Evidence for different sites of action of reserpine and guanethidine

Positive and Negative Chronotropic Response of the S-A Node to Oxyfedrine

“…It may be possible, therefore, that oxyfedrine produced bradycardia partly due to the fact of its ;3-blocking action. However, even in the reserpinized preparations in which the myocardial catecholamine stores could be depleted over 90% (19), bradycardia was induced by high doses of oxyfedrine. This finding presumably excludes the possibility that the oxyfedrine-induced bradycardia is caused by blocking the effect of circulating catecholamines spontaneously released.…”

Difference in the Actions of Nicotine and Tyramine on Isolated Atria

“…Muskus (22) showed that the CA content in the heart decreased greatly after injec tion of guanethidine and the potency of the action of tyramine upon the atrium was weakened. Nevertheless, in our experiments when guanethidine was added to the organ bath it had an effect but did not influence the action of tyramine.…”