Receptor binding sites for BK have been located in the intermediolateral columns of the spinal cord that correspond with the location of the cell bodies of preganglionic sympathetic neurons Furthermore, intrathecal injections of this peptide cause dose dependent increases in arterial blood pressure that are eliminated by similar injection of selective bradykinin B2 receptor antagonists Consequently, we wondered if BK could cause 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 (o> chloralose) to provoke reflex-induced increases in mean arterial pressure, myocardial contractility, and heart rate (i.e , the exercise pressor reflex). These two responses were compared before and 15 min after intrathecal injection of the selective BK, receptor antagonist HOE 140 (10 ug) into the thoracic (n=6) or lumbar fn=3) spinal cord In 3 of the 6 cats in which HOE 140 was injected into the thoracic spmai cord, an additional contraction was performed 60-90 mm after treatment. Injection of HOE 140 into the thoracic spinal cord reduced the contraction-evoked pressor. myocardial contractile, and heart rate responses by 52±7, 58±4, and 64±13%, respectively, (P<0 05) In the 3 cats where an additional contraction was performed 60-90 min after treatment with the antagonist, we found that the blood pressure and myocardial contractile responses had returned, in part, to initial values Neither intravenous (n=3) nor intrathecal injection of 10 ug HOE 140 into the lumbar spinal cord had any effect on the contraction-induced cardiovascular responses. These data suggest that endogenous BK acts in the thoracic spinal cord to enhance the magnitude of the exercise pressor reflex.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology