title: Frequency and pattern dependence of adrenergic and purinergic vasoconstriction in rat skeletal muscle arteries.
abstract: 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 degrees 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 alpha(1)-antagonist prazosin (1.59 microM). 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 alpha(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 alpha(1)-receptors in the femoral artery are sensitive to frequency and patterns of electrical stimulation.
authors.affiliation: Department of Anesthesiology and Physiology, Medical College of Wisconsin, Milwaukee, WI 53295, USA.
authors.forename: Heidi A
authors.initials: HA
authors.lastname: Kluess
authors.forename: John B
authors.initials: JB
authors.lastname: Buckwalter
authors.forename: Jason J
authors.initials: JJ
authors.lastname: Hamann
authors.forename: Darren S
authors.initials: DS
authors.lastname: DeLorey
authors.forename: Philip S
authors.initials: PS
authors.lastname: Clifford
mesh_terms: D058668:Adrenergic alpha-1 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D005263:Femoral Artery / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply*; D011224:Prazosin / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058476:Receptors, Purinergic P2X2; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
chemical_list: D058668:Adrenergic alpha-1 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; C546403:P2rx2 protein, rat; D058919:Purinergic P2 Receptor Antagonists; D018340:Receptors, Adrenergic, alpha-1; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D011224:Prazosin