On the mechanism of tachyphylaxis to tyramine in the isolated rat heart.
Tyramine was shown to release [(3)H]-catecholamines from an isolated rat heart previously perfused with [(3)H]-noradrenaline. With successive injections of tyramine the amount of [(3)H]-catecholamine released fell progressively and there was a parallel decrease in the increment of amplitude and rate of contraction of the heart. Reserpinized hearts were shown to take up less [(3)H]-noradrenaline than normal hearts. Release of radioactivity and loss of responsiveness to tyramine occurred more rapidly in the reserpinized heart. In the same preparation the uptake of [(14)C]-tyramine exceeded the quantity of the noradrenaline released.
D000818:Animals; D002395:Catecholamines; D006321:Heart / Q000494:pharmacology*; D009638:Norepinephrine; D051381:Rats; D013618:Tachyphylaxis; D014439:Tyramine / Q000494:pharmacology*
D002395:Catecholamines; D009638:Norepinephrine; D014439:Tyramine
HEART/pharmacology; TYRAMINE/pharmacology