Abstract
The distribution of adrenergic fibers in the guinea pig esophagus, trachea and bronchi were fluorescence microscopically examined by modified Falck's method. In the esophagus, the fibers were seen running mainly along the blood vessels in the submucosal layer and in the endomysium of the muscle layer. There was no evidence to show direct distribution of the fibers to the muscle fibers. In the trachea and bronchi, the adrenergic fibers are supplied to the submucosal and muscle layers after passing through the annular ligament. They course longitudinally to the axis of the tubes within the muscle layer and membranous part.
The fibers reach to the terminal bronchioles. Most of the fibers are seemed to be the vasomotor of the sympathetic postganglionic fibers. The mechanism of relaxation and dilation of the tubes was briefly discussed.
