Received June 12, 2006
Revised July 10, 2006
Accepted after revision September 7, 2006
Frequency and pattern dependence of adrenergic and
purinergic vasoconstriction in skeletal muscle arteries
Heidi A Kluess 1,
John B Buckwalter 1,
Jason J Hamann 1,
Darren S DeLorey 1,
Philip S Clifford 1*
1 Medical College of Wisconsin
* To whom correspondence should be addressed. E-mail: pcliff{at}mcw.edu.
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Abstract |
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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; the femoral arteries
dissected out and mounted in organ tissue baths at
37oC and pH=7.4. Field stimulation was
applied to artery rings from five rats at constant
frequencies of 2 to 6Hz for 144 impulses. In twelve
rats, artery rings were stimulated with two burst
pattern protocols consisting of repeating pairs,
triplets, quadruplets, or sextuplets performed using
either 8Hz or 30Hz as the instantaneous frequency for a
total of 144 impulses. All protocols were repeated with
the P2 purinergic antagonist, PPADs (0.42M), or the &
[alpha]1 antagonist, prazosin (1.59mM).
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 8Hz and 30Hz 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.
Key Words:
Adenosine 5'-triphosphate (ATP), Noradrenaline, Vasoconstriction
