|
|
||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Department of 1 Anesthesiology and Physiology, Medical College of Wisconsin2 Veterans Affairs Medical Center, Milwaukee, WI 53295, USA
Sympathetic nerves fire in bursts followed by brief periods of quiescence. Periods of quiescence may be a valuable part of coding for different neurotransmitters. We compared adrenergic- and non-adrenergic-mediated vasoconstriction with repeating burst patterns versus constant frequency stimulation. Seventeen rats were killed, and the femoral arteries dissected out and mounted in organ tissue baths at 37°C and pH 7.4. Field stimulation was applied to artery rings from five rats at constant frequencies of 2–6 Hz for 144 impulses. In 12 rats, artery rings were stimulated with two burst pattern protocols consisting of repeating pairs, triplets, quadruplets or sextuplets performed using either 8 or 30 Hz as the instantaneous frequency for a total of 144 impulses. All protocols were repeated with the P2 purinergic antagonist pyridoxal-phosphate-6-azophenyl-2'4'-disulphonic acid (PPADs; 0.42 M) or the
1-antagonist prazosin (1.59 µM). Tension was decreased by the addition of the P2 antagonist PPADs (P < 0.05). Prazosin abolished tension at all constant frequencies (P < 0.05). P2 and
1-antagonism decreased tension with 8 and 30 Hz burst pattern field stimulation. However, the magnitude of decrease in tension with prazosin was less with burst patterns compared to the same average constant frequencies (P < 0.05). It appears that P2X receptors and
1-receptors in the femoral artery are sensitive to frequency and patterns of electrical stimulation.
(Received 12 June 2006;
accepted after revision 7 September 2006; first published online 14 September 2006)
Corresponding author P. S. Clifford: Anesthesia Research 151, Veterans Affairs Medical Center, Milwaukee, WI 53295, USA. Email: pcliff{at}mcw.edu
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |