NOS3 and type 2 diabetes mellitus: In many studies of diabetic rat models, and particularly in the T2DM model, vasodilatory signaling is impaired by a decrease in nNOS activity, non-adrenergic non-cholinergic (NANC) dysfunction, impaired eNOS activation, oxidative stress, cavernosal hypercontractility, veno-occlusive dysfunction, and androgen deficiency.