Abstract
1. In anaesthetized cats, stimulation of efferent components of the carotid sinus or aortic nerves depressed chemoreceptor discharge from the relevant chemoreceptor afferents. The local application of 2% procaine hydrochloride to the sinus nerve trunk, peripheral to the site of the stimulating electrodes and proximal to that of the afferent nerve twig, abolished the depression of afferent chemoreceptor discharge caused by electrical stimulation; on washing the procaine away electrical stimulation once more induced depression of chemoreceptor discharge.