Sympatho-inhibitory baroreflex in conscious rabbits: simultaneous recordings of sympathetic and aortic nerve activity.

The purpose of this study was to evaluate simultaneously the activity of afferent and efferent neuronal pathways of the sympatho-inhibitory baroreceptor reflex in conscious rabbits. Bipolar electrodes were implanted around the intact aortic nerve and cervical sympathetic trunk. Baroreceptor activity and sympathetic discharges were continuously recorded along with mean blood pressure. The baroreceptor reflex response was evoked by changes in mean arterial pressure induced by i.v. administration of phenylephrine 10 micrograms/kg and sodium nitroprusside 10 micrograms/kg. The baroreflex was analysed as parallel changes of afferent and efferent activities per mmHg of mean blood pressure rise or fall. This method of investigation of baroreflex responsiveness permits analysis of afferent and efferent neural activities under different behavioural conditions in conscious animals.