Reflex relaxation of tracheal smooth muscle by thin-fiber muscle afferents in dogs

Publisher Website
Google Scholar
Abstract
Although the reflex cardiovascular and ventilatory responses evoked by stimulation of groups III and IV muscle afferents have been extensively investigated, less is known about the effects of stimulation of these afferents on airway caliber. In 11 chloralose-anesthetized dogs, transverse smooth muscle tension was recorded from an innervated segment of the trachea, while groups III and IV muscle afferents were stimulated with capsaicin and bradykinin. Injection of both substances into the arterial supply of the skinned hindlimb evoked dose-dependent decreases in tracheal tension; injection into the femoral vein either increased or had no effect on tension. Injection of capsaicin and bradykinin into the arterial supply of the gracilis muscle also decreased tracheal tension. Cutting the sciatic, gracilis and femoral nerves abolished the decreases in tracheal tension caused by injection of capsaicin and bradykinin into the arterial supply of the hindlimb. Chemical stimulation of groups III and IV muscle afferents causes reflex relaxation of tracheal smooth muscle in dogs.