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Orhan I, Onur R, Tasdemir C, Ayar A, Kadioglu A. Sildenafil Citrate Inhibits Agonist Induced Contractions in Isolated Rat Seminal Vesicles. J Urol 2006;175:2350-2353.

It has been suggested the NO-cGMP pathway regulates seminal vesicle smooth muscle tone through the balance between generation and degradation of NO and cGMP. Sildenafil regulates this pathway in corpus cavernosum, but is not completely selective for this tissue. This research utilises Wistar rat seminal vesicles to investigate the effect of sildenafil citrate agonist induced isometric contractions.

Seminal vesicles were taken from 38 rats aged at least 60 days and placed in Krebs solution after removal of the thick seminal fluid. Strips were placed in a jacketed tissue bath, attached (using silk threads) to a fixed hook and an isometric force displacement transducer and equilibrated. Contractions were evoked with NE (10mM), ACh (10mM) or KCl (60mM) and the effects of sildenafil citrate (100mM and 300mM) were quantified by changes in mean amplitude, area under force-time curves (AUFTC’s) and isometric contractility indexes.

In preliminary experiments sildenafil citrate (10mM) had no effect hence the use of 100 and 300mM concentrations. Sildenafil citrate 300mM inhibited contractile responses to NE (1061 +/- 153 vs 271 +/- 65mg, p<0.0001), Ach (475 +/- 51 vs 68 +/- 17mg, p<0.0001) and KCl (546 +/- 71 vs 51 +/- 18mg, p<0.0002). It also decreased the AUFTC, and pre-treatment with sildenafil citrate prevented the contractile response to NE, ACh and KCl. They conclude that sildenafil citrate may be able to improve ejaculatory control by the inhibition of seminal vesicle muscle smooth contraction but further in vivo and in vitro assessment is required. This is an interesting paper that may pave the way for further research into an area where further treatment options would be extremely useful. However, they did recognise with this study that high concentrations of sildenafil citrate were required, furthermore a rat model was used, which may limit conclusions that can be drawn with regards to humans.