Vagal Relaxation of the Stomach Induced by Apomorphine in the Cat

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Abstract
In anesthetized or decerebrate unanesthetized cats administration of the emetic drug apomorphine produced pronounced and long‐lasting relaxation of the stomach. When apomorphine induced somatomotor retching or vomiting movements they were always preceded by gastric relaxation. The gastric relaxatory response to apomorphine could not be blocked by atropine or guanethidine but was completely abolished after vagotomy. Vagotomy, if performed during the relaxed state of the stomach after apomorphine administration, resulted in a prompt decrease of gastric volume. Injection of apomorphine had no essential effect on gastric contractions induced by efferent electrical vagal stimulation, indicating that the splanchnic nerves were of minor or no importance for the apomorphine induced gastric relaxation.—It is concluded that the emetic drug apomorphine produces gastric relaxation by activation of the vagal non‐adrenergic relaxatory nerve fibres to the stomach. The results indicate that the relaxation of the proximal part of the stomach known to appear early in the vomiting act, is mediated by these relaxatory nerve fibres.