Vomiting and Reflex Vagal Relaxation of the Stomach Elicited from Heart Receptors in the Cat

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Abstract
The effect of afferent stimulation of the vagal cardiac nerves on gastric motility, heart rate and arterial blood pressure was studied in cats. Electric stimulation of the right cardiac nerve elicited, beside bradycardia and hypotension, a prompt and pronounced gastric relaxation and, after a latency, somatomotor vomiting movements.—Frequency‐response curves showed maximal circulatory effects already around 6 Hz while the curve for gastric relaxatory response was less steep. Frequent retching was observed at stimulations of 10 Hz or more.—The gastric relaxation upon afferent cardiac nerve stimulation was abolished by sectioning the right vagus caudad to the cardiac nerve and the left vagus in the neck, showing that vagal efferents mediated the gastric relaxation. The gastric response persisted after atropine and guanethidine ad was mimicked by reflex activation of the vagal “relaxatory” fibres to the stomach by esophageal distension. Intrapericardial nicotine and coronary artery occlusion also activated the described gastric reflex.—It is concluded that vomiting can be elicited by thin vagal cardiac afferents, probably of ventricular origin. Gastric relaxation, mediated by the vagal non‐adrenergic relaxatory fibres, constitute part of this vomiting response, as when vomiting is induced by apomorphine.