Some effects of propranolol on the cardiovascular responses of the monkey to simulated subarachnoid haemorrhage.

StmAaaCHNOm ~EMOnnHAC~ rL~S BF_~N ASSOC~TED with electrocardiographic changes in in the experimental animal) ,z These may vary greatly in eharaoter and them have been changes consisterlt with increased activity of the sympathetic nervous system. Structural changes in the myoeardium have been described that could be produc ~d by a period of sympathetic nervous system overactivity ~ and increased tissue catecholamine levels have been measured following subaraehnoid haemorrhage and other forms of stimulation of the brain in the laboratory animals. 4 The importance of the cateeholamines is also suggested by the abolition of eneephalogenic cardhe arrhythmias in dogs following treatment with reserpine, s The portion of sympathetic nervous activity mediated by B-receptor stimulation has received some a~ention, not only because of the intrinsic interest in the mechanism of these arrhythmias, but because of the effect of rapid arrythmias on cardiac out-put and the possible reduction of cerebral blood flow. Accordingly it seemed of interest to study the effects of the prior administration of propranolol on such changes in cardiac rhythm and cerebral blood Bow as might occur following simulated subarachnoid haemorrhage in the monkey.