| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Dalton Cardiovascular Research Center and Departments of Biomedical Sciences and Medical Pharmacology, University of Missouri-Columbia, Columbia, MO, USA
2 Dalton Cardiovascular Research Center and Departments of Biomedical Sciences and Medical Pharmacology, University of Missouri-Columbia, Columbia, MO, USA; Department of Physiology, University of Missouri-Columbia, Columbia, MO, USA
* To whom correspondence should be addressed. E-mail: muellerp{at}missouri.edu.
Exercise training (ExTr) has been associated with alterations in neural control of the circulation including effects on arterial baroreflex function. The nucleus tractus solitarius (NTS) is the primary termination site of cardiovascular afferents and critical in the regulation of baroreflex mediated changes in heart rate (HR) and sympathetic nervous system outflow. The purpose of the present study was to determine whether ExTr is associated with alterations in neurotransmitter regulation of neurons involved in control of cardiovascular function at the level of the NTS. We hypothesized that ExTr would increase glutamatergic and reduce GABAergic transmission in the NTS, and that collectively; these changes would result in a greater overall sympathoinhibitory drive from the NTS in ExTr animals. To test these hypotheses, male Sprague-Dawley rats were treadmill trained or maintained under sedentary conditions (Sed) for 8-10 wks. NTS microinjections were performed in Inactin anesthetized animals instrumented to record mean arterial pressure (MAP), HR, and lumbar sympathetic nerve activity (LSNA). Generalized activation of the NTS with unilateral microinjections of glutamate (1-10 mM, 30 nl) produced dose dependent decreases in MAP, HR, and LSNA that were unaffected by ExTr. Bilateral inhibition of NTS with the GABAA agonist, muscimol (1mM, 90 nl) produced increases in MAP and LSNA which were blunted by ExTr. In contrast, pressor and sympathoexcitatory responses to bilateral microinjections of the ionotropic glutamate receptor antagonist, kynurenate (40 mM, 90 nl), were similar between groups. Bradycardic responses to bilateral microinjections of the GABAA antagonist bicuculline (0.1 mM, 90 nl) were attenuated by ExTr. These data indicate that alterations in neurotransmission at the level of the NTS contribute importantly to regulation of HR and LSNA in ExTr animals. In addition to alterations at NTS, these experiments suggest indirectly that changes in other cardiovascular nuclei contribute to the observed alterations in neural control of the circulation following ExTr.
This article has been cited by other articles:
|
|
 |
|
  L. C. Michelini and J. E. Stern Exercise-induced neuronal plasticity in central autonomic networks: role in cardiovascular control Exp Physiol, September 1, 2009; 94(9): 947 - 960. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Komine, J. Sugawara, K. Hayashi, M. Yoshizawa, and T. Yokoi Regular endurance exercise in young men increases arterial baroreflex sensitivity through neural alteration of baroreflex arc J Appl Physiol, May 1, 2009; 106(5): 1499 - 1505. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. A. Mandel and A. M. Schreihofer Glutamatergic inputs to the CVLM independent of the NTS promote tonic inhibition of sympathetic vasomotor tone in rats Am J Physiol Heart Circ Physiol, October 1, 2008; 295(4): H1772 - H1779. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Yao, C. Sumners, S. T. O'Rourke, and C. Sun Angiotensin II increases GABAB receptor expression in nucleus tractus solitarii of rats Am J Physiol Heart Circ Physiol, June 1, 2008; 294(6): H2712 - H2720. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Shi, F. A. Schaller, N. Tierney, P. Chanthavong, S. Chen, P. B. Raven, and M. L. Smith Physically Active Lifestyle Enhances Vagal-Cardiac Function but Not Central Autonomic Neural Interaction in Elderly Humans Experimental Biology and Medicine, February 1, 2008; 233(2): 209 - 218. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y.-W. Chen, S.-H. Chen, W. Chou, Y.-M. Lo, C.-H. Hung, and M.-T. Lin Exercise pretraining protects against cerebral ischaemia induced by heat stroke in rats Br. J. Sports Med., September 1, 2007; 41(9): 597 - 602. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. J. Mueller Exercise training attenuates increases in lumbar sympathetic nerve activity produced by stimulation of the rostral ventrolateral medulla J Appl Physiol, February 1, 2007; 102(2): 803 - 813. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
