Cardiac arrhythmic response evoked by stimulation of fastigial nuclei in the anesthetized cat.

Using the Horsley-Clarke sterotaxic technique for positioning electrodes in the cerebellum of the cat, the present study has shown that electrical stimulation of the nucleus fastigius produces cardiac arrhythmia in addition to the already known pressor response. These arrhythmias ranged from sinus tachycardia to various kinds of ectopic beats, and the effects of the arrhythmias on cardiovascular haemodynamics are discussed. Administration of the beta-adrenergic-blocking drug (propranolol) and the adrenergic neuron-blocking drug (bretylium tosylate) showed that the cardiac arrhythmic responses were predominantly due to sympathetic activation. Bilateral cervical vagotomy facilitated the production of ectopic beats during fastigial stimulation, but either abolished those ectopic beats previously arising in the post-stimulation period or modified them to the extent that they characteristically became beats with short P-R intervals and wide QRS complexes. This evidence indicates a cerebellar control of autonomic system functions.