title: Sympathetic cotransmission in rabbit saphenous artery in vitro: effect of electric stimulation and potentiation by alpha,beta-methylene ATP.
abstract: OBJECTIVE
  To analyze the cotransmission characteristics of contractile responses to electric field stimulation with submaximal voltage and short train in the rabbit saphenous artery.
  
  
  METHODS
  Isometric vasoconstriction of the rabbit saphenous arterial rings was recorded, and the sympathetic nerves of the arterial rings were activated with electric field stimulation.
  
  
  RESULTS
  Electric stimulation produced contractile responses in a frequency-dependent manner in the rabbit saphenous artery. Selective alpha1-adrenoceptor antagonist, prazosin (1 micromol/L) did not affect the vasoconstriction induced by electric stimulation at 2 Hz significantly, but inhibited 39.9 % - 53.8 % of the vasoconstriction at 8 - 16 Hz. On the other hand, desensitization of the P2X1 receptor with alpha,beta-methylene ATP (3 micromol/L) abolished all the vascular responses induced by stimulation at 2 Hz, and obviously potentiated those induced by stimulation at 16 Hz, but it did not affect the concentration-dependent response curves for exogenous norepinephrine. The vasoconstriction responses induced by electric stimulation were all abolished by the treatment of a combination of prazosin (1 micromol/L) and alpha,beta-methylene ATP (3 micromol/L).
  
  
  CONCLUSIONS
  The sympathetic and purinergic contractile responses can be induced by 2 Hz stimulation, and ATP is the sole transmitter causing the vasoconstriction in the rabbit saphenous artery. Contractile responses to higher frequencies are related to both norepinephrine and ATP. Desensitization of the P2X1 receptor with alpha,beta-methylene ATP potentiates the vascular responses to electric stimulation via a presynaptic mechanism.
authors.affiliation: Department of Pharmacology, School of Pharmacy, Hebei Medical University, Shijiazhuang 050017, China.
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: L M
authors.initials: LM
authors.lastname: Ren
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000320:Adrenergic Fibers / Q000502:physiology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001158:Arteries / Q000294:innervation; D004357:Drug Synergism; D004558:Electric Stimulation; D006614:Hindlimb / Q000098:blood supply*; D006838:Hydrocarbons; D066298:In Vitro Techniques; D008297:Male; D008697:Methane / Q000031:analogs & derivatives* / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology; D011817:Rabbits; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058469:Receptors, Purinergic P2X; D009435:Synaptic Transmission; D014661:Vasoconstriction / Q000502:physiology
chemical_list: D000317:Adrenergic alpha-Antagonists; D006838:Hydrocarbons; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; C030011:carbene; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D008697:Methane; D011224:Prazosin