The exercise pressor reflex is attenuated by intrathecal oxytocin

Charles L Stebbins, A. Ortiz-Acevedo

Research output: Contribution to journalArticle

Abstract

We tested the hypothesis that oxytocin (Oxt) acts in the lumbar spinal cord to attenuate reflex pressor (mean arterial pressure, MAP) and heart rate (HR) responses to static hindlimb contraction (i.e., the exercise pressor reflex). Thus we compared MAP and HR responses to electrically stimulated hindlimb static contraction in the anesthetized cat before and after intrathecal injection of Oxt (30 pmol, n = 3; 300 pmol, n = 6; or 3 nmol, n = 6). The 300-pmol dose was most effective, it attenuated the pressor response to static contraction by 39 ± 10% but had no effect on HR. In three other cats, contraction-induced increases in MAP and HR were monitored before and after intrathecal injection of 300 pmol of Oxt + 300 nmol of the selective Oxt receptor antagonist [d(CH2 5 1,O-Me-Tyr2,Thr4,Tyr9,Orn8)]vasotocin. Pretreatment with the antagonist eliminated the effect of Oxt on MAP. In an additional 10 cats, increases in these same variables in response to static contraction were compared before and after intrathecal injection of the Oxt antagonist (30 nmol, n = 3 or 300 nmol, n = 7) into the lumbar spinal cord (L1-L7). Whereas 30 nmol of the Oxt antagonist had no effect, the 300-nmol dose augmented the contraction-induced pressor and HR responses by 28 ± 7 and 32 ± 17%, respectively. These data imply that endogenous Oxt modulates the exercise pressor reflex by its action on Oxt receptors in the lumbar spinal cord that can attenuate sensory nerve transmission from skeletal muscle.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume267
Issue number4 36-4
StatePublished - 1994

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Oxytocin
Reflex
Spinal Cord
Spinal Injections
Heart Rate
Arterial Pressure
Oxytocin Receptors
Cats
Hindlimb
Vasotocin
Skeletal Muscle

Keywords

  • cats
  • lumbar spinal cord
  • oxytocin receptor blockade
  • static contraction

ASJC Scopus subject areas

  • Physiology

Cite this

The exercise pressor reflex is attenuated by intrathecal oxytocin. / Stebbins, Charles L; Ortiz-Acevedo, A.

In: American Journal of Physiology - Regulatory Integrative and Comparative Physiology, Vol. 267, No. 4 36-4, 1994.

Research output: Contribution to journalArticle

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