To determine if the penis of the rat is supplied by long or short adrenergic neurons, hypogastric and perivascular neurectomies were performed. Reserpine, a drug which depletes the store of norepinephrine from long adrenergic nerves more rapidly than from short adrenergic neurons, has also been used to aid in characterizing this innervation. Hypogastric neurectomy, with or without denervation of the common iliac vessels, had no effect on the density or fluorescence intensity of adrenergic fibers in the rat penis. The long adrenergic fibers to the atria did not fluoresce in reserpine‐treated rats; however, fluorescent adrenergic fibers in the penis and vas deferens remained visible. Reserpine depressed atrial levels of norepinephrine by 75%, while norepinephrine in the penis and vas deferens was reduced only by 32% and 29%, respectively. The absence of any effect of hypogastric neurectomy on the adrenergic fibers of the penis indicates that such fibers arise from neurons distal to the site of lesion of the hypogastric nerves. This result and the similar response of the vas deferens and penis to reserpine strongly suggest that the penis of the rat is supplied by short adrenergic neurons.
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