Noradrenergic innervation of the penis in control and streptozotocin-diabetic rats: Evidence of autonomic neuropathy

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Abstract
The noradrenergic sympathetic innervation of the penis of control and 4-month streptozotocin-diabetic rats was examined with the glyoxylic acid histofluorescence method. Noradrenergic varicosities were found in the corpora cavernosa in a dense subtunical plexus and in the perisinusoidal and trabecular regions of the erectile tissue, in the corpus spongiosum in perisinusoidal tissue, around large arteries and veins, and around small tortuous arterioles and small draining veins of the corpora cavernosa and spongiosum. Noradrenergic varicosities were diminished in number and fluorescent intensity in all regions of the penis of diabetic rats compared with controls. The subtunical plexus was absent, perisinusoidal and trabecular varicosiities were sparse, and only occasional intermittent, discontinuous, dull fluorescent fibers or plexuses were found around the vessels. Quantitation with highperformance liquid chromatography revealed a significant reduction of norepinephrine in the penis of diabetic rats compared with controls. The present study suggests that long-term streptozotocin diabetes in the rat is accompained by sympathetic autonomic neuropathy of the penis that seems to parallel changes in the noradrenergic content of penile corpora of men with diabetes and erectile impotence. The streptozotocin-diabetic rat merits further study to explore the relationship between noradrenergic innervation of the penis and erectile tissue.