THE ROLE OF INTRACELLULAR CA2-STORES IN PENILE CAVERNOUS SMOOTH-MUSCLE()

The presynaptic release of norepinephrine leads to a rise in cytosolic Ca2+ and promotes contraction of the cavernous smooth muscle. Ca2+ de rives from the extracellular space and sarcoplasmic stores. The import ance of intracellular stores was investigated in an organ bath study u sing tissue strips of rabbit cavernous muscle, Contractions were induc ed by phenylephrine and electrical stimulation. After incubation in Ca 2+-free solution as well as after administration of nifedipine till co ntractile responses were encountered. Ryanodine, a functional blocker of intracellular Ca2+-channels, significantly inhibited contractions a nd caffeine pronounced this effect. Rabbit cavernous smooth muscle con traction seems to involve an influx of Ca2+-ions from the extracelluar space and sarcoplasmic Ca2+-stores.