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Hypothalamic GABAergic influences on treadmill exercise responses in rats
J M Overton1, M W Redding, S L Yancey
1Department of Nutrition, Food, and Movement Sciences, College of Human Sciences, Florida State University, Tallahassee 32306-4079.
Brain Research Bulletin
|January 1, 1994
Summary
The posterior hypothalamic GABAergic system influences iliac blood flow during exercise but does not affect heart rate or mesenteric vascular resistance in rats. This system may play a role in regulating exercise capacity.
Area of Science:
- Neuroscience
- Physiology
- Exercise Science
Background:
- GABAergic antagonists in the posterior hypothalamus (PH) mimic exercise-like cardiovascular adjustments.
- The role of the PH GABAergic system in modulating cardiovascular responses during dynamic exercise is not fully understood.
Purpose of the Study:
- To investigate the hypothesis that a hypothalamic GABAergic mechanism within the PH modulates cardiovascular adjustments during dynamic exercise in conscious rats.
Main Methods:
- Sprague-Dawley rats were surgically prepared with cannulas in the PH and vascular probes.
- GABA-A receptor agonist muscimol or saline was microinjected into the PH during treadmill exercise.
- Mean arterial pressure, heart rate, and mesenteric and iliac vascular resistance were monitored.
Main Results:
- Muscimol injection into the PH during exercise did not alter mean arterial pressure, heart rate, or mesenteric vascular resistance.
- Muscimol significantly increased iliac vascular resistance during exercise.
- Treadmill run time was significantly reduced following muscimol injection, accompanied by mild sedation.
Conclusions:
- The posterior hypothalamic GABAergic system modulates iliac blood flow during exercise in rats.
- This system does not appear to modulate heart rate or mesenteric vascular resistance responses to dynamic exercise.
- The PH GABAergic system may influence overall exercise capacity, potentially through behavioral effects like sedation.