title: Cardiac arrhythmias induced in cats by stimulation of the anteromedial hypothalamus.
abstract: Negative emotional behavior induced during stimulation of the anteromedial hypothalamus is frequently accompanied by cardiac arrhythmias just after cessation of the stimulation (the poststimulus arrhythmias: the PSAs). A mechanism related to the PSAs may be neurogenic in origin. Whether or not the PSAs are influenced by hypothalamically induced adrenal catecholamines has not been settled. We assessed the correlation between these influences on the PSAs induced by anteromedial hypothalamic stimulation in anesthetized cats. Thirty-five adult cats were given stimulation through an electrode inserted stereotaxically into the hypothalamus and arterial blood pressure, electrocardiogram and heart rate were recorded on a polygraph. PSAs were never observed after vagotomy and intravenous injections of methyl-atropine and phentolamine. Carteolol was without effect. When an intentional gradual reduction of stimulus intensity was applied instead of sudden cessation of hypothalamic stimulation, there was a gradual decline in the blood pressure and no PSAs. Adrenalectomy did not alter the threshold for the PSAs but did reduce the frequency of the PSAs. Intravenous injections of catecholamines produced cardiac arrhythmias similar to those seen in PSAs. After vagotomy, stimulation of the distal nerve of the right vagus during or just after hypothalamic stimulation produced the same arrhythmias as seen in PSAs, but vagus stimulation alone did not. These results suggest that the PSAs are due to 'sudden' change from sympathetic to parasympathetic influences on the heart and that adrenal catecholamines are involved in the prolongation of the train of the PSAs. These findings support the proposal that the PSAs are a stress-related symptom induced by stimulation of the anteromedial hypothalamus.
authors.affiliation: Department of Neuropsychiatry, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Tashiro
authors.forename: K
authors.initials: K
authors.lastname: Hirata
authors.forename: S
authors.initials: S
authors.lastname: Maki
authors.forename: H
authors.initials: H
authors.lastname: Nakao
mesh_terms: D000313:Adrenal Medulla / Q000503:physiopathology; D000818:Animals; D001143:Arousal / Q000502:physiology; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D001794:Blood Pressure; D001931:Brain Mapping; D002415:Cats; D004558:Electric Stimulation; D004562:Electrocardiography; D005260:Female; D006321:Heart / Q000294:innervation; D006339:Heart Rate; D007033:Hypothalamus, Middle / Q000503:physiopathology*; D008297:Male; D013564:Sympathetic Nervous System / Q000503:physiopathology; D014630:Vagus Nerve / Q000503:physiopathology