Differential effects of omega-conotoxin GVIA, tetrodotoxin and prolonged cold storage on purinergic and adrenergic transmission in isolated canine splenic artery.
Double-peaked vasoconstrictions (biphases of vasoconstrictions) were readily induced in the conditions of 30 s trains of pulses at 1 Hz in the isolated, perfused canine splenic artery. P2X purinoceptors have previously been shown to be involved mainfy in the first-peaked response and alpha1-adrenoceptors mostly in the second. The treatment with 10 nM omega-conotoxin GVIA (omega-CTX) produced a parallel inhibitory effect on the first- and second-peaked vasoconstrictor responses to nerve stimulation. A submaximal concentration of tetrodotoxin (TTX) (3 nM) did not affect the first peak of constriction, but strongly inhibited the second peak, although a larger dose of TTX (30 nM) abolished either the first- or second-peaked response. On the other hand, after cold storage at 4 degrees C for 7 days, the first-peaked vasoconstriction markedly decreased, whereas the second-peaked response was not significantly modified.


CONCLUSIONS
(1) omega-CTX-sensitive calcium channels may produce a parallel modulation of purinergic and adrenergic components of sympathetic cotransmission; (2) TTX-sensitive sodium channels may have a more important role in controlling the adrenergic rather than purinergic transmission; and (3) the function of purinergic transmission of sympathetic nerve might be affected more strongly than that of adrenergic transmission in the cold-stored canine splenic artery.
Yang
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X
Department of Pharmacology, Shinshu University School of Medicine, Matsumoto, Japan.
Chiba
S
S
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000502:physiology; D003080:Cold Temperature; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D015222:Sodium Channels / Q000502:physiology; D013157:Splenic Artery / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology*; D014661:Vasoconstriction; D020866:omega-Conotoxin GVIA / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D015222:Sodium Channels; D013779:Tetrodotoxin; D000255:Adenosine Triphosphate; D020866:omega-Conotoxin GVIA; D009638:Norepinephrine