Stimulation of splanchnic afferents reflexly relaxes tracheal smooth muscle in dogs

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Abstract
Although chemical stimulation of abdominal visceral afferents reflexly increases cardiovascular and ventilatory function, the effect of stimulating these afferents on airway smooth muscle is unknown. Transverse smooth muscle tension from an innervated segment of trachea was recorded in chloralose-anesthetized dogs while topically applying capsaicin (200 .mu.g/ml) and bradykinin (0.01-10 .mu.g/ml) to the serosal surfaces of the stomach, small intestine and gallbladder. Application of these irritant substances to the stomach and small intestine decreased tracheal tension and increased mean arterial pressure. Application of capsaicin and bradykinin to the gallbladder had only small effects on both of these variables. Cutting the splanchnic nerves abolished or greatly attenuated the decreases in tension and increases in mean arterial pressure; cutting the vagi had no effect on them. Stimulation of splanchnic afferent endings in the stomach and small intestine reflexly relaxes tracheal smooth muscle in dogs. This effect may be one component of the constellation of autonomic responses reflexly evoked by abdominal visceral pain and inflammation.