Endogenous bradykinin in the thoracic spinal cord contributes to the exercise pressor reflex

Charles L Stebbins, Stefanie Bonigut

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

This investigation tested the hypothesis that bradykinin causes excitatory effects in the thoracic spinal cord that augment the exercise pressor reflex. Thus we performed 30 s of electrically stimulated static contraction of the hindlimb in the anesthetized cat (α-chloralose) to provoke reflex-induced increases in mean arterial pressure, maximal rate of rise of left ventricular pressure (dP/dt), and heart rate (i.e., the exercise pressor reflex). These three responses were compared before and 15 min after intrathecal injection of 2 μg (n = 3), 10 μg (n = 6), or 50 μg (n = 3) of the selective bradykinin B2-receptor antagonist HOE-140 into the thoracic spinal cord or 10 μg of this antagonist into the lumbar (n = 3) spinal cord. In three of the six cats in which 10 μg of HOE-140 were injected into the thoracic spinal cord, an additional contraction was performed 60-90 min after treatment. The 2-μg dose of HOE-140 had no effect on the exercise pressor reflex. Injection of 10 μg of this antagonist into the thoracic spinal cord reduced the contraction-evoked pressor, maximal dP/dt, and heart rate responses by 49 ± 7, 58 ± 4, and 64 ± 13%, respectively (P < 0.05). Fifty micrograms of HOE-140 failed to attenuate these responses further. In the three cats in which an additional contraction was performed 60-90 min after treatment with 10 μg of the antagonist, blood pressure and dP/dt responses had returned, in part, toward initial values. Neither intravenous (n = 3) nor intrathecal injection of 10 μg of HOE-140 into the lumbar spinal cord had any effect on the contraction-induced cardiovascular responses. Thoracic injection of 50-200 ng of bradykinin provoked a pressor response of 26 ± 5 mmHg that was abolished by a similar injection of 10 μg of HOE-140. These data suggest that endogenous bradykinin contributes to the exercise pressor reflex by an excitatory action in the thoracic spinal cord.

Original languageEnglish (US)
Pages (from-to)1288-1294
Number of pages7
JournalJournal of Applied Physiology
Volume81
Issue number3
StatePublished - Sep 1996

Keywords

  • anesthetized cats
  • bradykinin B receptors
  • HOE-140
  • static muscle contraction

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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