Objectives : This study aimed to investigate the relaxation effects and its underlying mechanisms of Rubus coreanus(RC) extract in contracted rabbit corpus cavernous tissues by phenylephrine(PE) 1 μM.

Methods : In order to define the relaxation effects of RC, rabbit corpus cavernous tissues were prepared in 2×2×6 ㎜ sized strip.
The dose-dependent relaxation responses of RC at 0.01-3.0 ㎎/㎖ in contracted strips induced by PE were measured and also observed after endothelial denudation.
To analyze the underlying mechanisms of RC-induced relaxation, indomethacin(IM), tetraethylammonium chloride(TEA), Nω-nitro-L-arginine (L-NNA), methylene blue(MB) were treated before RC extract infused into precontracted strips induced by PE.
To study the effect of RC extract on influx of extracellular Ca2+ in corpus cavernous strips, calcium chloride(Ca) 1 mM infused into precontracted strips induced by PE after pretreatment of RC extract in Ca2+-free krebs-ringer solution.
To investigate cytotoxic activity and nitric oxide(NO) concentration of RC extract on human umbilical vein endothelial cell(HUVEC), cell viability on HUVEC was measured by MTT assay, and NO concentration was measured by Griess reagent system.

Results : The cavernous strips were significantly relaxed by RC extract at 1.0 ㎎/㎖, 3.0 ㎎/㎖ and the relaxation responses to RC were inhibited significantly by endothelial disruption.
The pretreatment of IM, TEA didn''t affect RC extract-induced endothelium -dependent relaxation, but the pretreatment of L-NNA, MB reduced RC extract-induced endothelium-dependent relaxation.
When Ca2+ was supplied the cavernous strips which were precontracted by PE in a Ca2+-free krebs-ringer solution, contraction of strips was increased, but pretreatment of RC inhibited contractile response to Ca2+.
When RC extract was applicated on HUVEC, NO concentration was increased.

Conclusions : Our findings have shown that RC extract exerts a relaxing effect on corpus cavernosum in part by suppressing influx of extracellular Ca2+ through activating the NO-cGMP system.