Ventilatory responses during electrically induced muscular work in anesthetized dogs, after both deafferentation and cross circulation of hindlimbs.

1. The role of the neural afferent component from moving limbs during exercise hyperpnea has been studied in dogs. The influence of neural and humoral effects was evaluated by dorsal root section and limb cross-circulation. 2. Respiratory minute volume (Ve), frequency (f), tidal volume (VT) and oxygen consumption (VO2) were measured in anesthetized dogs submitted to light electrically-induced exercise (ventral root stimulation of L6 or L7), both before and after deafferentation. 3. In control experiments the increase of respiratory minute volume (Ve) was directly proportional to VO2, and primarily due to changes in frequency. After dorsal root section (L1 to S1), VO2 increased, but no significant changes were observed in the other respiratory parameters. 4. In contrast to the deafferentation experiments, no changes were detected either in Ve or in f during exercise in the cross-circulation experiments. 5. It is concluded that during light exercise reflexes generated by moving limbs are important for triggering the exercise tachypneic response.