ABSTRACT
Introduction Cavernous smooth muscle contraction and relaxation, and the resultant states of penile flaccidity and erection, are primarily dependent upon cytosolic calcium levels. 1 Smooth muscle tone is itself regulated by the complex interplay between extracellular signals and intracellular events governing vasorelaxant and vasoconstrictive physiologic mechanisms. 2 The neurotransmitters of the corpus cavernosum are responsible for smooth muscle effects via activation of downstream second messenger molecules, alteration of ion channel permeabilities, and activation of cell-to-cell communication through gap junctions. 3 The primary molecular events for penile erection may be summarized as follows.
