise in the heat.
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