ON THE MECHANISM OF TACHYPHYLAXIS TO TYRAMINE IN THE ISOLATED RAT HEART

Tyramine was shown to release [³H]‐catecholamines from an isolated rat heart previously perfused with [³H]‐noradrenaline. With successive injections of tyramine the amount of [³H]‐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 [3H]‐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 [¹⁴C]‐tyramine exceeded the quantity of the noradrenaline released.

DOI: 10.1111/j.1476-5381.1962.tb01426.x

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