<font><font color="#555555"><span style="font-size: 10pt; font-family: Tahoma">Background. Seminal vesicle smooth muscle contraction is mediated through sympathetic and parasympathetic neurons activity. Although seminal vesicle plays an important role in male fertility, but little attention is given to mechanism involved in contraction of this organ.<br />Methods. In this study effects of drugs which activate ATP - sensitive K channels and blockers of K and Ca channels were examined on contraction of guinea - pig isolated seminal vesicle due to electrical filled stimulation (EFS), noradrenaline, carbachol and KCI.<br />Results. The K channel blocker tetraethyl ammonium potentate the EFS responses at all frequencies, while, the ATP - sensitive K channel inhibitor glibenclamide and the K channel opener levcromakalim, diazoxide, minoxidil and Ca channel blocker nifedipine all had relaxant effect on guinea - pig seminal vesicle.<br />Discussion. This study indicate that activities of K and Ca channels is important in regulation of seminal vesicle contraction due to nerve stimulation, noradrenaline or carbachol.</span></font></font>