| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Physiology, Wayne State University, School of Medicine, Detroit, Michigan
Submitted 7 July 2005 ; accepted in final form 8 August 2005
Our previous studies concluded that stimulation of the nucleus of the solitary tract (NTS) A2a receptors evokes preferential hindlimb vasodilation mainly via inducing increases in preganglionic sympathetic nerve activity (pre-ASNA) directed to the adrenal medulla. This increase in pre-ASNA causes the release of epinephrine and subsequent activation of 
-adrenergic receptors that are preferentially located in the skeletal muscle vasculature. Selective activation of NTS A1 adenosine receptors evokes variable, mostly pressor effects and increases pre-ASNA, as well as lumbar sympathetic activity, which is directed to the hindlimb. These counteracting factors may have opposite effects on the hindlimb vasculature resulting in mixed vascular responses. Therefore, in chloralose-urethane-anesthetized rats, we evaluated the contribution of vasodilator versus vasoconstrictor effects of stimulation of NTS A1 receptors on the hindlimb vasculature. We compared the changes in iliac vascular conductance evoked by microinjctions into the NTS of the selective A1 receptor agonist N6-cyclopentyladenosine (330 pmol in 50 nl volume) in intact animals with the responses evoked after -adrenergic blockade, bilateral adrenalectomy, bilateral lumbar sympathectomy, and combined adrenalectomy + lumbar sympathectomy. In intact animals, stimulation of NTS A1 receptors evoked variable effects: increases and decreases in mean arterial pressure and iliac conductance with prevailing pressor and vasoconstrictor effects. Peripheral -adrenergic receptor blockade and bilateral adrenalectomy eliminated the depressor component of the responses, markedly potentiated iliac vasoconstriction, and tended to increase the pressor responses. Lumbar sympathectomy tended to decrease the pressor and vasoconstrictor responses. After bilateral adrenalectomy plus lumbar sympathectomy, a marked vasoconstriction in iliac vascular bed still persisted, suggesting that the vasoconstrictor component of the response to stimulation of NTS A1 receptors is mediated mostly via circulating factors (e.g., vasopressin, angiotensin II, or circulating catecholamines released from other sympathetic terminals). These data strongly suggest that stimulation of NTS A1 receptors exerts counteracting effects on the iliac vascular bed: activation of the adrenal medulla and -adrenergic vasodilation versus vasoconstriction mediated by neural and humoral factors.
nucleus of the solitary tract; purinergic receptors; -adrenergic blockade; adrenalectomy; lumbar sympathectomy; iliac vascular conductance
This article has been cited by other articles:
|
|
 |
|
  T. J. Scislo, T. K. Ichinose, and D. S. O'Leary Stimulation of NTS A1 adenosine receptors differentially resets baroreflex control of regional sympathetic outputs Am J Physiol Heart Circ Physiol, January 1, 2008; 294(1): H172 - H182. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Burnstock Physiology and Pathophysiology of Purinergic Neurotransmission Physiol Rev, April 1, 2007; 87(2): 659 - 797. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M McClure, T. J Scislo, and D. S O'Leary Mechanisms Mediating Regional Vascular Responses to Stimulation of Adenosine A1 Receptors in the Nucleus of the Solitary Tract (NTS) FASEB J, April 1, 2007; 21(5): A466 - A466.
|
|
|
|
|
|
T. J. Scislo and D. S. O'Leary Adenosine receptors located in the NTS contribute to renal sympathoinhibition during hypotensive phase of severe hemorrhage in anesthetized rats Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2453 - H2461. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
