Release of endogenous noradrenaline from the rat tail artery induced by veratridine.
The overflow of endogenous noradrenaline from the isolated rat tail artery was measured using a radioenzymatic method. Veratridine increased the overflow markedly even in the absence of external Ca2+. Modifications of the effect of 5 microM veratridine by tetrodotoxin, pargyline, cocaine, lidocaine, and phenoxybenzamine indicated that interaction of the alkaloid with the sodium channel induces primarily nonexocytotic release of noradrenaline. Ouabain inhibited the effect of 5 microM veratridine on the overflow into Ca2+-free solution, but it greatly potentiated the effect if external Ca2+ was present. Potentiation of the effect of veratridine in Ca2+-free solution by cyanide was ouabain sensitive. These observations are consistent with the hypothesis that, at low concentrations of veratridine such as 5 microM, the initial cause of enhanced release of noradrenaline may be a consequence of increased activity of the sodium pump, namely increased consumption of ATP by the pump.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001158:Arteries / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D013623:Tail / Q000098:blood supply; D014701:Veratridine / Q000494:pharmacology*; D014702:Veratrine / Q000031:analogs & derivatives*
D010042:Ouabain; D014701:Veratridine; D000255:Adenosine Triphosphate; D012964:Sodium; D014702:Veratrine; D002118:Calcium; D009638:Norepinephrine