Table 2 The exclusion criteria for diabetic patients and normal volunteers in this study

1. Penile anatomical defect.

11. History of alcohol or drug abuse.

2. History of priapism.

12. Hypotension (BP < 90/60 mmHg)

3. History of prostatectomy

13. Uncontrolled hypertension (BP > 170/100)

4. History of cerebrovascular disease transient ischaemic attack (TIA), complete stroke or extracranial or intracranial steno-occlusive lesions or altered cerebral hemodynamic.

14. Proliferative retinopathy, retinitis pigmentosa.

5. Major hematological, renal, or Hepatic disorder.

15. Autonomic neuropathy

6. Any major psychiatric disorder

16. History of ketoacidosis in the previous 2 years

7. Treatment with nitrates

17. History of asthma or chronic obstructive pulmonary disease (COPD).

8. Coronary artery disease

18. Recent abdominal surgery.

9. History of myocardial infarction (MI).

19. Eye disease like cataract, glaucoma, intra-ocular lens implantation.

10. Peptic ulcer disease.

20. Diabetic nephropathy.