The Action of Ergotamine on the Chemical and Mechanical Reflexes from the Carotid Sinus Region.

Summary. Ergotarnine in small doses (0.1 mg/kg) inhibits selectively the. carotid sinus pressor reflex, elicited by lowering the intrs carotid pressure, whereas the response to chemical stimuli, such as hypoxia. cyanides, or nicotine, still can be obtained, not only on respiration but also on the blood pressure. If a pressor response to carotid occlusion still occurs after ergotamine, it disappears when oxygen is administered. The effect in the former case is then due to occlusion hypoxia which stimulates the chemoreceptors connected with the vasomotor system. It could be shown that the abolishment of the sinus pressor reflex, following administration of ergotamine, is not due to an effect upon the receptors, since the action potentials set up in the sinus nerve by the intrasinusal pressure can still be elicited. Treatment of the experimental animal with small doses of ergotamine affords a convenient way of suppressing the sinus and aortic presso‐regulating system.