Potassium-induced ventilatory reflexes originating from the dog hindlimb during rest and passive exercise.

1. It has been previously shown that Ketalar-anesthetized dogs do not exhibit alterations either in ventilation or in oxygen uptake during passive motion. In the present study, the same model was used to study the effects induced by increasing extracellular K+ to the concentration achieved during active exercise. 2. The isolated hindlimbs of twelve dogs anesthetized with ketamine hydrochloride i.v., after induction with sodium pentobarbital, were perfused with control (2.8 mM KCl) and experimental (8 mM KCl) physiological solutions under resting conditions, and in passive motion. 3. Respiratory minute volume (VE), respiratory rate (f) and tidal volume (VT) were determined by collecting the expired air in a Tissot gasometer. 4. During the control perfusion, the values of VE, f and VT for passive exercise did not differ significantly from those obtained under resting conditions. However, during perfusion with 8 mM KCl, a significant increase in VE was observed, possibly due to an increase of VT under resting conditions and to an increase of f during passive exercise. 5. The results suggest that passive exercise can induce a significant increase in ventilation only when accompanied by local chemical changes such as an increase in extracellular K+.