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The exercise pressor reflex is attenuated by intrathecal oxytocin
C L Stebbins1, A Ortiz-Acevedo
1Department of Internal Medicine, University of California, Davis 95616.
The American Journal of Physiology
|October 1, 1994
Summary
Oxytocin (Oxt) in the spinal cord reduces blood pressure responses during exercise. This study shows Oxt acts on spinal Oxt receptors to dampen the exercise pressor reflex, highlighting its role in cardiovascular regulation.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Pharmacology
Background:
- The exercise pressor reflex increases blood pressure and heart rate during physical activity.
- The role of oxytocin (Oxt) in modulating this reflex within the spinal cord is not fully understood.
Purpose of the Study:
- To investigate if oxytocin (Oxt) in the lumbar spinal cord attenuates the reflex cardiovascular responses to static hindlimb muscle contraction.
- To determine the involvement of oxytocin receptors in this modulatory effect.
Main Methods:
- Administered varying doses of oxytocin (Oxt) intrathecally in anesthetized cats before and after electrically stimulated hindlimb contraction.
- Utilized a selective Oxt receptor antagonist to block Oxt's effects.
- Compared mean arterial pressure (MAP) and heart rate (HR) responses before and after treatments.
Main Results:
- A 300-pmol dose of Oxt significantly attenuated the pressor response to contraction by 39% but did not affect heart rate.
- Pretreatment with an Oxt receptor antagonist blocked Oxt's blood pressure-lowering effect.
- A high dose of the Oxt antagonist (300 nmol) augmented both pressor and heart rate responses to contraction by 28% and 32%, respectively.
Conclusions:
- Endogenous oxytocin (Oxt) modulates the exercise pressor reflex via Oxt receptors in the lumbar spinal cord.
- Oxt acts to attenuate sensory nerve transmission from skeletal muscles, thereby reducing cardiovascular responses during exercise.