| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Prince of Wales Medical Research Institute
2 the University of New South Wales, Randwick, NSW 2031, Australia
Spinal cord transection produces a marked increase in the response of the isolated rat tail artery to sympathetic nerve stimulation, possibly as a result of a decrease in ongoing sympathetic activity. We have tested the effects of removing ongoing nerve activity on neurovascular transmission by cutting the preganglionic input to postganglionic neurones supplying the tail artery (decentralization). Isometric contractions to nerve stimulation were compared between decentralized arteries and those from age-matched and sham-operated controls. Nerve-evoked responses of decentralized arteries were much larger than those of control arteries at 2 and 7 weeks post operatively. The extent of blockade of nerve-evoked contraction by 
-adrenoceptor antagonists prazosin (10 nM) or idazoxan (0.1 µM) was reduced. Decentralized arteries were transiently supersensitive to the 1-adrenoceptor agonist phenylephrine and the 2-adrenoceptor agonist clonidine; the unchanged sensitivity to methoxamine and phenylephrine after 2 weeks indicated no effect on the neuronal noradrenaline uptake transporter. Decentralized arteries were hypersensitive to ,ß methylene-ATP, but the P2-purinoceptor antagonist suramin (0.1 mM) did not reduce nerve-evoked contractions. Enlarged responses to 60 mM K+ after both 2 and 7 weeks were correlated with the response of the arteries to nerve stimulation, suggesting that increased postjunctional reactivity contributes to the enhanced contraction. Comparison between data from decentralized arteries and our previous data from spinalized animals showed that the two lesions similarly potentiate nerve-evoked contractions and have similar but not identical postjunctional effects. The enhanced vascular responses following a reduction in tonic nerve activity may contribute to the hypertensive episodes of autonomic dysreflexia in spinally injured patients.
(Received 1 September 2004;
accepted after revision 8 October 2004;
first published online 14 October 2004)
Corresponding author J. Brock: Prince of Wales Medical Research Institute, Gate 1, Barker Street, Randwick, Sydney, NSW 2031, Australia. Email: j.brock{at}unsw.edu.au
This article has been cited by other articles:
|
|
 |
|
  A. S. Laird, A. M. Finch, P. M. E. Waite, and P. Carrive Peripheral changes above and below injury level lead to prolonged vascular responses following high spinal cord injury Am J Physiol Heart Circ Physiol, February 1, 2008; 294(2): H785 - H792. [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]
|
|
|
|
 |
|
 N. Charkoudian, M. J. Joyner, L. A. Sokolnicki, C. P. Johnson, J. H. Eisenach, N. M. Dietz, T. B. Curry, and B. G. Wallin Vascular adrenergic responsiveness is inversely related to tonic activity of sympathetic vasoconstrictor nerves in humans J. Physiol., May 1, 2006; 572(3): 821 - 827. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Brock, M. Yeoh, and E. M. McLachlan Enhanced neurally evoked responses and inhibition of norepinephrine reuptake in rat mesenteric arteries after spinal transection Am J Physiol Heart Circ Physiol, January 1, 2006; 290(1): H398 - H405. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
