ACTIVATION OF CAROTID BARORECEPTORS INHIBITS SPINAL REFLEXES IN MAN

The present study was designed to investigate the effect of baroreceptors on a spinal reflex. The Achilles tendon reflex (T reflex), a monosynaptic spinal reflex, was chosen as an indicator of descending influences of central activation. The baroreceptors are stretch receptors which respond to extensions of the arterial wall. Carotid sinus baroreceptors can be manipulated non-invasively by means of a cuff around the neck. In this study, the phase-related external suction (PRES) neck cuff technique was used. PRES applies short changes in cuff pressure as a function of heart cycle phase, controlling for non-specific effects found in other baroreceptor manipulation methods. The T reflex was reduced when elicited during the highest levels of baroreceptor activation. Reflex amplitude was largest when elicited during the lowest levels of baroreceptor activation. These results are consistent with previous findings that baroreceptor activation reduces CNS excitability.