The Effect of Acetylstrophanthidin on the Responsiveness of Left Atrial Type B Receptors to Saline Infusion and Veratrine Injection in Anaesthetized Cats

In order to investigate whether the cardiac glycoside, acetylstrophanthidin, influenced the sensitivity of atrial receptors to saline infusion and veratrine injection, experiments were performed on anaesthetized, artificially ventilated and thoracotomised cats. The following was found: Intravenous injection of acetylstrophanthidin did not change the basal activity or the stimulus-response relationship of left atrial type B receptors. Before acetylstrophanthidin, administration of small doses of veratrine (10-20 micrograms/kg) produced either a mild stimulation or no stimulation of these receptors. After acetylstrophanthidin, injections of veratrine (10-20 micrograms/kg) produced a marked/sustained stimulation of all the type B receptors investigated; in the case of a few units, even subthreshold doses of veratrine produced significant stimulation. The data indicate that acetylstrophanthidin does not sensitize the type B atrial receptors to their natural stimulus; however, it increases their sensitivity to drugs probably by enhancing the drug-induced depolarisation caused by blocking the sodium pump.