Cellular perspective of the erection pathway and mechanism of action of PDE5 inhibitors

  • During sexual stimulation signals in the brain cause nitric oxide (NO) to be released in the penis.
  • NO is transported into the smooth-muscle cells where it activates the enzyme guanilate cyclase, which produces cGMP (cyclic guanosine monophosphate).
  • Increased concentration of cGMP causes the outflow of calcium ions (Ca++) from the cell, resulting in smooth-muscle relaxation.
  • Consequently the arteries dilate, inflow of blood into the corpora cavernosa increases and blood accumulates, which results in an erection.
Cellular perspective
  • After ejaculation the enzyme phosphodiesterase type 5 (PDE5) reduces cGMP levels and the penis becomes flaccid.

PDE5 inhibitors (e.g. sildenafil) prevent the reduction of cGMP levels and thus help achieve and maintain an erection.

Speak to your doctor about your  problems with erectile dysfunction
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