Background-Arginine vasopressin (AVP) not only acts directly on blood vessels through V 1 receptor stimulation but also may modulate adrenergic-mediated responses in animal experiments in vivo and in vitro. The aim of the present study was to investigate whether AVP can contribute to an abnormal adrenergic constrictor response of human saphenous veins. Methods and Results-Saphenous vein rings were obtained from 32 patients undergoing coronary artery bypass surgery. The vein rings were suspended in organ bath chambers for isometric recording of tension. AVP (3ϫ10 Ϫ9 mol/L) enhanced the contractions elicited by electrical field stimulation at 1, 2, and 4 Hz (by 80%, 70%, and 60%, respectively) and produced a leftward shift of the concentration-response curve to norepinephrine (half-maximal effective concentration decreased from 6.

The objective of this work was to assess the efficacy and safety of sildenafil in patients with erectile dysfunction (ED) from Colombia, Ecuador, and Venezuela. One hundred and fifty-eight outpatients with ED participated in a double-blind, flexible-dose, randomized-controlled trial. Efficacy measures included question 3 (achieving an erection) and question 4 (maintaining an erection) from the International Index of Erectile Function (IIEF), the five functional domains of the IIEF, a global efficacy question, and patient event log. Sildenafil increased patients' ability to achieve=maintain erections (P < 0.01). Seventy-seven per cent of sildenafil-vs 46% of placebotreated patients reported improved erections (P < 0.001). Sixty-five percent and 35% of intercourse attempts were successful among sildenafil and placebo patients, respectively (P < 0.05). Sildenafil patients showed significant improvements in three of the five IIEF functional domains (P < 0.05). Adverse events were reported for 51% and 33% of sildenafil and placebo patients, respectively. It can be concluded that sildenafil is an effective, well-tolerated treatment for ED in patients from Latin America.

The present study was designed to characterize the response of human penile dorsal artery and deep dorsal vein to dilator drugs used in the diagnosis and treatment of erectile dysfunction with special emphasis on the effects on sympathetic neurotransmission. Ring segments of penile dorsal artery and deep dorsal vein were obtained from 20 multi-organ donors during procurement of organs for transplantation. The rings (3 mm long) were suspended in organ bath chambers for isometric recording of tension. We then studied the relaxant responses to prostaglandin E1 (PGE1), vasoactive intestinal peptide (VIP), papaverine (PV), sodium nitroprusside (SNP) and linsidomine chlorhydrate (SIN-1), and analysed the effects of these drugs on contractions induced by stimulation of perivascular sympathetic nerves. In artery and vein rings contracted by noradrenaline, all the drugs tested caused concentration-dependent relaxation. The order of potencies in terms of IC50 values (concentration of agonist causing 50% of the maximal relaxation) was PGE1=VIP>SNP>SIN-1=PV. Both arteries and veins contracted to electrical field stimulation (15 V, 0.5-2 Hz, 0.2 ms duration for 15 s) in a frequency-dependent manner. All relaxant drugs caused concentration-dependent inhibition of neurogenic contractions; the relative order of potencies was PGE1>VIP>SNP>SIN-1=PV. It is concluded that inhibition of sympathetic activity constitutes an effective relaxing mechanism in penile dorsal artery and vein. Modulation of sympathetic activity together with the direct effects on smooth muscle should be considered to evaluate adequately the efficacy of relaxant drugs to increase human penile blood supply.

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