Both central command and exercise pressor reflex reset carotid sinus baroreflex

In decerebrate unanesthetized cats, we determined whether either "central c ommand," the exercise pressor reflex, or the muscle mechanoreceptor reflex reset the carotid baroreflex. Both carotid sinuses were vascularly isolated , and the carotid baroreceptors were stimulated with pulsatile pressure. Ca rotid baroreflex function curves were determined for aortic pressure, heart rate, and renal vascular conductance. Central command was evoked by electr ical stimulation of the mesencephalic locomotor region (MLR) in cats that w ere paralyzed. The exercise pressor reflex was evoked by statically contrac ting the triceps surae muscles in cats that were not paralyzed. Likewise, t he muscle mechanoreceptor reflex was evoked by stretching the calcaneal ten don in cats that were not paralyzed. We found that each of the three maneuv ers shifted upward the linear relationship between carotid sinus pressure a nd aortic pressure and heart rate. Each of the maneuvers, however, had no e ffect on the slope of these baroreflex function curves. Our findings show t hat central command arising from the MLR as well as the exercise pressor re flex are capable of resetting the carotid baroreflex.