An acute rise in aortic pressure causes ventricular arrhythmias which are suppressed by β adrenergic antagonism.1 ,2 The fact that these arrhythmias occur in isolated heart preparations,2 and after stellate ganglion excision,1 excludes the possibility that the effectiveness of β blockade could be caused by the blocking of a reflex with sympathetic efferent limb. In order to find the reason for this, we utilised the well established chronically denervated canine preparation3 in which the ventricles are almost completely depleted of catecholamines. The corresponding clinical situation is cardiac transplantation, but our study could not be performed ethically in such patients.

Beagle dogs, weighing between 13.7–17.0 kg of either sex, were denervated under 1.5% halothane in N₂O/O₂, removing the parasympathetic preganglionic neurones and the sympathetic postganglionic neurones. Adequate postoperative pain killing drugs were administered routinely. The study was made after …