Selective nitrergic neurodegeneration in diabetes mellitus–a nitric oxide‐dependent phenomenon

• Published in: British journal of pharmacology Vol. 128; no. 8; pp. 1804 - 1812
• Main Authors: Cellek, Selim, Rodrigo, José, Lobos, Edgar, Fernández, Patricia, Serrano, Julia, Moncada, Salvador
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-12-1999; Nature Publishing
• Subjects: Animals; Biological and medical sciences; diabetes mellitus; Diabetes Mellitus, Experimental - complications; Diabetes Mellitus, Experimental - metabolism; Enzyme Inhibitors - pharmacology; erectile dysfunction; Erectile Dysfunction - etiology; Erectile Dysfunction - metabolism; impotence; Male; Medical sciences; Miscellaneous; Nerve Degeneration - etiology; Nerve Degeneration - metabolism; neurodegeneration; Neuropharmacology; Neurotransmitters. Neurotransmission. Receptors; NG-Nitroarginine Methyl Ester - pharmacology; nitrergic; Nitric oxide; Nitric Oxide Synthase - drug effects; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; penile erection; Penile Erection - drug effects; Penile Erection - physiology; Penis - drug effects; Penis - metabolism; Pharmacology. Drug treatments; Rats; Rats, Wistar; streptozotocin; Endocrinopathy; Animal model; Erection disorders; Rat; Enzyme; Diabetes mellitus; Rodentia; In vitro; Nitric-oxide synthase; In vivo; Tissue; Vertebrata; Mammalia; Penis; Animal; Nitric oxide; Degeneration; Oxidoreductases; Mechanism of action; Neurotransmission
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0702981

In vitro and in vivo studies have demonstrated a dysfunctional nitrergic system in diabetes mellitus, thus explaining the origin of diabetic impotence. However, the mechanism of this nitrergic defect is not understood.
In the penises of streptozotocin (STZ)‐induced diabetic rats, here, we show by immunohistochemistry that nitrergic nerves undergo selective degeneration since the noradrenergic nerves which have an anti‐erectile function in the penis remained intact.
Nitrergic relaxation responses in vitro and erectile responses to cavernous nerve stimulation in vivo were attenuated in these animals, whereas noradrenergic responses were enhanced.
Activity and protein amount of neuronal nitric oxide synthase (nNOS) were also reduced in the penile tissue of diabetic rats.
We, thus, hypothesized that NO in the nitrergic nerves may be involved in the nitrergic nerve damage, since only the nerves which contain neuronal NO synthase underwent degeneration.
We administered an inhibitor of NO synthase, NG‐nitro‐L‐arginine methyl ester (L‐NAME), in the drinking water of rats for up to 12 weeks following the establishment of diabetes with STZ.
Here we demonstrate that this compound protected the nitrergic nerves from morphological and functional impairment. Our results show that selective nitrergic degeneration in diabetes is NO‐dependent and suggest that inhibition of NO synthase is neuroprotective in this condition.
British Journal of Pharmacology (1999) 128, 1804–1812; doi:10.1038/sj.bjp.0702981