Cardiac arrhythmia induced by electrical stimulation of the fastigial nucleus in cats.

Electrical stimulation of the fastigial nucleus produced a pressor response with cardiac arrhythmia in cats. The arrhythmic response was abolished by tetrodotoxin (3 microgram/kg, i.v.), atropine (0.5 mg/kg, i.v.) or vagotomy, and suppressed slightly by propranolol or verapamil (0.5-1.0 mg/kg, i.v.). It was not abolished by the carotid sinus nerve section. The effects of the drug suggest that arrhythmia seems to be due to an interplay of sympathetic and parasympathetic influences with the latter effect predominating. The pressor and arrhythmic response to stimulation of the fastigial nucleus was increased by stimulation, and decreased by lesion of the posterior hypothalamus, indicating that some connection between the two structures exists.