ADRENERGIC INNERVATION OF SPHINCTERIC AND NONSPHINCTERIC SMOOTH MUSCLE IN THE RAT INTESTINE

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Abstract
The Falck and Hillarp fluorescence technique has been used to investigate the density of adrenergic innervation of smooth muscle at different levels in the alimentary canal of the rat. Special attention was given to potential sphincteric regions. The density of smooth muscle innervation was in general low. No special innervation was found in the region of the cardiac sphincter or at the ileocecal junction. A sharply circumscribed region of muscle with a high density of adrenergic innervation was observed in the pylorus just short of the pyloroduodenal junction and may represent a sphincteric region. In the terminal colon the anococcygeus muscle was found to form a powerful muscular loop around the colon. This muscle has a density of adrenergic innervation as high as that of the vas deferens. It can be easily isolated and forms an admirable in vitro preparation. It has not previously been described in the rat nor has its adrenergic innervation been described in any species.