Figure 18

Figure 18 Norepinephrine is released from dense-core vesicles in sympathetic nerve terminals within the corpora. Norepinephrine then diffuses across the synaptic gap to activate α-adrenoceptors located on the cavernosal smooth muscle cell membrane. Second-messenger systems amplify the signal and induce smooth muscle contraction by increasing levels of intracellular calcium. By contrast, &lpha-blockers such as phentolamine (Vasomax®) interrupt this pathway thereby enhancing penile erection