LETTERS TO THE EDITOR The Role of Arterial Baroreceptors in Mediating the Cardiovascular Response to a Cardiac Clycoside in Conscious Dogs

1976) raises some questions regarding a possible important effect of ouabain to sensitize baroreceptors. Based on their data, they concluded that "cardiac glycosides do not exert a major action in sensitizing the arterial baroreceptors. " They base their viewpoint on data obtained with ouabain adminis-tered to animals with and without sectioned carotid sinus and aortic nerves, and also on comparable data obtained with methoxamine. The pressor effect of both these agents was enhanced threefold by denervating the reflexes. They reasoned that if sensitization of baroreceptors was impor-tant in the response to ouabain "a greater difference in arterial pressure response should have been observed in- response to ouabain than tamethoxamine, because methox-amine is not known to exert a direct effect on the arterial baroreceptors. " This is in contrast with our previous results in decerebrate unanesthetized cats wherein animals with cardiovascular reflexes denervated exhibited a greater differ-ence in arterial pressure response to ouabain than to norepinephrine (Gillis et al., J. Pharmacol. Exp. Ther. 170: 294, 1969). One difference between our experiments and those described in the present study is that, in addition to carotid sinus and aortic arch nerves being sectioned, afferent vagal nerves were also sectioned in our study. This was done because digitalis had been shown to have important actions on cardiac sensory receptors (Kido, Kyushu J. Med. Sci. 3: 149, 1952; Melville, J. Pharmacol. Exp. Ther. 106: 208, 1952). Indeed, more recent data have indicated an important role of cardiac sensory receptors (via afferent vagal fibers) i