| Abstract: | During the inhalation of normally oxygenated gas mixtures containing light or middle concentrations of FC 12, the presence of perfused epinephrine is necessary to induce cardiac arrhythmia in rabbits and dogs. The only inhalation of normally oxygenated gas mixtures containing a very high concentration of FC 12 produces in rabbits and dogs an important decrease in arterial pressure, tachycardia, a fall in respiratory amplitude, an acceleration reflex of respiratory frequency and cardiac arrhythmia. The same experiments in baro and chemodenervated animals show that : respiratory depression due to FC 12 still occurs, but not through the arterial chemoreceptors ; tachycardia has a reflex origin : barodenervation reveals the negative chromotropic effect of FC 12 and increases the fall in arterial pressure, mainly due to the negative inotropic effect of FC 12 ; adrenaline is necessary for FC 12-induced arrhythmia : barodenervation suppresses tachycardia due to the release of endogenous epinephrine and abolishes any arrhythmia. |
